Ascomycin,Chemically, pimecrolimus is (1R,9S,12S,13R,14S,17R,18E,21S,23S,24R,25S,27R)-12-[(1E)-2-{(1R,3R,4S)-4-chloro- 3-methoxycyclohexyl}-1-methylvinyl]-17-ethyl-1,14-dihydroxy-23,25-dimethoxy- 13,19,21,27-tetramethyl-11,28-dioxa-4-aza-tricyclo[22.3.1.0^4,9]octacos-18-ene-2,3,10,16- tetraone.The compound has the empirical formula C₄₃H₆₈CINO₁₁ and the molecular weight of 810.47. Pimecrolimus is a white to off-white fine crystalline powder. It is soluble in methanol and ethanol and insoluble in water. Each gram of ELIDEL Cream 1% contains 10 mg of pimecrolimus in a whitish cream base of benzyl alcohol, cetyl alcohol, citric acid, mono- and di-glycerides, oleyl alcohol, propylene glycol, sodium cetostearyl sulphate, sodium hydroxide, stearyl alcohol, triglycerides, and water.