Antimicrobial Stability, pH, and Physical Appearance of Cardiovascular Drug Suspensions in SyrSpend® SF PH4: A...

The compounding of extemporaneous oral liquid formulations is essential for personalized pharmacotherapy, particularly for pediatric, geriatric, and dysphagic patients who require tailored doses and flexible dosage forms. However, preservative-free liquid vehicles require thorough evaluation to ensure antimicrobial safety and physicochemical integrity over time. This complementary study aimed to assess the antimicrobial effectiveness, pH stability, and physical appearance of cardiovascular drug formulations prepared with SyrSpend® SF PH4 liquid, in order to support beyond-use dating (BUD) in compliance with United States Pharmacopeia (USP) standards. The pH and appearance were monitored at predefined intervals over 90 days under room temperature (25 ± 2°C) and refrigerated (5 ± 3°C) storage conditions, and the antimicrobial effectiveness was evaluated following the USP <51> protocol at the end of this period. Nine oral formulations of seven cardiovascular drug suspensions were included: amlodipine (as besylate) 1.0 mg/mL, enalapril maleate 1.0 mg/mL, hydrochlorothiazide 2.0 and 5.0 mg/mL, lisinopril (as dihydrate) 1.0 mg/mL, metoprolol tartrate 10.0 mg/mL, pentoxifylline 20.0 mg/mL, and spironolactone 2.0 and 2.5 mg/mL. All formulations met USP criteria for antimicrobial effectiveness, while maintaining stable pH values and no relevant changes in physical appearance throughout the study. These results, when combined with previously demonstrated chemical stability (HPLC), confirm that SyrSpend® SF PH4 is a robust and reliable vehicle for preservative-free extemporaneous oral liquid formulations, supporting its safe use within USP-compliant BUD limits.