Dose-response effect of intrathecal alfentanil on canine lower urinary tract dynamics.

The effect of intrathecal (IT) administration of three different doses (1, 2.5, and 5 μg/kg) of alfentanil on lower urinary tract dynamics was examined by urodynamic studies, cystometrograms (CMG), and urethral pressure profiles (UPP) in seven anesthetized dogs. Simultaneous serum drug concentrations were determined by specific radioimmunoassay for time-response analysis. A significant dose-dependent relaxation of urethral musculature expressed by a reduction in UPP values of 41.5% and 38.4% (P<0.03) was noted 30 min after 5 and 2.5 μg/kg IT alfentanil, respectively, whereas the decrease of 13.4-22% in mean CMG values was not significant