Effect of pregabalin on the EC50 of intravenous alfentanil in capsaicin induced pain.

OBJECTIVE: To apply the sequential up-down method to a human experimental pain model in order to examine the opioid-sparing effect of oral pregabalin on intravenous alfentanil.

DESIGN: Double-blind, randomized, crossover.

SETTING: Academic University Medical Center.

SUBJECTS: 31 healthy males.

METHODS: The EC50 of intravenous Alfentanil was determined under two conditions: Alfentanil alone (PHASE I) and Alfentanil + Pregabalin (300 mg po) (PHASE II). The alfentanil plasma level (using a computer-controlled infusion) producing a success criterion (at least 30% intradermal capsaicin induced pain reduction compared to placebo) was used to determine higher or lower doses of each sequential subject. The median dose producing a success criterion and its confidence interval was determined.

RESULTS: Based on the t-test for a difference across phase and regression coefficients across groups, there was no opioid sparing effect of pregabalin on alfentanil. Four subjects in phase I and 5 subjects in phase II did not complete the study. Two in phase I were technical failure with the rest in both phases stopped due to side effects. Of the subjects who completed the study, 6 of 19 subjects in phase I and 11 of 12 subjects in phase II reported side effects.

CONCLUSIONS: Using the intradermal capsaicin induced pain model in healthy volunteers, oral pregabalin had no opioid sparing effects on intravenous alfentanil. This experimental model may be useful in studying analgesic interaction.