Background: The aim of this study was to compare the efficacy and side effects of gabapentin, amitriptyline, and their combination in women with chronic pelvic pain.
Methods: In this open-label, prospective, randomized trial, 56 women with chronic pelvic pain were investigated with a two-year follow-up at the Vienna Medical University Hospital. If pain intensity assessed by a visual analog scale (VAS) was 5 or more (0, no pain; 10, maximal pain), despite analgesic therapy using the nonopioid drug metamizol together with weak opioids, patients were randomized to receive gabapentin (n = 20), amitriptyline (n = 20), or a combination of both drugs (n = 16). Doses of gabapentin and amitriptyline were increased to maximum daily doses of 3600 mg and 150 mg, respectively, until sufficient pain relief or the occurrence of side effects. VAS and side effects were evaluated before treatment and at 1, 3, 6, 12 and 24 months afterwards.
Results: All patients experienced significant pain relief during the observation period. However, after 6, 12 and 24 months, pain relief was significantly better in patients receiving gabapentin either alone or in combination with amitriptyline than in patients receiving monotherapy with amitriptyline (gabapentin: 0 months, 7.7 +/- 1.5; 6 months, 1.6 +/- 0.9; 12 months, 1.5 +/- 0.9; 24 months, 1.9 +/- 0.9; amitriptyline: 0 months, 7.3 +/- 1.5; 6 months, 2.2 +/- 1.6; 12 months, 2.2 +/- 1.6; 24 months; 3.4 +/- 0.9; amitriptyline-gabapentin: 0 months, 7.6 +/- 0.8; 6 months, 1.3 +/- 0.9; 12 months, 1.7 +/- 1.0; 24 months, 2.3 +/- 0.9). Side effects were lower in the gabapentin group than in the two other groups, the difference reaching statistical significance after three months (P < 0.05).
Conclusion: Gabapentin alone or in combination with amitriptyline is better than amitriptyline alone in the treatment of female chronic pelvic pain.