STABILITY OF BETHANECHOL CHLORIDE, PYRAZINAMIDE, QUINIDINE SULFATE, RIFAMPIN, AND TETRACYCLINE HYDROCHLORIDE IN EXTEMPORANEOUSLY COMPOUNDEDORAL LIQUIDS

The stability of five drugs commonly prescribed for use in oral liquid s but not commercially available as such was studied. Bethanechol chlo ride 5 mg/mL, pyrazinamide 10 mg/mL, quinidine sulfate 10 mg/mL, rifam pin 25 mg/mL, and tetracycline hydrochloride 25 mg/mL were each prepar ed in a 1:1 mixture of Ora-Sweet and Ora-Plus (Paddock Laboratories), a 1:1 mixture of Ora-Sweet SF and Ora-Plus, and cherry syrup and place d in 120-mL amber clear polyethylene terephthalate bottles. Three bott les of each liquid were stored at 5 degrees C and three at 25 degrees C, all in the dark. Samples were taken initially and at various times up to 60 days for analysis by high-performance Liquid chromatography a nd assessment of appearance and odor; pH was measured. A mean of at le ast 90% of the initial drug concentration was retained for 60 days in the liquids containing bethanechol chloride, pyrazinamide, or quinidin e sulfate and for 28 days in the rifampin-containing liquids and the m ixture of tetracycline hydrochloride and Ora-Sweet-Ora-Plus at both 5 and 25 degrees C. Tetracycline hydrochloride concentrations of 90% or more of the initial concentration were retained in the liquids prepare d with Ora-Sweet SF-Ora-Plus for 10 days at 5 degrees C and 7 days at 25 degrees C and in those prepared with cherry syrup for 7 days at 5 d egrees C and 2 days at 25 degrees C. No substantial changes in the app earance, odor, or pH of any liquid were observed. At 5 and 25 degrees C, bethanechol chloride 5 mg/mL, pyrazinamide 10 mg/mL, and quinidine sulfate 10 mg/mL were stable in three extemporaneously compounded oral liquids for 60 days and rifampin 25 mg/mL was stable for 28 days. The stability of tetracycline hydrochloride 25 mg/mL varied with the vehi cle.