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Topiramate for Painful Diabetic Neuropathy

Two new studies yielded mixed results.

Results from small studies suggest that the anticonvulsant topiramate (Topamax) reduces pain among patients with diabetic neuropathy. Now, the effectiveness of topiramate has been examined in large randomized, double-blind, industry-sponsored multicenter trials among patients with painful diabetic neuropathy.

In one study, 323 patients received topiramate (doses titrated to 400 mg daily) or placebo. During 12 weeks, reduction in mean pain score in the topiramate group (from 68 to 46 mm on a 100-mm visual analog scale) was significantly greater than reduction in the placebo group (from 69 to 54 mm; P<0.04). Topiramate recipients were significantly more likely than placebo recipients to experience a 50% reduction in pain (36% vs. 21%). However, topiramate recipients were more likely to withdraw from the trial because of adverse effects (24% vs. 8%).

In another report, researchers describe outcomes from three placebo-controlled trials that involved 1259 patients; various topiramate doses (100, 200, and 400 mg daily) were tested. At 22 weeks, no significant differences were noted between the topiramate and placebo groups: Mean pain intensity had been 55 mm to 60 mm on a 100-mm scale at baseline, and it decreased by about 15 mm to 20 mm in most of the groups. Again, more topiramate recipients than placebo recipients withdrew because of adverse effects (24% vs. 8%).

Comment: Taken together, these findings suggest that topiramate is beneficial for only a small minority of diabetic patients with moderately severe neuropathic pain. But why the contradictory results? One reason might be a higher baseline level of pain in the first study; another might be that rescue analgesia was not allowed in the first study but was allowed in the others. Even in the first study, however, the average benefit was modest, and adverse events were common.

— Allan S. Brett, MD

Published in Journal Watch General Medicine October 12, 2004

Citation(s):

Raskin P et al. Topiramate vs placebo in painful diabetic neuropathy: Analgesic and metabolic effects. Neurology 2004 Sep 14; 63:865-73.

• Original article (Subscription may be required)
• Medline abstract (Free)

The Topiramate Diabetic Neuropathic Pain Study Group. Topiramate in painful diabetic polyneuropathy: Findings from three double-blind placebo-controlled trials. Acta Neurol Scand 2004 Oct; 110:221-31.

• Medline abstract (Free)