Anorexic effect of (R)-sibutramine: comparison with (RS)-sibutramine [corrected] and (S)-sibutramine.

Sibutramine is one of the very few drugs that are approved for long-term treatment of obesity. Sibutramine is a racemic mixture (RS) containing two equal forms of the R(+) and S(-) enantiomers. In this paper, we have investigated comparative anorexic effect of sibutramine enantiomers and their recemate form in rats. After obtaining two days of baseline results, rats were administered orally either with (RS)-sibutramine or its enantiomers (R)- or (S)-sibutramine at dose levels of 5, 10, 20 mg/kg each for 4 days and body weight, food intake and water intake were measured daily. Locomotor activity score of each rat was also recorded on each day. R-Sibutramine and (RS)-sibutramine produced dose dependant decrease in the body weight and food intake. On the other hand, (S)-sibutramine was shown to increase in these parameters. Neither sibutramine nor it's enantiomers showed any consistent effects on spontaneous motor activity (SMA) scores. In conclusion, (R)-sibutramine is better anorexic than or (RS)-sibutramine or it's (S)-enantiomers.