Antimicrobial Effectiveness and Physicochemical Stability of Compounded Psychiatric and Neurological Drug Suspensions in SyrSpend® SF PH4.

Many psychiatric and neurological medications lack commercial liquid formulations, requiring extemporaneous compounding for patients unable to swallow solid dosage forms. While chemical stability data support extended beyond-use dating for various APIs in SyrSpend® SF PH4, antimicrobial effectiveness data essential for USP <795> compliance remain limited. To evaluate antimicrobial effectiveness and physicochemical stability of seven commonly compounded psychiatric and neurological drug suspensions in SyrSpend® SF PH4 to support evidence-based beyond-use dating decisions. Suspensions of amitriptyline hydrochloride (10.0 mg/mL), clonazepam (0.2 mg/mL), haloperidol (0.5 mg/mL), lorazepam (1.0 mg/mL), naltrexone hydrochloride (1.0 mg/mL), pregabalin (20.0 mg/mL), and sertraline hydrochloride (10.0 mg/mL) were prepared and stored at ambient and refrigerated conditions. USP <51> antimicrobial effectiveness testing was conducted alongside pH and visual appearance assessments. All formulations achieved USP <51> bacterial reduction criteria for E. coli, P. aeruginosa, and S. aureus. Complete C. albicans control was demonstrated in all formulations. A. brasiliensis showed variable responses, with persistent counts in naltrexone, pregabalin, and sertraline formulations, though remaining within USP acceptance limits. pH stability was maintained (3.3 - 5.1) with no visual changes observed. Storage temperature did not significantly affect stability. Results support beyond-use dating recommendations for all APIs at all conditions. These evidence-based recommendations provide compounding pharmacists with USP-compliant guidance for safe extended beyond-use dating while maintaining appropriate safety margins for pediatric, geriatric, and other vulnerable populations.