Antihistamine
PREGNANCY RECOMMENDATION: Compatible
BREASTFEEDING RECOMMENDATION: Limited Human Data—Potential Toxicity
PREGNANCY SUMMARY
In general, antihistamines are considered compatible with pregnancy. However, a possible association with retrolental fibroplasia in premature infants has been reported.
FETAL RISK SUMMARY
Reproductive studies with the antihistamine, clemastine, in rats and rabbits have revealed no evidence of teratogenic effects (1). No published reports describing the use of clemastine in human pregnancy have been located.
In a surveillance study of Michigan Medicaid recipients involving 229,101 completed pregnancies conducted between 1985 and 1992, 1617 newborns had been exposed to clemastine during the 1st trimester (F. Rosa, personal communication, FDA, 1993). A total of 71 (4.4%) major birth defects were observed (68 expected). Specific data were available for six defect categories, including (observed/expected) 13/16 cardiovascular defects, 3/3 oral clefts, 3/1 spina bifida, 4/5 polydactyly, 4/4 hypospadias, and 5/1.9 limb-reduction defects. Only with the latter defect is there a suggestion of a possible association, but other factors, including the mother’s disease, concurrent drug use, and chance, may be involved.
A 2002 study found no increased risk of teratogenicity or other pregnancy or newborn complications for antihistamines when used in early pregnancy for the treatment of nausea and vomiting (N =12,394) and allergy (N = 5041) (2). Clemastine was used by 1230 women.
An association between exposure to antihistamines during the last 2 weeks of pregnancy and retrolental fibroplasia in premature infants has been reported. See Brompheniramine for details.
BREASTFEEDING SUMMARY
Clemastine is excreted into breast milk (3). A 10-week-old girl developed drowsiness, irritability, refusal to feed, neck stiffness, and a high-pitched cry 12 hours after the mother began taking the antihistamine, 1 mg twice daily. The mother also was also taking phenytoin and carbamazepine. Twenty hours after the last dose, clemastine levels in maternal plasma and milk were 20 and 5–10 ng/mL, respectively, a milk:plasma ratio of 0.25–0.5. The drug could not be detected in the infant’s plasma. Symptoms in the baby resolved within 24 hours after the drug was stopped, although breastfeeding was continued. Examination 3 weeks later was also normal. Owing to the above case report, the American Academy of Pediatrics states that the drug should be used with caution during breastfeeding (4).
References
1.Product information. Tavist. Sandoz Pharmaceuticals, 1993.
2.Kallen B. Use of antihistamine drugs in early pregnancy and delivery outcome. J Matern Fetal Neonatal Med 2002;11:146–52.
3.Kok THHG, Taitz LS, Bennett MJ, Holt DW. Drowsiness due to clemastine transmitted in breast milk. Lancet 1982;1:914–5.
4.Committee on Drugs, American Academy of Pediatrics. The transfer of drugs and other chemicals into human milk. Pediatrics 2001;108:776–89.