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High-Yield Pharmacology for Medical Exams: Revision Guide
High-yield pharmacology for licensing exams: drug classes, mechanisms, classic adverse effects, interactions, antidotes, P450 rules and common exam traps.
Pharmacology runs through every system in a licensing exam. A cardiology question becomes a pharmacology question the moment it asks "which drug caused this?" or "what should be avoided?". This revision guide is organised around the facts that most often decide a question: mechanism, signature adverse effect, interaction and antidote. It is exam material, not prescribing advice.
Learn by class
For every drug class, build a five-line card:
- Mechanism in one sentence.
- Two main indications.
- The signature adverse effect (the one that identifies the drug in a stem).
- The key interaction or contraindication.
- Monitoring, if any.
If you can produce those five lines from memory, you can answer most questions about the class.
Pharmacokinetics in five ideas
- Half-life determines time to steady state: roughly four to five half-lives. Loading doses reach target levels faster for drugs with long half-lives (amiodarone, digoxin).
- First-pass metabolism explains why some drugs are given sublingually or intravenously (glyceryl trinitrate).
- Zero-order kinetics (constant amount eliminated per unit time) applies to phenytoin, ethanol and high-dose aspirin, so small dose increases can cause large level increases.
- Volume of distribution: drugs with a large volume (lipophilic, tissue-bound) are poorly removed by dialysis.
- Renal elimination: reduce doses of renally cleared drugs (aminoglycosides, lithium, metformin, many antibiotics, low molecular weight heparins) in kidney impairment.
Cytochrome P450: the short list
| Inducers (reduce levels of other drugs) | Inhibitors (raise levels of other drugs) |
|---|---|
| Rifampicin | Macrolides (clarithromycin, erythromycin) |
| Carbamazepine | Azole antifungals (fluconazole, ketoconazole) |
| Phenytoin | Grapefruit juice |
| Phenobarbital | Amiodarone |
| St John's wort | HIV protease inhibitors (ritonavir) |
| Chronic alcohol use | Ciprofloxacin, isoniazid, omeprazole, cimetidine |
Classic stems: a woman on the combined pill starts rifampicin or carbamazepine and becomes pregnant (inducer). A patient on warfarin starts clarithromycin or fluconazole and has an INR rise with bleeding (inhibitor). A patient on simvastatin starts clarithromycin and develops myopathy.
Cardiovascular drugs
| Class | Example | Signature adverse effect / trap |
|---|---|---|
| ACE inhibitor | Ramipril | Dry cough, angioedema, hyperkalaemia, contraindicated in pregnancy and bilateral renal artery stenosis |
| ARB | Losartan | Hyperkalaemia; no cough |
| Beta blocker | Bisoprolol | Bronchospasm in asthma, bradycardia, masks hypoglycaemia |
| Dihydropyridine CCB | Amlodipine | Ankle oedema, flushing |
| Rate-limiting CCB | Verapamil | Constipation; heart block with beta blockers |
| Thiazide | Indapamide | Hyponatraemia, hypokalaemia, hyperuricaemia (gout), hyperglycaemia |
| Loop diuretic | Furosemide | Hypokalaemia, ototoxicity |
| Spironolactone | Hyperkalaemia, gynaecomastia | |
| Amiodarone | Hypo- or hyperthyroidism, pulmonary fibrosis, liver toxicity, photosensitivity, corneal deposits | |
| Digoxin | Nausea, yellow-green vision, arrhythmias; toxicity worse with hypokalaemia | |
| Statin | Atorvastatin | Myopathy, raised transaminases |
| Nitrate | GTN | Headache, hypotension; avoid with sildenafil |
Anticoagulants and antiplatelets
| Drug | Mechanism | Reversal |
|---|---|---|
| Warfarin | Vitamin K antagonist (factors II, VII, IX, X) | Vitamin K; prothrombin complex concentrate for major bleeding |
| Unfractionated heparin | Potentiates antithrombin | Protamine |
| Low molecular weight heparin | Mainly anti-Xa | Protamine (partial) |
| Dabigatran | Direct thrombin inhibitor | Idarucizumab |
| Apixaban, rivaroxaban | Direct factor Xa inhibitors | Andexanet alfa where available, or prothrombin complex |
| Aspirin | Irreversible COX inhibition | Platelet transfusion in selected bleeding |
| Clopidogrel | P2Y12 inhibitor | Platelet transfusion in selected bleeding |
Trap: heparin-induced thrombocytopenia causes a falling platelet count with thrombosis, typically 5โ10 days after starting heparin. Stop all heparin and switch to a non-heparin anticoagulant.
