Benzthiazide Pregnancy and Breastfeeding Warnings

Brand names: Exna

Benzthiazide Pregnancy Warnings

Benzthiazide has been assigned to pregnancy category C by the FDA. Animal data have failed to reveal evidence of an embryocidal effect after doses several hundred times the human dose were given to rats. The manufacturer states that benzthiazide can cause fetal harm when administered to a pregnant woman. Fetal or neonatal jaundice has been reported. There are no controlled data from human pregnancy. Some retrospective reviews have shown an increased risk of malformations associated with thiazide diuretics. Benzthiazide should only be given during pregnancy when there are no alternatives and benefits outweigh risks, keeping in mind that the use of benzthiazide during pregnancy in patients without heart disease is considered contraindicated by some experts.

Thiazides readily cross the human placenta, with umbilical cord blood thiazide levels approximately equivalent to those in maternal plasma.

The Collaborative Perinatal Project monitored 50,282 mother-child pairs, of whom 233 were exposed to thiazide or related diuretics during the first trimester. An increased risk of malformations was found for thiazide diuretics, although the fact that the population studied had underlying cardiovascular disease makes implication of drug use alone difficult. Use of thiazides after the first trimester does not seem to carry this risk. Thiazide diuretics may, however, pose metabolic risks to the mother and fetus (hyponatremia, hypokalemia, thrombocytopenia, hyperglycemia), and may have a direct effect on smooth muscle, resulting in inhibition of labor.

The Michigan Medicaid surveillance study showed no association between some thiazide diuretics and congenital defects (written communication, Franz Rosa, MD, Food and Drug Administration, 1994). This report is a summary of information from two studies, one in which 390 of 104,000 pregnant women from 1980 to 1983, and one in which 567 of 229,000 pregnant women from 1985 to 1992 received a related drug, hydrochlorothiazide (HCTZ). In the first study 28 total defects and 6 cardiovascular defects were observed (25 and 4 were expected, respectively). In the second study, 24 total defects and 7 cardiovascular defects were observed (22 and 6 were expected, respectively). Cleft palate was not observed in either study. These data do not support an association between HCTZ and congenital defects, and are considered pertinent to other thiazide diuretics.

Cases of neonatal thrombocytopenia associated with antepartum administration of thiazide diuretics have been reported.

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Benzthiazide Breastfeeding Warnings

There are no data on the excretion of benzthiazide into human milk. Many other thiazides are excreted into human milk in low concentrations. While a rare case of thrombocytopenia has been reported in one nursing infant whose mother was taking a related drug, chlorothiazide, adverse effects in the nursing infant are unlikely. Some thiazides are considered compatible with breast-feeding by the American Academy of Pediatrics.

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Further information

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