Guanethidine / hydrochlorothiazide Pregnancy and Breastfeeding Warnings

Guanethidine / hydrochlorothiazide is also known as: Esimil

Guanethidine / 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. Neonatal thrombocytopenia associated with antepartum administration of thiazide diuretics has been reported.

Guanethidine has been assigned to pregnancy category C by the FDA. There are no data on the use of guanethidine during animal or human pregnancy. 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. Guanethidine-hydrochlorothiazide should only be given during pregnancy when benefit outweighs risk.

Guanethidine / hydrochlorothiazide Breastfeeding Warnings

The manufacturer states that guanethidine is excreted into human milk in small amounts. There are no data on the use of guanethidine during breast-feeding. 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 HCTZ milk concentration of 125 ng per mL was measured between 4 and 12 hours after a dose in a 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 average milk HCTZ level is approximately 80 ng per mL, the infant would be exposed to approximately 0.05 mg of 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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