Drugs in Pregnancy and Lactation: Tenth Edition

PHENAZOPYRIDINE

Urinary Tract Agent (Analgesic)

PREGNANCY RECOMMENDATION: Compatible

BREASTFEEDING RECOMMENDATION: Contraindicated

PREGNANCY SUMMARY

No reports linking the use of phenazopyridine with congenital defects have been located. There are no relevant animal reproduction data. However, the human pregnancy experience suggest low risk for the embryo–fetus.

FETAL RISK SUMMARY

The Collaborative Perinatal Project monitored 50,282 mother–child pairs, 219 of whom had 1st trimester exposure to phenazopyridine (1, pp. 299–308). For use anytime during pregnancy, 1109 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. A brief 2008 review of urinary tract infections in pregnancy also cited the above data (2).

In a surveillance study of Michigan Medicaid recipients involving 229,101 completed pregnancies conducted between 1985 and 1992, 496 newborns had been exposed to phenazopyridine during the 1st trimester (F. Rosa, personal communication, FDA, 1993). A total of 27 (5.4%) major birth defects were observed (21 expected), including (observed/expected) 7/5 cardiovascular defects and 1/1 oral cleft. No anomalies were observed in four other defect categories (spina bifida, polydactyly, limb reduction defects, and hypospadias) for which specific data were available. These data do not support an association between the drug and congenital defects.

It is not known if phenazopyridine crosses the human placenta. The molecular weight (about 214 for the free base) suggests that the drug will cross to the embryo–fetus.

In a large 1985 study involving 6509 women with live births, 217 were exposed to phenazopyridine in the 1st trimester (3). One infant had a congenital disorder. Although the defect was not described, the incidence (0.5%) was very low.

BREASTFEEDING SUMMARY

No reports describing the use of phenazopyridine during human lactation have been located. The molecular weight (about 214 for the free base) suggests that the drug will be excreted into breast milk. Because phenazopyridine can cause methemoglobinemia, sulfhemoglobinemia, and hemolytic anemia, it should not be used during breastfeeding, especially with an infant under 1 month of age or with G-6-PD deficiency (4).

References

1.Heinonen OP, Slone D, Shapiro S. Birth Defects and Drugs in Pregnancy. Littleton, MA: Publishing Sciences Group, 1977.

2.Lee M, Bozzo P, Einarson A, Koren G. Urinary tract infections in pregnancy. Can Fam Physician 2008;54:853–4.

3.Aselton P, Jick H, Milunsky A, Hunter JR, Stergachis A. First-trimester drug use and congenital disorders. Obstet Gynecol 1985;65:451–5.

4.Phenazopyridine. September 7, 2013. Available at NIH LactMed database at http://toxnet.nih.nih.gov/cgi-bin/sis/search/f?./temp/~jTTJoI:1. Accessed March 19, 2014.