Physicochemical and Microbiological Stability of Commonly Prescribed APIs in SyrSpend® SF PH4: A Comprehensive Compatibility Study.

SyrSpend® SF PH4 is a preservative-light, starch-based oral suspending vehicle formulated for personalized medicine in vulnerable populations such as pediatric and geriatric patients. This study evaluated the physicochemical and microbiological stability of eleven active pharmaceutical ingredients (APIs) compounded in SyrSpend® SF PH4 (liquid and dry forms). The following formulations were tested: azithromycin (40.0 mg/mL), bismuth subsalicylate (17.5 mg/mL), budesonide (0.25 mg/mL), buspirone (2.5 mg/mL), cephalexin (50.0 mg/mL), chlorpromazine hydrochloride (100.0 mg/mL), citalopram hydrobromide (2.0 mg/mL), cyanocobalamin (0.2 mg/mL), famotidine (8.0 mg/mL), meloxicam (0.2 mg/mL), and orphenadrine citrate (5.0 mg/mL). Each formulation was stored under refrigerated (2-8°C) and room temperature (20-25°C) conditions, then evaluated over 90 days using validated ultra-high-performance liquid chromatography (UHPLC) and antimicrobial effectiveness testing (AET) per USP <51>. Azithromycin was not stable at room temperature but maintained stability for 60 days under refrigeration; bismuth subsalicylate remained stable for 14 days under both storage conditions; cephalexin remained stable for 14 days at room temperature and 30 days refrigerated; budesonide, buspirone, chlorpromazine hydrochloride, citalopram hydrobromide, cyanocobalamin, famotidine, meloxicam, and orphenadrine citrate all demonstrated stability for 90 days under both conditions. AET confirmed microbial control throughout the storage period for all samples. These results confirm that SyrSpend® SF PH4 is a reliable vehicle for extemporaneous compounding of a broad range of oral liquid formulations, offering extended BUDs for most APIs tested. Its excipient profile - free from harmful substances like alcohol, parabens, propylene glycol, and sorbitol - supports safe use in pediatric and geriatric patients. The study provides evidence-based guidance for pharmacists in assigning appropriate BUDs and optimizing personalized therapy through compounded oral suspensions.