Some observations on the pharmacology of 'deep-heat', a topical rubifacient

A topically applied rubifacient delivered by aerosol (Deep-Heat) was studied. After spray application to the forearms of volunteers, without massage, the erythema produced was measured by thermography and correlated with the concentration of 2 salicylate components of the mixture found in local and systemic venous blood. Maximum erythema occurred at about 30 minutes, while blood salicylate levels were maximal between 20 and 30 minutes after application. Methyl salicylate was absorbed before ethyl salicylate. Over the time period of the erythematous response oxygen levels in local venous blood were raised. Finally, platelets collected from venous blood draining from the sprayed site, when induced to clump by the addition of arachidonic acid in an aggregometer, showed increased resistance to clumping when compared with control cells. The mechanism of these observed phenomena and the mode of action of the constituents of Deep-Heat are discussed.