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.
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Definition
Insulin is the anabolic hormone from pancreatic β-cells, used therapeutically to lower blood glucose in diabetes mellitus.
Types (by duration)
- Rapid-acting — lispro, aspart (onset 15 min)
- Short-acting — regular insulin
- Intermediate — NPH (isophane)
- Long-acting — glargine, detemir (peakless, 24 h)
Actions
- ↑ Glucose uptake (GLUT4 in muscle, fat)
- ↑ Glycogenesis, ↓ gluconeogenesis
- ↑ Lipogenesis, ↑ protein synthesis
- Drives potassium into cells
Indications
- Type 1 diabetes (essential)
- Type 2 when oral drugs fail
- Diabetic ketoacidosis, pregnancy, surgery, infection
Insulin drives glucose into cells, lowering blood levels. Type Onset Example Rapid 15 min Lispro Short 30 min Regular Long 1–2 h, flat Glargine Applied
- Hypoglycaemia is the main adverse effect
- Also lipodystrophy at injection sites — rotate sites
🔑KEY POINTS TO REMEMBER- Insulin types: rapid, short, intermediate, long-acting.
- ↑ Glucose uptake via GLUT4; also drives K⁺ into cells.
- Essential in type 1 diabetes and DKA; hypoglycaemia is the main risk.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Oral antidiabetic drugs lower blood glucose in type 2 diabetes by increasing insulin secretion, improving sensitivity or reducing glucose absorption.
Classes
- Biguanides — metformin (first-line; ↓ hepatic glucose output)
- Sulfonylureas — glibenclamide, glimepiride (↑ insulin release)
- Thiazolidinediones — pioglitazone (↑ insulin sensitivity)
- DPP-4 inhibitors — sitagliptin; GLP-1 agonists — liraglutide
- SGLT2 inhibitors — empagliflozin (↑ urinary glucose loss)
- α-glucosidase inhibitors — acarbose
Choice
- Metformin first-line (unless contraindicated)
- Add second drug if HbA1c remains high
- SGLT2 inhibitors preferred with heart failure / kidney disease
Therapy is stepped up from metformin as control demands. Class Action Risk Metformin ↓ Hepatic glucose Lactic acidosis Sulfonylurea ↑ Insulin release Hypoglycaemia SGLT2 ↑ Urinary glucose Genital infection Applied
- Sulfonylureas cause weight gain and hypoglycaemia
- Stop metformin before contrast studies
🔑KEY POINTS TO REMEMBER- Metformin is first-line in type 2 diabetes.
- Sulfonylureas ↑ insulin release (hypoglycaemia, weight gain).
- SGLT2 inhibitors benefit heart failure and kidney disease.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Thyroid drugs replace deficient hormone in hypothyroidism, while antithyroid drugs reduce hormone synthesis in hyperthyroidism.
Thyroid Hormone (replacement)
- Levothyroxine (T4) — drug of choice
- Once daily, empty stomach
- Monitor by TSH
Antithyroid Drugs
- Thioamides — carbimazole, methimazole, propylthiouracil (inhibit thyroid peroxidase)
- Iodides — Lugol’s iodine (before surgery)
- Radioactive iodine (I-131) — destroys thyroid tissue
- β blockers — symptomatic relief (propranolol)
Blocking peroxidase halts hormone synthesis and restores balance. Condition Drug Hypothyroidism Levothyroxine Hyperthyroidism Carbimazole Thyroid storm PTU + β blocker Applied
- Propylthiouracil preferred in first trimester of pregnancy
- Carbimazole → agranulocytosis (warn about sore throat)
🔑KEY POINTS TO REMEMBER- Levothyroxine is the drug of choice for hypothyroidism (monitor TSH).
- Thioamides inhibit thyroid peroxidase.
- Carbimazole → agranulocytosis; PTU preferred in early pregnancy.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Corticosteroids are adrenal hormones (and synthetic analogues) with potent anti-inflammatory and immunosuppressive actions.
Classification
- Glucocorticoids — hydrocortisone, prednisolone, dexamethasone
- Mineralocorticoid — fludrocortisone
- Vary in potency and duration
Actions
- Anti-inflammatory (↓ phospholipase A2, ↓ cytokines)
- Immunosuppressive
- Metabolic — ↑ glucose, protein breakdown, fat redistribution
- Mineralocorticoid — sodium and water retention
Uses
- Asthma, allergy, anaphylaxis (adjunct)
- Autoimmune disease, rheumatoid arthritis
- Adrenal insufficiency (replacement)
- Nephrotic syndrome, transplant rejection
Steroids act on gene transcription to suppress inflammatory mediators. Drug Potency Duration Hydrocortisone 1 Short Prednisolone 4 Intermediate Dexamethasone 25 Long Applied
- Never stop long-term steroids abruptly (adrenal crisis)
- Taper the dose gradually
🔑KEY POINTS TO REMEMBER- Glucocorticoids are anti-inflammatory and immunosuppressive.
