What are the recommended medications and dosing regimens for managing pregnancy‑induced hypertension?

Medications and Dosing for Pregnancy-Induced Hypertension

For pregnancy-induced hypertension, initiate treatment with methyldopa, labetalol, or long-acting nifedipine when blood pressure reaches ≥140/90 mmHg, targeting a diastolic BP of 85 mmHg and systolic BP of 110-140 mmHg. 1, 2

Blood Pressure Thresholds for Treatment Initiation

• Start antihypertensive therapy at BP ≥140/90 mmHg in women with gestational hypertension, pre-existing hypertension with superimposed gestational hypertension, or hypertension with organ damage or symptoms at any time during pregnancy. 1, 2

• For uncomplicated chronic hypertension without these features, treatment may be delayed until BP reaches ≥150/95 mmHg. 2

• BP ≥160/110 mmHg constitutes a hypertensive emergency requiring immediate treatment within 15-60 minutes in a monitored setting to prevent maternal stroke. 1, 2, 3

First-Line Medications for Chronic Blood Pressure Control

Methyldopa

• Dosing: Start 250 mg twice or three times daily, titrate up to a maximum of 2000-3000 mg/day in divided doses. 4, 5
• Has the longest safety record with documented child follow-up to 7.5 years. 4, 6
• Critical caveat: Must be switched to an alternative agent postpartum due to risk of postnatal depression. 2, 6

Labetalol

• Dosing: Start 100 mg twice daily, titrate up to a maximum of 2400 mg/day in divided doses (typically three or four times daily). 6
• Efficacy comparable to methyldopa with a better side effect profile. 4, 6
• Contraindication: Do not use in women with asthma or reactive airway disease. 6
• Important interaction: Should not be used concomitantly with calcium channel blockers due to risk of severe hypotension. 2

Long-Acting Nifedipine (Extended-Release)

• Dosing: Start 30 mg once daily, titrate up to a maximum of 120 mg/day. 2, 6
• Preferred by many clinicians due to once-daily dosing, which improves adherence. 6
• Use only extended-release formulation for maintenance therapy; never use sublingual administration. 2, 6

Acute Management of Severe Hypertension (≥160/110 mmHg)

When BP reaches ≥160/110 mmHg, treat immediately with one of the following:

Immediate-Release Oral Nifedipine

• Dosing: 10-20 mg orally, repeat every 20-30 minutes if BP remains severely elevated, maximum 30 mg in the first hour. 1, 2, 6
• Works fastest among oral agents for acute management. 3
• Never administer sublingually due to risk of uncontrolled hypotension and maternal myocardial infarction. 2, 6

Intravenous Labetalol

• Dosing: 20 mg IV bolus initially, then escalate to 40 mg, then 80 mg every 10 minutes as needed, maximum single dose 300 mg. 1, 6
• Equally effective as nifedipine for acute management. 2

Intravenous Hydralazine

• Dosing: 5-10 mg IV bolus, repeat as needed. 1, 5
• May be considered for acute management but is generally less preferred than labetalol or nifedipine. 4

Absolutely Contraindicated Medications

ACE inhibitors, angiotensin receptor blockers, direct renin inhibitors, and mineralocorticoid receptor antagonists are strictly contraindicated throughout pregnancy due to severe fetotoxicity, renal dysgenesis, and oligohydramnios, with effects especially pronounced in the second and third trimesters. 4, 2, 6, 7

Target Blood Pressure During Treatment

• Target diastolic BP: 85 mmHg 4, 1, 2
• Target systolic BP: 110-140 mmHg 4, 1, 2
• Reduce or discontinue antihypertensives if diastolic BP falls below 80 mmHg to avoid compromising uteroplacental perfusion. 6

Special Considerations for Preeclampsia

• Magnesium sulfate should be administered for seizure prophylaxis in preeclampsia and for treatment of eclampsia. 1, 6
• Do not administer magnesium sulfate with calcium channel blockers due to risk of severe hypotension and myocardial depression. 2, 6
• Antenatal corticosteroids should be given between 24+0 and 34+0 weeks if delivery is likely within 7 days. 1

Postpartum Management

• Switch from methyldopa to labetalol or nifedipine immediately postpartum due to methyldopa's association with postnatal depression. 2, 6
• Continue antihypertensive therapy postpartum as BP typically rises between days 3-6. 2, 6, 3
• Both labetalol and nifedipine are safe for breastfeeding mothers. 2, 6
• Treat urgently if postpartum BP reaches ≥160/110 mmHg for more than 15 minutes. 2, 6
• Taper medications gradually when diastolic BP consistently falls below 80 mmHg, adjusting only one medication at a time with 3-7 day intervals between changes. 6

Common Pitfalls to Avoid

• Do not use atenolol specifically, as it has a higher risk of fetal growth restriction compared to other beta-blockers. 6
• Avoid diuretics for blood pressure control in pregnancy, though they may be used in late pregnancy if needed for volume control; they can reduce milk production postpartum. 4, 6
• Do not combine labetalol with calcium channel blockers due to additive hypotensive effects. 2
• Never use immediate-release nifedipine for maintenance therapy—reserve it exclusively for acute severe hypertension. 6

Long-Term Cardiovascular Risk

Women with pregnancy-induced hypertension have a significantly increased lifetime cardiovascular risk, with more than doubled risk of ischemic heart disease and approximately 4-fold increased risk of developing chronic hypertension. 1, 2, 6 Annual lifelong medical review is recommended for ongoing cardiovascular risk assessment, along with lifestyle modifications including weight management, regular physical activity, and heart-healthy diet. 1, 2, 6