This drug should be used during pregnancy only if the benefit outweighs the risk.
-According to some authorities: Use is contraindicated.

AU TGA pregnancy category: B3
US FDA pregnancy category: Not assigned.

Risk summary: Insufficient data available on use of this drug in pregnant women to inform a drug-related risk.

Comments:
-Risks to mother and fetus associated with untreated helminth infection during pregnancy should be considered.
-According to some authorities: This drug should not be used in patients who think they are or may be pregnant.

Animal studies have revealed evidence of embryofetal toxicity and teratogenicity; in rats, adverse developmental effects (i.e., skeletal malformations, soft tissue malformations, decreased pup weight, embryolethality) were observed when single oral doses as low as 10 mg/kg (about 0.5-fold [100 mg] or 0.2-fold [500 mg] the maximum recommended human dose) were administered during organogenesis. There are no controlled data in human pregnancy; however, this drug has been used during pregnancy without evidence of fetal harm.

Untreated soil-transmitted helminth infections in pregnancy are associated with adverse outcomes (including maternal iron deficiency anemia, low birth weight, neonatal and maternal death).

AU TGA pregnancy category B3: Drugs which have been taken by only a limited number of pregnant women and women of childbearing age, without an increase in the frequency of malformation or other direct or indirect harmful effects on the human fetus having been observed. Studies in animals have shown evidence of an increased occurrence of fetal damage, the significance of which is considered uncertain in humans.

US FDA pregnancy category Not Assigned: The US FDA has amended the pregnancy labeling rule for prescription drug products to require labeling that includes a summary of risk, a discussion of the data supporting that summary, and relevant information to help health care providers make prescribing decisions and counsel women about the use of drugs during pregnancy. Pregnancy categories A, B, C, D, and X are being phased out.

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Limited data suggest this drug is poorly excreted into breast milk and poorly absorbed orally. Reports regarding use of this drug during breastfeeding have shown no adverse effects in breastfed infants; rare cases of decreased milk production reported after use of this drug, but no compelling proof that such cases were due to this drug.

In 1 report, the peak milk level was 6 mcg/L after a single 100 mg oral dose was given to a nursing mother (time postpartum not stated); drug was not detectable (less than 1 mcg/L) in milk 13.25 hours after dosing. No inhibition of lactation was noted.

Starting the first day postpartum, 1 woman was given 100 mg orally twice a day for 3 days. When measured after treatment (exact timing not stated), this drug was undetectable (less than 20 mcg/L) in milk. The authors stated that this result was similar to those reported by the manufacturer and that the infant probably absorbed negligible drug from breast milk.

A case series reported 45 nursing mothers were administered doses ranging from 100 mg once to 200 mg twice a day for 3 days; about half repeated 100 mg once after 7 to 14 days. At ages ranging from 1 to 30 weeks of age, 33 of their infants were exclusively breastfed; 8 of the 12 partially breastfed infants were older than 20 weeks. None of the infants had any adverse reactions reported by their mothers; 1 mother reported a slight decrease in milk production.

At 13 weeks postpartum, a nursing mother was taking metronidazole 250 mg orally 3 times a day; milk production seemed unaffected. On day 8 of therapy, she passed a roundworm; metronidazole was discontinued, and this drug was started (100 mg orally twice a day). On day 2 of therapy, she started supplementing with formula due to markedly decreased milk production; by day 7, milk production had stopped. According to the authors, this drug may have caused the reduced milk production, but no further proof (other than temporal relationship) was offered.

Starting the first day postpartum, 4 patients were treated with 100 mg orally twice a day for 3 days; 2 had pinworm (Enterobius), 1 had roundworm (Ascaris), and 1 had hookworm (Ancylostoma) infestations. Each patient breastfed successfully.

LactMed: No special precautions required.
WHO: Use is considered acceptable.
-According to some authorities: Breastfeeding is not recommended after use of this drug.

Excreted into human milk: Yes (poorly)
Excreted into animal milk: Unknown

Comments:
-Developmental and health benefits of breastfeeding should be considered as well as the mother's clinical need for this drug.
-The effects in the nursing infant are unknown; potential side effects in the breastfed child due to this drug or the mother's underlying condition should be considered.

See references