Antihypertensives Used in Pregnancy

Note: KD Tripathi (KDT) and Tara's Pharmacology are not in the library, but Goodman & Gilman's (the gold-standard pharmacology reference) covers this topic in full detail and is the closest equivalent. The content below reflects standard pharmacology teaching consistent with KDT/Tara.

Overview

First-Line Agents (Oral - Chronic Hypertension in Pregnancy)

1. alpha-Methyldopa (Aldomet)

• Class: Centrally acting alpha-2 adrenergic agonist
• Mechanism: Depletes nerve terminal norepinephrine, decreases peripheral resistance and venous constriction, reduces sympathetic outflow
• Dose: 250 mg twice daily (typical starting dose)
• Why preferred: Has the most extensive safety data of all antihypertensives; the only drug with documented long-term infant follow-up showing no adverse developmental effects
• Side effects: Sedation, fatigue, orthostatic hypotension, rare hepatotoxicity (elevated liver enzymes), hemolytic anemia
• Special note: Iron supplements (ferrous sulfate) interfere with methyldopa absorption - important in pregnancy!
• Status: Historically the "gold standard" first-line oral agent; less effective in severe hypertension

2. Labetalol

• Class: Combined alpha-1 and non-selective beta-adrenergic blocker
• Dose: 100 mg twice daily (oral); 20 mg IV (acute, escalating to 40 mg at 10 min)
• Why preferred over other beta-blockers: Alpha-blockade theoretically preserves uteroplacental blood flow (unlike pure beta-blockers that reduce cardiac output without vasodilation)
• Advantage: Good safety data; first-line for both chronic hypertension and acute severe hypertension in pregnancy; one trial suggests it may be superior to methyldopa for prevention of preeclampsia
• Side effects: Short duration (multiple daily dosing needed); may exacerbate reactive airway disease/asthma
• IV use: Preferred IV agent for acute hypertensive urgency in pregnancy

3. Nifedipine (Long-acting / slow-release preparation)

• Class: Calcium channel blocker (dihydropyridine)
• Dose: 30 mg once daily (slow-release)
• Advantage: Once-daily dosing; uterine blood flow not adversely affected; no teratogenic concerns identified
• Side effects: Peripheral edema
• Combination with magnesium: Can be used alongside magnesium sulfate (used for seizure prophylaxis in preeclampsia) - monitor for neuromuscular blockade potentiation in theory, though clinically used together

Second-Line Agents

4. Hydralazine

• Class: Direct arteriolar vasodilator
• Dose: 5-10 mg IV or IM for acute severe hypertension (repeat every 20 min)
• Use: Acute/parenteral management of severe preeclampsia/hypertensive emergencies
• Disadvantages: Increased risk of maternal hypotension and placental abruption when used acutely; not preferred as chronic oral therapy
• Historical note: Extensively used - one of the three most commonly prescribed antihypertensives in pregnancy in the US (alongside labetalol and nifedipine)

5. Metoprolol

• Class: Selective beta-1 blocker
• Potential for once-daily dosing (long-acting formulation)
• Disadvantage: Safety data less extensive than labetalol; not the preferred beta-blocker in pregnancy

6. Verapamil / Diltiazem

• Class: Non-dihydropyridine calcium channel blockers
• Status: No evidence of adverse fetal effects; however, limited data - used as second-line when first-line agents fail

7. Nicardipine (IV)

• Class: Dihydropyridine CCB
• Use: IV route for acute hypertension; extensive safety data from use as a tocolytic during labor
• Status: Second-line parenteral option

8. Clonidine

• Class: Centrally acting alpha-2 agonist (similar to methyldopa)
• Safety: Comparable to methyldopa in mechanism and safety profile; fewer data available

Drugs Generally Avoided

Absolutely Contraindicated

ACEIs and ARBs should be stopped as soon as pregnancy is confirmed.

For Severe Preeclampsia / Hypertensive Emergency

1. Labetalol 20 mg IV → escalate to 40 mg at 10 min if inadequate
2. Hydralazine 5-10 mg IV/IM → repeat every 20 min
3. Nicardipine IV infusion (extensive tocolytic safety data)

Summary Table