Axsain (Capsaicin / Lidocaine Hydrochloride) - Description and Clinical Pharmacology

DESCRIPTION

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:

CLINICAL PHARMACOLOGY

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.

CLINICAL STUDIES

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.