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Pharmacology: Pharmacodynamics: Methyl salicylate: Methyl salicylate is a salicylic acid derivative. It inhibits cyclooxygenase, thereby reducing the formation of prostaglandins and cause platelet dysfunction. It is used topically as a counter irritant. It is absorbed through skin upon application for the relief of rheumatic, joint or muscle pain.
Menthol: Menthol dilated blood vessels causing cold sensation, followed by analgesic effect. It acts as penetration enhancer to give faster onset of action.
Camphor: Camphor is a stimulant, rubefacient, antipruritic, and feebly antiseptic. It becomes ideal for neuralgia and other painful area when combine with ingredient like menthol, and methyl salicylate.
Capsaicin: Capsaicin possesses the same action with camphor but perform more slowly and less completely. However, it is more effective than camphor.
Pharmacokinetics: Methyl salicylate: Methyl salicylate can be absorbed through skin. It is metabolized to salicylic acid in the dermal and subcutaneous tissues after topical application. The half-life of salicylates is 2-4 hours at therapeutic levels. As salicylate level increase into the toxic range, the half-life can be greater than 18 hours.
Menthol: Menthol is excreted in the urine and bile as a glucuronide.
Camphor: Camphor is readily absorbed from all administration sites. It is hydroxylated in the liver to yield hydroxycamphor metabolites which are then conjugated with glucuronic acid and excreted in the urine. It can cross the placenta.
Capsaicin: Capsaicin is absorbed through skin and metabolized by microsomes. Capsaicin is mainly eliminated through kidneys with a small untransformed proportion excreted in faeces and urine.
