Pharmacology
MBBS Pharmacology — high-yield long questions and short notes from K.D. Tripathi, covering general pharmacology, autonomic and cardiovascular drugs, CNS, autacoids, chemotherapy, endocrine and more, written to the marks with mechanisms, classification, clinical uses, adverse effects and pearls.
12chapters144questions99High-Yield
Definition
Vitamins are organic micronutrients required in small amounts for normal metabolism; they must largely be supplied in the diet.
Fat-Soluble (A, D, E, K)
- Stored in the body; toxicity possible
- A — vision, epithelium; D — calcium homeostasis
- E — antioxidant; K — clotting factors
Water-Soluble (B complex, C)
- Not stored (except B12); daily intake needed
- B1 (beriberi), B2, B3 (pellagra), B6, B12, folate
- Vitamin C — collagen synthesis (scurvy)
Therapeutic Uses
- Deficiency states, pregnancy, malabsorption
- Vitamin A prophylaxis in children
- Vitamin K in newborns
Solubility determines storage, dosing frequency and toxicity risk. Vitamin Deficiency A Night blindness D Rickets B1 Beriberi C Scurvy Applied
- Hypervitaminosis A and D are real risks
- Avoid indiscriminate multivitamin use
🔑KEY POINTS TO REMEMBER- Fat-soluble (A, D, E, K) are stored — toxicity possible.
- Water-soluble (B complex, C) need regular intake.
- Deficiencies: night blindness, rickets, beriberi, pellagra, scurvy.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Management of poisoning combines supportive care, decontamination, elimination enhancement and specific antidotes.
General Principles
- Supportive care first — airway, breathing, circulation
- Decontamination — gastric lavage, activated charcoal, skin wash
- Enhanced elimination — urine alkalinisation, dialysis
- Specific antidote where available
Important Antidotes
- Organophosphates — atropine + pralidoxime
- Paracetamol — N-acetylcysteine
- Opioids — naloxone; benzodiazepines — flumazenil
- Methanol — ethanol/fomepizole; heavy metals — chelators
Stabilisation always precedes decontamination and antidote therapy. Poison Antidote Paracetamol N-acetylcysteine Opioid Naloxone Organophosphate Atropine + pralidoxime Iron Desferrioxamine Applied
- Activated charcoal most useful within 1 hour
- Never induce vomiting with corrosives or kerosene
🔑KEY POINTS TO REMEMBER- Priority: supportive care, then decontamination, elimination, antidote.
- Key antidotes: NAC (paracetamol), naloxone (opioid), atropine+PAM (OP).
- Charcoal works best within the first hour.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
A drug interaction occurs when one drug alters the effect of another, resulting in reduced efficacy or increased toxicity.
Pharmacokinetic Interactions
- Absorption — antacids ↓ tetracycline absorption
- Distribution — displacement from protein binding (aspirin + warfarin)
- Metabolism — enzyme induction (rifampicin) or inhibition (erythromycin)
- Excretion — probenecid ↓ penicillin excretion
Pharmacodynamic Interactions
- Synergism — co-trimoxazole components
- Antagonism — naloxone and morphine
- Additive toxicity — aminoglycoside + furosemide (ototoxicity)
One drug changes another’s handling by the body, or its action. Type Example Result Induction Rifampicin + OCP Contraceptive failure Inhibition Erythromycin + theophylline Toxicity Displacement Aspirin + warfarin Bleeding Applied
- Narrow-TI drugs (warfarin, digoxin, phenytoin) are most affected
- Always review the full drug list before prescribing
🔑KEY POINTS TO REMEMBER- Interactions are pharmacokinetic (ADME) or pharmacodynamic (effect).
- Enzyme inducers ↓ levels; inhibitors ↑ levels.
- Narrow therapeutic index drugs are most at risk.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Immunomodulators alter immune function; vaccines give active immunity and sera provide passive immunity.
Vaccines (active immunity)
- Live attenuated — BCG, measles, oral polio, MMR
- Killed / inactivated — rabies, injectable polio, hepatitis A
- Subunit / toxoid — tetanus toxoid, hepatitis B
- Slow onset, long-lasting protection
Sera & Immunoglobulins (passive)
- Antitetanus serum, antirabies immunoglobulin, antivenom
- Immediate but short-lived protection
- Risk of hypersensitivity / serum sickness
Immunomodulators
- Stimulants — interferons, levamisole, BCG
- Suppressants — ciclosporin, corticosteroids
Vaccines teach the immune system; sera lend ready-made antibodies. Type Onset Duration Vaccine Slow Years Serum Immediate Weeks Applied
- Live vaccines avoided in pregnancy and immunodeficiency
- Post-exposure prophylaxis often uses both together
🔑KEY POINTS TO REMEMBER- Vaccines: live, killed, subunit/toxoid — active immunity.
