A comparison of the circulatory effects in man of the analgesics fentanyl, pentazocine and pethidine

TLDR: Pentazocine, pethidine and fentanyl exert different haemodynamic effects in conscious and anaesthetized subjects, and all three analgesics caused a 20–25 per cent fall in blood pressure and heart rate in anaesthenized patients.

Abstract: SUMMARY The cardiovascular responses to five sequential intravenous injections of pentazocine (5×0.6 mg/kg), fentanyl (5×0.001 mg/kg) and pethidine (5×1.0 mg/kg) were assessed in conscious and anaesthetized subjects. In conscious volunteers pentazocine raised the systolic pressure by 30 per cent. Pentazocine and pethidine raised the diastolic pressure by 10 per cent and the heart rate by 15 per cent; with pethidine the increases were not sustained but tended to fluctuate. Fentanyl did not affect the pressure or heart rate. In anaesthetized patients, all three analgesics caused a 20–25 per cent fall in blood pressure and heart rate, fluctuations in pressures occurring in the pentazocine and pethidine group. No changes of e.c.g. pattern were observed. Pentazocine, pethidine and fentanyl thus exert different haemodynamic effects in conscious and anaesthetized subjects.