Imipramine and Pregabalin Combination for Painful Polyneuropathy. A Randomized Controlled Trial

Monotherapy with first-line drugs for neuropathic pain often fails to provide sufficient pain relief or has unacceptable side effects (SE) because of the need for high doses. The aim of this trial was to test whether the combination of imipramine and pregabalin in moderate doses would relieve pain more effectively than monotherapy with either of the drugs.This was a randomized, double-blind, placebo-controlled, cross-over, multicenter trial consisting of four 5 week treatment periods in patients with painful polyneuropathy. Treatment arms were imipramine 75 mg/day versus pregabalin 300 mg/day versus combination therapy versus placebo. Patients with polyneuropathy and symptoms for more than 6 months, age 20-85 years, pain intensity ≥4 on a 0-10-point numeric rating scale (NRS) and pain at least 4 days a week were included in the trial.Two-hundred-sixty-two patients were screened for participation, 73 patients were randomized and 69 patients were included in the data analysis. The effect on average pain in comparison with placebo was: combination (- 1.67 NRS points, p<0.001), imipramine (- 1.08 NRS points, p<0.001) and pregabalin (- 0,48 NRS points, p=0.03). The combination therapy had significantly lower pain scores than both monotherapies: combination vs imipramine (p=0.009), combination vs pregabalin (p<0.001). During combination therapy, the dropout rate was higher and the patients reported a higher rate and severity of SE.Combination of moderate doses of TCA and pregabalin could be considered as an alternative to high- dosage monotherapy. However, the trial also emphasized that balance between efficacy and safety is an issue.