Pharmacological study of pentazocine-naloxone combination: interest as a potentially non abusable oral form of pentazocine.

The hypothesis that co-administration of naloxone would not affect oral but would block parenteral pentazocine's activities was tested in two rat models, the Randall-Selitto and the hypertonic saline writhing tests. A 100:1 dose ratio of pentazocine-naloxone was shown to be optimal and equivalent in oral analgesic effects to pentazocine alone. The same combination, administered parenterally, showed little or no analgesia indicating a suppression of pentazocine activity. Pentazocine-naloxone combination appears, therefore, as a feasible means to retain full analgesic activity of pentazocine when administered orally while any attempt to extract pentazocine from this formulation for intravenous administration would result in little or no pharmacological effect and, therefore, eliminate the potential parenteral abuse of tablets.