Pharmacology and medication management
Pharmacology items test safe administration and the arithmetic and physiology behind it: right dose, right route, right rate, correct monitoring, and recognition of toxicity. Calculation errors and failure to check renal function are the most common failures.
Safe administration
- Rights of administration: patient, drug, dose, route, time, documentation, reason, and the patient's right to refuse.
- High-alert medicines (insulin, heparin, opioids, concentrated potassium, chemotherapy) require an independent double-check and, for insulin and heparin, a standardised protocol.
- Check renal and hepatic function before renally cleared drugs such as gentamicin or low-molecular-weight heparin.
Calculations
Dose required divided by stock strength, multiplied by the volume. Infusion rate equals the dose per hour divided by the concentration.
Monitoring and antidotes
- Vancomycin: AUC-guided dosing (400-600 mg·h/L) is preferred; trough-based monitoring uses 10-15 mg/L for uncomplicated and 15-20 mg/L for severe infection.
- Digoxin 0.5-0.9 ng/mL in heart failure; phenytoin 10-20 mg/L total.
- Antidotes: naloxone for opioids, flumazenil for benzodiazepines, N-acetylcysteine for paracetamol, protamine for heparin, vitamin K and prothrombin complex for warfarin, calcium gluconate for magnesium toxicity, dantrolene for malignant hyperthermia.
- Avoid ACE inhibitors, angiotensin receptor blockers and warfarin in pregnancy; avoid NSAIDs in the third trimester.
Worked example
A heparin infusion contains 25,000 IU in 500 mL, which is 50 IU/mL. The prescription is 1000 IU/h. Reasoning: 1000 divided by 50 equals 20 mL/h. The nurse checks the concentration on the bag, not just the label on the pump, and has a second nurse verify.
Traps that cost marks
Confusing milligrams and micrograms; misplaced decimal points; giving intravenous potassium undiluted; failing to reassess after an antidote or a rate change.