Stability of ketoconazole, metolazone, metronidazole, procainamide hydrochloride, and spironolactone in extemporaneously compounded oral liquids

The stability of drugs commonly prescribed for use in oral liquid dosage forms but not commercially available as such was studied. Ketoconazole 20 mg/mL, metolazone 1 mg/mL, metronidazole 50 mg/mL, procainamide hydrochloride 50 mg/mL, and spironolactone 25 mg/mL were prepared in a 1:1 mixture of Ora-Sweet and Ora-Plus (Paddock Laboratories), a 1:1 mixture of Ora-Sweet SF and Ora-Plus (Paddock Laboratories), and cherry syrup and placed in 120-mL polyethylene terephthalate bottles. The sources of the drugs were powder, capsules, and tablets. Six bottles were prepared per liquid; three were stored at 5 degrees C and three at 25 degrees C, all in the dark. A sample was removed from each bottle immediately after preparation and at intervals up to 60 days and analyzed for drug concentration by stability-indicating high-performance liquid chromatography. At least 93% of the initial drug concentration was retained in all the oral liquids for up to 60 days. There were no substantial changes in the appearance or odor of the liquids, or in the pH. Ketoconazole 20 mg/mL, metolazone 1 mg/mL, metronidazole 50 mg/mL, procainamide hydrochloride 50 mg/mL, mt, and spironolactone 25 mg/mL were stable for up to 60 days at 5 and 25 degrees C in three extemporaneously compounded oral liquids.