Results of the preplanned interim analysis ( n = @ in each group ) of the primary endpoint showed that futility criteria had been met , and the trial was stopped ( the mean rate of change -LSB- slope analysis -RSB- of UMSARS I score was @ points -LSB- SD @ -RSB- per month in the rifampicin group vs @ points -LSB- @ -RSB- per month in the placebo group ; futility p = @ ; efficacy p = @ ) .