Pharmacokinetics of the oral narcotic analgesic bezitramide and preliminary observations on its effect on experimentally induced pain.
The oral absorption of bezitramide 5 mg was studied in 7 human volunteers, using a specific radioimmuno-assay which measured both bezitramide and its active metabolite R-4618. A lag time of 0.5-1.0 h and a Cmax of 5.4 ng/ml plasma were found, the latter occurring 2.5-3.5 h after administration. The apparent elimination half-life varied from 11 to 24 h. Less than 0.3% of the dose was excreted unchanged in the urine. High concentrations in the faeces of some individuals indicate incomplete absorption and/or biliary secretion. The analgesic effect, using a standardized superficial electrical stimulation method, reached its maximum between 2.5 and 3.5 h after dosing, in accordance with the absorption phase. The duration of the effect was highly variable. Experiments in rats (n = 6, 3H-bezitramide 2.5 micrograms), demonstrated extensive biliary excretion (up to 70% of total radioactivity) and less than 3% of the label was removed by urinary excretion.
D000328:Adult; D000700:Analgesics / Q000378:metabolism* / Q000627:therapeutic use; D000818:Animals; D001562:Benzimidazoles / Q000378:metabolism* / Q000627:therapeutic use; D001646:Bile / Q000378:metabolism; D004558:Electric Stimulation; D006801:Humans; D007408:Intestinal Absorption; D007700:Kinetics; D008297:Male; D010146:Pain / Q000188:drug therapy*; D051381:Rats; D011919:Rats, Inbred Strains; D012684:Sensory Thresholds / Q000187:drug effects
D000700:Analgesics; D001562:Benzimidazoles; C004461:bezitramide