- Potency: dexamethasone > prednisolone > hydrocortisone.
- Taper long-term therapy to avoid adrenal crisis.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Sex hormones (oestrogens, progestins, androgens) regulate reproduction; oral contraceptives use them to prevent pregnancy.
Types of Oral Contraceptive
- Combined pill — oestrogen + progestin (most effective)
- Progestin-only pill — safe in lactation
- Emergency contraception — levonorgestrel within 72 hours
Mechanism
- Suppress FSH/LH → inhibit ovulation
- Thicken cervical mucus
- Make endometrium unreceptive
Non-Contraceptive Benefits
- Regular cycles, ↓ dysmenorrhoea
- ↓ Risk of ovarian and endometrial cancer
- Treatment of acne, endometriosis
Suppressing gonadotrophins stops ovulation, the main contraceptive action. Type Contains Note Combined Oestrogen + progestin Most effective Progestin-only Progestin Safe in lactation Applied
- Adverse: venous thromboembolism, hypertension, nausea
- Avoid combined pill in smokers over 35, migraine with aura
🔑KEY POINTS TO REMEMBER- Combined pill suppresses FSH/LH → inhibits ovulation.
- Progestin-only pill is safe during lactation.
- Main risk is venous thromboembolism (avoid in smokers over 35).
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Metformin is a biguanide and the first-line drug for type 2 diabetes mellitus.
Mechanism
- Activates AMP-kinase
- ↓ Hepatic gluconeogenesis (main action)
- ↑ Peripheral insulin sensitivity, ↑ glucose uptake
- ↓ Intestinal glucose absorption
- Does not stimulate insulin release → no hypoglycaemia alone
Uses & Adverse Effects
- Type 2 diabetes (especially with obesity)
- Polycystic ovary syndrome
- Adverse: nausea, diarrhoea, metallic taste, vitamin B12 deficiency
- Rare but serious: lactic acidosis
Metformin mainly stops the liver from over-producing glucose. Feature Detail Main action ↓ Gluconeogenesis Weight Neutral / loss Danger Lactic acidosis Applied
- Contraindicated in renal failure, hypoxia, severe liver disease
- Withhold before contrast radiography and surgery
🔑KEY POINTS TO REMEMBER- Metformin ↓ hepatic gluconeogenesis and ↑ insulin sensitivity.
- First-line in type 2 diabetes; no hypoglycaemia when used alone.
- Contraindicated in renal failure (lactic acidosis risk).
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Oxytocin is a posterior pituitary hormone that stimulates uterine contraction and milk ejection.
Actions
- Contracts uterine smooth muscle (rhythmic)
- Sensitivity ↑ markedly at term
- Milk ejection (contracts myoepithelial cells)
- Weak antidiuretic effect at high doses
Uses
- Induction and augmentation of labour
- Postpartum haemorrhage (control of bleeding)
- Following incomplete abortion
- Milk let-down failure
Oxytocin makes the uterus contract, driving labour and stopping bleeding. Use Route Labour induction IV infusion Postpartum haemorrhage IM / IV Applied
- Adverse: uterine rupture, fetal distress, water intoxication
- Contraindicated in obstructed labour and malpresentation
🔑KEY POINTS TO REMEMBER- Oxytocin contracts the uterus and causes milk ejection.
- Used for labour induction and postpartum haemorrhage.
- Risks: uterine rupture, fetal distress, water intoxication.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Corticosteroid adverse effects result mainly from prolonged use, reflecting exaggerated glucocorticoid and mineralocorticoid actions.
Systemic Effects
- Cushingoid — moon face, buffalo hump, truncal obesity
- Metabolic — hyperglycaemia, dyslipidaemia
- Bone — osteoporosis, avascular necrosis
- Immune — infections, reactivation of tuberculosis
- Peptic ulcer, hypertension, oedema, cataract, glaucoma
- Growth retardation in children; psychosis
Withdrawal
- Hypothalamic-pituitary-adrenal suppression
- Abrupt stop → acute adrenal crisis
- Always taper gradually
Prolonged steroids suppress the adrenal axis and mimic Cushing syndrome. System Effect Bone Osteoporosis Metabolic Hyperglycaemia Immune Infection risk Applied
- Use lowest effective dose for shortest time
- Add calcium, vitamin D, bisphosphonates for bone protection
🔑KEY POINTS TO REMEMBER- Long-term steroids → Cushingoid features, osteoporosis, hyperglycaemia, infection.
