Is meclizine (antihistamine) safe to use during pregnancy?

From the Guidelines

Meclizine is generally considered relatively safe during pregnancy, but it should be used with caution and only when necessary, as it is classified as FDA Pregnancy Category B, which means animal studies have not shown risk to the fetus, but there are no adequate studies in pregnant women 1. When considering the use of meclizine during pregnancy, it's essential to weigh the potential benefits against the potential risks. The FDA Pregnancy Category B classification indicates that while animal studies have not demonstrated a fetal risk, there is a lack of controlled studies in pregnant women 1.

Key Considerations

• Meclizine should be used at the lowest effective dose and for the shortest duration necessary to minimize potential risks.
• Non-medication approaches, such as avoiding triggers, staying hydrated, and eating small, frequent meals, should be tried first to manage motion sickness or vertigo during pregnancy.
• The second and third trimesters are generally considered safer than the first trimester for medication use.
• It's crucial to inform your doctor about your pregnancy before taking any medication, as they may recommend alternatives or adjusted dosing based on your specific situation and stage of pregnancy.

FDA Pregnancy Categories

The FDA pregnancy categories are as follows:

• Category A: Controlled studies in women fail to demonstrate a risk to the fetus in the first trimester (and there is no evidence of a risk in later trimesters) and the possibility of fetal harm appears remote.
• Category B: Either animal reproduction studies have not demonstrated a fetal risk but there are no controlled studies in pregnant women, or animal reproduction studies have shown an adverse effect that was not confirmed in controlled studies in women.
• Category C: Either studies in animals have revealed adverse effects on the fetus and there are no controlled studies in women, or studies in women and animals are not available.
• Category D: There is evidence of human fetal risk, but the benefits from use in pregnant women may be acceptable despite the risk.
• Category X: Studies in animals or human beings have demonstrated fetal abnormalities, or there is evidence of fetal risk based on human experience, or both, and the risk of the use of the drug in pregnant women clearly outweighs any possible benefit. Given the available evidence, meclizine can be used during pregnancy, but with caution and under the guidance of a healthcare provider 1.

From the FDA Drug Label

1. 1 Pregnancy Risk Summary: Data from epidemiological studies have not generally indicated a drug-associated risk of major birth defects with meclizine during pregnancy. However, in a published study, an increased incidence of fetal malformations was observed following oral administration of meclizine to pregnant rats during the period of organogenesis, at doses similar to those used clinically.

The safety of meclizine in pregnancy is not fully established. Epidemiological studies in humans have not shown a significant association between meclizine use and major birth defects. However, animal studies have raised concerns about potential fetal malformations at doses similar to those used in humans. Therefore, meclizine should be used with caution in pregnant women, and the benefits of treatment should be weighed against the potential risks to the fetus 2.

From the Research

Meclizine Safety in Pregnancy

• Meclizine is an antihistamine used to treat nausea and vomiting, and its safety during pregnancy has been studied in several research papers 3, 4, 5.
• A study published in the European journal of epidemiology in 2003 found that the use of meclizine in early pregnancy was associated with a reduced rate of preterm birth, low birth weight, and congenital malformations 4.
• Another study published in Clinical pharmacy in 1986 reviewed the safety and efficacy of antiemetic drugs used to treat nausea and vomiting during pregnancy and found that meclizine was not teratogenic in humans and presented a low risk of teratogenicity 5.
• A randomized trial published in Obstetrics and gynecology in 2000 found that pretreatment with meclizine reduced the incidence of nausea and vomiting associated with emergency contraceptive pills 6.
• However, it's worth noting that meclizine is not the focus of the study published in Malaria journal in 2014, which reviewed the safety and tolerability of mefloquine in pregnancy, a different medication 7.
• Overall, the available evidence suggests that meclizine can be used safely during pregnancy, but as with any medication, the benefit of the drug should outweigh the risk to the fetus 3, 4, 5.

Key Findings

• Meclizine is associated with a reduced rate of preterm birth, low birth weight, and congenital malformations 4.
• Meclizine is not teratogenic in humans and presents a low risk of teratogenicity 5.
• Meclizine can be effective in preventing nausea and vomiting associated with emergency contraceptive pills, but may cause drowsiness 6.