Assessment of topical anti-inflammatory activity in rats with cantharidin-induced inflammation.

Topical application of 400 mug of cantharidin to the rat's ear caused an approximate doubling in the mean weight of uniform ear punch samples when compared to vehicle-treated controls at 72 hr, and produced a maximal response at 7 days. Dexamethasone reduced the increase in weight when applied topically, but was ineffective when given subcutaneously or orally at the same doses. Hydrocortisone, prednisolone, triamcinolone, betamethasone, flurometholone, paramethasone acetate, fluocinolone acetonide, fluocinonide, and flurandrenolide showed significant suppression of cantharidin-induced inflammation. Cholesterol, diphenhydramine, tripelennamine, chlorpheniramine, promethazine, cyproheptadine, epinephrine, phenylephrine, alpha-tocopherol, indomethacin, and bufexamac were inactive. It is suggested that the procedure employed may be useful in the screening and evaluation of topical anti-inflammatory agents.