Zolpidem is differentiated from triazolam in humans using a three-responsedrug discrimination procedure

The discriminative stimulus effects of the imidazopyridine hypnotic zolpide m and the classic benzodiazepine hypnotic triazolam were examined in seven healthy volunteers using a three-response drug discrimination procedure and a within subject design. During an initial sampling phase, the training dr ug conditions (placebo, 20 mg/70 kg zolpidem, and 0.5 mg/70 kg triazolam) w ere identified to subjects by letter codes before oral drug administration. During a subsequent training phase, subjects earned money for correct drug identifications made 3.75 h after drug administration. Five out of seven s ubjects acquired the three-response discrimination. Analyses of standardize d and unstructured self-report questionnaires revealed that zolpidem and tr iazolam produced different profiles of effects; zolpidem aas associated wit h a number of negative somatic symptoms including nausea, blurred vision, v isual images/hallucinations, and heavy limbs, whereas triazolam was associa ted with greater sedative effects. These results demonstrate a distinct pro file of discriminative stimulus and subjective effects for zolpidem,relativ e to triazolam, which is consistent with its somewhat distinct pharmacologi cal profile, and provide evidence for the sensitivity of the three-response drug discrimination procedure for detecting between-drug differences. Beha v Pharmacol 1998; 9:545-559 (C) 1998 Lippincott Williams & Wilkins.