Glyceryl trinitrate (GTN) is metabolized to nitric oxide, which activates guanylyl cyclase, increasing cGMP and causing venodilation.

Sublingual administration bypasses first-pass metabolism, providing onset within 1–3 minutes.

Isosorbide dinitrate causes venodilation and hypotension, triggering reflex sympathetic tachycardia.

A nitrate-free interval of 8–12 hours daily prevents sulfhydryl group depletion and maintains drug efficacy.

Nitrates cause venodilation (reducing preload) at low doses and arteriolar dilation (reducing afterload) at higher doses.

Prinzmetal angina results from coronary artery spasm.

Ivabradine selectively blocks the If (funny) current in the SA node, reducing heart rate without affecting contractility or BP.

Both sildenafil (PDE-5 inhibitor) and nitrates increase cGMP causing vasodilation.

Nitrates cause vasodilation of meningeal blood vessels, stretching pain-sensitive structures and causing throbbing headache.

Nicorandil opens ATP-sensitive potassium channels (causing arterial dilation) and has a nitrate moiety (causing venodilation).

Statins competitively inhibit HMG-CoA reductase, the rate-limiting enzyme in cholesterol synthesis.

Pravastatin is hydrophilic and not metabolized by CYP450, minimizing drug interactions.

Rhabdomyolysis is a rare but serious complication involving muscle breakdown, myoglobinuria, and potential renal failure.

Fibrates like fenofibrate activate PPAR-alpha, increasing lipoprotein lipase activity and reducing triglycerides by 30–50%.

Cholestyramine is an anion exchange resin that binds bile acids in the intestine, preventing reabsorption.

Ezetimibe selectively blocks NPC1L1 (Niemann-Pick C1-Like 1) protein at the intestinal brush border, inhibiting cholesterol absorption.

Combining statins with fibrates (especially gemfibrozil) significantly increases myopathy and rhabdomyolysis risk due to pharmacokinetic interactions.

PCSK9 normally degrades LDL receptors.

Niacin (nicotinic acid) causes prostaglandin-mediated cutaneous vasodilation, resulting in flushing.

Statins have beneficial pleiotropic effects: improving endothelial function, reducing inflammation (CRP), and stabilizing plaques.

Heparin binds to antithrombin III, accelerating its inhibition of thrombin (Factor IIa) and Factor Xa 1000-fold.

Protamine sulfate is a positively charged molecule that binds negatively charged heparin, neutralizing it within minutes.

Warfarin inhibits vitamin K epoxide reductase (VKORC1), preventing regeneration of active vitamin K needed for synthesis of factors II, VII, IX, X.

Factor VII has the shortest half-life (4–6 hours), so it decreases first.

INR (International Normalized Ratio) standardizes prothrombin time for warfarin monitoring.

Serious warfarin bleeding requires stopping warfarin, IV vitamin K (takes 6–24 hours), and immediate FFP/prothrombin complex concentrate for rapid factor replacement.

LMWH has better bioavailability, longer half-life, and more predictable dose-response, eliminating routine monitoring.

Rivaroxaban directly inhibits Factor Xa without needing antithrombin.

Dabigatran (direct thrombin inhibitor) has predictable pharmacokinetics, no routine monitoring needed, and fewer drug-food interactions.

Fondaparinux is a synthetic pentasaccharide that selectively inhibits Factor Xa via antithrombin.

Aspirin irreversibly acetylates COX-1 in platelets, preventing thromboxane A2 (TXA2) synthesis, which normally promotes aggregation.

Platelets lack nuclei and cannot synthesize new COX.

Clopidogrel is a prodrug that irreversibly blocks the P2Y12 ADP receptor on platelets, inhibiting ADP-induced aggregation.

Abciximab is a monoclonal antibody blocking GP IIb/IIIa receptor, the final common pathway of platelet aggregation.

Streptokinase binds plasminogen, forming a complex that converts other plasminogen molecules to plasmin, which degrades fibrin clots.

Aminocaproic acid (and tranexamic acid) inhibit plasmin and plasminogen activators, reversing fibrinolysis.

TPA preferentially activates plasminogen bound to fibrin clots, making it more fibrin-specific with less systemic fibrinolysis.

Ticagrelor is a direct-acting, reversible P2Y12 inhibitor with faster onset and offset than clopidogrel.

Dipyridamole inhibits phosphodiesterase (increasing cAMP) and blocks adenosine reuptake (adenosine inhibits platelets).

Streptokinase is antigenic (derived from streptococcus), producing antibodies that neutralize subsequent doses and may cause anaphylaxis. tPA derivatives (alteplase, tenecteplase, reteplase) are non-antigenic.

ACE inhibitors block conversion of angiotensin I to angiotensin II (a potent vasoconstrictor).

ACE (kininase II) normally degrades bradykinin.

Losartan blocks AT1 receptors, preventing angiotensin II effects without affecting bradykinin (no cough).

Labetalol (alpha and beta blocker) is safe in pregnancy.

Amlodipine is a dihydropyridine CCB causing arteriolar vasodilation with minimal cardiac effects.

Prazosin (alpha-1 blocker) causes profound first-dose orthostatic hypotension, especially in volume-depleted patients.

Thiazides initially reduce blood volume through diuresis.

ACE inhibitors/ARBs reduce intraglomerular pressure and proteinuria, providing renal protection beyond BP control.

Thiazides cause hypokalemia through increased potassium excretion.

Clonidine stimulates alpha-2 receptors in brainstem, reducing sympathetic outflow and lowering BP and heart rate.

Digoxin inhibits Na+/K+-ATPase, increasing intracellular sodium.

ACE inhibitors reduce mortality by blocking neurohormonal activation.

Furosemide and other loop diuretics block Na-K-2Cl cotransporter in thick ascending limb of Henle, causing massive natriuresis and relieving congestion.

Aldosterone causes myocardial fibrosis, remodeling, and inflammation.

This combination contains valsartan (ARB) plus sacubitril (neprilysin inhibitor increasing natriuretic peptides).

Beta blockers initially worsen HF symptoms due to negative inotropy.

Dobutamine primarily stimulates cardiac beta-1 receptors, providing positive inotropy with some beta-2 vasodilation.

Milrinone inhibits PDE-3, increasing cAMP in heart (positive inotropy) and vessels (vasodilation).

Ivabradine reduces heart rate by blocking If current.

