Stability of mechlorethamine hydrochloride 0.01% ointment in aquaphor base

The purpose of this project was to evaluate the short-term shelf-life stability of an extemporaneously compounded mechlorethamine hydrochloride 0.01% topical ointment stored at room temperature. Mechlorethamine hydrochloreide injection 10-mg vials were reconstituted with 1 mL of dehydrated alcohol injection, USP, yielding a 10-mg/mL solution. One milliliter of the reconstituted liquid was incorporated by spatulation into 100 g of Aquaphor ointment base, yielding an ointment containing mechlorethamine hydrochloride 0.01%. The ointment was packaged in screw-cap ointment jars and stored at 23 deg C. Chemical stability was evaluated over a 90 day-period using derivatization and a stability-indicating high-performance liquid chromatographic analytical method. Decomposition of the intact drug occurred at a mcuh slower rate than that observed in aqueous solutions. The loss appeared to be biphasic, occurring more rapidly during the first week and proceeding much more slowly thereafter. Mechlorethamine hydrochloride solubilized with dehydrated alcohol injection and incorporated into Aquaphor ointment base at a concentration of 0.01% lost 10% potency in seven days when stored at 23 deg C.