Long term microbial stability study for implementation of batch production for cytotoxic drugs in hospital pharmacy.

Objective of our work was to assess the microbial stability of cytotoxic preparations performed as standardized doses following a batch production process. The method developed was to use culture media (trypticase soya broth) in place of original drug (as used in process validation) combined to iterative sterility tests during 60 days of storage at +4°C. The use of culture media in place of original drug was justified as the worst case in term of microbial contamination risk [1]. Moreover, the substitution of drug by culture media avoided the possible risk of inhibition of microbial growth by the original drug [2]. The sterility test was using an automated and rapid microbial detection system BD Bactec® allowing detection of microbial growth within 24-48 hours. Moreover, this non destructive method allowed a close transfer of the sample in culture medium avoiding false positive. Validation of the method was performed using fertility test of the culture media in accordance with the European Pharmacopeia [3] involving 6 recommended species (Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus subtilis, Candida albicans, Clostridium sporogenes, Aspergillus niger). Preparation process was simulating the further real process producing a big bag of 2500 mL with the help of a peristaltic pump (BAXA®) followed by the filling of 20 smaller bags of 100 ml. 3 independent batches of 20 bags were performed and sterility was assessed with Bactec® using 2 culture media (Bactec Plus® aerobic and lytic® anaerobic, BD) on 20 bags of each batch at J0 and 5 bags at J7, J14, J30, J60. Moreover, at the end of the 60 day storage period at +4°C, the remaining bags were incubated for 14 days at 35°C for visual inspection of potential microbial growth.

The results showed no microbial growth in bags incubated at the end of the 60 day storage period and all sterility tests were negative. Fertility test performed both with culture media used for the preparations and Bactec® media were positive at <100 CFU for the 6 recommended species.

Our work validated for our specific working procedures, the long term microbial stability of 60 days of our preparations produced as a batch and stored in their final container at +4°C. Physical integrity testing of the overwrapping and the ability of Bactec® media to be used for sterility test in the presence of cytotoxic drugs will complete the present investigation.