Pharmacokinetic studies of the antiarrhythmic drugs ajmaline and N-propylajmaline bitartrate in dogs.

A rapid, sensitive fluorometric method for the determination of ajmaline and N-propylajmaline (NPA) was used to follow serum concentrations after an i.v. administration of ajmaline, after an oral administration of ajmaline, and an oral dose of NPA bitartrate (NPAB) in beagle dogs. Ajmaline was eliminated from serum with an apparent half-life of approximately 1 h and NPA with one of approximately 4 h. 1 h after i.v. and oral administration of 50 mg of ajmaline the serum levels were of the same order of magnitude. The bioavailability of oral ajmaline, calculated from the area under the serum concentration/time curves, was about 90%. The peak serum concentrations of ajmaline and NPA after a single oral dose of 50 mg of ajmaline and NPAB were about 1.4 microgram/ml and 0.6 microgram/ml, respectively, the latter calculated as its bitartrate, with about the same peak time: 1 h.