Analgesic effect of pregabalin and magnesium sulfate postmastectomy with axillary lymphadenectomy

INTRODUCTION: Mastectomy and lymphadenectomy are associated with moderate to severe pain immediately after surgery. Several reportedly effective and safe analgesics are available, including pregabalin and magnesium sulfate. OBJECTIVE: To evaluate and compare the analgesic effect of pregabalin and magnesium sulfate after mastectomy with axillary lymphadenectomy. METHODOLOGY: Double-blind, randomized study involving 80 patients submitted to mastectomy and axillary lymphadenectomy under general anesthesia. Magnesium sulfate (or placebo) was administered during anesthesia (50 mg/kg; maintenance 10 mg/kg/h), while pregabalin 150 mg (or placebo) was administered before and 12 hours after surgery. The patients were distributed into 4 groups. CG: control (no medication), GM: magnesium sulfate + placebo, GP+M: magnesium sulfate + pregabalin, and GP: pregabalin + placebo. A questionnaire (SRQ-20) was administered to all patients to detect potental mental disorders. The patients’ condition was monitored at 1 12 and 24 hours after surgery (anamnesis, pain questionnaire, opioid requirements, complications and/or adverse events such as nausea, vomiting and drowsiness). RESULTS: At 1 hour, the number of patients with mild or no pain was significantly greater in GP+M than in any other group. At 12 hours, mild or no pain was more frequently observed in GP+M and GP than in CG and GM. At 24 hours, no patient reported moderate or severe pain. The four groups did not differ significantly with regard to nausea, vomiting or sleep scores. CONCLUSION: The combination of pregabalin and magnesium sulfate provided satisfactory analgesia in the first hour after mastectomy with axillary lymphadenectomy. When used alone however, magnesium sulfate had no measurable analgesic effect, and pregabalin was only slightly effective one hour after surgery.