General information

Pentazocine is a partial agonist at opioid receptors. Adverse reactions to effective doses are largely typical of its class [ , ], with some quantitative exceptions.

Drug studies

Comparative studies

Pentazocine and morphine were compared in 16 non-abusing volunteers recruited via posters and local newspaper advertisements [ ]. Pentazocine had dose-related effects on subjective, psychomotor, and physiological variables, and the clinically relevant dose of 30 mg produced a greater magnitude of dysphoric subjective effects than morphine 10 mg and, unlike morphine, impaired psychomotor performance. With pentazocine, peak ratings from the adjective checklist were significantly increased for “dry mouth,” “sweating,” and “turning of stomach.” Compared with morphine, pentazocine led to higher ratings for “drunk,” “feel bad,” “having pleasant bodily sensations,” and “having unpleasant bodily sensations.”

Placebo-controlled studies

Pentazocine 30 mg had no effect on motor skills but impaired sensory processing and extraocular muscle imbalance [ ]. Other adverse events reported in this study were slight respiratory depression (enhanced by concurrent amitriptyline) and feelings of clumsiness, drowsiness, friendliness, and contentedness, and a muzzy head.

Organs and systems

Psychological

Perceptual disturbances are generally thought to occur more often with pentazocine than with other opioids. Objective definition of such phenomena is difficult, but in a study of postoperative dreaming after the use of pentazocine and morphine as premedicants there was no statistically significant difference between the two drugs [ ].

Hematologic

There have been reports of pentazocine-induced agranulocytosis in the absence of other predisposing factors [ ].

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