Bupropion in breast milk: an exposure assessment for potential treatment to prevent post-partum tobacco use.

OBJECTIVES To assess potential infant exposure to bupropion and its active metabolites in breast milk such as would occur during treatment to prevent post-partum relapse to tobacco use, and to compare the concentrations of bupropion in urine and saliva with plasma and breast milk. DESIGN AND SETTING Cohort study, outpatient clinical research centre. SUBJECTS Ten healthy post-partum volunteers who agreed to take bupropion for seven days, pump and discard their breast milk, and have samples of breast milk, plasma, saliva, and urine analysed. INTERVENTION Bupropion 150 mg a day for three days and then 300 mg a day for four days. MAIN OUTCOME MEASURES Concentrations of bupropion and its active metabolites (hydroxybupropion, erythrohydrobupropion, threohydrobupropion) in breast milk, plasma, saliva, and urine. Determination of average infant exposure. RESULTS The calculated average dosage of bupropion in breast milk was 6.75 microg/kg/day. Therefore, the average infant exposure is 0.14% of the standard adult dose of bupropion, corrected for the difference in body weight. Considering the sum of bupropion and its active metabolites, the average infant exposure is expected to be 2% of the standard maternal dose on a molar basis. The concentration of bupropion and its active metabolites in breast milk was not associated with age, body mass index, use of oral contraceptive pills, age of infant, or the frequency of breast feeding at the time the study was initiated. The coefficient of determination (r2) between the concentration of bupropion in breast milk and in urine was 0.77 (p < 0.01). CONCLUSIONS Bupropion and its active metabolites are present in the breast milk of lactating women. The concentrations of bupropion in breast milk and urine were highly correlated. These results indicate that the daily dose of bupropion and metabolites that would be delivered to an infant of a woman taking a therapeutic dose of bupropion is small. These results suggest that the effectiveness of bupropion to prevent post-partum relapse to tobacco use should be evaluated without excluding women who plan to breast feed.