Excretion of verapamil in human milk

The concentration of verapamil in milk and serum was determined in samples taken within the same hour 3-5 days after delivery of a 25 year old women treated with verapamil (Isoptin) 240 mg daily for paroxysmal supraventricular tachycardia. The average concentration of verapamil in milk was found to be 23% of that in serum, and the total excretion in milk was less than 0,01% of the administered dose.