An experimental study on dependence liability of zipeprol.

Zipeprol, a piperazine ethanol derivative, is a non-essential but widely used (paediatric) antitussive, which is not legally considered as being capable of creating dependence or abuse liability. A first group of experimental results was obtained assaying the displacement of 1 nM [3H]naloxone by zipeprol vs morphine on the rat brain homogenate fractions. A second group was carried out on the longitudinal muscle of guinea-pig ileum, using the field stimulation technique, either in the absence or in the presence of naloxone 1 x 10(-5)M or in the absence or in the presence of yohimbine 1 x 10(-5)M. Further investigations concerning the pharmacological and the biochemical characterization of the mechanisms involved in abuse liability were carried out by means of the in vitro inhibition of ACh response on the guinea-pig ileum preparation. The results indicate zipeprol as a moderate opioid agonist, which also shows a direct anticholinergic effect, independent of presynaptic alpha 2 interaction.