Digoxin has a long half-life (36–48 hours), taking 5–7 days to reach steady state.

Class I drugs (Ia, Ib, Ic) block fast sodium channels, reducing phase 0 depolarization velocity.

Amiodarone is primarily Class III (potassium channel blocker), prolonging action potential duration.

Amiodarone accumulates in lungs causing pneumonitis and fibrosis (10–17% of patients).

Lidocaine (Class Ib) preferentially binds to inactivated sodium channels in ischemic/depolarized tissue, minimally affecting normal myocardium.

Adenosine causes transient AV nodal block, terminating re-entrant SVT involving the AV node.

Sotalol (Class III + beta blocker) prolongs QT interval by blocking potassium channels.

In WPW with AF, verapamil blocks AV node but not the accessory pathway, allowing rapid conduction through the bypass tract leading to VF.

Class II antiarrhythmics are beta blockers.

CAST trial showed Class Ic drugs increased mortality in post-MI patients despite suppressing PVCs.

Digoxin increases parasympathetic (vagal) tone, prolonging AV node refractory period and slowing ventricular response.

Codeine (opioid) directly depresses the cough center in the medulla.

Dextromethorphan is the D-isomer of a codeine analog without opioid effects, meaning minimal addiction, sedation, and constipation.

Atherosclerosis predominantly affects large elastic and medium-sized muscular arteries, with coronary arteries being the most clinically significant site.

Foam cells are lipid-laden macrophages that accumulate in the intima and form fatty streaks, the earliest lesion of atherosclerosis.

Brain undergoes liquefactive necrosis due to high lipid content and lack of substantial extracellular matrix.

Lungs have dual blood supply (pulmonary and bronchial arteries), allowing blood to seep into necrotic tissue, causing hemorrhagic infarcts.

Normal BP is defined as systolic <120 mmHg and diastolic <80 mmHg.

Hypovolemic shock results from reduced circulating blood volume due to hemorrhage or fluid loss.

Renal artery stenosis activates the renin-angiotensin-aldosterone system, causing renovascular hypertension–the most common secondary cause.

Berry aneurysms are saccular aneurysms occurring at arterial bifurcations in the Circle of Willis due to congenital weakness of the media.

Hypertension is the major risk factor for aortic dissection, causing hemodynamic stress that tears the intima.

Giant cell (temporal) arteritis almost exclusively affects individuals >50 years, with peak incidence at 70–80 years.

DVT most commonly occurs in deep veins of the calf and thigh due to stasis, especially in immobilized patients.

Varicose veins result from incompetent venous valves causing retrograde blood flow and venous dilation.

Left heart failure causes blood to back up into pulmonary circulation, leading to pulmonary congestion and edema.

Left heart failure increases pulmonary pressures, leading to right ventricular strain and eventual failure.

Dilated cardiomyopathy shows four-chamber dilation with thin, weakened walls and systolic dysfunction.

HCM is an autosomal dominant disorder caused by mutations in sarcomere protein genes (commonly β-myosin heavy chain).

Tetralogy of Fallot is the most common cyanotic CHD, comprising VSD, overriding aorta, pulmonary stenosis, and RV hypertrophy.

VSD accounts for ~25–30% of all CHDs, making it the most common.

Rheumatic heart disease is responsible for almost all cases of mitral stenosis, causing commissural fusion and “fish-mouth” valve deformity.

Aschoff bodies are granulomatous lesions with Anitschkow cells (caterpillar cells) found in myocardium during rheumatic fever.

Jones criteria (major: carditis, polyarthritis, chorea, erythema marginatum, subcutaneous nodules; plus minor criteria) diagnose acute rheumatic fever.

Virchow’s triad (endothelial injury, stasis, hypercoagulability) describes factors predisposing to thrombosis.

>95% of pulmonary emboli originate from deep veins of the legs (femoral, iliac, popliteal).

Mitral valve is most commonly affected in native valve endocarditis due to high-pressure regurgitant jets causing endothelial damage.

aureus causes aggressive acute endocarditis with rapid valve destruction.

Streptococcus pneumoniae (pneumococcus) is the leading cause of CAP in all age groups.

Ghon focus is the initial parenchymal lesion (usually mid-lung zone) in primary TB.

Tuberculosis produces caseating (cheese-like necrosis) granulomas due to mycobacterial lipids.

Aspiration of oropharyngeal or gastric contents (during unconsciousness, alcohol intoxication, seizures) is the most common cause of lung abscess, typically affecting right lower lobe.

Empyema is accumulation of pus (purulent exudate) in the pleural space, usually complicating bacterial pneumonia.

Squamous cell carcinoma accounts for >95% of laryngeal cancers, strongly associated with smoking and alcohol.

Resorption (obstructive) atelectasis occurs when airway obstruction (mucus plug, tumor, foreign body) prevents air entry; trapped air is absorbed.

ARDS involves diffuse alveolar damage with hyaline membrane formation, caused by sepsis, trauma, or aspiration.

Hyaline membrane disease (neonatal RDS) occurs in premature infants due to surfactant deficiency.

Centriacinar (centrilobular) emphysema affects respiratory bronchioles in upper lobes and is strongly linked to smoking.

Α1-antitrypsin deficiency allows unopposed elastase activity, destroying entire acini predominantly in lower lobes (panacinar pattern).

Chronic bronchitis is a clinical diagnosis: productive cough ≥3 months/year for ≥2 consecutive years.

Asthma shows reversible bronchoconstriction that improves with bronchodilators, unlike COPD which shows irreversible obstruction.

Curschmann spirals are twisted mucus plugs found in sputum of asthmatic patients, along with Charcot-Leyden crystals (eosinophil breakdown) and eosinophils.

Pulmonary fibrosis (idiopathic or secondary) causes stiff lungs with reduced compliance–a restrictive pattern.

IPF shows usual interstitial pneumonia (UIP) pattern with temporal heterogeneity, fibroblastic foci, and honeycombing.

A saddle embolus straddles the bifurcation of the main pulmonary artery, causing sudden death by blocking both pulmonary arteries.

Dual blood supply (bronchial + pulmonary arteries) usually prevents infarction.

Adenocarcinoma is now the most common lung cancer overall, especially in non-smokers and women.

Pancoast (superior sulcus) tumor arises in the lung apex and invades brachial plexus, sympathetic chain (Horner syndrome), and ribs.