Antimicrobials
| Class | Example | Signature adverse effect / trap |
|---|---|---|
| Aminoglycoside | Gentamicin | Nephrotoxicity, ototoxicity; monitor levels |
| Macrolide | Clarithromycin | QT prolongation, P450 inhibition |
| Fluoroquinolone | Ciprofloxacin | Tendon rupture, QT prolongation, lowers seizure threshold |
| Tetracycline | Doxycycline | Photosensitivity, avoid in pregnancy and young children (teeth) |
| Vancomycin | Red man (flushing) syndrome with fast infusion, nephrotoxicity | |
| Metronidazole | Disulfiram-like reaction with alcohol, metallic taste | |
| Trimethoprim | Hyperkalaemia, folate antagonism (avoid early pregnancy) | |
| Nitrofurantoin | Avoid in significant renal impairment and near term in pregnancy | |
| Isoniazid | Peripheral neuropathy (give pyridoxine), hepatitis | |
| Rifampicin | Orange body fluids, P450 induction, hepatitis | |
| Ethambutol | Optic neuritis (colour vision) | |
| Clindamycin, broad-spectrum agents | Clostridioides difficile infection |
Central nervous system and psychiatry
| Drug | Signature adverse effect / trap |
|---|---|
| Lithium | Narrow therapeutic range; tremor, hypothyroidism, nephrogenic diabetes insipidus; toxicity with dehydration, NSAIDs, ACE inhibitors, thiazides |
| SSRIs | Hyponatraemia, GI bleeding with NSAIDs, serotonin syndrome with MAOIs, tramadol, linezolid |
| Tricyclics | Anticholinergic effects; overdose causes broad QRS and arrhythmia, treated with sodium bicarbonate |
| Clozapine | Agranulocytosis (mandatory blood monitoring), myocarditis, constipation |
| Typical antipsychotics | Extrapyramidal effects, hyperprolactinaemia, neuroleptic malignant syndrome |
| Valproate | Teratogenic (neural tube defects), weight gain, hepatotoxicity, pancreatitis |
| Carbamazepine | P450 induction, hyponatraemia, Stevens-Johnson syndrome (HLA-B*1502 risk) |
| Phenytoin | Gum hypertrophy, hirsutism, ataxia, zero-order kinetics |
| Levodopa | Dyskinesia, on-off phenomenon |
Serotonin syndrome vs neuroleptic malignant syndrome: serotonin syndrome develops over hours with hyperreflexia and clonus; NMS develops over days with "lead pipe" rigidity and very high creatine kinase.
Endocrine and metabolic drugs
| Drug | Signature adverse effect / trap |
|---|---|
| Metformin | GI upset, lactic acidosis risk in severe renal impairment; B12 deficiency |
| Sulfonylureas | Hypoglycaemia, weight gain |
| SGLT2 inhibitors | Genital infections, euglycaemic diabetic ketoacidosis |
| GLP-1 receptor agonists | Nausea, weight loss; caution with pancreatitis history |
| Pioglitazone | Fluid retention, heart failure, fracture risk |
| Levothyroxine | Overtreatment causes AF and osteoporosis |
| Carbimazole / propylthiouracil | Agranulocytosis (sore throat: check full blood count); PTU liver toxicity |
| Corticosteroids | Hyperglycaemia, osteoporosis, adrenal suppression; never stop long-term steroids abruptly |
| Bisphosphonates | Oesophagitis, osteonecrosis of the jaw, atypical femoral fracture |
Other high-yield adverse effects
- Methotrexate: marrow suppression, pneumonitis, liver fibrosis; give folic acid on a different day; trimethoprim increases toxicity.
- NSAIDs: peptic ulcer, renal impairment, worsened asthma in sensitive patients, fluid retention.
- Allopurinol: severe skin reactions; interacts with azathioprine (marrow toxicity).
- Opioids: constipation, respiratory depression, miosis.
- Isotretinoin and many anticonvulsants: teratogenic.