- Sera give immediate, short-lived passive immunity.
- Live vaccines contraindicated in pregnancy and immunosuppression.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Prescribing in special situations requires dose and drug adjustment in pregnancy, lactation, children, the elderly and organ failure.
Pregnancy & Lactation
- Avoid teratogens (warfarin, ACE inhibitors, valproate, retinoids, tetracyclines)
- Safe: paracetamol, penicillins, methyldopa, heparin
- Consider drug excretion in breast milk
Extremes of Age
- Children — dose by body weight or surface area; avoid tetracyclines, quinolones, aspirin
- Elderly — ↓ renal/hepatic function, polypharmacy; ‘start low, go slow’
Organ Failure
- Renal failure — ↓ dose of renally excreted drugs (aminoglycosides, digoxin)
- Hepatic failure — avoid hepatotoxic and highly metabolised drugs
Patient factors dictate both the choice of drug and its dose. Situation Principle Pregnancy Avoid teratogens Elderly Start low, go slow Renal failure ↓ Dose Applied
- Check pregnancy category before prescribing
- Review polypharmacy at every visit in elderly patients
🔑KEY POINTS TO REMEMBER- Avoid teratogens in pregnancy; dose children by weight.
- Elderly: start low, go slow; beware polypharmacy.
- Reduce doses of renally excreted drugs in kidney failure.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Chelating agents bind heavy metals to form stable, non-toxic complexes that are excreted in the urine.
Agents & Their Metals
- Desferrioxamine — iron
- Penicillamine — copper (Wilson’s disease), lead
- Dimercaprol (BAL) — arsenic, mercury, gold
- Calcium disodium EDTA — lead
- DMSA (succimer) — lead in children
The chelator locks up the metal so the kidney can excrete it safely. Metal Chelator Iron Desferrioxamine Copper Penicillamine Lead EDTA, DMSA Arsenic Dimercaprol Applied
- Desferrioxamine also used in transfusional iron overload (thalassaemia)
- Chelators may also remove essential metals (zinc)
🔑KEY POINTS TO REMEMBER- Chelators bind heavy metals into excretable complexes.
- Iron → desferrioxamine; copper → penicillamine; lead → EDTA/DMSA.
- Also used in thalassaemia iron overload.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Vitamin D is a fat-soluble prohormone essential for calcium absorption and bone mineralisation.
Sources & Activation
- Skin synthesis from 7-dehydrocholesterol (sunlight)
- Diet — fish oil, fortified milk, egg yolk
- Liver → 25-hydroxylation; kidney → 1-hydroxylation → calcitriol
Actions & Preparations
- ↑ Intestinal calcium and phosphate absorption
- Bone mineralisation; works with parathyroid hormone
- Preparations: cholecalciferol (D3), calcitriol, alfacalcidol
- Deficiency → rickets (children), osteomalacia (adults)
Two hydroxylation steps produce active calcitriol. Preparation Use Cholecalciferol Deficiency Calcitriol Renal failure Applied
- Calcitriol needed in chronic kidney disease (1-hydroxylation fails)
- Excess → hypercalcaemia, nephrocalcinosis
🔑KEY POINTS TO REMEMBER- Vitamin D is activated in liver then kidney to calcitriol.
- ↑ Calcium absorption and bone mineralisation.
- Deficiency → rickets/osteomalacia; excess → hypercalcaemia.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Vitamin K is a fat-soluble vitamin essential for the synthesis of functional clotting factors.
Function & Forms
- Cofactor for γ-carboxylation of factors II, VII, IX, X (and proteins C, S)
- K1 (phytonadione) — green vegetables; K2 — gut bacteria
- Requires bile for absorption
Uses & Deficiency
- Newborn prophylaxis — haemorrhagic disease of the newborn
- Reversal of warfarin over-anticoagulation
- Obstructive jaundice, malabsorption, prolonged antibiotics
- Deficiency → bleeding, prolonged prothrombin time
Carboxylation makes clotting factors able to bind calcium and work. Use Detail Newborn IM at birth Warfarin reversal Oral/IV Applied
- All newborns receive vitamin K at birth
- Deficiency likely in fat malabsorption
🔑KEY POINTS TO REMEMBER- Vitamin K enables γ-carboxylation of factors II, VII, IX, X.