Horner syndrome (sympathetic chain damage) causes miosis (constricted pupil), ptosis (drooping eyelid), and anhidrosis (lack of sweating).

Light’s criteria define exudate: pleural/serum protein >0.5, pleural/serum LDH >0.6, or pleural LDH >⅔ upper normal serum LDH.

CHF causes transudative effusions due to increased hydrostatic pressure.

Pleuritic chest pain is sharp, stabbing, and worsens with breathing or coughing due to inflamed parietal pleura rubbing together.

Takayasu arteritis is a granulomatous large-vessel vasculitis affecting the aortic arch and its branches, causing “pulseless disease” in young Asian women.

Legionella is acquired by inhaling aerosols from contaminated water sources (cooling towers, air conditioners, showers).

Legionella stains poorly with Gram stain (gram-negative but faint).

BCYE agar contains L-cysteine and iron, essential for Legionella growth.

Legionella causes Legionnaires’ disease (severe pneumonia) and Pontiac fever (mild flu-like illness).

Mycoplasma has no cell wall, making it resistant to β-lactams and invisible on Gram stain.

Mycoplasma causes “walking pneumonia”–mild atypical pneumonia where patients remain ambulatory despite respiratory symptoms.

Mycoplasma infection induces IgM antibodies (cold agglutinins) that agglutinate RBCs at 4°C, sometimes causing hemolytic anemia.

influenzae requires Factor X (hemin) and Factor V (NAD) for growth–demonstrated by satellitism around S. aureus on blood agar.

Hib capsule is polyribosylribitol phosphate (PRP), a polysaccharide that inhibits phagocytosis and is the target of the Hib conjugate vaccine.

Hib conjugate vaccine prevents invasive type b disease (meningitis, epiglottitis, sepsis).

Pertussis has paroxysmal coughing episodes followed by inspiratory “whoop” due to forceful inspiration against closed glottis.

Bordet-Gengou (potato-blood-glycerol) agar is the classic medium for B. pertussis, showing “mercury drop” colonies.

Pertussis toxin ADP-ribosylates inhibitory Gi proteins, preventing them from inhibiting adenylate cyclase, leading to increased cAMP.

tuberculosis is an acid-fast bacillus due to mycolic acid in its cell wall, which retains carbol fuchsin despite acid-alcohol decolorization.

Ziehl-Neelsen (acid-fast) stain uses heat to drive carbol fuchsin into mycolic acid; TB appears pink/red against blue background.

LJ medium (egg-based with malachite green dye) supports slow-growing mycobacteria.

tuberculosis divides slowly (15–20 hours), explaining prolonged culture time (weeks) and need for extended treatment.

Mantoux test is a delayed-type (Type IV) hypersensitivity reaction mediated by sensitized T cells, read at 48–72 hours.

BCG (Bacillus Calmette-Guérin) is a live attenuated strain of M. bovis, providing partial protection against severe childhood TB (miliary, meningitis).

Cord factor (trehalose dimycolate) is a virulence factor causing serpentine cord-like growth and inhibiting phagolysosome fusion.

Primary TB Ghon focus typically occurs in mid-lung zones (lower part of upper lobe or upper part of lower lobe) where ventilation is greatest.

Miliary TB results from hematogenous spread causing countless tiny (millet seed-sized) granulomas in multiple organs.

Isoniazid monotherapy for 6–9 months is standard LTBI treatment.

influenzae is a small, pleomorphic gram-negative coccobacillus.

Hib causes life-threatening epiglottitis (“cherry-red epiglottis”) in unvaccinated children, presenting with drooling, stridor, and tripod position.

Langhans giant cells have nuclei arranged peripherally in a horseshoe pattern, characteristic of TB granulomas.

Pontiac fever is a mild, self-limited flu-like illness caused by Legionella (same organism as Legionnaires’ disease but without pneumonia).

Mycoplasma lacks a cell wall, so Gram stain is useless.

Factor X is hemin (for cytochromes in respiration); Factor V is NAD (coenzyme for metabolism).

Hemothorax Hemothorax (blood accumulation in pleural cavity) is the most common fatal complication of blunt chest trauma due to massive blood loss and respiratory compromise.

Two or more adjacent ribs are fractured at two or more points Flail chest requires at least two adjacent ribs fractured at two or more sites, creating a free-floating segment that moves paradoxically during respiration.

Coronary artery disease Coronary artery disease (CAD) accounts for approximately 80% of sudden cardiac deaths due to acute myocardial infarction or fatal arrhythmias from ischemia.

Sudden death Sudden death is defined as unexpected death occurring within 24 hours of symptom onset in an apparently healthy individual.

Left ventricle The left ventricle is most commonly ruptured because it has the highest pressure, thickest wall, and is most frequently affected by coronary artery occlusion (LAD territory).

Digitalis Digitalis (foxglove) contains cardiac glycosides that inhibit Na⁺/K⁺-ATPase pump, causing increased intracellular calcium and cardiac arrhythmias.

Digitalis Xanthopsia (yellow-tinted vision) is a classic sign of digitalis toxicity due to effects on retinal cones.

Blocking sodium channels Aconitine from Aconitum (monkshood) binds to voltage-gated sodium channels, keeping them open, causing persistent depolarization, numbness, and fatal ventricular arrhythmias.

Aconite Aconite is called “Queen of Poisons” due to its rapid action, extreme toxicity, and historical use in homicides.

Cardiotoxicity Oleander contains oleandrin, a cardiac glycoside causing digitalis-like effects including bradycardia, heart block, and ventricular fibrillation.

Without pulse Asphyxia is derived from Greek “a” (without) + “sphyxis” (pulse), though clinically it refers to oxygen deprivation leading to unconsciousness and death. “Without breath” would be “apnea.” “Without oxygen” would be “anoxia.”.

Pallor The classic triad of asphyxia is cyanosis (blue discoloration), congestion (vascular engorgement), and petechiae (Tardieu spots).

Petechial hemorrhages on serous surfaces Tardieu spots are pinpoint (1-2mm) petechial hemorrhages seen on pleura, pericardium, and other visceral surfaces due to increased venous pressure during asphyxia.

3-5 minutes Brain cells begin dying after 3-5 minutes of oxygen deprivation, making this the minimum time for asphyxial death.

