Hydrochlorothiazide / methyldopa Pregnancy and Breastfeeding Warnings
Hydrochlorothiazide / methyldopa Pregnancy Warnings
Methyldopa crosses the placenta and may cause mild hypotension in neonates of treated mothers. Because it has been safely and successfully used to treat hypertension during pregnancy, some experts consider it to be the drug of choice for the treatment of nonemergent hypertension during pregnancy. Of 3,248 children with any malformation related to a diuretic or a drug taken for a cardiovascular disorder from a population of 50,282 mother-child pairs in the Collaborative Perinatal Project (CPP), only one case associated with methyldopa was monitored, and no abnormalities were observed. An infant born with congenital heart disease, esophageal atresia, an absent kidney, and hypospadias whose mother received methyldopa throughout her pregnancy and clomiphene in the first trimester has been reported. In one study a decrease in mean head circumference of 202 neonates of mothers who were begun on methyldopa during gestation weeks 16 and 20 has been reported. Long-term follow-up of 98% of these children has not revealed abnormalities, and the developmental delay seen in children of hypertensive mothers was less in children whose mothers received methyldopa than in children of untreated mothers. A review of 1,157 hypertensive pregnancies has revealed no evidence of teratogenicity or fetotoxicity associated with methyldopa. The Michigan Medicaid surveillance study showed no association between the use of methyldopa 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 120 of 104,000 pregnant women from 1980 to 1983, and one in which 242 of 229,101 pregnant women from 1985 to 1992 received methyldopa during pregnancy. Eight and 11 total defects were observed in these studies, respectively (8 and 10 were expected, respectively). The one instance each of cardiovascular defects, cleft palate, and polydactyly in the second study did not achieve statistical significance. These data do not support an association between methyldopa and congenital defects. The various features of the fetal heart rate pattern, as evaluated in a controlled trial by computerized cardiotocography in human pregnancy, were not influenced by methyldopa 250 mg three times a day in 19 women with preeclampsia. Of the 50,282 mother-child pairs from the CPP, 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. This report is a summary of two studies, one in which 390 of 104,000 pregnant women from 1980 to 1983, and one in which 567 of 229,101 pregnant women from 1985 to 1992 received a related drug, hydrochlorothiazide (HCTZ). In the first study 29 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-type diuretics. Cases of neonatal thrombocytopenia associated with antepartum administration of thiazide diuretics have been reported.
Methyldopa-hydrochlorothiazide (HCTZ) has been assigned to pregnancy category C by the FDA. Animal studies have failed to reveal evidence of teratogenicity or fetotoxicity. Some retrospective reviews have shown an increased risk of malformations associated with thiazide diuretics. There are no controlled data from human pregnancy. Methyldopa-HCTZ should only be given during pregnancy when there are no alternatives and benefit outweighs risk.
Hydrochlorothiazide / methyldopa Breastfeeding Warnings
Both methyldopa and hydrochlorothiazide (HCTZ) are excreted into human milk. Adverse effects in the nursing infant are unlikely. Hydrochlorothiazide and methyldopa are 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.
Limited data from four nursing women who were taking methyldopa 750 to 2,000 mg per day reveal milk concentrations ranging from 0.1 to 0.9 mcg per mL. A peak milk HCTZ level of 125 ng per mL was measured between 4 and 12 hours after a dose in one woman who was taking HCTZ 50 mg per day. A simultaneously measured maternal serum HCTZ level was approximately 275 ng per 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 mean milk HCTZ level is approximately 80 ng per mL, the infant would be exposed to approximately 0.05 mg HCTZ daily. This should represent an insignificant amount of HCTZ to the infant such that adverse effects in the nursing infant are unlikely.
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