Evaluation of efficacy of the perioperative administration of Venlafaxine or gabapentin on acute and chronic postmastectomy pain.

Objectives: Postmastectomy pain syndrome is a neuropathic pain syndrome that is known to develop after breast surgery. Preemptive analgesia has been shown to be efficacious in reducing postoperative pain, and may be effective in reducing the incidence of certain types of neuropathic pain. We investigated the analgesic efficacy of Venlafaxine and gabapentin on acute and chronic pain associated with cancer breast surgery.

Patients And Methods: The study was carried out on 150 patients scheduled for either partial or radical mastectomy with axillary dissection. They were randomized in a double-blinded manner to receive, extended release Venlafaxine 37.5 mg/d, gabapentin 300 mg/d, or placebo for 10 days starting the night before operation. Pain scores were recorded at rest and movement (visual analog scale) at 4, 12, and 24 hours on the first day postoperatively, daily from the second to tenth day postoperatively and visual analog scale in addition to pain character 6 months later. Analgesic requirements were compared between the 3 groups.

Results: Pain after movement was reduced by gabapentin from the second to tenth postoperative day and venlafaxine group in the last 3 days but no difference was found between the groups regarding pain during rest. Gabapentin reduced morphine consumed in the first 24 hours postoperatively. The analgesic requirements from the second to tenth days for codeine and paracetamol were reduced in venlafaxine and gabapentin groups compared to the control group. Six months later, the incidence of chronic pain, its intensity, and need for analgesics were reduced in venlafaxine compared to gabapentin and the placebo group. However, burning pain was more frequent in the control groups than in the gabapentin.

Conclusion: Venlafaxine 37.5 mg/d extended release or gabapentin 300 mg/d have equipotent effects (except on the first day in venlafaxine group) in reducing analgesic requirements, although gabapentin is more effective in reducing pain after movement. Venlafaxine significantly reduced the incidence of postmastectomy pain syndromes (chronic pain) 6 months in women having breast cancer surgery. Gabapentin had no effect on chronic pain except decreasing incidence of burning pain.