Hanging Le Facie Sympathique refers to facial appearance in hanging with unilateral ptosis, miosis, and enophthalmos due to cervical sympathetic chain compression.

Back of neck (occiput) In typical hanging, the knot is at the occiput (back of head), allowing even pressure distribution and efficient airway/vessel obstruction.

Antemortem hanging Saliva dribbling occurs when the person was alive during hanging, as reflexive salivation and gravity cause saliva to escape before death.

Asphyxia Asphyxia from airway obstruction is the most common mechanism of death in hanging.

3-4 kg Only 3-4 kg of pressure is needed to occlude jugular veins, explaining why partial hanging (body partially supported) is often fatal.

Fracture-dislocation of C2-C3 In judicial (long drop) hanging, the calculated drop causes fracture-dislocation of C2-C3 vertebrae with spinal cord transection, causing instant death.

Discontinuous, oblique, above thyroid cartilage In hanging, the ligature mark is oblique (following upward pull), discontinuous (gap at knot position), and above thyroid cartilage (neck compressed superiorly).

Horizontal and below thyroid cartilage In ligature strangulation, force is applied horizontally from behind, creating a mark below thyroid cartilage that is horizontal and continuous (encircles entire neck).

Throttling (manual strangulation) Throttling involves hands gripping the neck, leaving crescent-shaped fingernail abrasions and fingertip contusions.

Manual strangulation (throttling) Hyoid bone fracture is most common in throttling due to direct lateral compression by fingers, especially in elderly (ossified hyoid).

Strangulation using forearm Mugging (arm-lock/choke hold) involves compressing the neck in the crook of the elbow (forearm against throat).

Ligature strangulation using a stick Bansdola (bamboo stick strangulation) is an Indian method where a bamboo stick (bans) is used to twist a ligature around the victim’s neck, tightening it mechanically.

Fine white froth at mouth and nostrils Fine, white, lathery froth (mushroom-shaped) at mouth/nostrils is pathognomonic of drowning, formed by mixing of water, air, and mucus during respiratory efforts.

Drowning Diatoms (microscopic algae) found in bone marrow, organs, or brain confirm antemortem drowning because they can only reach these sites via circulation in living persons.

Both A and B Cutis anserina results from rigor mortis of arrector pili muscles AND cold water exposure causing their contraction.

Wet drowning Wet drowning (water aspiration into lungs) accounts for 85-90% of cases.

1-2 days Bodies initially sink due to higher density than water, then float after 1-2 days (summer) or longer (winter) when putrefactive gases accumulate.

Ventricular fibrillation Freshwater is hypotonic, rapidly absorbed into circulation, causing hemodilution, hyponatremia, and hyperkalemia, leading to ventricular fibrillation.

Pulmonary edema Saltwater is hypertonic, drawing fluid from blood into alveoli, causing massive pulmonary edema and hypoxia.

Obstruction of external air passages or oxygen deficiency Suffocation is a broad term for asphyxia from external airway obstruction (nose/mouth) or environmental oxygen deficiency.

Smothering Smothering (covering nose/mouth with soft material) often leaves minimal or no external injuries, making it difficult to prove.

Closing external airways (mouth and nose) Smothering specifically means closing the mouth and nose, preventing air entry.

Infants and elderly Infants and elderly are vulnerable due to inability to resist; minimal force is needed, and injuries are minimal.

Choking on food mimicking heart attack Café coronary describes sudden death from food bolus obstructing the airway, often mistaken for heart attack (person clutches throat, collapses).

Internal airway obstruction by foreign body Choking specifically means internal (larynx/trachea/bronchi) blockage by a foreign body (food, toys).

Peanuts Peanuts are the most common aspirated foreign bodies in children due to size, shape, and tendency to swell when wet, causing complete obstruction and chemical pneumonitis.

Forcing material into the mouth Gagging involves forcing cloth or material into the mouth to silence and obstruct the airway.

Burking (smothering + chest compression) Burke and Hare (Edinburgh, 1828) killed victims by sitting on chest while covering mouth/nose, leaving minimal marks – called “burking.” They sold bodies to anatomy schools.

Adult lying on infant causing suffocation Overlaying occurs when an adult (often sleeping/intoxicated) rolls onto an infant, compressing chest and covering airways.

Accidental Overlaying is typically accidental, occurring during co-sleeping when intoxicated or exhausted parents roll onto infants.

External compression of chest and abdomen Traumatic asphyxia occurs from crushing of chest/abdomen (stampede, vehicle, machinery), preventing respiratory movements and causing venous congestion above compression.

Traumatic asphyxia Masque ecchymotique refers to intense cyanosis and petechiae confined to face, neck, and upper chest (above compression level) due to impaired venous return in traumatic asphyxia.

Self-induced asphyxia for sexual pleasure Autoerotic asphyxia involves intentional oxygen restriction to enhance sexual pleasure, often through self-ligature.

Accident Deaths from autoerotic asphyxia are accidental – the person intends transient hypoxia for pleasure, not death.

Displacement of oxygen and acidosis High CO₂ displaces oxygen (simple asphyxiant) and causes respiratory acidosis.

Airway burns and pulmonary edema Mustard gas (sulfur mustard) is a vesicant causing severe burns to skin, eyes, and respiratory mucosa, leading to airway damage, pulmonary edema, and secondary infections.

Cardiovascular diseases (CVDs) account for approximately 31% of all global deaths, making them the number one killer worldwide.

Hypertension is the most important modifiable risk factor for CVD and is highly prevalent in Pakistan (affecting ~30% adults).

HEARTS stands for Healthy lifestyle, Evidence-based protocols, Access to medicines, Risk-based management, Team-based care, and Systems for monitoring.

Trans fats increase LDL cholesterol and decrease HDL cholesterol, significantly raising cardiovascular risk.

Primary prevention aims to prevent disease onset in healthy individuals through lifestyle modification, risk factor control, and health education.

The WHO and most international guidelines define hypertension as sustained blood pressure ≥140/90 mmHg.

Hypertension is called the “silent killer” because most patients remain asymptomatic until target organ damage (stroke, heart attack, kidney failure) occurs.

Hypertension primarily damages the brain (stroke), heart (LVH, heart failure), kidneys (nephrosclerosis), eyes (retinopathy), and blood vessels.

