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Systemic availability of oral verapamil and effect on PR interval in man.
Author(s) -
Johnston A,
Burgess CD,
Hamer J
Publication year - 1981
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.1365-2125.1981.tb01233.x
Subject(s) - verapamil , medicine , pharmacology , interval (graph theory) , mathematics , calcium , combinatorics
1 The plasma levels of verapamil and its major metabolite norverapamil were related to its effect as a Ca‐antagonist on atrio‐ventricular (AV) conduction, judged from prolongation of the PR interval in six normal volunteers. 2 Intravenous administration (0.1 mg kg‐1) was compared to oral administration (120 mg) in each subject. 3 Intravenous verapamil showed a mean distribution half‐life (alpha) of 8.5 min and elimination half‐life (beta) of 2.0 h. The volume of distribution was about 112.1. Oral dosage gave an elimination half‐life of 2.7 h, and a norverapamil half‐life which averaged 4.6 h. The bioavailability of the oral dose averaged 22% (17 to 29%). 4 After the oral dose the percentage change in PR interval in the five appropriate subjects correlated significantly with the log plasma verapamil level (r = 0.732), but not with the log plasma norverapamil level (r = 0.078); norverapamil could not be detected after the intravenous dose. One subject developed Wenckebach type second degree AV block after each dose.