Comparison of fentanyl and butorphanol for postoperative pain relief with intravenous patient controlled analgesia

Background

Opioids are very effective as postoperative analgesics, influencing emotional aspects of pain as well as reducing the actual pain threshold. Fentanyl, a phenylpiperidine derivative and potent opioid agonist, has already been studied for postoperative analgesia. Butorphanol, a synthetic morphinan derivative – agonist–antagonist, has few studies to substantiate its use. The present study was undertaken to compare the effects of the two drugs on postoperative pain relief in terms of efficacy and safety.

Methods

A prospective, randomized controlled study of 100 patients [ASA I and II] undergoing total abdominal hysterectomies was conducted. Group F of 50 patients received fentanyl [0.4 μg/kg/h] and group B received butorphanol [4 μg/kg/h] as postoperative pain treatment via intravenous patient controlled analgesia [i.v. PCA]. Parameters monitored were pain score [VAS], pulse, blood pressure, respiratory rate, sedation score and side effects. The infusion rate, number of boluses, PCA demands and requirement of rescue analgesia were noted.

Results

Butorphanol had a better maintenance phase than fentanyl. The VAS scores were found to be reduced in the butorphanol group when compared with fentanyl group, significantly at 8 h [F: 1.16 ± 1.037; B: 0.78 ± 0.582; p-value: 0.026]. The incidences of complications were comparable in both the groups.

Conclusion

Both the drugs are equally effective and safe as postoperative analgesics with i.v. PCA. The dose of 4 μg/kg/h of butorphanol appeared effective but the dosage of fentanyl used, 0.4 μg/kg/h, was not as effective as evidenced by the increased number of boluses taken by patients and needs to be increased.