DISTRIBUTION AND EXCRETION OF SUMATRIPTAN IN HUMAN-MILK

1 The excretion of a 6 mg subcutaneous dose of sumatriptan in breast m ilk was studied in five lactating volunteer subjects with a mean age o f 27.6 years and a mean body weight of 75 kg. Drug concentrations in m ilk and plasma over the ensuing 8 h were measured by high-performance liquid chromatography. 2 The mean milk:plasma ratio estimated from the areas under the milk and plasma concentration-time curves (AUC) was 4 .9 (95% CI 4.1-5.7), indicating a significant transfer of sumatriptan into the milk compartment. 3 The mean total recovery of drug in milk w as estimated to be only 14.4 mu g (95% CI 6.1-22.7 mu g), or 0.24% of the 6 mg administered dose. On a weight-adjusted basis this correspond ed to a mean infant exposure of 3.5% of the maternal dose (95% CI 0.3- 6.7%). 4 If oral bioavailability in the infant is similar to that in a dults (14%), the weight-adjusted infant dose is reduced to 0.49%. Furt hermore, allowance for reduced clearance in the infant predicts an inf ant exposure varying from 4.9% in a very premature neonate to 0.7% in a 30 week old infant. 5 Since sumatriptan is usually administered as a single dose at infrequent intervals, the low level of excretion in br east milk suggests that continued breast feeding following its use wil l not pose a significant risk to the suckling infant. Even this minor exposure could be largely avoided by expressing and discarding all mil k for 8 h after the dose.