J. Kienlen et al., PHARMACOKINETICS OF ALFENTANIL IN PATIENTS TREATED WITH EITHER CIMETIDINE OR RANITIDINE, Drug investigation, 6(5), 1993, pp. 257-262
The pharmacokinetics of alfentanil were studied after single dose intr
avenous administration of 125 mug/kg to 19 intensive care unit patient
s who were divided into 3 groups. Group I was given oral antacid, and
groups II and III were given, respectively, cimetidine 1200 mg/day IV
and ranitidine 300 mg/day IV for 48 hours before administration of alf
entanil. Alfentanil plasma concentrations were determined over the 8 h
ours following drug administration using a radio immunoassay. Pharmaco
kinetic parameters were calculated using a noncompartmental analysis.
In group II, alfentanil plasma concentrations were significantly highe
r than in the other groups. In addition, significant changes involving
the elimination half-life (142.3 +/- 35 vs 81.14 +/- 11 and 88.1 +/-
33 minutes), total clearance (1.27 +/- 0.5 vs 3.56 +/- 1.17 and 2.74 /- 1 ml/kg/min) and total volume of distribution related to the pseudo
distribution phase (226 +/- 73 vs 336 +/- 76 and 271 +/- 61 ml/kg) we
re found in group II vs groups I and III. These results suggest that p
retreatment with cimetidine alters alfentanil pharmacokinetics after s
ingle dose administration. In contrast, ranitidine does not appear to
have a significant effect.