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Disopyramide Pregnancy and Breastfeeding Warnings

Disopyramide is also known as: Norpace, Norpace CR

Disopyramide Pregnancy Warnings

The use of disopyramide is considered relatively safe during human pregnancy, but data are limited and most experts do not recommend it as routine or first-line antiarrhythmic therapy during pregnancy. Disopyramide and its main metabolite, MND, cross the human placenta. Data reveal umbilical cord blood disopyramide levels ranging from 26% to 78% of the corresponding maternal plasma levels. There are case reports of uterine contractions without vaginal bleeding or cervical changes within one to two hours after disopyramide administration. These contractions resolved upon discontinuation of therapy. In one study of 10 pregnant women at term who were given disopyramide 150 mg every 6 hours for 48 hours, 8 delivered within 48 hours, compared to none in a placebo group. It is not known whether disopyramide has immediate or delayed adverse effects on the fetus, or whether it prolongs the duration of labor or increases the need for forceps delivery or other obstetric intervention.

Disopyramide has been assigned to pregnancy category C by the FDA. Animal studies failed to reveal evidence of teratogenicity, but have shown decreased implantation sites and decreased pup growth and survival at dosages at least 20 times the recommended daily human dosage. Animal studies have also revealed increased resorption rates at dosages equal to or greater than 5 times the recommended daily human dosage. There are no controlled studies in human pregnancy. Disopyramide should be given during pregnancy only when benefit outweighs risk.

Disopyramide Breastfeeding Warnings

Disopyramide is excreted into human milk. The primary metabolite, MND, is excreted into and concentrates in human milk. There are no reports of adverse effects in nursing infants of mothers with therapeutic disopyramide plasma levels. The American Academy of Pediatrics considers disopyramide to be compatible with breast-feeding.

Average milk to maternal plasma disopyramide concentration ratios of approximately 1:1 and 6:1 for the parent drug and MND, respectively, have been reported. There were no measurable amounts of either disopyramide or MND in the nursing infants, and no adverse effects were observed. Disopyramide and MND were detected in the urine of one infant whose plasma disopyramide levels were undetectable (assay sensitivity 0.45 mcg/mL).

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