Flecainide excretion in human breast milk

• Published in: Clinical pharmacology and therapeutics Vol. 48; no. 3; p. 262
• Main Authors: McQuinn, R L, Pisani, A, Wafa, S, Chang, S F, Miller, A M, Frappell, J M, Chamberlain, G V, Camm, A J
• Format: Journal Article
• Language: English
• Published: United States 01.09.1990
• Subjects: Adolescent; Adult; Biological Availability; Flecainide - analysis; Flecainide - blood; Flecainide - pharmacokinetics; Humans; Milk, Human - analysis; Postpartum Period
• ISSN: 0009-9236
• DOI: 10.1038/clpt.1990.148

Healthy human volunteers who intended not to breast feed were placed on a regimen of 100 mg oral flecainide every 12 hours for 5 1/2 days beginning 1 day after parturition. Milk and blood samples were collected during the dosing period and for 2 days after the last dose. Concentrations of flecainide in milk and plasma were assayed by HPLC. Apparent steady-state levels of flecainide in both milk and plasma were achieved in most cases by day 4 of the study. Highest daily average concentration of flecainide in milk ranged from 270 to 1529 ng/ml for the 11 subjects. Mean +/- SD milk to plasma flecainide ratios were 3.7 +/- 3.5, 3.2 +/- 2.3, 3.5 +/- 2.1, and 2.6 +/- 0.7 on study days 2, 3, 4, and 5, respectively. After the last dose of flecainide, peak milk levels of the drug occurred at 3 to 6 hours and then declined monoexponentially. The half-life for elimination of flecainide from milk was 14.7 +/- 3.5 hours and is very similar to the plasma elimination half-life of flecainide in healthy human subjects. The mean milk to plasma ratios for flecainide after the last dose were 2.3 +/- 1.0 and 2.9 +/- 1.1 at 24 and 48 hours after the dose, respectively. Based on the pharmacokinetics of flecainide in infants, the expected average steady-state plasma concentration of flecainide in a newborn infant consuming all of the milk production of its mother (approximately 700 ml/day) would not be expected to exceed about 62 ng/ml.