DASH (Dietary Approaches to Stop Hypertension) emphasizes fruits, vegetables, whole grains, low-fat dairy, and lean proteins while limiting sodium, saturated fats, and red meat.

WHO recommends <5 grams of salt (approximately 2 grams sodium) daily for adults, with even lower targets for hypertensives.

Mycobacterium tuberculosis (MTB) is an acid-fast bacillus causing TB.

Pakistan ranks 5th globally among high TB burden countries, contributing significantly to the worldwide TB epidemic.

TB spreads through inhalation of droplet nuclei (1-5 microns) expelled when an infected person coughs, sneezes, or speaks.

Lymph node TB (tuberculous lymphadenitis/scrofula) is the most common extrapulmonary TB site, often affecting cervical nodes.

Mantoux test (Tuberculin Skin Test/TST) indicates TB infection (current or past) but cannot distinguish active disease from latent infection.

DOTS (Directly Observed Treatment, Short-course) is the WHO-recommended TB control strategy where healthcare workers observe patients taking medications.

Standard TB treatment has two phases: intensive phase (2 months with 4 drugs: HRZE) and continuation phase (4 months with 2 drugs: HR).

First-line anti-TB drugs are: Isoniazid (H), Rifampicin (R), Pyrazinamide (Z), Ethambutol (E), and Streptomycin (S).

DOTS aims to ensure treatment completion and cure through direct observation of drug intake, preventing default and drug resistance.

A defaulter (now called “lost to follow-up”) is a patient who interrupts treatment for ≥2 consecutive months.

Influenza viruses belong to family Orthomyxoviridae.

COVID-19 (Coronavirus Disease 2019) is caused by SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2).

Vaccination is the most effective prevention for both influenza and COVID-19.

Anosmia (loss of smell) and ageusia (loss of taste) are relatively specific to COVID-19 and less common in influenza.

COVID-19 incubation period ranges from 2-14 days, with average of 5-6 days.

Antigenic drift involves minor, gradual mutations in hemagglutinin (HA) and neuraminidase (NA) surface proteins, causing seasonal flu variations.

R₀ (basic reproduction number) represents the average number of people one infected person will infect in a susceptible population.

Asthma is a chronic non-communicable disease (NCD) characterized by airway inflammation and reversible obstruction.

Respiratory infections (especially viral) are the most common triggers for asthma exacerbations.

Global asthma prevalence is approximately 5-10% of the population, affecting over 300 million people worldwide.

Air pollution (vehicular emissions, industrial smoke, biomass fuel burning) is a major asthma contributor in Pakistani cities like Lahore and Karachi.

Primary prevention involves avoiding triggers and allergens before disease develops (e.g., reducing indoor allergens, avoiding smoking).

The hygiene hypothesis proposes that reduced exposure to infections in early childhood (due to improved hygiene) may increase allergic diseases including asthma.

Pneumoconiosis is occupational lung disease caused by prolonged inhalation of mineral or organic dust particles (coal, silica, asite).

Coal workers’ pneumoconiosis (CWP) is called “black lung disease” due to coal dust accumulation making lungs appear black.

Silicosis results from inhaling crystalline silica (quartz) dust, common in mining, sandblasting, and stone cutting.

Prevention involves engineering controls (ventilation, wet drilling, dust suppression) and personal protective equipment (respirators, masks).

Asbestos exposure specifically increases risk of mesothelioma (pleural cancer) and lung cancer.

Mine workers, stone crushers, sandblasters, and construction workers face highest pneumoconiosis risk due to silica and mineral dust exposure.

Corynebacterium diphtheriae is a gram-positive bacillus that produces diphtheria toxin causing the disease.

Diphtheria classically presents with an adherent grayish-white pseudomembrane in the pharynx that bleeds when removed.

Pertussis is called “whooping cough” due to the characteristic inspiratory “whoop” sound after severe coughing paroxysms.

Bordetella pertussis is a gram-negative coccobacillus causing whooping cough.

DPT (Diphtheria-Pertussis-Tetanus) or DTaP (acellular pertussis) vaccine prevents all three diseases.

Pertussis has three stages: Catarrhal (1-2 weeks of cold-like symptoms, most contagious), Paroxysmal (severe coughing with whoop), and Convalescent (recovery).

Under Pakistan’s Expanded Program on Immunization (EPI), DPT is given as pentavalent vaccine at 6, 10, and 14 weeks of age.

Diphtheria toxin can cause myocarditis (heart inflammation) leading to cardiac failure and death–the most serious complication.

Infants <6 months have highest pertussis morbidity and mortality because they haven’t completed primary vaccination series and have immature airways prone to apnea.

Schick test determines susceptibility or immunity to diphtheria by injecting diphtheria toxin intradermally.

Pertussis requires 92-94% population immunity to achieve herd protection due to its high transmissibility (R₀ = 12-17).

Nitroglycerin is a short-acting nitrate that primarily causes venodilation, reducing preload and myocardial oxygen demand.

Calcium channel blockers (e.g., amlodipine, diltiazem) are first-line for Prinzmetal’s (vasospastic) angina because they directly relax coronary smooth muscle, relieving spasm.

Nitrate tolerance develops primarily due to depletion of sulfhydryl (-SH) groups required for conversion of nitrates to nitric oxide.

Ranolazine inhibits the late sodium current (INa-late) in cardiac myocytes, reducing sodium and calcium overload during ischemia.

Ivabradine selectively inhibits the If (funny current) in the sinoatrial node, slowing the rate of diastolic depolarization and reducing heart rate without affecting contractility or blood pressure.

Trimetazidine is a metabolic modulator that shifts cardiac energy metabolism from fatty acid oxidation to glucose oxidation, which is more oxygen-efficient.

Nitrates increase cGMP by releasing nitric oxide, while sildenafil inhibits PDE-5 (which breaks down cGMP).

Statins inhibit HMG-CoA reductase, the rate-limiting enzyme in hepatic cholesterol synthesis.

Combining statins with fibrates (especially gemfibrozil) significantly increases the risk of myopathy and rhabdomyolysis due to pharmacokinetic interactions and additive muscle toxicity.

Fibrates (fenofibrate, gemfibrozil) activate PPAR-α, increasing lipoprotein lipase activity and reducing triglyceride synthesis.

Ezetimibe inhibits the NPC1L1 protein on intestinal brush border, blocking cholesterol absorption.

PCSK9 normally binds to LDL receptors and promotes their lysosomal degradation.

