With ST200 as the commercial source of L-acetylcarnitine hydrochloride, 94 patients were enrolled in this study; 31 were assigned to placebo, 31 to ST200 at 0.5 g/die and 32 to ST200 at 1 g/die, the i.m. treatments being injected daily for 15 consecutive days. In general, concerning the efficacy assessment, the administration of ST200 at 1 g/die appeared to be better than ST200 at 0.5 g/die when compared with the placebo administration. Statistically significant differences were revealed by the comparison of ST200 at 1 g/die to placebo, for the following variables: a) total motility as rated at the end of the 15-day study and confirmed by intention-to-treat analysis, b) visual analogue scale for all the patients having observation at day 15, and c) the objective and subjective judgements on efficacy. Safety and tolerability were good over the entire course of the study.