Is it safe to use albendazole and ivermectin during pregnancy, and what are the trimester-specific recommendations?

Albendazole and Ivermectin Use in Pregnancy

Both albendazole and ivermectin should be avoided in the first trimester of pregnancy due to potential teratogenic risks, but can be considered in the second and third trimesters when treatment is necessary.

First Trimester: Avoid Both Agents

The FDA drug label for albendazole explicitly states it "may cause fetal harm when administered to a pregnant woman" based on animal studies showing embryotoxicity and skeletal malformations 1. Pregnancy testing is recommended for females of reproductive potential prior to initiating albendazole 1.

For ivermectin, the FDA label indicates it "should not be used during pregnancy since safety in pregnancy has not been established" and was teratogenic in animal studies at 0.2,8.1, and 4.5 times the maximum recommended human dose 2. The evidence from human studies is insufficient—a 2020 systematic review and meta-analysis found "very low certainty of evidence" regarding spontaneous abortions, stillbirths, and congenital anomalies, concluding there is "insufficient evidence to conclude on the safety profile of ivermectin during pregnancy" 3.

Second and Third Trimesters: Can Be Used When Necessary

The 2025 UK guidelines for eosinophilia management state that the WHO suggests albendazole "can be used in second/third trimesters" and that ivermectin shows "no teratogenicity or toxicity attributable to ivermectin has been observed in limited human pregnancy experience" 4.

The guidelines note:

• Albendazole: "If required, avoiding the first trimester should be considered" 4
• Ivermectin: "No teratogenicity or toxicity attributable to ivermectin has been observed in limited human pregnancy experience" 4

A 2019 systematic review examining albendazole and mebendazole exposure found that among five observational studies comparing first-trimester exposure to no exposure, "none reported higher rates of adverse birth outcomes in the exposed group" 5. However, the authors emphasized that "inadvertent exposure" data should not be interpreted as evidence supporting intentional first-trimester use.

Clinical Decision Algorithm

For pregnant women requiring treatment for helminth infections:

1. First Trimester (weeks 1-13):

   • Delay treatment until second trimester if clinically feasible
   • If treatment cannot be delayed due to severe infection (e.g., hyperinfection strongyloidiasis), seek expert consultation
   • Consider alternative monitoring strategies

2. Second and Third Trimesters (weeks 14-40):

   • Albendazole 400 mg can be used for indicated helminth infections 4
   • Ivermectin 200 μg/kg can be used for indicated infections 4
   • The combination can be used when clinically indicated for empirical treatment of eosinophilia or specific parasitic infections 4

3. Critical Precaution: Before using ivermectin in any trimester, exclude Loa loa infection in people who have traveled to endemic regions (West or Central Africa) to prevent serious or fatal encephalopathy 4, 2

Lactation Considerations

Both medications are considered compatible with breastfeeding:

• Albendazole: "Concentrations of albendazole and the active metabolite, albendazole sulfoxide, have been reported to be low in human breast milk" with no reports of adverse effects on breastfed infants 1
• Ivermectin: "Excreted in human milk in low concentrations" and the American Academy of Pediatrics considers it compatible with breastfeeding, though treatment should only be undertaken "when the risk of delayed treatment to the mother outweighs the possible risk to the newborn" 4, 2

Important Caveats

The evidence base has significant limitations. A 2026 observational study from the Embryotox database reported five major malformations among 75 live-born infants with first-trimester mebendazole exposure (including three heart defects), though the authors emphasized these should be "interpreted as descriptive observations and possible signals only" 6. This underscores the need for caution with all benzimidazoles in early pregnancy.

The key principle: weigh the maternal morbidity and mortality risk from untreated helminth infection against the uncertain but potentially real teratogenic risk in the first trimester. For most soil-transmitted helminth infections, delaying treatment until the second trimester is the safest approach. For life-threatening infections like disseminated strongyloidiasis, treatment cannot wait regardless of trimester.