- Given to all newborns to prevent haemorrhagic disease.
- Used to reverse warfarin; deficiency prolongs prothrombin time.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Activated charcoal is an adsorbent used in poisoning to bind ingested toxins in the gut and prevent their absorption.
Mechanism & Use
- Large surface area adsorbs the poison
- Prevents systemic absorption
- Most effective within 1 hour of ingestion
- Repeated doses enhance elimination of some drugs (theophylline, carbamazepine, phenobarbitone)
Limitations
- Not effective for: iron, lithium, alcohols, corrosives, hydrocarbons, cyanide
- Contraindicated with unprotected airway (aspiration risk)
- Adverse: vomiting, constipation, black stools
Charcoal traps the poison in the gut so it is never absorbed. Feature Detail Best timing Within 1 hour Ineffective for Iron, lithium, alcohol Applied
- Protect the airway first in a drowsy patient
- Multiple-dose regimen for selected drugs
🔑KEY POINTS TO REMEMBER- Activated charcoal adsorbs ingested poisons in the gut.
- Most effective within 1 hour; repeat doses for some drugs.
- Useless for iron, lithium, alcohols and corrosives.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Active immunisation stimulates the body to produce its own antibodies; passive immunisation supplies ready-made antibodies.
Active Immunisation
- Vaccines (live, killed, toxoid, subunit)
- Slow onset (weeks) but long-lasting
- Produces immunological memory (booster response)
- Used for prevention
Passive Immunisation
- Immunoglobulins, antisera, antivenom, maternal antibodies
- Immediate protection but short-lived (weeks)
- No immunological memory
- Used post-exposure or in immunodeficiency
Active builds lasting defence; passive lends immediate protection. Feature Active Passive Onset Slow Immediate Duration Years Weeks Memory Yes No Applied
- Both given together after dog bite (rabies vaccine + immunoglobulin)
- Tetanus: toxoid (active) + antitetanus serum (passive)
🔑KEY POINTS TO REMEMBER- Active = vaccine, slow onset, long-lasting, produces memory.
- Passive = ready antibodies, immediate but short-lived.
- Combined in post-exposure prophylaxis (rabies, tetanus).
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Teratogenic drugs cause structural or functional fetal abnormalities when taken during pregnancy, especially in the first trimester.
Important Teratogens
- Thalidomide — phocomelia
- Warfarin — fetal warfarin syndrome
- Valproate, phenytoin — neural tube defects, hydantoin syndrome
- ACE inhibitors — renal dysgenesis, oligohydramnios
- Retinoids — craniofacial and CNS defects
- Tetracyclines (teeth), aminoglycosides (deafness), methotrexate
Principles
- Organogenesis (weeks 3–8) is the most vulnerable period
- Avoid all non-essential drugs in pregnancy
- Use the safest alternative and lowest effective dose
Drugs crossing the placenta during organogenesis can deform developing organs. Drug Defect Warfarin Fetal warfarin syndrome Valproate Neural tube defect ACE inhibitor Renal dysgenesis Applied
- Heparin replaces warfarin in pregnancy
- Folic acid supplementation reduces neural tube defects
🔑KEY POINTS TO REMEMBER- Teratogens act mainly during organogenesis (weeks 3–8).
- Key examples: thalidomide, warfarin, valproate, ACE inhibitors, retinoids.
- Use heparin instead of warfarin; give folic acid.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Antiseptics are applied to living tissue to inhibit microbes, while disinfectants are used on inanimate objects.
Common Agents
- Alcohols — ethanol, isopropanol (hand rub)
- Iodine compounds — povidone-iodine (skin preparation)
- Chlorhexidine — skin and hand antisepsis
- Hydrogen peroxide — wound cleansing
- Formaldehyde, glutaraldehyde — instrument disinfection
Mechanisms
- Protein denaturation (alcohols, phenols)
- Oxidation (hydrogen peroxide, iodine)
- Membrane disruption (chlorhexidine, detergents)
The same chemistry is applied either to skin or to surfaces. Agent Main use Povidone-iodine Surgical skin prep Chlorhexidine Hand antisepsis Glutaraldehyde Endoscopes Applied
- Alcohol hand rub is the most effective routine hand hygiene
- Hydrogen peroxide can delay wound healing with prolonged use
🔑KEY POINTS TO REMEMBER- Antiseptics for living tissue; disinfectants for objects.
- Act by protein denaturation, oxidation or membrane disruption.
- Povidone-iodine and chlorhexidine are the main skin antiseptics.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.