indication

For the relief of moderate to severe pain.

pharmacology

Pentazocine is a potent analgesic which when administered orally in a 50 mg dose appears equivalent in analgesic effect to 60 mg (1 grain) of codeine. Onset of significant analgesia usually occurs between 15 and 30 minutes after oral administration, and duration of action is usually three hours or longer. Onset and duration of action and the degree of pain relief are related both to dose and the severity of pretreatment pain. Pentazocine weakly antagonizes the analgesic effects of morphine and meperidine; in addition, it produces incomplete reversal of cardiovascular, respiratory, and behavioral depression induced by morphine and meperidine. Pentazocine has about 1/50 the antagonistic activity of nalorphine. It also has sedative activity.

mechanism of action

The preponderance of evidence suggests that pentazocine antagonizes the opioid effects by competing for the same receptor sites, especially the opioid mu receptor.

biotransformation

Hepatic

absorption

Well absorbed from the gastro-intestinal tract.

half life

2 to 3 hours