Sensitivity of repeated interdigital web pinching to detect antinociceptive effects of ibuprofen

The aim of the current study was to assess the viability of the interdigital web pinch model as a test for analgesic activity in volunteer-based early phase drug development.

Pain thresholds and sensitization to a series of four sessions of interdigital web pinching (12 Newtons force) were measured in 26 male volunteers before and 1 and 3 h after oral dosing with ibuprofen (800 mg) or placebo to ibuprofen. Within each time point, the pain thresholds were measured by calculating the average visual analogue scores (VAS) for the first session of pinching (VAS-1). Sensitization to pinching was assessed by calculating the average changes in these scores for the three subsequent sessions of pinching (VAS-2). Moreover, the difference between the VAS score after the first session of pinching and that obtained at the end of the fourth session of pinching was calculated as a secondary endpoint (VAS-3).

Treatment with ibuprofen had no significant effect on VAS-1 at either 1 or 3 h after dosing. However, the mean values of VAS-2 and VAS-3, were significantly reduced (P < 0.05) following treatment with ibuprofen.

This model has been able to detect an antinociceptive effect with ibuprofen. However, large numbers of subjects were required in order to demonstrate this effect and this feature would restrict the model's utility in early phase clinical trials where small numbers of subjects are normally employed.