Possible Interaction: Capsaicin and Formalin

“Pretreatment with capsaicin , a neurotoxin selective for unmyelinated small diameter primary afferent nerves, markedly reduced the adenosine released by 1.5% formalin and the early phase of release by 5% formalin.”

“5 Desensitization of small diameter sensory neurones with a single subplantar injection of capsaicin (100 μg) abolished all behaviours indicative of spontaneous nociceptive sensation in animals subsequently injected with α,β‐methylene ATP (600 nmol), bradykinin (1 nmol) or formalin (0.5%, 0.1 ml).”

“Paw swelling, flinching and release of spinal prostaglandin E2 induced by injection of formalin into the hindpaw were also reduced in capsaicin-treated rats compared with controls, whereas glutamate, aspartate and taurine release was unaffected.”

“The capsaicin treatment markedly reduced the sensitivity of formalin test pain to morphine.”

“The inflammation produced by an injection of formalin to the plantar surface of the hind paw was reduced equally by capsaicin or capsaicin + guanethidine.”

“2 In rats pretreated … of 50 mg capsaicin over 4 … to capsaicin, formalin , HCl, KCl, prostaglandin E1, bradykinin and bradykinin with prostaglandin E1 (10−6 m) were greatly reduced, the responses … 5‐hydroxytryptamine were slightly reduced and those to adenosine 5′‐triphosphate (ATP) and compound 48/80 were unaffected.”