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Amiloride / hydrochlorothiazide Pregnancy and Breastfeeding Warnings

Amiloride / hydrochlorothiazide is also known as: Moduretic, Moduretic 5-50

Amiloride / hydrochlorothiazide Pregnancy Warnings

Amiloride-hydrochlorothiazide has been assigned to pregnancy category B by the FDA. Animal studies have revealed no evidence of teratogenicity or impaired fertility, although reduced maternal weight gain during and after gestation has been observed in rats that were given 25 times the maximum recommended human dose (on a per kg basis). There are no controlled data in human pregnancy, although retrospective reviews have shown an increased risk of malformations associated with thiazide diuretics. Amiloride-hydrochlorothiazide should only be given during pregnancy when need has been clearly established.

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, such as 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 study 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. Three cases of amiloride exposure during pregnancy have been reported. In one, gross fetal malformations were observed following a voluntary abortion in a woman who had received amiloride, captopril, and propranolol during her first trimester. Since angiotensin converting enzyme inhibitors are known teratogens, the defects were attributed to captopril. In two other cases a normal pregnancy and mild intrauterine growth retardation were reported in women treated for Bartter's syndrome and atrial fibrillation, respectively. Both infants were healthy and normal at birth.

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Amiloride / hydrochlorothiazide Breastfeeding Warnings

A case report in which a mother taking hydrochlorothiazide (HCTZ) 50 mg daily resulted in a peak milk concentration of 125 ng per mL between 4 and 12 hours after her daily dose. 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.

There are no data on the excretion of amiloride into human milk; however, hydrochlorothiazide is excreted into human milk in low concentrations. Adverse effects in the nursing infant are unlikely, therefore, hydrochlorothiazide is considered compatible with breast-feeding by the American Academy of Pediatrics. The manufacturer, however, 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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References for pregnancy information

  1. Rodriguez SU, Sanford LL, Hiller MC "Neonatal thrombocytopenia associated with ante-partum administration of thiazide drugs." N Engl J Med 270 (1964): 881-4
  2. Heinonen O, Slone D, Shapiro S; Kaufman DW ed. "Birth Defects and Drugs in Pregnancy." Littleton, MA: Publishing Sciences Group, Inc. (1977): 297
  3. Lindheimer MD, Katz AI "Sodiuim and diuretics in pregnancy." N Engl J Med 288 (1973): 891-4
  4. Robson DJ, Raj MV, Storey GC, Holt DW "Use of amiodarone during pregnancy." Postgrad Med J 61 (1985): 75-7
  5. Almeida O, Spinnato J "Maternal Bartter's syndrome and pregnancy." Am J Obstet Gynecol 160 (1989): 1225-6
  6. "Product Information. Moduretic (amiloride-hydrochlorothiazide)." Merck & Co, Inc, West Point, PA.

References for breastfeeding information

  1. "Product Information. Moduretic (amiloride-hydrochlorothiazide)." Merck & Co, Inc, West Point, PA.
  2. Werthmann MW, Krees SV "Excretion of chlorothiazide in human breast milk." J Pediatr 81 (1972): 781-3
  3. Miller ME, Cohn RD, Burghart PH "Hydrochlorothiazide disposition in a mother and her breast-fed infant." J Pediatr 101 (1982): 789-91

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