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. 2006 Oct;62(4):453-6.
doi: 10.1111/j.1365-2125.2006.02639.x.

Exposure to thiopurine drugs through breast milk is low based on metabolite concentrations in mother-infant pairs

Sharon J Gardiner  1 , Richard B Gearry, Rebecca L Roberts, Mei Zhang, Murray L Barclay, Evan J Begg
Affiliations

Exposure to thiopurine drugs through breast milk is low based on metabolite concentrations in mother-infant pairs

Sharon J Gardiner et al. Br J Clin Pharmacol. 2006 Oct.

Abstract

Aims: To determine infant exposure to 6-thioguanine and 6-methylmercaptopurine nucleotides (6-TGN and 6-MMPN, respectively) during maternal use of azathioprine in breastfeeding.

Methods: Mother-infant pairs provided blood for determination of 6-TGN and 6-MMPN concentrations, and TPMT genotype.

Results: Four women taking azathioprine 1.2-2.1 mg kg(-1) day(-1) and their infants were studied. All had the wild-type TPMT genotype. Maternal 6-TGN and 6-MMPN concentrations ranged from 234 to 291 and 284 to 1178 pmol per 8 x 10(8) red blood cells, respectively, and were consistent with those associated with improved therapeutic outcomes. Neither 6-TGN nor 6-MMPN was detected in any of the infants, despite a sensitive assay.

Conclusions: The data suggest that azathioprine may be 'safe' during breastfeeding in patients with the wild-type TPMT genotype ( approximately 90% of caucasian patients) taking 'normal' doses.

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