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Exposure to thiopurine drugs through breast milk is low based on metabolite concentrations in mother‐infant pairs
Author(s) -
Gardiner Sharon J.,
Gearry Richard B.,
Roberts Rebecca L.,
Zhang Mei,
Barclay Murray L.,
Begg Evan J.
Publication year - 2006
Publication title -
british journal of clinical pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.216
H-Index - 146
eISSN - 1365-2125
pISSN - 0306-5251
DOI - 10.1111/j.1365-2125.2006.02639.x
Subject(s) - breast milk , metabolite , infant formula , thiopurine methyltransferase , breast feeding , medicine , pharmacology , lactation , physiology , pregnancy , pediatrics , chemistry , biology , biochemistry , azathioprine , genetics , disease
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 × 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 (∼90% of caucasian patients) taking ‘normal’ doses.