Comparison of four narcotic analgesics for extradural analgesia.

The effectiveness of extradural injections of morphine sulphate 6 mg, methadone 6 mg, pethidine 60 mg and fentanyl 60 micrograms in relieving pain after operation were compared in 24 patients. The average duration of pain relief following morphine was 12.3 h; methadone 8.7 h, pethidine 6.6 h and fentanyl 5.7 h. There was no significant difference in the efficacy of the four drugs. There were no effects of clinical importance on heart rate, respiratory frequency or arterial pressure, but arterial systolic pressure decreased after morphine and pethidine. Pethidine also caused a statistically significant reduction in diastolic pressure.