Analgesic Effects of DA-5018, a New Capsaicin Derivative, in Hyperalgesia of Experimental Diabetic Neuropathy

Bae, Eun Ju; Kim, Soon How; Son, Moon Ho; Kim, Hee Kee; Shin, Myeong Soo; Kim, Hyun Ji; Kim, Won Bae

Abstract

BACKGROUND: Painful peripheral neuropathy is one of the most common complications of diabetes and not responsive to conventional analgesics. Capsaicin cream has been used to treat the pain associated with diabetic neuropathy, rheumatoid arthritis, osteoarthritis and postherpetic neuralgia. But its common side effect, burning sensation, limits the use of it. DA-5018 is a newly synthesized capsaicin derivative which shows more potent systemic and topical analgesia than capsaicin in various animal models of acute and chronic pain, but has little skin irritaion. This study was designed to evaluate the effect of DA-5018 administered systemically or topically on hyperalgesia in streptozotocin-induced diabetic and galactosaemic rats.
METHODS
One group of SD rats was treated with streptozotocin(60mg/kg, I.v.) and the pain thresholds were determined weekly by Randall-Selitto paw pressure test. And the other group of SD rats was maintained on 50%-galactose diet until 4~5 weeks and the pain thresholds were determined as well, Drugs were administered subcutaneously once a day for 7 days or topically to the paw for 5 hours a day for 10 days at a time when the hyperalgesia was already present. The increase of pain thresholds by drug was regarded as an indication of analgesia.
RESULTS
Streptozotocin-diabetic rats displayed a reduction of pain threshold. Similarly, galactosefeeding resulted in significant reduction of pain threshold. It is concluded that hyperalgesia is a constant feature of sensory dysfunction in experimental models of diabetic and nutritional neuropathy. DA-5018(0.2, 0.5mg/kg, s.c.) produced significant antinociception with efficacy similar to that of capsaicin(10mg/kg, s.c.) in streptozotocin-induced hyperalgesia and furthermore, no tolerance developed for 7 days. And this analgesic effect was superior to desipramine(10mg/kg, s.c.). But ketoprofen(10mg/kg, s.c.) produced no analgesia. Topically, 0.3% DA-5018 cream was as effective as Zostrix-HP(capsaicin 0.075%) both in streptozotocin-diabetic and galactosefed rats while Kenofen gel(ketoprofen 3%) was ineffective to reduce pain.
CONCLUSION
These results demonstrate the potent analgesic efficacy of DA-5018 in diabetic pain models and suggest that topical DA-5018 cream may relieves pain caused by diabetic neuropathy offering an alternative for patients not responsive to other treatments or unable to tolerate capsaicin.