Effectiveness of tizanidine in neuropathic pain: an open-label study.

Abstract

The purpose of this research trial is to assess the effectiveness and tolerability of tizanidine in neuropathic pain. In an open-label study, patients with neuropathic pain received 1 to 4 mg of tizanidine once daily for 7 days, followed by weekly dose escalation of 2 to 8 mg to his/her effective or maximum tolerated dose or a maximum of 36 mg over an 8-week period. Treatment effects were assessed, using average weekly pain scores as well as biweekly scores for patient global assessment of pain relief, the neuropathic pain scale, and wisconsin brief pain inventory. Frequency and severity of adverse events were examined also. Twenty-three patients were enrolled. The mean average weekly pain score at baseline was 6.9, which decreased by 1.7 points at the end of week 8 to 5.2 (p < or =.01). A total of 15 patients (68%) reported that their pain relief was improved or much improved with tizanidine therapy, and 2 of these patients became completely pain-free. The following neuropathic pain qualities were significantly lower at week 8 compared with baseline: intense, sharp, hot, dull, cold, sensitive, unpleasant, and deep pain. There was a significant decline in pain quantity and interference of pain on quality of life from baseline to week 8. The mean effective or maximum tolerated dose was 23 mg/day (range 6 to 36 mg/day). Side effects consisted primarily of dizziness/lightheadedness (52%), drowsiness (48%), fatigue/weakness (43%), dry mouth (39%), gastrointestinal upset (30%), and sleep difficulty (22%). One patient developed significant elevation in liver function tests (LFTS) With symptoms at week 4. Tizanidine therapy was discontinued. LFTS returned to normal in 3 weeks. Tizanidine might be an effective treatment for neuropathic pain, offering an alternative for patients poorly responsive to other medications. A larger, randomized placebo-controlled trial is recommended. In addition, comparative studies with alternative agents should be sought.