Teratogens worth knowing
| Drug | Effect |
|---|---|
| Valproate | Neural tube defects, developmental delay |
| Warfarin | Fetal warfarin syndrome (nasal hypoplasia, bone stippling) |
| ACE inhibitors / ARBs | Fetal renal damage, oligohydramnios |
| Isotretinoin | Craniofacial, cardiac and CNS malformations |
| Lithium | Cardiac anomalies (Ebstein anomaly) |
| Tetracyclines | Tooth discoloration, bone growth effects |
| Methotrexate | Miscarriage and malformations |
Overdose and antidotes
| Toxin | Key feature | Antidote / key treatment |
|---|---|---|
| Paracetamol | Often asymptomatic early; liver failure later | Acetylcysteine guided by timed level and nomogram or by staggered-overdose rules |
| Opioids | Pinpoint pupils, respiratory depression | Naloxone |
| Benzodiazepines | Sedation | Supportive; flumazenil only in selected cases (seizure risk) |
| Tricyclic antidepressants | Broad QRS, seizures, anticholinergic signs | Sodium bicarbonate |
| Organophosphates | Salivation, lacrimation, miosis, bradycardia | Atropine, pralidoxime |
| Digoxin | Arrhythmia, hyperkalaemia | Digoxin-specific antibody fragments |
| Beta blockers | Bradycardia, hypotension | Atropine, glucagon, high-dose insulin therapy |
| Iron | GI bleeding, metabolic acidosis | Desferrioxamine |
| Methanol / ethylene glycol | High anion gap acidosis, osmolar gap | Fomepizole (or ethanol), dialysis |
| Carbon monoxide | Headache, normal pulse oximetry reading | High-flow oxygen |
| Salicylates | Tinnitus, mixed respiratory alkalosis and metabolic acidosis | Sodium bicarbonate, dialysis if severe |
| Heparin | Bleeding | Protamine |
Common exam traps
- Assuming a drug interaction is pharmacodynamic when the stem shows a new P450 inhibitor or inducer.
- Missing hyperkalaemia when ACE inhibitor, spironolactone and trimethoprim are combined.
- Forgetting that lithium toxicity is triggered by dehydration or a new diuretic or NSAID.
- Giving a non-selective beta blocker to a patient with asthma.
- Choosing flumazenil in a mixed overdose with a tricyclic (seizure risk).
- Treating a sore throat on carbimazole as simple pharyngitis without checking neutrophils.
How to revise
Make class cards and test yourself without notes, then use mixed question blocks where drugs appear inside clinical stems. The MediFlow Exam Prep app tags pharmacology questions so you can re-test adverse effects and interactions you keep missing. Pair this guide with high-yield cardiology and high-yield infectious diseases.
Summary
- Learn by class: mechanism, indication, signature adverse effect, interaction, monitoring.
- Memorise a short P450 inducer and inhibitor list.
- Know the classic teratogens and the core antidote table.
- In every stem, check for a recent new drug: it is often the answer.
Practice questions in MediFlow Exam Prep
Daily questions with explanations, a study plan and mock exams. Start free.
App StoreFrequently asked questions
How should I learn pharmacology for exams?
Learn by class, not by individual drug. For each class know the mechanism, one or two indications, the signature adverse effect, key interactions and contraindications. Then test yourself with vignette questions.
Which adverse effects are tested most?
Signature effects that point to one drug: ACE inhibitor cough and angioedema, amiodarone thyroid and lung toxicity, lithium tremor and nephrogenic diabetes insipidus, aminoglycoside ototoxicity, and methotrexate marrow suppression.
Do I need to memorise cytochrome P450 lists?
Yes, a short list of strong inducers and inhibitors. Exams use them to explain warfarin bleeding, contraceptive failure or drug toxicity after a new prescription.
What antidotes are most commonly tested?
Acetylcysteine for paracetamol, naloxone for opioids, flumazenil for benzodiazepines (with caution), atropine and pralidoxime for organophosphates, vitamin K and prothrombin complex for warfarin, and digoxin-specific antibody fragments.
Is this guide prescribing advice?
No. It is revision material for exams. Prescribing follows the current national formulary, local protocols and senior review.
Educational content only, not individual medical, legal or immigration advice. Fees, formats and rules change: always confirm with the responsible authority before you apply.
MediFlow Editorial Team
Medical education editors
The MediFlow editorial team researches licensing exams, medical education and healthcare careers worldwide. Every figure is checked against the official exam body, regulator or statistics office and dated; articles are re-reviewed when rules change. MediFlow is operated by ICSL FZE, SPC Free Zone, Sharjah, UAE, with a branch office: Exchange Tower, Business Bay, Dubai.
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