The effect of nefopam and its enantiomers on the uptake of 5-hydroxytryptamine, noradrenaline and dopamine in crude rat brain synaptosomal preparations.

The effect of (+/-), (+) and (-)-nefopam on the uptake of 5-hydroxytryptamine (5-HT), noradrenaline and dopamine in synaptosomal preparations from rat forebrain, hippocampus and striatum has been investigated. All three forms of nefopam inhibited the amine uptake in the investigated structures, the order of potency being (+) greater than (+/-) greater than (-). (+)-Nefopam was 7-30 times more potent than (-)-nefopam. The same order of potency has also been found for the antinociceptive effect of these three forms, however, the differences were smaller. Inhibition of 5-HT and noradrenaline uptake may not be the sole mechanism underlying the analgesic effect of nefopam.