Axsain contains capsaicin USP, in a patented emollient base containing benzyl alcohol, cetyl alcohol, glyceryl stearate, isopropyl myristate, lidocaine hydrochloride, PEG-100 stearate, purified water; sorbitol solution and white petrolatum.
Capsaicin is designated chemically as trans-8-methyl-N-vanillyl-6-nonenamide with an empirical formula of C18H27NO3 and molecular weight of 305.4. The structural formula is:
Although the precise mechanism of action of Axsain (capsaicin) is not fully understood, current evidence suggests that capsaicin relieves neuralgia pain by depleting and preventing reaccumulation of substance P in peripheral sensory neurons. Substance P is thought to be the principal chemomediator of pain impulses from the periphery to the central nervous system. Initial release of substance P from sensory neurons is believed to be responsible for burning or stinging sensations experienced by some individuals. Such unpleasant sensations may be reduced or prevented by Axsain's patented Lidocare vehicle system which contains lidocaine.
A multi-center study was conducted to assess the clinical effectiveness and safety of Axsain for treatment of painful diabetic neuropathy (PDN) and postherpetic neuralgia (PHN). Eighty-three (83) patients with PDN (n=56) or PHN (n=27) who were taking oral antiepileptics or tricyclic antidepressants with incomplete pain relief were enrolled. Axsain was applied to painful areas three times daily for 6 weeks. Following 1, 3, and 6 weeks of treatment, pain was reduced by 21%, 40%, and 50%, respectively, in patients with PDN, and by 24%, 39%, and 51%, respectively, in patients with PHN. Following treatment, 90% of patients with PDN and 94% with PHN rated themselves as Improved. When evaluated by physicians, 89% of PDN and 88% of PHN patients were rated as Improved. Transient stinging/burning sensations at the application sites were the most commonly reported adverse events, while no serious adverse events related to study drug were observed.