SyrSpend® SF PH 4 as a Safe Vehicle for Extemporaneous Oral Suspensions: Microbiological Stability of Seven APIs

SyrSpend® SF PH4 is a preservative-free oral suspending vehicle widely used in extemporaneous compounding. While its chemical stability has been previously demonstrated for various active pharmaceutical ingredients (APIs), microbiological stability data remain limited. This study aimed to evaluate the microbiological stability of oral suspensions containing dapsone, griseofulvin, levofloxacin, terbinafine, indometacin, naproxen, and paracetamol in SyrSpend® SF PH4, under both room temperature and refrigerated conditions. Formulations were assessed over 90 days for physical appearance and pH. Antimicrobial effectiveness testing (AET) was conducted according to USP <51> against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans, and Aspergillus brasiliensis. All formulations maintained stable pH and appearance throughout the study. AET results showed a reduction of microbial counts to below detectable levels (log 1.0) by day 14, sustained through day 28, meeting USP <51> acceptance criteria. SyrSpend® SF PH4 effectively preserved the microbiological integrity of all tested formulations without added preservatives. These findings complement existing chemical stability data and support the use of SyrSpend® SF PH4 as a safe and effective vehicle for extemporaneous oral suspensions, particularly in populations requiring preservative-free formulations.