Pentazocine and codeine: effects on human performance and mood and interactions with diazepam

Area of Science:

• Pharmacology
• Neuroscience
• Human Performance

Background:

• Opioid analgesics and benzodiazepines are commonly prescribed medications.
• Understanding their combined effects on cognitive and psychomotor performance is crucial for patient safety.
• Interactions between different drug classes can lead to unpredictable outcomes.

Purpose of the Study:

• To investigate the effects of codeine and pentazocine on performance in healthy students.
• To examine the interactions between these opioid analgesics and diazepam.
• To assess subjective and objective measures of drug-induced impairment.

Main Methods:

• Double-blind, cross-over study in ten healthy students.
• Administration of placebo, codeine (100 mg), or pentazocine (75 mg) followed by diazepam (0.25 mg/kg).
• Objective performance tests and subjective visual analogue scales were used; naloxone was administered as an antagonist.

Main Results:

• Codeine and pentazocine alone did not significantly affect objective performance but altered subjective states.
• Diazepam impaired performance; interactions with opioids were minimal in objective tests, except for increased nystagmus.
• Codeine appeared to reduce diazepam absorption, and both opioids subjectively counteracted diazepam's effects, leading to overestimations of performance.

Conclusions:

• Opioid analgesics codeine and pentazocine have limited impact on objective performance when administered alone.
• Interactions with diazepam primarily manifest as subjective alterations and overestimations of performance, rather than significant objective impairment.
• Codeine may affect diazepam absorption, highlighting potential pharmacokinetic interactions.