Chlorthalidone Pregnancy and Breastfeeding Warnings
Chlorthalidone is also known as: Hygroton, Thalitone
Chlorthalidone Pregnancy Warnings
A series of 211 pregnant women who were given chlorthalidone to prevent toxemia of pregnancy has been reported. Patients were entered into the study at gestation week 16, and were given chlorthalidone 50 mg once a day or placebo in a single-blinded fashion. There were significant decreases in the serum sodium and potassium in the treated patients, especially between gestation months four through nine. There appeared to be no benefit from the drug since there were no differences in blood pressure or the incidence of edema or proteinuria between the groups. The average height and weight of the offspring of treated patients was significantly higher; there were no deaths and no malformations. Placental weights were significantly greater among women who received chlorthalidone, but no differences in the amount or nature of amniotic fluid, placental calcification, or number of placental infarctions. The authors speculated whether the increased placental size in the treated group was related to alterations in glycogen metabolism. 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. 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 2 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. These data are considered pertinent to other thiazide diuretics. Cases of neonatal thrombocytopenia associated with antepartum administration of thiazide diuretics have been reported.
Chlorthalidone has been assigned to pregnancy category B by the FDA. Animal studies have failed to reveal evidence of teratogenicity. There are no controlled data in human pregnancy. Some retrospective reviews have shown an increased risk of malformations associated with thiazide diuretics. Chlorthalidone is only recommended during pregnancy when benefit outweighs risk.
Chlorthalidone Breastfeeding Warnings
Thiazides are excreted into human milk in low concentrations. 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.
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