Medicines evaluation and monitoring group: central nervous system effects of pentazocine.

Hospital-based drug monitoring facilities have been used to investigate the frequency of perceptual disturbances in inpatients receiving pentazocine and the occurrence of dependence upon this drug after discharge from hospital. A pilot study was carried out in which seven out of 70 hospital inpatients receiving pentazocine reported such episodes, while in a prospective study, 9 out of 132 patients receiving pentazocine and 1 out of 112 receiving cyclimorph, dihydrocodeine, or pethidine reported their occurrence. A total of 135 patients who received pentazocine for disorders likely to require longterm analgesia were followed up for six months after their discharge from hospital. 24 had received pentazocine after discharge; two required an increase in dosage and four expressed a preference for pentazocine.