Fetal Risk Summary
Cloxacillin is a penicillin antibiotic (see also Penicillin G). No published reports linking its use with congenital defects have been located. The Collaborative Perinatal Project monitored 50,282 mother-child pairs, 3,546 of which had 1st trimester exposure to penicillin derivatives (1, pp. 297313). For use anytime during pregnancy, 7,171 exposures were recorded (1, p. 435). In neither group was evidence found to suggest a relationship to large categories of major or minor malformations or to individual defects.
In a surveillance study of Michigan Medicaid recipients involving 229,101 completed pregnancies conducted between 1985 and 1992, 46 newborns had been exposed to cloxacillin during the 1st trimester (F. Rosa, personal communication, FDA, 1993). Three (6.5%) major birth defects were observed (two expected), including three cardiovascular defects (0.5 expected) and one hypospadias (none expected). Only with the former 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.
Breast Feeding Summary
No reports describing the use of cloxacillin during lactation have been located. Because other penicillins are excreted in milk in low concentrations (e.g., see Ampicillin and Penicillin G), the presence of cloxacillin should also be expected. Although adverse effects from penicillins in breast milk are rare, three potential problems exist for the nursing infant: modification of bowel flora, direct effects on the infant (e.g., allergic response), and interference with the interpretation of culture results if a fever workup is required.
- Heinonen OP, Slone D, Shapiro S. Birth Defects and Drugs in Pregnancy. Littleton, MA:Publishing Sciences Group, 1977.