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
Antiulcer drugs heal peptic ulcers by reducing gastric acid, neutralising it, or strengthening mucosal defence.
Classification
- Proton-pump inhibitors — omeprazole, pantoprazole (most effective)
- H2 blockers — ranitidine, famotidine
- Antacids — aluminium/magnesium hydroxide (symptomatic)
- Mucosal protectives — sucralfate, misoprostol
- Anti-H. pylori — amoxicillin, clarithromycin, metronidazole
Principles
- Eradicate H. pylori if present
- Stop NSAIDs where possible
- Continue PPI for 4–8 weeks
Acid suppression plus eradication of H. pylori heals most ulcers. Drug Action Omeprazole Blocks H⁺/K⁺ ATPase Ranitidine Blocks H2 receptor Sucralfate Coats ulcer base Applied
- Misoprostol prevents NSAID-induced ulcers
- PPIs are the drugs of choice for healing
🔑KEY POINTS TO REMEMBER- PPIs are the most effective antiulcer drugs (block H⁺/K⁺ ATPase).
- H2 blockers, antacids and mucosal protectives are alternatives.
- Eradicate H. pylori and stop NSAIDs.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Antiemetic drugs prevent or relieve nausea and vomiting by blocking receptors in the vomiting centre and chemoreceptor trigger zone.
Classes
- 5-HT3 antagonists — ondansetron (chemotherapy, post-operative)
- D2 antagonists — metoclopramide, domperidone, prochlorperazine
- Antihistaminics — promethazine, cyclizine (motion sickness)
- Anticholinergic — hyoscine (motion sickness)
- NK1 antagonists — aprepitant; corticosteroids (dexamethasone)
Choice by Cause
- Chemotherapy — ondansetron + dexamethasone ± aprepitant
- Motion sickness — hyoscine, promethazine
- Pregnancy — doxylamine + pyridoxine
- Gastric stasis — metoclopramide
Antiemetics interrupt signals reaching the vomiting centre. Cause Drug of choice Chemotherapy Ondansetron Motion sickness Hyoscine Gastric stasis Metoclopramide Applied
- Metoclopramide → extrapyramidal effects in young patients
- Domperidone does not cross the blood-brain barrier
🔑KEY POINTS TO REMEMBER- Antiemetics act on the CTZ and vomiting centre.
- Ondansetron (5-HT3) for chemotherapy; hyoscine for motion sickness.
- Metoclopramide causes extrapyramidal effects.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Laxatives promote defaecation in constipation, while antidiarrhoeals reduce stool frequency and fluid loss in diarrhoea.
Laxatives
- Bulk-forming — ispaghula, bran (safest, long-term)
- Osmotic — lactulose, magnesium salts, polyethylene glycol
- Stimulant — bisacodyl, senna
- Stool softeners — docusate, liquid paraffin
Antidiarrhoeals
- ORS — first and most important (prevents dehydration)
- Zinc — in childhood diarrhoea
- Opioids — loperamide (↓ motility)
- Adsorbents — kaolin, pectin; antimicrobials if indicated
One group speeds transit; the other slows it and restores fluid. Condition First choice Constipation Bulk-forming Hepatic encephalopathy Lactulose Acute diarrhoea ORS + zinc Applied
- Avoid loperamide in dysentery and in children
- Lactulose lowers ammonia in hepatic encephalopathy
🔑KEY POINTS TO REMEMBER- Laxatives: bulk-forming, osmotic, stimulant, softeners.
- ORS and zinc are the mainstay in acute diarrhoea.
- Avoid loperamide in bloody diarrhoea and young children.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Antiasthmatic drugs relieve bronchospasm (relievers) and suppress airway inflammation (controllers).
Relievers (bronchodilators)
- Short-acting β₂ agonists — salbutamol (first-line reliever)
- Anticholinergics — ipratropium, tiotropium (important in COPD)
- Methylxanthines — theophylline
Controllers (anti-inflammatory)
- Inhaled corticosteroids — budesonide, fluticasone (mainstay)
- Long-acting β₂ agonists — salmeterol, formoterol (with ICS)
- Leukotriene antagonists — montelukast
- Anti-IgE — omalizumab (severe asthma)
Bronchodilators give quick relief; inhaled steroids control the disease. Drug Role Salbutamol Reliever Budesonide Controller Ipratropium COPD bronchodilator Applied
- Acute severe asthma — oxygen, nebulised salbutamol, systemic steroids
- Never use LABA alone in asthma
🔑KEY POINTS TO REMEMBER- Relievers = short-acting β₂ agonists; controllers = inhaled corticosteroids.
