Psychiatry: basic sciences
Psychopharmacology (basic)
Psychopharmacology is the science of how psychiatric medicines work in the body and brain, how they are absorbed and cleared, and why they cause side effects and interactions. It is the scientific basis of safe prescribing.
Depth by stage, Pre-U → Consultant (details)
What is it?
Psychopharmacology combines general pharmacology with brain science. It explains what the body does to a drug (absorption, distribution, metabolism, excretion) and what the drug does to the body (receptor binding, therapeutic and unwanted effects).
The main psychiatric drug classes are antidepressants, antipsychotics, mood stabilisers, anxiolytics and hypnotics, drugs for dementia, stimulants for ADHD, and drugs used in addiction. Each has a characteristic receptor profile that predicts both benefit and side effects.
This page covers the scientific basis examined in the basic sciences papers. The practical skill of choosing and monitoring medicines for an individual patient is covered under clinical pharmacotherapy.
Why does a psychiatrist need it?
Medication is one of the psychiatrist's main tools, and psychiatrists are the mental health professionals in Malaysia who prescribe. Understanding mechanisms lets them predict weight gain, sedation, sexual side effects or heart rhythm problems, avoid dangerous combinations, adjust doses in liver or kidney disease and pregnancy, and explain choices to patients honestly.
What level is expected at each stage?
Scale: 1. Aware → 2. Understands → 3. Applies → 4. Masters / Teaches. What the levels mean.
- Pre-UNot expected
- Pre-clinicalUnderstandsLearns general pharmacokinetics and pharmacodynamics and the broad drug classes.
- ClinicalUnderstandsRecognises common psychotropics and their major side effects in the psychiatry posting.
- HousemanshipAppliesPrescribes common drugs safely under supervision and spots interactions and toxicity.
- Medical officerAppliesStarts and adjusts psychotropics for routine cases with specialist oversight.
- Psych traineeMasters / TeachesExplains mechanisms, receptor profiles, kinetics and interactions in exam depth and applies them to complex cases.
- Specialist / consultantMasters / TeachesExpert prescriber for treatment-resistant and high-risk patients; teaches and sets local prescribing practice.
What are the key topics?
Pharmacokinetics
- Absorption, bioavailability and first-pass metabolism
- Distribution, protein binding and the blood–brain barrier
- Hepatic metabolism and cytochrome P450 enzymes (e.g. CYP2D6, CYP3A4, CYP1A2)
- Half-life, steady state and dosing intervals
- Renal excretion; lithium as a key example
- Long-acting injectable (depot) preparations
- Pharmacogenetics: fast and slow metabolisers
Pharmacodynamics
- Receptor occupancy and dose–response
- Agonists, antagonists, partial agonists
- Tolerance, dependence and withdrawal
- Therapeutic index and therapeutic drug monitoring
Main drug classes and mechanisms
- Antidepressants: SSRIs, SNRIs, tricyclics, MAOIs, mirtazapine, agomelatine, vortioxetine, bupropion
- Antipsychotics: first- and second-generation, clozapine, partial agonists (aripiprazole)
- Mood stabilisers: lithium, valproate, lamotrigine, carbamazepine
- Anxiolytics and hypnotics: benzodiazepines, Z-drugs, pregabalin, buspirone
- Cognitive enhancers: cholinesterase inhibitors, memantine
- Stimulants and non-stimulants for ADHD
- Drugs in addiction: methadone, buprenorphine, naltrexone, acamprosate, disulfiram
Adverse effects and their mechanisms
- Extrapyramidal effects, tardive dyskinesia and neuroleptic malignant syndrome
- Metabolic syndrome with antipsychotics
- Serotonin syndrome
- QTc prolongation
- Hyponatraemia, hyperprolactinaemia, sexual dysfunction
- Agranulocytosis with clozapine
- Teratogenicity (e.g. valproate) and lactation
Special populations and interactions
- Children, older adults, pregnancy and breastfeeding
- Liver and kidney impairment
- Common interactions: enzyme inducers and inhibitors, smoking and clozapine
- Drug–food and drug–herbal interactions, including traditional remedies used in Malaysia
How is it learned and assessed?
- Pharmacology in pre-clinical years; prescribing questions in clinical exams
- Supervised prescribing as a house officer and medical officer
- Basic sciences teaching in psychiatry training; examined in MMed Psychiatry Part I and MRCPsych Paper A
- Case-based discussions and pharmacy-led teaching during rotations
Typical textbooks and resources
- Stahl's Essential Psychopharmacology and Stahl's Prescriber's Guide — Stephen Stahl
- The Maudsley Prescribing Guidelines in Psychiatry — Taylor, Barnes and Young; practical evidence summary
- Rang and Dale's Pharmacology — general pharmacology text
- British National Formulary (BNF) — prescribing reference widely used in Malaysia
- MOH Malaysia Clinical Practice Guidelines on relevant disorders
Titles are widely used examples; editions change. Use university libraries or legitimate purchases.
Common questions
Why do psychiatric medicines often take weeks to work?
Many act first on receptors within hours, but the clinical benefit seems to depend on slower adaptive changes in the brain, such as receptor regulation and neuroplasticity. That is why antidepressants are usually judged after several weeks, not days.
Is this the same as knowing how to prescribe?
Not quite. Psychopharmacology is the science; clinical pharmacotherapy is applying it to a particular patient, with their preferences, other illnesses and risks. Psychiatrists need both.