Formulation of suspending vehicles for extemporaneous oral liquid compounding with diltiazem hydrochloride as a drug model

Objective: This study aimed to determine the optimum concentrations of a suspending vehicle and develop a physically and chemically stable formulation containing diltiazem hydrochloride (DTZ). Methods: Stability testing was performed for 30 days in selected suspending vehicle formulas (Formulas A and E). Physical stability tests were performed at room temperature, and physical properties (odor and color) and pH values of suspensions were evaluated. Results: The oral suspensions of DTZ were white and had a drug-like odor, and the pH had significantly decreased during storage. Chemical stability tests of suspensions were performed at room temperature and 4°C±2°C using ultraviolet-visible spectrophotometry. Conclusion: The concentrations of DTZ in oral suspensions fluctuated during the storage period, suggesting that the oral suspensions of DTZ are physically stable but not chemically stable during storage.