Antihistamine
PREGNANCY RECOMMENDATION: Limited Human Data—Probably Compatible
BREASTFEEDING RECOMMENDATION: No Human Data—Probably Compatible
PREGNANCY SUMMARY
Pyrilamine is used infrequently during pregnancy. One source found an increased risk of structural anomalies, but confirmation has not been reported. In general, antihistamines are considered low risk in pregnancy. However, exposure near birth of premature infants has been associated with an increased risk of retrolental fibroplasia.
FETAL RISK SUMMARY
The Collaborative Perinatal Project monitored 50,282 mother–child pairs, 121 of whom had pyrilamine exposure in the 1st trimester (1, pp. 323–324). No evidence was found to suggest a relationship to large categories of major or minor malformations. For use anytime during pregnancy, 392 exposures were recorded (1, pp. 436–437). A possible association with malformations was found on the basis of 12 defects, 6 of which involved benign tumors (1, p. 489).
It is not known if pyrilamine crosses the human placenta. The molecular weight (about 402) is low enough that exposure of the embryo–fetus should be expected.
An association between exposure during the last 2 weeks of pregnancy to antihistamines in general and retrolental fibroplasia in premature infants has been reported. See Brompheniramine for details.
BREASTFEEDING SUMMARY
No reports describing the use of pyrilamine during human lactation have been reported. The molecular weight (about 402) is low enough for excretion into breast milk. The effect of this exposure on a nursing infant is unknown.
Reference
1.Heinonen OP, Slone D, Shapiro S. Birth Defects and Drugs in Pregnancy. Littleton, MA: Publishing Sciences Group, 1977.