Comparative efficacy of epidural clonidine versus epidural fentanyl for treating breakthrough pain during labor: a randomized double-blind clinical trial

Background: Breakthrough pain during neuraxial labor analgesia is typically alleviated with additional administration of epidural local anesthetics, with or without adjuvants. Sometimes avoiding neuraxial opioids may be warranted and clonidine is an alternative. In a randomized double-blind trial we compared the efficacy of clonidine versus fentanyl, added to bupivacaine, for the management of breakthrough pain. Methods: Term parturients (n=98) receiving bupivacaine 0.0625% with fentanyl 2 μg/mL at 12 mL/h, a patient-administered bolus of 5 mL at lockout 6–10 min and a maximum of four boluses per hour, and experiencing breakthrough pain ≥5/10, were randomized to receive a 10 mL bolus containing 12.5 mg bupivacaine and either clonidine 100 μg or fentanyl 100 μg. The primary outcome was ‘success’ of study drug treatment, defined as a pain score reduction ≥4/10 within 15 min of administration. Maternal hemodynamics and fetal heart rate were documented for two hours after treatment. Results: There was no significant difference between groups in success rates (66.0% after clonidine (n=47) vs 74.5% after fentanyl (n=51), P=0.48) or in the incidence of hypotension (systolic blood pressure ≤80% of baseline or <90 mmHg) or sedation at 15 min, with 2/51 and 1/47 subjects in the fentanyl and clonidine groups, respectively, receiving phenylephrine. Conclusion: Epidural clonidine 100 μg was not superior to fentanyl 100 μg for decreasing pain scores within 15 min of co-administration with bupivacaine 0.125% for intrapartum breakthrough pain. The analgesic efficacy and hemodynamic side effects did not significantly differ.