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The kinetic profile of diltiazem, a novel calcium antagonist, was studied in 12 volunteers following oral (60 mg) and intravenous (15 mg) administration. After i.v. administration biphasic elimination was observed, with a distribution half-life of 0.3 +/- 0.2 h and an elimination half-life of 3.1 +/- 1.0 h; the apparent volume of distribution was 5.3 +/- 1.71/kg and the total clearance was 1.28 +/- 0.48 l/kg/h. After the oral dose the elimination had a half-life of 3.2 +/- 1.3 h. The absolute bioavailability of diltiazem ranged from 24 to 74% (mean 42 +/- 18%). The interindividual variation may be explained by a variable first pass effect.

WORDS: human urinary steroids , methoxime-t rimethyls ilyl derivatives, gas chromatography, mass s p e c t r o m e t r y ABSTRACT Sterically hindered 1 7~-h y d r o x y l groups in steroids a r e silylated by trimethylsilylimidazole (TSIM) a t 100' C . Decreasing rates of reaction w e r e found for the following s t r u c t u r e s : 17a, 20p, 21-trio1 > 17a, 20a-diol > 17a, 2 0 a , 21-triol. When methoxime derivatives a r e formed a s the f i r s t s t e p , HC1 present in the excess of reagent catalyses the silylation reaction of hydroxyl groups. A simple procedure i s described whereby methoxime (MO) derivatives a r e formed in 15 minutes a t boo C (the 11-one group does not react under these conditions) and persilylated compounds a r e then prepared in 2 hours a t 100 0 C by reaction with t r imethyls ilylimidazole .