Topical clonidine reduces pain level in diabetic neuropathy

A topical clonidine gel applied to the site of pain in patients with painful diabetic neuropathy reduced the level of pain in those patients with intact nociceptors in the skin, said James N Campbell, MD.
     There are currently no prescription topical agents approved by the U.S. Food and Drug Administration for the treatment of painful diabetic neuropathy.
     The finding draws upon a hypothesized biology underlying neuropathic pain: that signals for pain may arise at least in part from sensitized/hyperactive cutaneous nociceptors, and that this abnormal signaling may be reduced by local administration of the alpha-2 adrenergic agonist clonidine, according to Campbell, President and Chief Executive Officer at Arcion Therapeutics, the developer of the clonidine gel, and Professor of Neurosurgery and Director of the Blaustein Pain Treatment Center at Johns Hopkins University in Baltimore.
     To be eligible, patients had to be responsive to a 30-minute application of topical 0.1% capsaicin cream on the pretibial area of both legs. The purpose of this screening was to test for expression of functional nociceptors in the skin. One hundred seventy nine patients who reported pain to the capsaicin stimulus were randomized to clonidine gel or matching placebo applied 3 times daily to their feet for 12 weeks. The subjects kept daily diaries of their average foot pain on a 0-to-10 numeric pain-rating scale.
     The mean pain level at week 12 compared with baseline in the clonidine-treated group decreased by 2.3 compared with 1.7 in the placebo group, which did not achieve significance (P=.07). Topical clonidine had no efficacy over placebo in patients who reported no pain to the capsaicin stimulus. However, in those subjects who felt any level of pain to the capsaicin stimulus, clonidine significantly lowered the pain score by 0.9 compared with placebo (P<.05).
     If the pain rating of the capsaicin stimulus was 2 or higher, the mean change in pain at week 12 was -2.5 for clonidine compared with -1.4 for the placebo (P=.01).