Niacin (nicotinic acid) is the most effective drug for raising HDL cholesterol (by 25-35%) while also lowering LDL and triglycerides.

Cholestyramine is a bile acid sequestrant that binds bile acids and also many other drugs (digoxin, warfarin, thyroid hormones, thiazides) in the GI tract, reducing their absorption.

Warfarin inhibits vitamin K epoxide reductase, blocking the carboxylation of vitamin K-dependent clotting factors II, VII, IX, and X (plus proteins C and S).

For elevated INR with minor bleeding, oral vitamin K (1-2.5 mg) is appropriate as it reverses warfarin effect within 24-48 hours.

Heparin binds to antithrombin III (AT-III), causing a conformational change that accelerates its inhibition of thrombin (IIa) and factor Xa by 1000-fold.

Heparin-induced thrombocytopenia (HIT) type II typically occurs 5-14 days after heparin initiation, causing thrombocytopenia with paradoxical thrombosis due to antibodies against platelet factor 4-heparin complex.

LMWH has shorter chain length that provides predominantly anti-Xa activity with less anti-IIa activity (anti-Xa:anti-IIa ratio of 3:1 to 4:1), compared to unfractionated heparin (1:1).

Rivaroxaban is a direct factor Xa inhibitor (suffix “-xaban”).

Idarucizumab is a monoclonal antibody fragment that specifically binds dabigatran with high affinity, reversing its anticoagulant effect within minutes.

Aspirin irreversibly acetylates COX-1 in platelets, blocking thromboxane A2 (TXA2) synthesis.

Clopidogrel’s active metabolite irreversibly binds to the P2Y12 ADP receptor on platelets, preventing ADP-mediated platelet activation and aggregation.

Abciximab is a monoclonal antibody that blocks GP IIb/IIIa receptors, the final common pathway for platelet aggregation (binding fibrinogen bridges between platelets).

Dipyridamole inhibits adenosine reuptake (increasing local adenosine levels) and phosphodiesterase (increasing cAMP in platelets).

TPA is a fibrinolytic that preferentially activates plasminogen bound to fibrin in clots, converting it to plasmin which degrades fibrin.

Streptokinase is a bacterial protein from beta-hemolytic streptococci, making it antigenic.

Tranexamic acid (and aminocaproic acid) are antifibrinolytic agents that inhibit plasminogen activation and plasmin activity, helping control bleeding from thrombolytics.

ACE inhibitors also inhibit bradykinin breakdown (ACE = kininase II), leading to accumulation of vasodilatory bradykinin.

Losartan is an angiotensin receptor blocker (ARB) that selectively blocks AT1 receptors, preventing angiotensin II effects.

Prazosin selectively blocks alpha-1 adrenergic receptors, causing vasodilation (lowering BP) and relaxation of prostatic smooth muscle (improving urinary symptoms).

Alpha-1 blockers like prazosin can cause significant first-dose orthostatic hypotension due to sudden vasodilation.

Abrupt clonidine withdrawal causes rebound hypertension due to sudden increase in sympathetic activity (norepinephrine surge).

Dihydropyridines (amlodipine, nifedipine) primarily cause peripheral arterial vasodilation by blocking L-type calcium channels in vascular smooth muscle.

ACE inhibitors and ARBs are contraindicated in pregnancy (especially 2nd/3rd trimester) due to fetal toxicity: oligohydramnios, renal dysgenesis, pulmonary hypoplasia, and death.

Hydralazine causes direct arterial vasodilation, triggering baroreceptor-mediated reflex tachycardia and increased cardiac output.

Nitroprusside releases cyanide during metabolism.

ACE inhibitors (and ARBs) reduce intraglomerular pressure by dilating efferent arterioles, providing renoprotection independent of BP lowering.

In heart failure, chronic sympathetic activation is harmful, causing cardiac remodeling and arrhythmias.

Digoxin inhibits the Na+/K+-ATPase pump, increasing intracellular sodium.

Loop diuretics cause hypokalemia, which increases digoxin binding to Na+/K+-ATPase and predisposes to digoxin toxicity (arrhythmias, nausea, visual disturbances).

Sacubitril inhibits neprilysin, the enzyme that degrades natriuretic peptides (ANP, BNP).

Loop diuretics inhibit the Na+/K+/2Cl- cotransporter (NKCC2) in the thick ascending limb of the loop of Henle, the site responsible for 25% of sodium reabsorption.

Spironolactone blocks aldosterone receptors, preventing aldosterone-mediated cardiac fibrosis, collagen deposition, and adverse remodeling.

Dobutamine is a synthetic catecholamine that primarily stimulates beta-1 receptors, increasing cardiac contractility and output with relatively less effect on heart rate.

In WPW, blocking the AV node allows all atrial impulses to conduct through the faster accessory pathway, potentially causing ventricular fibrillation.

Amiodarone is primarily a Class III antiarrhythmic (blocks potassium channels, prolonging repolarization), but also has Class I (sodium block), Class II (beta-block), and Class IV (calcium block) properties.

Amiodarone contains 37% iodine by weight and releases significant iodine during metabolism.

Class IB drugs (lidocaine, mexiletine) have rapid binding/unbinding kinetics (“fast on-off”) and shorten action potential duration.

Flecainide can slow the atrial flutter rate from 300 to around 200 bpm.

Verapamil blocks L-type calcium channels in the AV node, slowing conduction and increasing refractoriness.

Sotalol (Class III) prolongs QT interval by blocking potassium channels.

Adenosine activates A1 receptors in the AV node, opening potassium channels (IKAdo) and causing hyperpolarization.

Codeine suppresses the cough reflex by acting on opioid receptors in the medullary cough center, raising the threshold for cough initiation.

Dextromethorphan is the D-isomer of levorphanol’s methyl ether and lacks significant opioid effects (no analgesia, respiratory depression, or physical dependence at therapeutic doses).

Dextromethorphan has weak serotonin reuptake inhibition.

Guaifenesin increases the volume and reduces the viscosity of respiratory tract secretions, making cough more productive and mucus easier to clear.

Acetylcysteine (NAC) has a free sulfhydryl group that breaks disulfide bonds (S-S) in the mucin glycoprotein network, reducing mucus viscosity.

Benzonatate is structurally related to tetracaine (local anesthetic).