- Anticholinergics are especially useful in COPD.
- LABA must always be combined with an inhaled steroid in asthma.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Cough remedies either suppress the cough reflex (antitussives) or help clear secretions (expectorants and mucolytics).
Antitussives (dry cough)
- Opioid — codeine, dextromethorphan (central action)
- Peripheral — demulcents, lozenges
- Antihistamines — chlorpheniramine (with sedative effect)
Expectorants & Mucolytics (productive cough)
- Expectorants — guaifenesin, potassium iodide (↑ secretion volume)
- Mucolytics — bromhexine, ambroxol, N-acetylcysteine (↓ viscosity)
Other Respiratory Uses
- Nasal decongestants — xylometazoline, pseudoephedrine
- Surfactant — neonatal respiratory distress syndrome
- Oxygen therapy
Suppress a dry cough; help clearance when it is productive. Type Drug Antitussive Codeine Mucolytic Bromhexine Decongestant Xylometazoline Applied
- Never suppress a productive cough
- Rebound congestion with prolonged nasal decongestant use
🔑KEY POINTS TO REMEMBER- Antitussives (codeine, dextromethorphan) for dry cough only.
- Expectorants and mucolytics help productive cough.
- Prolonged nasal decongestants → rebound congestion.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Proton-pump inhibitors (PPIs) are the most effective acid-suppressing drugs, irreversibly inhibiting the gastric H⁺/K⁺ ATPase.
Mechanism
- Prodrugs activated in acidic parietal-cell canaliculi
- Irreversibly inhibit H⁺/K⁺ ATPase (proton pump)
- Block the final common step of acid secretion
- Long duration despite short half-life
Uses & Adverse Effects
- Peptic ulcer, GERD, H. pylori regimens
- Zollinger-Ellison syndrome, stress-ulcer prophylaxis
- Adverse: headache, diarrhoea, ↓ vitamin B12 and magnesium
- Long term: ↑ fracture and enteric infection risk
The pump is permanently disabled, so acid output stays low for days. Feature Detail Target H⁺/K⁺ ATPase Binding Irreversible Timing Before meals Applied
- Take 30–60 minutes before breakfast
- Omeprazole inhibits clopidogrel activation
🔑KEY POINTS TO REMEMBER- PPIs irreversibly inhibit gastric H⁺/K⁺ ATPase.
- Most effective for peptic ulcer and GERD.
- Long-term use → ↓ B12/magnesium, ↑ fracture risk.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Ondansetron is a selective 5-HT3 receptor antagonist and a potent antiemetic.
Mechanism
- Blocks 5-HT3 receptors in the chemoreceptor trigger zone
- Also blocks peripheral 5-HT3 on vagal afferents in the gut
- Prevents serotonin-mediated emetic signals
Uses & Adverse Effects
- Chemotherapy-induced vomiting (drug of choice)
- Post-operative and radiation-induced vomiting
- Hyperemesis gravidarum (when others fail)
- Adverse: headache, constipation, QT prolongation
Blocking 5-HT3 receptors intercepts the emetic signal at its source. Feature Detail Target 5-HT3 receptor Best use Chemotherapy vomiting Caution QT prolongation Applied
- Combined with dexamethasone for better effect
- No extrapyramidal effects (unlike metoclopramide)
🔑KEY POINTS TO REMEMBER- Ondansetron blocks 5-HT3 receptors centrally and peripherally.
- Drug of choice for chemotherapy-induced vomiting.
- No extrapyramidal effects; watch for QT prolongation.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
H. pylori eradication uses combination therapy to cure the infection responsible for most peptic ulcers.
Standard Triple Therapy (14 days)
- PPI — omeprazole twice daily
- Amoxicillin 1 g twice daily
- Clarithromycin 500 mg twice daily
- Metronidazole substituted if penicillin-allergic
Other Regimens & Follow-up
- Quadruple therapy — PPI + bismuth + tetracycline + metronidazole
- Used where clarithromycin resistance is high
- Confirm eradication (urea breath test) after 4 weeks
Combining acid suppression with two antibiotics clears the organism. Component Purpose PPI ↑ Antibiotic efficacy Amoxicillin Bactericidal Clarithromycin Bactericidal Applied
- Eradication markedly reduces ulcer relapse
- Compliance is essential to prevent resistance
🔑KEY POINTS TO REMEMBER- Triple therapy: PPI + amoxicillin + clarithromycin for 14 days.
- Quadruple therapy (with bismuth) where resistance is high.
