[Pharmacokinetics and pharmacodynamics of verapamil in healthy volunteers after single oral and sublingual administration]. / Pharmakokinetik und Pharmakodynamik von Verapamil bei gesunden Versuchspersonen nach einmaliger oraler und sublingualer Applikation.

ABSTRACT

5-[3,4-Dimethoxyphenethyl)-methylamino]-2-(3,4-dimethoxyphenyl)-2- isopropylvaleronitril (verapamil, Isoptin) was administered p.o. (80 mg) and via the sublingual route (20 mg as the hydrochloride) in 6 healthy volunteers. After p.o. administration the mean peak serum concentration of 125.6 ng/ml was attained on average 80 min later. The half-life for the distribution phase (t1/2a) was 0.95 h and for the elimination phase (t1/2 beta) 6.08 h. After sublingual administration the mean peak serum concentration of verapamil was 26 ng/ml attained on average after 71.7 min. The mean t1/2a was 0.73 h and the mean T1/2 beta 4.39 h. There was an 18.4 min delay after oral administration and 0.8 min delay after sublingual administration before verapamil was detected in the serum. The relative bioavailability of verapamil sublingually was 2.7 (p.o. = 1.0). There were close correlations between the verapamil concentration in serum and the prolongation of the PQ-interval (0.725 sublingually; 0.853 p.o.). Approximately three times higher concentrations of verapamil were required when given by the oral route to produce the same prolongation of the PQ-interval obtained with sublingual administration. The variability of several important pharmacokinetic parameters of verapamil was reduced by sublingual application in comparison to the oral route. The coefficient of variation for the peak concentration, time to peak and t1/2 beta were 49.7%, 25.0% and 26.4%, respectively, after sublingual administration in comparison to 120.6%, 54.7% and 68.9%, respectively, when given p.o.