To evaluate the analgesic interaction between butorphanol and sufentanil.

Ninety patients, aged 18-64 yr, with body mass index <30 kg/m², of American Society of Anesthesiologists physical status Ⅰ or Ⅱ, undergoing elective laparoscopic gynecological surgery, were divided into 3 groups(n=30 each)using a random number table: butorphanol group(group B), sufentanil group(group S)and butorphanol mixed with sufentanil group(group BS1). The doses of butorphanol and sufentanil were determined by the modified Dixon′s up-and-down method.In B and S groups, the initial doses of butorphanol and sufentanil were 0.5 mg and 5 μg, respectively, with 0.1 mg and 1 μg increment/decrement, respectively.In group BS1, butorphanol combined with sufentanil at the ratio of 2∶1 based on the equivalent dose, and the initial dose was butorphanol 0.25 mg plus sufentanil 2.5 μg with 0.05 mg and 0.5 μg increment/decrement for butorphanol and sufentanil, respectively.Effective analgesia was defined as numeric rating scale pain score ≤ 3 or the extent of decrease in numeric rating scale scores > 50% within 15 min after administration.The median effective dose(ED₅₀)and 95% confidence interval(CI)of butorphanol and sufentanil were calculated by probit analysis.Isobolographic analysis was used to analyze the analgesic interaction between butorphanol and sufentanil.When the equivalent dose of two drugs was very different from that selected in group BS1 on the basis of the actually calculated ED₅₀ in B and S groups, the combination of butorphanol and sufentanil in group BS2(n=30)was set at the ratio of 1∶1 based on the actual equivalent dose: the initial dose was butorphanol 0.4 mg plus sufentanil 1.8 μg with 0.1 mg and 0.45 μg increment/decrement for butorphanol and sufentanil, respectively.

The ED₅₀ of butorphanol was 0.80 mg(95% CI 0.74-0.87 mg), and the ED₅₀ of sufentanil was 3.68 μg(95% CI 3.07-4.41 μg). The ED₅₀ of butorphanol and sufentanil was 0.28 mg(95% CI 0.25-0.32 mg)and 2.82 μg(95% CI 2.52-3.16 μg), respectively, in group BS1.The ED₅₀ of butorphanol and sufentanil was 0.38 mg(95% CI 0.33-0.43 mg)and 1.7 μg(95% CI 1.5-1.9 μg), respectively, in group BS2.The isobolographic analysis showed that the combination of butorphanol and sufentanil at 2∶1 or 1∶1 produced an additive analgesic effect.

The analgesic effect of butorphanol and sufentanil is additive when combined at the ratio of 2∶1 or 1∶1 based on the equivalent dose.

Butorphanol; Sufentanil; Drug interactions