Relative bioavailability of (+/-)-verapamil hydrochloride administered in tablets and chewing gum

The absorption of verapamil administered orally in chewing gum (23.4-29.7 mg) and perorally in tablets (80 mg) to seven healthy volunteers in a study using an open cross-over design, was compared. Following peroral administration the mean +/- SD AUC/D was (5.4 +/- 1.9) x 10(-3) micrograms ml-1 h per microgram dose and after administration of chewing gum (6.6 +/- 2.3) x 10(-3) micrograms ml-1 h per microgram dose (NS). The AUC ratio of verapamil to the metabolite norverapamil was 1.5 after oral and 0.8 after peroral administration, indicating that a part of the verapamil administered in chewing gum was absorbed through the oral mucosa.