- Suppress the HPA axis — never stop abruptly.
- Use the lowest dose for the shortest duration.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Levothyroxine (T4) is synthetic thyroid hormone and the drug of choice for hypothyroidism replacement therapy.
Features
- Converted peripherally to active T3
- Long half-life (~7 days) → once-daily dosing
- Taken on an empty stomach (absorption)
- Dose titrated against TSH
Uses & Cautions
- Hypothyroidism (all forms), myxoedema
- Suppression therapy in thyroid cancer
- Start low in elderly and cardiac patients (angina risk)
- Over-treatment → features of thyrotoxicosis, atrial fibrillation, osteoporosis
Replacement T4 is converted to active T3, normalising TSH. Feature Detail Monitoring Serum TSH Half-life ~7 days Over-dose Thyrotoxic features Applied
- Iron, calcium and antacids reduce absorption — separate doses
- Requirement ↑ in pregnancy
🔑KEY POINTS TO REMEMBER- Levothyroxine is the drug of choice for hypothyroidism.
- Long half-life; dose titrated by TSH.
- Start low in elderly/cardiac patients; needs rise in pregnancy.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Carbimazole is a thioamide antithyroid drug that inhibits thyroid hormone synthesis, used in hyperthyroidism.
Mechanism
- Converted to active methimazole
- Inhibits thyroid peroxidase
- ↓ Iodination of tyrosine and coupling
- ↓ T3 / T4 synthesis (no effect on stored hormone → delayed action)
Uses & Adverse Effects
- Graves’ disease and other hyperthyroidism
- Preparation before thyroid surgery / radioiodine
- Adverse: rash, arthralgia, agranulocytosis (rare but serious)
- Hepatotoxicity; teratogenic (aplasia cutis)
Blocking peroxidase stops new hormone synthesis; stored hormone delays effect. Feature Detail Target Thyroid peroxidase Onset Delayed (weeks) Danger Agranulocytosis Applied
- Warn: report sore throat or fever immediately (check blood count)
- Propylthiouracil preferred in the first trimester
🔑KEY POINTS TO REMEMBER- Carbimazole inhibits thyroid peroxidase → ↓ T3/T4 synthesis.
- Effect delayed because stored hormone is unaffected.
- Agranulocytosis is the serious adverse effect — warn about sore throat.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Sulfonylureas are oral antidiabetic drugs that lower blood glucose by stimulating insulin secretion from pancreatic β-cells.
Mechanism
- Block ATP-sensitive potassium channels in β-cells
- Depolarisation → calcium influx
- ↑ Insulin release (needs functioning β-cells)
- Ineffective in type 1 diabetes
Drugs & Adverse Effects
- Glibenclamide, glipizide, gliclazide, glimepiride
- Adverse: hypoglycaemia (main), weight gain
- Caution in elderly and renal impairment
Closing the potassium channel triggers insulin release from β-cells. Feature Detail Requires Functioning β-cells Main risk Hypoglycaemia Weight Gain Applied
- Second-line after metformin in type 2 diabetes
- Prolonged hypoglycaemia with glibenclamide in elderly
🔑KEY POINTS TO REMEMBER- Sulfonylureas block K⁺-ATP channels → ↑ insulin secretion.
- Need functioning β-cells (useless in type 1 diabetes).
- Main adverse effects: hypoglycaemia and weight gain.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.Definition
Bisphosphonates are drugs that inhibit osteoclastic bone resorption, used mainly for osteoporosis.
Mechanism
- Bind hydroxyapatite in bone
- Taken up by osteoclasts → inhibit their function and induce apoptosis
- ↓ Bone resorption → ↑ bone mineral density
Uses & Adverse Effects
- Osteoporosis (postmenopausal, steroid-induced)
- Paget’s disease of bone
- Hypercalcaemia of malignancy, bone metastases
- Adverse: oesophagitis, osteonecrosis of jaw, atypical femoral fracture
Osteoclasts ingest the drug and stop resorbing bone. Drug Route Alendronate Oral weekly Zoledronic acid IV yearly Applied
- Take with water, sit upright 30 minutes (avoid oesophagitis)
- Ensure adequate calcium and vitamin D
🔑KEY POINTS TO REMEMBER- Bisphosphonates inhibit osteoclastic bone resorption.
- Used in osteoporosis, Paget’s disease, hypercalcaemia of malignancy.
- Adverse: oesophagitis, osteonecrosis of the jaw.
📚SOURCES: Essentials of Medical Pharmacology (K.D. Tripathi); Goodman & Gilman’s The Pharmacological Basis of Therapeutics; Katzung’s Basic & Clinical Pharmacology.