The antagonistic effect of pentazocine on fentanyl induced respiratory depression compared with nalorphine and naloxone.

The effect of pentazocine, a strong analgesic with a weak opiate antagonistic activity, on fentanyl-induced respiratory depression was studied after anaesthesia in patients undergoing gynaecological laparotomy. Pentazocine (1 mg/kg) was given intravenously at the end of operation. The postoperative respiratory depression in these patients was compared with that in patients who received strong opiate antagonists, nalorphine and naloxone, or no opiate antagonists. Respiratory depression was evaluated by measuring respiratory rate, respiratory minute volume and blood gases. The results show that pentazocine has a clear antagonistic effect on fentanyl-induced respiratory depression but the effect of 1 mg/kg is weaker and shorter than that produced by 5 mg of nalorphine or 0.4 mg of naloxone. Postoperative analgesia in patients who received pentazocine was not longer than that in patients who received no opiate antagonists at the end of the operation.