Comparative in vitro antimicrobial potency, stability, colouration and dissolution time of generics versus innovator of meropenem in Europe.

Meropenem generics are often imposed on prescribers, however scarce information is available on key properties such as antimicrobial potency, stability and colouration in solution, and dissolution time. This study aimed to generate comparative information for products available in Europe. The originator (ASTRA) and four generics (HOSPIRA, SANDOZ, FRESENIUS and AUROVIT) were compared for: (i) MICs against Pseudomonas aeruginosa clinical isolates (range, 0.125-191 mg/L); (ii) colouration (visual and photometry) and stability of concentrated solutions for prolonged or continuous infusion and maintained at 25-37 °C for up to 8 h (acceptable limit, ≥90% of original concentration); and (iii) dissolution time of concentrated solutions (50 mg/mL [for bolus administration]: turbidimetry and nursing personnel assessment). No significant difference was observed for MICs (except 2/80 isolates). For concentrated solutions storage: (i) SANDOZ produced about two times more yellow-coloured degradation products than the other preparations; (ii) meropenem loss was time-, concentration- and temperature-dependent; (iii) FRESENIUS was the least stable (limit for 1 g/48 mL, ~8 h at 25 °C and 4.5 h at 37 °C); (iv) at 2 g/48 mL, the storage time limit was 5-6 h at 25 °C and ~3 h at 37 °C for all preparations. Complete dissolution (turbidimetry) required 240 s for generics (120 s for ASTRA), and nurses reported longer but highly variable times for generics. Substantial differences between innovator and generics have been identified that could impact on their clinical use and/or make multicentric studies difficult to interpret, requiring suitability studies in the environments of their intended use.