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April 3, 2006

Olanzapine and Breastfeeding

Filed under: Lactation,Pharmacology — mental1 @ 4:14 am

A colleague asked me about benztropine today in breastfeeding Mums because a client is on haloperidol. I asked why she wasn't on olanzapine.

Reply: "Because its contraindicated".

Not quite. The drug companies are covering their butts. For anyone that's interested, here's the useful article on olanzapine.

http://ajp.psychiatryonline.org/cgi/content/full/160/8/1428

The bottom line?

The median and maximum relative infant doses of approximately 1.0% and 1.2% indicate that infant exposure to olanzapine through milk is much less than the notional cutoff of 10.0% that has been used to guide drug safety during breast-feeding (26). This low infant exposure was confirmed by failure to detect olanzapine in the plasma of six suckling infants and the lack of observed side effects in seven infants. Of interest, our median milk-to-plasma ratio for olanzapine of 0.38 is identical to the theoretical milk-to-plasma ratio of 0.38 calculated by the method of Begg et al. (27). It is also similar to the mean of 0.46 measured by Croke et al. (16) from nine single-point milk and plasma concentrations measured in five patients. The time at which maximum olanzapine concentrations occurred in milk was slightly later in the dosing interval than the corresponding maximum concentration in plasma. Mothers trying to minimize infant exposure may wish to avoid breast-feeding at peak milk concentrations of the drug (i.e., 5 hours postdose). These data indicate that olanzapine may be considered relatively safe when mothers are breast-feeding healthy term infants. However, as always, risks and benefits should be considered before using any drug in breast-feeding mothers.

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