Counterirritants salicylate-containing

Topical analgesics sometimes are used for mild pain or as an adjunct to systemic therapy. There are limited data to support the use of salicylate-containing rubefacients (e.g., methyl salicylate and trolamine salicylate) or other counterirritants (e.g., menthol, camphor, and methyl nicotinate) in OA.32 See Chap. 57 for more information on these products when used for musculoskeletal disorders. 

Application of topical salicylates can lead to systemic effects, especially if the product is applied liberally. Repeated application and occlusion with a wrap or bandage also can increase systemic concentrations.41 Salicylate-containing counterirritants should be used with caution in patients in whom systemic salicylates are contraindicated, such as patients with severe asthma or aspirin allergy.42 Topical salicylates have been reported to increase prothrombin time in patients on warfarin and should be used with caution in patients on oral anticoagulants.43... 

The best counterirritants are physical agents, especially heat. Many drugs, however, have been used for this purpose and suitable preparations containing salicylates, nicotinates, menthol, camphor and capsaicin (depletes skin substance P) are also available. 

Products containing combinations of constituents with local anaesthetic and analgesic effects, such as lidocaine, choline salicylate and phenol, counterirritants such as ammonia solution and menthol, and astringents such as zinc sulphate and tannic acid, are marketed to reduce discomfort and promote faster healing of sores while the infection takes its course. Some are formulated with alcoholic bases, which may have a drying effect on sores and speed up healing. The bland cream bases of some products may have a soothing effect. 

Various over-the-counter preparations containing methyl salicylate and menthol have been used to treat musculoskeletal pain for many years, but few have been the subjects of clinical trials. Menthol is class ed as a counterirritant, producing a cooling sensation via activation of sped c thermoreceptors (Patel et al., 2007), while methyl salicylate has analgesic, anti-in ammatory, and vasodila-tory effects (Green and Flammer, 1989). 

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