Performance Evaluation and Operational Limits of Five Automated Sterile Compounding Systems

Objective
With the increasing production of ophthalmic medicines and the need to limit musculoskeletal disorders among pharmacy technicians, peristaltic and volumetric pumps are commonly used to prepare bulk solutions and dispense them into ophthalmic bottles or injectable preparations. Reliable and reproducible dispensing over a wide range of volumes is essential for routine sterile compounding. The aim of this study was to compare the performance of five automated dispensing systems—Baxa Repeater^®, Added Pharma SmartPump^® (first- and second-generation models), Medimix Mini^®, and Vigo^® pump—using gravimetric analysis to define their operational limits in routine practice.

Methods
Five dispensing systems were evaluated at five target volumes (10, 20, 50, 120, and 200 mL of 0.9% sodium chloride). For each target volume, ten consecutive dispenses were gravimetrically assessed to evaluate dispensing accuracy, repeatability, and linearity across the operating range. In addition, dispensing stability was assessed by performing four series of 100 consecutive 10-mL dispenses. Gravimetric measurements were performed under all experimental conditions. For each series, the mean delivered volume, standard deviation, accuracy, repeatability, and process capability index (Cpk) were calculated using predefined acceptance criteria (±5% for dispensing volumes between 10 and 20 mL and ±2% for volumes greater than 20 mL).

Results
The Medimix Mini demonstrated the highest repeatability (CV < 0.1%) and excellent process capability at low dispensing volumes. The Baxa Repeater showed robust performance up to 200 mL (Cpk = 2.25), despite a slight systematic drift. The Vigo pump combined good accuracy with satisfactory repeatability (CV ≤ 0.3%), although process capability varied according to the target volume. The Added Pharma SmartPump systems achieved satisfactory performance at low dispensing volumes but exhibited a progressive decline in process capability as dispensing volume increased, reaching a Cpk of 0.33 at 200 mL. All systems demonstrated excellent linearity over the evaluated range (R² > 0.99). During repeated dispensing, the Vigo pump maintained stable performance throughout the study, whereas the Baxa Repeater exhibited a gradual drift over successive dispensing cycles and the Added Pharma SmartPump systems showed greater variability.

Conclusion
This study highlights significant differences in the metrological performance of the evaluated dispensing systems. The Medimix Mini and the Baxa Repeater fulfilled the predefined process capability requirements for the routine production of ophthalmic preparations. The Added Pharma SmartPump systems should be restricted to dispensing volumes below 50 mL, whereas the Vigo pump represents an effective compromise for dispensing bulk solutions. In addition, the ProCare devices offer practical advantages owing to their compact footprint and ergonomic design when operated in a biological safety cabinet. Further investigations are currently being conducted in collaboration with the manufacturers to better characterize the observed performance and optimize operating conditions for routine pharmaceutical compounding.