Diphenhydramine is a first-generation antihistamine with significant CNS penetration (causing sedation) and anticholinergic effects (dry mouth, urinary retention, constipation).

Isoniazid (INH) is a prodrug activated by mycobacterial catalase-peroxidase (KatG).

INH interferes with pyridoxine (B6) metabolism, depleting pyridoxal phosphate and causing peripheral neuropathy (especially in malnourished, diabetic, or slow acetylators).

Rifampicin strongly induces CYP3A4, accelerating metabolism of estrogen and progestins in oral contraceptives, reducing their efficacy.

Rifampicin and its metabolites cause harmless orange-red discoloration of body fluids (urine, tears, sweat, saliva).

Ethambutol causes dose-dependent optic neuritis with red-green color blindness, decreased visual acuity, and central scotomas.

Pyrazinamide (PZA) is a prodrug converted to pyrazinoic acid, which is active only at acidic pH (as found inside macrophages and in inflammatory lesions).

Pyrazinoic acid (PZA metabolite) inhibits renal tubular uric acid secretion, causing hyperuricemia.

Aminoglycosides (streptomycin, amikacin) cause dose-dependent ototoxicity (vestibular > cochlear for streptomycin) and nephrotoxicity (acute tubular necrosis).

Salbutamol (albuterol) is a short-acting beta-2 agonist (SABA) that activates beta-2 receptors on bronchial smooth muscle, increasing cAMP and causing bronchodilation within minutes.

Inhaled corticosteroids (ICS) are the most effective anti-inflammatory agents for asthma.

Oropharyngeal deposition of ICS promotes Candida growth.

Montelukast is a leukotriene receptor antagonist (LTRA) that blocks CysLT1 receptors.

LABAs provide bronchodilation but do not address underlying inflammation.

Ipratropium is a short-acting muscarinic antagonist (SAMA) that blocks M3 receptors on airway smooth muscle, preventing acetylcholine-mediated bronchoconstriction.

Tiotropium has slow dissociation from M1 and M3 muscarinic receptors, providing 24-hour bronchodilation with once-daily dosing.

Theophylline inhibits phosphodiesterases (especially PDE3 and PDE4), increasing cAMP and cGMP in smooth muscle and inflammatory cells.

Erythromycin inhibits CYP1A2 and CYP3A4, reducing theophylline metabolism and causing toxicity.

Omalizumab is an anti-IgE monoclonal antibody that binds free IgE, preventing its attachment to high-affinity IgE receptors (FcεRI) on mast cells and basophils.

Cromolyn sodium stabilizes mast cell membranes, preventing release of histamine, leukotrienes, and other mediators that cause bronchoconstriction and inflammation.

Roflumilast is a selective PDE4 inhibitor.

Stage 1 hypertension is defined as systolic BP 130-139 mmHg OR diastolic BP 80-89 mmHg according to ACC/AHA, while JNC-8 uses 140-159/90-99 mmHg.

Cardiovascular diseases (CVDs) are responsible for approximately 29-35% of all deaths in Pakistan, making them the leading cause of mortality.

Hypertension is the most important modifiable risk factor for CVD and is responsible for the highest attributable mortality globally.

Proper cuff size is critical for accurate BP measurement – the bladder should cover 80% of arm circumference and 40% of arm length.

WHO recommends reducing salt intake to <5 grams/day (approximately 1 teaspoon) to prevent hypertension and CVD.

Primordial prevention aims to prevent risk factors from developing in the first place through population-wide policies.

Epidemiological transition describes the shift from communicable diseases (infections, malnutrition) as leading causes of death to non-communicable diseases (CVD, cancer, diabetes) as countries develop.

The Rule of Halves illustrates gaps in hypertension care: only 50% of hypertensives know their diagnosis, 50% of those are on treatment, and 50% of treated patients achieve control.

Rose’s population strategy states that small reductions in risk factors across the entire population prevent more disease than treating only high-risk individuals.

DALYs combine years of life lost (YLL) due to premature death and years lived with disability (YLD), providing a comprehensive measure of disease burden.

Pakistan’s NTP defines a “presumptive TB case” as anyone with cough lasting ≥2 weeks.

DOTS stands for Directly Observed Treatment, Short-course.

The five elements of DOTS are: (1) Political commitment, (2) Case detection via sputum microscopy, (3) Standardized short-course chemotherapy with DOT, (4) Regular drug supply, and (5) Monitoring through recording and reporting.

Category I regimen (2HRZE/4HR) uses four drugs – Isoniazid (H), Rifampicin (R), Pyrazinamide (Z), and Ethambutol (E) – for the 2-month intensive phase, followed by HR for 4 months continuation.

If sputum remains positive at 2 months, the intensive phase is extended by 1 month (total 3 months) with repeat testing.

“Treatment completed” means the patient finished the full regimen but lacks bacteriological proof of cure (no sputum results in final month). “Cured” (A) requires documented smear/culture negativity at treatment completion. “Treatment success” (C) is the sum of cured plus treatment completed. “Not evaluated” (D) means no outcome assigned due to transfer or missing data.

A “previously treated case” is anyone who received TB treatment for ≥1 month in the past and now has active disease (regardless of previous outcome).

Recording and reporting tracks cohort outcomes (cure rates, failure rates, default rates), enabling program evaluation and identifying weaknesses.

Streptomycin is contraindicated in pregnancy because it crosses the placenta and causes ototoxicity (deafness) in the fetus – 8th cranial nerve damage.

The WHO End TB Strategy (2015-2035) has milestones: by 2035, reduce TB deaths by 95% and TB incidence by 90% compared to 2015.

MDR-TB is defined as resistance to at least Isoniazid AND Rifampicin, the two most powerful first-line drugs.

GeneXpert MTB/RIF is a rapid molecular test (results in 2 hours) that simultaneously detects TB bacteria and rifampicin resistance.

WHO prioritizes healthcare workers (HCWs) for influenza vaccination because they have high exposure risk, can transmit to vulnerable patients, and are essential for health system functioning during outbreaks.

Oseltamivir (Tamiflu) provides maximum benefit when started within 48 hours of symptom onset, reducing illness duration by 1-2 days and preventing complications.

Antigenic drift refers to gradual, minor changes from point mutations in HA and NA genes, causing seasonal variations that require annual vaccine updates.

WHO recommends maintaining at least 1 meter (3 feet) physical distance from others, as most respiratory droplets fall within this range.

