Is Losartan (angiotensin II receptor antagonist) safe during pregnancy?

From the Guidelines

Losartan is not safe during pregnancy and should be avoided. This medication, which belongs to the class of angiotensin II receptor blockers (ARBs), is contraindicated during all trimesters of pregnancy due to significant risks to fetal development, as stated in the most recent guideline 1. When taken during the second and third trimesters, losartan can cause serious fetal harm including decreased renal function, oligohydramnios (low amniotic fluid), skull hypoplasia, and even fetal death. Even first-trimester exposure carries potential risks.

Key Points to Consider

• Women who are taking losartan and discover they are pregnant should immediately contact their healthcare provider to switch to a pregnancy-safe alternative for blood pressure control, such as methyldopa, labetalol, or certain calcium channel blockers, as recommended by 1.
• The reason for losartan's harmful effects during pregnancy relates to its mechanism of action - by blocking angiotensin II receptors, it interferes with the renin-angiotensin system which is critical for normal fetal kidney development and function.
• Women of childbearing potential who are prescribed losartan should use reliable contraception and discuss pregnancy plans with their doctor before conception to allow for medication changes, as emphasized in 1.
• Alternative medications for hypertension during pregnancy include methyldopa, labetalol, and long-acting nifedipine, which are considered safe and effective, according to 1.

Clinical Implications

• Healthcare providers should be aware of the potential risks associated with losartan use during pregnancy and counsel their patients accordingly.
• Pregnant women with hypertension should be closely monitored and managed by a multidisciplinary team to minimize risks to both the mother and the fetus.
• The use of losartan during pregnancy should be avoided, and alternative medications should be used to control blood pressure, as recommended by the most recent guidelines 1.

From the FDA Drug Label

Use of drugs that act on the renin-angiotensin system during the second and third trimesters of pregnancy reduces fetal renal function and increases fetal and neonatal morbidity and death. Resulting oligohydramnios can be associated with fetal lung hypoplasia and skeletal deformations Potential neonatal adverse effects include skull hypoplasia, anuria, hypotension, renal failure, and death. When pregnancy is detected, discontinue losartan as soon as possible.

Losartan potassium has been shown to produce adverse effects in rat fetuses and neonates, including decreased body weight, delayed physical and behavioral development, mortality and renal toxicity

Losartan is not safe during pregnancy. The drug can cause significant harm to the fetus, particularly when used during the second and third trimesters. Potential adverse effects include fetal lung hypoplasia, skeletal deformations, and neonatal morbidity and death. If pregnancy is detected, losartan should be discontinued as soon as possible 2.

From the Research

Losartan Safety During Pregnancy

• Losartan, an angiotensin II receptor antagonist, is not recommended for use during pregnancy due to potential fetal toxicity 3, 4, 5, 6, 7.
• Studies have shown that losartan use during the second and third trimesters of pregnancy can cause serious fetal abnormalities, including oligohydramnios, fetal growth retardation, pulmonary hypoplasia, limb contractures, and calvarial hypoplasia 3, 5.
• The fetal abnormalities are thought to be related to the extreme sensitivity of the fetus to the hypotensive action of losartan, which can disrupt fetal vascular perfusion and renal function 5.
• There have been reports of stillbirth or neonatal death in association with maternal losartan treatment during pregnancy, and surviving infants may exhibit renal damage 5.
• It is recommended that women who become pregnant while taking losartan be changed to an antihypertensive drug of a different class as soon as the pregnancy is recognized 4, 5.
• Losartan should be avoided in pregnancy, and pregnant women who elect to continue using it should be informed about the risks and carefully monitored during pregnancy 4.

Fetal Risks Associated with Losartan Use

• Oligohydramnios (low amniotic fluid levels) 3, 4, 5, 7
• Fetal growth retardation 5
• Pulmonary hypoplasia (underdeveloped lungs) 5
• Limb contractures 5
• Calvarial hypoplasia (underdeveloped skull) 5
• Renal damage 5
• Stillbirth or neonatal death 5
• Fetal inferior vena cava thrombosis (blood clot in the fetus's inferior vena cava) 7

Clinical Recommendations

• Losartan should not be administered to pregnant women or breast-feeding mothers 3, 6.
• Women who become pregnant while taking losartan should be changed to an antihypertensive drug of a different class as soon as the pregnancy is recognized 4, 5.
• Pregnant women who elect to continue using losartan should be informed about the risks and carefully monitored during pregnancy 4.