- Eradication prevents ulcer relapse; confirm by urea breath test.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Metoclopramide is a dopamine D2 antagonist with both antiemetic and prokinetic actions.
Mechanism
- Blocks D2 receptors in the chemoreceptor trigger zone (antiemetic)
- Blocks peripheral D2 in the gut → prokinetic
- ↑ Gastric emptying, ↑ lower oesophageal sphincter tone
- Weak 5-HT3 antagonism at high dose
Uses & Adverse Effects
- Vomiting (drug-induced, gastric stasis, migraine)
- GERD, diabetic gastroparesis
- Adverse: extrapyramidal reactions (dystonia, especially in young)
- Hyperprolactinaemia, galactorrhoea, sedation
Central blockade stops vomiting; peripheral blockade speeds gastric emptying. Action Site Antiemetic CTZ (central) Prokinetic Gut (peripheral) Applied
- Dystonia treated with promethazine or anticholinergics
- Domperidone is a safer alternative (no CNS entry)
🔑KEY POINTS TO REMEMBER- Metoclopramide = D2 antagonist: antiemetic + prokinetic.
- Used in gastric stasis, GERD, drug-induced vomiting.
- Causes extrapyramidal reactions, especially in young patients.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Loperamide is a peripherally acting opioid used as an antidiarrhoeal, which does not enter the central nervous system.
Mechanism
- μ opioid agonist on gut receptors only
- ↓ Intestinal motility → ↑ transit time
- ↑ Water and electrolyte absorption
- ↑ Anal sphincter tone
- Poor CNS penetration → no analgesia or dependence
Uses & Contraindications
- Non-infective and travellers’ diarrhoea
- Chronic diarrhoea (ileostomy, irritable bowel)
- Contraindicated: dysentery, bloody diarrhoea, ulcerative colitis, children under 2
- Risk of toxic megacolon and paralytic ileus
Slowing the gut allows more water to be reabsorbed from the stool. Feature Detail Action Peripheral only Avoid in Bloody diarrhoea Risk Toxic megacolon Applied
- ORS remains the mainstay in acute diarrhoea
- Never use in children with acute gastroenteritis
🔑KEY POINTS TO REMEMBER- Loperamide is a peripherally acting μ agonist → ↓ gut motility.
- No CNS effects (no dependence).
- Contraindicated in dysentery, colitis and young children.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Inhaled corticosteroids (ICS) are the mainstay controller therapy for persistent asthma, suppressing airway inflammation.
Mechanism & Drugs
- ↓ Cytokine and mediator production
- ↓ Eosinophil and mast-cell infiltration
- ↓ Airway hyper-responsiveness and mucus
- Drugs: budesonide, fluticasone, beclometasone
Uses & Adverse Effects
- Persistent asthma (regular, preventive use)
- COPD with frequent exacerbations (with LABA)
- Adverse: oral candidiasis, hoarseness, sore throat
- Systemic effects rare at usual doses
Delivered straight to the airway, steroids suppress inflammation locally. Feature Detail Role Controller (preventer) Adverse Oral candidiasis Prevention Rinse mouth Applied
- Rinse mouth after use and use a spacer
- Not for relief of an acute attack
🔑KEY POINTS TO REMEMBER- Inhaled corticosteroids are the mainstay controllers in persistent asthma.
- Suppress airway inflammation and hyper-responsiveness.
- Oral candidiasis prevented by rinsing the mouth and using a spacer.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Theophylline is a methylxanthine bronchodilator with a narrow therapeutic index, used as an adjunct in asthma and COPD.
Mechanism
- Inhibits phosphodiesterase → ↑ cAMP → bronchodilation
- Adenosine receptor antagonism
- Also ↑ diaphragmatic contractility, mild anti-inflammatory
- CNS and respiratory stimulation
Uses & Toxicity
- Chronic asthma and COPD (adjunct)
- Neonatal apnoea (caffeine preferred)
- Narrow therapeutic range (10–20 mg/L)
- Toxicity: nausea, tremor, insomnia, tachycardia, arrhythmia, seizures
Raising cAMP relaxes bronchial smooth muscle. Feature Detail Range 10–20 mg/L Metabolism Hepatic (CYP450) Toxicity Seizures, arrhythmia Applied
- Levels ↑ by erythromycin, ciprofloxacin, cimetidine
- Levels ↓ by smoking, rifampicin, phenytoin
🔑KEY POINTS TO REMEMBER- Theophylline inhibits phosphodiesterase → ↑ cAMP → bronchodilation.
- Narrow therapeutic index (10–20 mg/L) — monitor levels.
- Many interactions; toxicity causes arrhythmias and seizures.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.