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The effects of diltiazem on hepatic drug metabolizing enzymes in man using antipyrine, trimethadione and debrisoquine as model substrates.
Author(s) -
Sakai H.,
Kobayashi S.,
Hamada K.,
Iida S.,
Akita H.,
Tanaka E.,
Uchida E.,
Yasuhara H.
Publication year - 1991
Publication title -
british journal of clinical pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.216
H-Index - 146
eISSN - 1365-2125
pISSN - 0306-5251
DOI - 10.1111/j.1365-2125.1991.tb05543.x
Subject(s) - debrisoquine , diltiazem , chemistry , volume of distribution , excretion , pharmacology , pharmacokinetics , medicine , cytochrome p450 , endocrinology , metabolism , cyp2d6 , calcium , biochemistry
Six healthy male subjects were given single oral doses of antipyrine (7 mg kg‐1), trimethadione (4 mg kg‐1) and debrisoquine (10 mg) before and during diltiazem treatment (30 mg three times daily orally for 8 days). Antipyrine clearance decreased from 33.7 +/‐ 9.1 to 22.5 +/‐ 4.9 ml min‐ 1 (P less than 0.05, mean +/‐ s.e. mean) after diltiazem treatment without any significant change in apparent volume of distribution (0.59 +/‐ 0.06 to 0.60 +/‐ 0.04 1 kg‐1), resulting in an increase in antipyrine elimination half‐life from 13.4 +/‐ 4.8 to 19.7 +/‐ 3.2 h (P less than 0.05). The formation clearance of antipyrine to 4‐ hydroxyantipyrine was decreased significantly from 10.8 +/‐ 2.7 to 6.6 +/‐ 2.7 ml min‐1 (P less than 0.05), while that to 3‐ hydroxymethylantipyrine and norantipyrine was not altered by diltiazem. The metabolic ratio of debrisoquine (urinary excretion of debrisoquine/4‐hydroxydebrisoquine) was increased significantly from 0.70 +/‐ 0.05 to 1.95 +/‐ 0.20 (P less than 0.05), while that of trimethadione (serum concentration of dimethadione/trimethadione) was not changed significantly (0.48 +/‐ 0.08 vs 0.41 +/‐ 0.06) after diltiazem treatment. Diltiazem selectively inhibits cytochrome P‐450 isoenzymes.