Pharmacology and Prescriptive Practice
Pharmacology and Prescriptive Practice
This domain tests safe prescribing in pregnancy and lactation, drug selection, contraindications, and monitoring. Items often present a common condition and ask which drug is safest or which must be avoided.
Core rules
- Pregnancy labeling now uses the Pregnancy and Lactation Labeling Rule; assess risk and benefit rather than relying on old letter categories.
- Hypertension in pregnancy: labetalol, nifedipine, and methyldopa are preferred. Avoid ACE inhibitors, ARBs, and direct renin inhibitors.
- Preeclampsia with severe features: magnesium sulfate for seizure prophylaxis; loading and maintenance doses require monitoring of reflexes, respirations, urine output, and magnesium level.
- Preterm birth 24-34 weeks: antenatal corticosteroids (betamethasone or dexamethasone) accelerate fetal lung maturity.
- GBS prophylaxis: penicillin is first-line; use cefazolin or clindamycin based on susceptibility.
- Lactation: check compatibility; most drugs pass into milk in small amounts, but avoid unsafe agents and monitor the infant.
- Controlled substances: check the prescription drug monitoring program, counsel on neonatal risks, and use the lowest dose.
Worked example
A 30-week patient has preeclampsia with severe features. Start magnesium sulfate per protocol and give betamethasone. Do not give an ACE inhibitor for blood pressure. Reasoning: magnesium prevents seizures, steroids mature fetal lungs, and ACE inhibitors are fetotoxic.
Traps
Prescribing ACE inhibitors in pregnancy; giving methergine to a hypertensive patient; using carboprost in asthma; missing GBS susceptibility; failing to monitor magnesium toxicity.