Pharmacology
Pharmacology tests how drugs act, how the body handles them, and how common medicines alter exercise tolerance, healing, and physiotherapy safety.
Core rules and concepts
- Pharmacokinetics: absorption, distribution, metabolism, excretion. First-pass metabolism reduces oral bioavailability.
- Half-life is the time for plasma concentration to fall by half; steady state is reached after about 4–5 half-lives.
- NSAIDs inhibit cyclo-oxygenase, reducing prostaglandins; adverse effects include gastric irritation, renal impairment, and bleeding risk.
- Corticosteroids suppress inflammation but cause hyperglycaemia, osteoporosis, infection risk, and require tapering after prolonged use.
- Anticoagulants increase bleeding risk; avoid vigorous manual therapy and falls.
- Beta-blockers blunt exercise heart-rate response; use perceived exertion and symptoms.
Worked example
A drug has a half-life of 8 hours. After 4–5 half-lives, about 32–40 hours, the plasma concentration reaches steady state. Reasoning: each half-life halves the remaining difference to steady state; after four half-lives about 94% is reached, and after five about 97%. This matters when interpreting a new prescription: full effect and toxicity risk are not immediate. If the patient starts physiotherapy within hours, exercise responses may still change as concentrations accumulate.
Traps that cost marks
- Advising a patient to stop corticosteroids abruptly; this can cause adrenal insufficiency.
- Missing renal or gastric risk when a patient takes regular NSAIDs.
- Using heart rate alone to prescribe intensity in a patient on beta-blockers.
- Confusing agonist and antagonist actions.