N95 respirators filter ≥95% of airborne particles and are essential for aerosol-generating procedures (intubation, bronchoscopy, CPR) where viral aerosols are produced.

Smart lockdowns targeted specific high-transmission areas (hotspots) with restrictions while allowing lower-risk areas to function, balancing disease control with economic survival.

Basic reproduction number (R0) represents average secondary cases from one case in a fully susceptible population.

Close contact is defined as being within 6 feet (approximately 2 meters) of an infected person for ≥15 minutes (cumulative over 24 hours).

AstraZeneca uses a non-replicating chimpanzee adenovirus vector (ChAdOx1) carrying spike protein gene.

The hygiene hypothesis suggests that reduced microbial exposure in early life leads to immune dysregulation and increased allergy/asthma risk.

According to GINA classification: Mild intermittent = <2×/week symptoms; Mild persistent = >2×/week but not daily; Moderate persistent = daily symptoms limiting activity; Severe persistent = continuous symptoms.

House dust mites are the most common indoor allergen triggering asthma worldwide, including Pakistan.

Secondary prevention involves early detection and treatment of disease to prevent progression and complications.

Low-dose ICS is the cornerstone of asthma control, recommended as first-line controller for persistent asthma.

Urban areas have higher asthma prevalence due to air pollution (vehicle emissions, industrial pollution), indoor allergens (better-sealed homes trapping dust mites), and Western lifestyle factors.

Coal worker’s pneumoconiosis (Black Lung Disease) presents in coal miners with dyspnea, productive cough with black sputum (melanoptysis), and nodular opacities on X-ray.

Silicosis occurs from crystalline silica exposure (sandblasting, stone cutting, mining).

Asbestos exposure causes pleural plaques (pathognomonic), pleural effusions, and lower zone pulmonary fibrosis.

The hierarchy of occupational hazard controls prioritizes elimination/substitution first (removing the hazard entirely), followed by engineering controls, administrative controls, and finally PPE (respirators) as last resort.

Byssinosis (Brown Lung Disease) occurs in cotton, flax, and hemp workers.

OSHA’s permissible exposure limit (PEL) for respirable crystalline silica is 0.05 mg/m³ as an 8-hour time-weighted average.

The hallmark of diphtheria is a thick, adherent grayish-white pseudomembrane on the tonsils/pharynx that bleeds when removal is attempted.

Diphtheria toxin inhibits protein synthesis by ADP-ribosylating elongation factor 2 (EF-2), halting ribosomal translation.

Classic pertussis (whooping cough) features: catarrhal phase (1-2 weeks), paroxysmal phase with characteristic “whoop” (inspiratory stridor after coughing spells), post-tussive vomiting, and worse symptoms at night.

Pakistan’s EPI schedule gives DPT (pentavalent vaccine: DPT + Hep B + Hib) at 6, 10, and 14 weeks of age.

All close contacts of diphtheria cases require antibiotic prophylaxis (erythromycin or benzathine penicillin) to eliminate carriage, PLUS booster vaccination if not up-to-date.

Pertussis has high transmissibility (R0 = 12-17), requiring 92-94% vaccination coverage for herd immunity (threshold = 1 – 1/R0).

Acellular pertussis vaccines contain purified pertussis antigens, causing significantly fewer local reactions (pain, swelling) and systemic reactions (fever, irritability, rare neurological events) compared to whole-cell vaccines containing killed whole bacteria.

Acute myocardial infarction results from rupture of a vulnerable plaque (thin fibrous cap, large lipid core, abundant inflammatory cells) with superimposed thrombosis causing acute coronary occlusion.

Renal infarcts due to arterial embolism (from atrial fibrillation) produce coagulative necrosis, where tissue architecture is preserved due to protein denaturation.

Cystic medial degeneration (mucoid degeneration of the tunica media with loss of smooth muscle and elastic fibers) predisposes to aortic dissection.

Libman-Sacks (nonbacterial verrucous) endocarditis occurs in SLE with small, sterile vegetations on BOTH surfaces of valve leaflets.

Takayasu arteritis (“pulseless disease”) is a granulomatous large-vessel vasculitis affecting the aortic arch and branches, primarily in young Asian women.

“Heart failure cells” are hemosiderin-laden alveolar macrophages resulting from phagocytosis of red blood cells that have leaked into alveoli due to pulmonary congestion.

Hypertrophic cardiomyopathy is caused by mutations in sarcomeric proteins, most commonly beta-myosin heavy chain (MYH7) and myosin-binding protein C (MYBPC3).

Patent ductus arteriosus causes left-to-right shunting (aorta to pulmonary artery) due to higher systemic pressure, leading to pulmonary overcirculation and volume overload.

Rheumatic heart disease most commonly affects the mitral valve, causing mitral stenosis with characteristic “fish-mouth” or “buttonhole” deformity due to commissural fusion.

In IV drug users, acute bacterial endocarditis predominantly affects the tricuspid valve (right-sided) due to direct venous inoculation.

Over 95% of pulmonary emboli originate from deep venous thrombosis (DVT) of the lower extremities, especially iliofemoral veins.

Abdominal aortic aneurysms (AAA) are most commonly caused by atherosclerosis, especially in elderly male smokers.

Antiphospholipid syndrome causes paradoxical thrombosis despite prolonged aPTT because lupus anticoagulant antibodies interfere with phospholipid-dependent coagulation assays in vitro but promote thrombosis in vivo by activating endothelial cells and platelets.

Significant blood loss causes hypovolemic shock with reduced preload leading to decreased cardiac output.

Varicose veins develop from incompetent venous valves leading to retrograde blood flow and sustained venous hypertension, causing vessel dilation and tortuosity.

Silicosis characteristically shows upper lobe predominance and “eggshell” calcification of hilar lymph nodes on imaging.

In immunocompromised patients (advanced HIV), reactivation TB often presents atypically with lower/middle lobe involvement, lymphadenopathy, and less cavitation due to impaired granuloma formation.

Bronchial asthma shows eosinophilic inflammation, basement membrane thickening, goblet cell hyperplasia, smooth muscle hypertrophy, and Charcot-Leyden crystals.

Chronic bronchitis is defined by chronic productive cough and shows mucus gland hypertrophy (Reid index >0.5 = ratio of gland thickness to bronchial wall thickness).