We have studied the disposition of
alfentanil in six patients (who had suffered 10-30% surface area
burns 5-21 days previously) undergoing surgical
debridement and grafting and compared the data with those from a control group of six patients matched for age, sex and weight undergoing body surface surgery of similar duration. Plasma samples were collected up to 480 min after an i.v. bolus of
alfentanil 50 micrograms kg-1.
Drug concentrations were measured by radioimmunoassay and
alfentanil binding to
plasma proteins by equilibrium dialysis. The
burns patients had significantly greater concentrations of alpha-1-acid
glycoprotein (AAG) and smaller concentrations of
albumin. The mean protein binding of
alfentanil was 94.2 (SEM 0.05)% in the
burns group and 90.7 (0.4)% in the control group (P = 0.004). There was a good correlation between AAG concentration and protein binding (r = 0.8). The volume of distribution and total clearance of
alfentanil were reduced significantly in the
burns group. The clearance of the unbound fraction and the elimination half-life of
alfentanil were not decreased significantly.