From the Guidelines
Hydralazine is considered safe for use in pregnancy, but only in specific situations, such as acute management of hypertension or severe preeclampsia 1.
Key Points
- Antihypertensive drugs known to be effective and safe in pregnancy include methyldopa, labetalol, and long-acting nifedipine 1.
- Hydralazine may be considered in the acute management of hypertension in pregnancy or severe preeclampsia 1.
- Diuretics are not recommended for blood pressure control in pregnancy but may be used during late-stage pregnancy if needed for volume control 1.
- The American College of Obstetricians and Gynecologists recommends that postpartum patients with gestational hypertension, preeclampsia, and superimposed preeclampsia have their blood pressures observed for 72 h in the hospital and for 7–10 days postpartum 1.
Management of Hypertension in Pregnancy
According to the International Society for the Study of Hypertension in Pregnancy, antihypertensive therapy should be used to maintain systolic blood pressure between 110 and 140 mmHg and diastolic blood pressure between 80 and 85 mmHg 1.
- Severe hypertension (>160/110 mmHg) requires urgent treatment in a monitored setting, with acceptable agents including oral nifedipine or intravenous labetalol or hydralazine 1.
- BP consistently at or >140/90 mmHg in clinic or office (or ≥135/85 mmHg at home) should be treated, aiming for a target diastolic BP of 85 mmHg in the office (and systolic BP of 110–140 mmHg) 1.
From the FDA Drug Label
Animal studies indicate that hydrALAZINE is teratogenic in mice at 20 to 30 times the maximum daily human dose of 200 to 300 mg and possibly in rabbits at 10 to 15 times the maximum daily human dose, but that it is nonteratogenic in rats. Teratogenic effects observed were cleft palate and malformations of facial and cranial bones There are no adequate and well-controlled studies in pregnant women. Although clinical experience does not include any positive evidence of adverse effects on the human fetus, hydrALAZINE should be used during pregnancy only if the expected benefit justifies the potential risk to the fetus.
Hydralazine is not proven to be safe for pregnancy. The drug label indicates that it is teratogenic in some animal studies, and there are no adequate and well-controlled studies in pregnant women. Therefore, it should be used during pregnancy only if the expected benefit justifies the potential risk to the fetus 2.
From the Research
Safety of Hydralazine in Pregnancy
- Hydralazine is used as a first-line therapy in controlling hypertension in pregnancy, particularly in cases of preeclampsia 3.
- Studies have shown that hydralazine can be effective in reducing blood pressure in pregnant women with severe hypertension 4, 5.
- However, hydralazine has been associated with more maternal side effects, such as hypotension, caesarean sections, placental abruption, and oliguria, compared to other antihypertensives like labetalol and nifedipine 6.
- A meta-analysis of randomized controlled trials found that hydralazine was associated with more severe hypertension, maternal hypotension, and adverse effects on fetal heart rate compared to other antihypertensives 6.
- Despite these findings, hydralazine is still considered a treatment option for hypertensive emergencies of pregnancy, particularly in cases where other antihypertensives are not effective or tolerated 7.
Efficacy of Hydralazine in Pregnancy
- Hydralazine has been shown to be effective in reducing blood pressure in pregnant women with severe hypertension, with some studies suggesting that it may be more effective than other antihypertensives like labetalol 5.
- A study comparing intravenous hydralazine and oral nifedipine found that both treatments were equally effective in lowering blood pressure in acute hypertensive emergencies of pregnancy 4.
- However, another study found that hydralazine was associated with a faster achievement of target blood pressure and a lower number of doses required compared to labetalol 5.
Maternal and Fetal Outcomes
- Hydralazine has been associated with more maternal side effects, such as hypotension, caesarean sections, placental abruption, and oliguria, compared to other antihypertensives like labetalol and nifedipine 6.
- A meta-analysis of randomized controlled trials found that hydralazine was associated with more adverse effects on fetal heart rate and low Apgar scores at one minute compared to other antihypertensives 6.
- However, another study found that perinatal outcomes did not differ significantly between women treated with hydralazine and those treated with labetalol 5.