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

Aims The aim of the current study was to assess the viability of the interd igital web pinch model as a test for analgesic activity in volunteer-based early phase drug development. Methods Pain thresholds and sensitization to a series of four sessions of i nterdigital web pinching (12 Newtons force) were measured in 26 male volunt eers before and 1 and 3 h after oral dosing with ibuprofen (800 mg) or plac ebo to ibuprofen. Within each time point, the pain thresholds were measured by calculating the average visual analogue scores (VAS) for the first sess ion of pinching (VAS-1). Sensitization to pinching was assessed by calculat ing the average changes in these scores for the three subsequent sessions o f pinching (VAS-2). Moreover, the difference between the VAS score after th e first session of pinching and that obtained at the end of the fourth sess ion of pinching was calculated as a secondary endpoint (VAS-3). Results Treatment with ibuprofen had no significant effect on VAS-1 at eith er 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. Conclusions This model has been able to detect an antinociceptive effect wi th 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 normall y employed.