Pharmacokinetics, CYP, Pharmacogenomics and TDM
Absorption, distribution, metabolism, elimination, kinetic models, CYP interactions, lifespan change, pharmacogenetics and therapeutic drug monitoring.
How to prepare for MRCPsych Paper A
Build mechanisms first, connect them to development and assessment, then practise distinguishing one best answer within SBA and extended-matching formats.
Core concepts
Concept 1
Pharmacokinetics describes absorption, distribution, metabolism and elimination, including bioavailability, volume of distribution, clearance, half-life and steady state.
Exam cue: When concentration changes, separate altered dose, absorption, distribution, clearance, interaction, timing and adherence.
Concept 2
CYP inhibition or induction, organ function, age, pregnancy, genetics and adherence can change exposure; therapeutic drug monitoring is useful only when concentration informs a decision.
Exam cue: Interpret a drug level with dose, sampling time, steady state, clinical response and toxicity.
Risk pitfalls and guardrails
Assuming half-life is independent of both clearance and volume of distribution.
Guardrail: Do not select an option because it is merely associated or familiar; choose the one that answers the exact lead-in.
Acting on an isolated concentration without checking sampling conditions and the patient.
Guardrail: Do not select an option because it is merely associated or familiar; choose the one that answers the exact lead-in.
Memory anchors
What does clearance describe?
The theoretical volume of plasma cleared of drug per unit time.
What determines half-life conceptually?
It increases with volume of distribution and decreases with clearance.
When is approximate steady state reached?
After about four to five half-lives during regular dosing, assuming stable linear kinetics.
How do enzyme inhibition and induction differ in timing?
Inhibition can occur relatively quickly; induction usually develops and resolves more slowly because enzyme expression changes.
What makes therapeutic drug monitoring clinically useful?
A meaningful concentration–response or toxicity relationship, variable kinetics, a reliable assay and a result that changes management.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
Pharmacokinetics is best summarised as what?
The fraction of an administered dose reaching systemic circulation unchanged is called what?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
What is Pass Harbor?
Completely free exam prep for 247 UK exams.
- Practice questions
- Flashcards
- Study guides
- Mock exams
- No registration
- No paywall
- Start instantly
“No more expensive exam prep. Quality study tools should be accessible to everyone.”