PREPIDIL Gel contains dinoprostone as the naturally occurring form of prostaglandin E2 (PGE2) and is designated chemically as (5Z, 11a, 13E, 15S)-11,15-Dihydroxy-9-oxo-prosta-5,13-dien-1-oic acid. The molecular formula is C20H32O5 and the molecular weight is 352.5. Dinoprostone occurs as a white to off-white crystalline powder with a melting point within the range of 65° to 69°C. It is soluble in ethanol, in 25% ethanol in water, and in water to the extent of 130 mg/100 mL. The active constituent of PREPIDIL Gel is dinoprostone 0.5 mg/3 g (2.5 mL gel); other constituents are colloidal silicon dioxide NF (240 mg/3 g) and triacetin USP (2760 mg/3 g).
The structural formula is represented below: