Transfer of the antidepressant mirtazapine into breast milk

Authors

  • J. H. Kristensen,

    1. Pharmacy Department, Women’s and Children’s Health Service, Subiaco, 1Pharmacology and Anaesthesiology Unit, School of Medicine and Pharmacology, University of Western Australia, Crawley,2Clinical Pharmacology & Toxicology Laboratory, PathWest Laboratory Medicine, Nedlands,3Department of Psychological Medicine, and4Department of Neonatal Services, Women’s and Children’s Health Service, Subiaco, Australia
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  • Kenneth F. Ilett,

    Corresponding author
    1. Pharmacy Department, Women’s and Children’s Health Service, Subiaco, 1Pharmacology and Anaesthesiology Unit, School of Medicine and Pharmacology, University of Western Australia, Crawley,2Clinical Pharmacology & Toxicology Laboratory, PathWest Laboratory Medicine, Nedlands,3Department of Psychological Medicine, and4Department of Neonatal Services, Women’s and Children’s Health Service, Subiaco, Australia
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  • 1,2 Jonathan Rampono,

    1. Pharmacy Department, Women’s and Children’s Health Service, Subiaco, 1Pharmacology and Anaesthesiology Unit, School of Medicine and Pharmacology, University of Western Australia, Crawley,2Clinical Pharmacology & Toxicology Laboratory, PathWest Laboratory Medicine, Nedlands,3Department of Psychological Medicine, and4Department of Neonatal Services, Women’s and Children’s Health Service, Subiaco, Australia
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  • 3 Rolland Kohan,

    1. Pharmacy Department, Women’s and Children’s Health Service, Subiaco, 1Pharmacology and Anaesthesiology Unit, School of Medicine and Pharmacology, University of Western Australia, Crawley,2Clinical Pharmacology & Toxicology Laboratory, PathWest Laboratory Medicine, Nedlands,3Department of Psychological Medicine, and4Department of Neonatal Services, Women’s and Children’s Health Service, Subiaco, Australia
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  • and 4 L. Peter Hackett 2

    1. Pharmacy Department, Women’s and Children’s Health Service, Subiaco, 1Pharmacology and Anaesthesiology Unit, School of Medicine and Pharmacology, University of Western Australia, Crawley,2Clinical Pharmacology & Toxicology Laboratory, PathWest Laboratory Medicine, Nedlands,3Department of Psychological Medicine, and4Department of Neonatal Services, Women’s and Children’s Health Service, Subiaco, Australia
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Emeritus Professor K. F. Ilett, Pharmacology and Anaesthesiology Unit, M510, School of Medicine and Pharmacology, University of Western Australia, Crawley, 6009 Western Australia.
Tel: + 618 9346 2985
Fax: + 618 9346 3469
E-mail:ken.ilett@uwa.edu.au

Abstract

What is already known about this subject

• There is presently only a single case report on mirtazapine transfer into breast milk and its effects in the breast-fed infant.

What this study adds

• Most importantly, we have provided quantitative data on the absolute and relative infant doses of mirtazapine and its active metabolite.

• We have also documented a lack of overt adverse effects in the breast-fed infants and low or absent plasma concentrations of mirtazapine in a subset of these infants.

• Hence we now know that breast-fed infants are unlikely to be adversely affected when their mothers need to take mirtazapine.

Aims

To investigate the transfer of mirtazapine and desmethylmirtazapine into milk and to calculate dose to the infant via milk.

Methods

Plasma and milk samples were obtained from eight breast-feeding women who were taking a median dose of 38 mg mirtazapine per day. Milk/plasma ratio (M/P) and infant doses were estimated by standard methods. The infants were examined clinically and in four infants blood was taken for analysis.

Results

Mean (95% confidence interval) relative infant doses for mirtazapine and desmethylmirtazapine (n = 8) were 1.5% (0.8, 2.2) and 0.4% (0.2, 0.6) respectively. The mean M/P (area under curve n = 4, single or paired samples n = 3) was 1.1 (0.7,1.5) for mirtazapine and 0.6 (0.5, 0.7) for desmethylmirtazapine. No adverse effects were seen. Mirtazapine was detected (1.5 µg l−1) in only one of four infants tested.

Conclusion

We suggest that mirtazapine use by lactating women is safe for the breast-fed infant. Nevertheless, each decision to breast feed should always be made on the basis of an individual risk/benefit analysis.

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