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Hydrochlorothiazide Pregnancy and Breastfeeding Warnings

Hydrochlorothiazide is also known as: Aquazide H, Carozide, Diaqua, Esidrix, Ezide, Hydro Par, HydroDIURIL, Loqua, Microzide, Oretic

Hydrochlorothiazide Pregnancy Warnings

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. 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. Data from the Michigan Medicaid Birth Defects Study has revealed an association between the use of hydrochlorothiazide (HCTZ) and congenital abnormalities (written communication, Franz Rosa, MD, Food and Drug Administration, 1994). This was a retrospective study of 229,101 completed pregnancies between 1985 and 1992, of which 567 were exposed to HCTZ at some time during the first trimester, and 1,173 were exposed to the drug at any time during pregnancy. Of the 567 pregnancies, there were 24 total and 7 cardiovascular birth defects (22 and 6 were expected, respectively). There were no observations of cleft palate, spina bifida, limb reduction, or hypospadias. The one instance of polydactyly did not achieve statistical significance. These data are consistent with an association between the use of HCTZ and birth defects, although other factors, including underlying disease(s) of the mother are not accounted for. Cases of neonatal thrombocytopenia associated with antepartum administration of thiazide diuretics have been reported.

Hydrochlorothiazide has been assigned to pregnancy category B by the FDA. Animal studies have failed to reveal evidence of fetal harm. There are no data from controlled human studies, but retrospective reviews have shown an increased risk of malformations associated with thiazide diuretics. The drug should be used during pregnancy only if clearly needed.

Hydrochlorothiazide Breastfeeding Warnings

Hydrochlorothiazide (HCTZ) is secreted into human milk in low concentrations. Adverse effects in the nursing infant are unlikely. HCTZ is considered compatible with breast-feeding by the American Academy of Pediatrics; however, the manufacturer recommends that due to the potential for serious adverse reactions in nursing infants, a decision should be made to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother.

In one case, a peak milk HCTZ concentration of 125 ng/mL was measured between 4 and 12 hours after a (usual daily) dose of HCTZ 50 mg in one subject. A simultaneously measured maternal serum HCTZ level was approximately 275 ng/mL. There were no detectable drug levels or electrolyte abnormalities in the baby's blood. The authors calculated that, if a 1-month-old infant takes approximately 600 mL of milk per day, and the average milk HCTZ level is approximately 80 ng/mL, the infant would be exposed to approximately 0.05 mg HCTZ a day. This usually represents an insignificant amount of HCTZ to the infant as adverse effects in the nursing infant are unlikely.

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