The excretion of ketorolac tromethamine into breast milk after multiple oral dosing.

We have studied the transfer of the analgesic ketorolac tromethamine into breast milk in ten women aged between 22 and 35 years. Ketorolac administration was started between 2 and 6 days after delivery. The breast milk was not fed to the infant because of maternal antibiotic use (6 patients) or because of jaundice of the baby. 10 mg of ketorolac was given four times daily for two days. Plasma and milk samples were collected on the two dosing days and on the first day after dosing. The plasma and milk were assayed for ketorolac concentrations by HPLC: the quantification limits were 10 ng.ml-1 and 5 ng.ml-1 respectively. The maternal plasma concentrations were within established ranges for ketorolac. In four patients the concentration of ketorolac in the milk was never above 5 ng.ml-1. At 2 h after dosing on both Days 1 and 2 there were quantifiable concentrations of ketorolac in the milk. The range was 5.2 ng.ml-1 to 7.9 ng.ml-1. The ratio of breast milk: plasma concentrations of ketorolac ranged from 0.015 to 0.037. The maximum potential amount of ketorolac that an infant may be exposed to daily could range from 3.16 mg to 7.9 mg, assuming a consumption of between 400 ml and 1 l of breast milk. On a weight-adjusted basis this is equivalent to between 0.16% and 0.40% of the total daily maternal dose.