ADVERSE EFFECTS (AEs) AND PATIENT BEHAVIORS DURING THE COURSE OF OPIOID THERAPY How Drug Causes AEs

How the Drug Works Pentazocine is an analgesic with agonist/ antagonist action. By competing for the mu receptor in certain circumstances it may act as a mu opioid receptor antagonist and a kappa opioid receptor agonist, which when administered orally is approximately equivalent on a mg-for-mg basis in analgesic effect to codeine. Onset and duration of action and the degree of pain relief are related both to dose and the severity of pretreatment pain Pentazocine is well absorbed from the GI tract. Plasma levels closely correspond to the onset, duration, and intensity of analgesia. The time to mean peak concentration is 1.7 hours and the mean plasma elimination half-life is 3.6 hours By parenteral route is usually as effective as an analgesic as morphine 10 mg or meperidine 75–100 mg; however, a few studies suggest the pentazocine to morphine ratio may range from 20 mg to 40 mg pentazocine to 10 mg morphine Pentazocine may weakly antagonize the analgesic effects of morphine and meperidine; in addition, it produces incomplete reversal of cardiovascular, respiratory, and behavioral depression induced by morphine and meperidine. The antagonistic activity of nalorphine for this compound is about 1/50. It also has sedative activity