Mexiletine in human blood and breast milk

Abstract

Twelve paired samples of breast milk and blood were obtained, between the 2nd and 5th days after she had given birth, from a 30-year-old woman who was on 8-hourly propranolol (20 mg) and mexiletine (200 mg). Propranolol was detectable in 9 of the samples of blood and in only 4 of the milk samples. Mexiletine was measurable in all samples, and the milk: plasma ratio varied between 0'78 and 1-89 with a mean of 1-45. However, the large volume of distribution of mexiletine makes it unlikely that the small dose of the drug received from the milk would be detrimental to the health of infants. © 1981 The Fellowship of Postgraduate Medicine.