Letters.

Drug Use in Pregnancy

There were several inaccuracies relating to the use of agents in pregnancy and breast feeding in "Drug Update: Recurrent Urinary Tract Infections in Women" (Sept. 15, 2002, p. 30).

It was stated that nitrofurantoin (Macrobid) is "generally safe, even during pregnancy." The product labeling, however, states that the drug should be avoided at term (38-42 weeks' gestation), during labor and delivery or when the onset of labor is imminent because of the risk of hemolytic anemia in newborns exposed in utero. I am not aware of any published research that states the risk of hemolytic anemia is low enough to ignore this warning.

The Drug Update stated that trimethoprim/sulfethoxazole (TMP/SMZ) should not be used "in late third trimester because of adverse effects on bilirubin levels. Don't use in breast-feeding women because sulfonamides are excreted in breast milk and can cause kernicterus."

The product information also notes that TMP/SMZ interferes with folic acid metabolism. In agreement, recent research has shown that there is a statistically significant increased risk for cardiovascular defects when TMP is used during the first trimester (N. Engl. J. Med. 343[22]:1608-14, 2000; N. Engl. J. Med. 344[12]:934-35, 2001).

In addition, there have been reports of neural tube defects thought to be secondary to the antifolate activity of TMP (Eur. J. Obstet. Gynecol. Reprod. Biol. 93[2]:215-17, 2000).

Finally, in regard to TMP alone, I don't know where the information came from to support the statement, "Don't use in late third trimester of pregnancy or in breast-feeding women."