Microbiological stability of a 10 µg/mL clonidine solution for paediatric use

Objective
Clonidine is used in the treatment of opioid withdrawal syndrome in infants. While the physicochemical stability [1] of a clonidine solution has already been demonstrated, a microbiological stability study is required due to differences in the materials used, in accordance with Good Preparation Practices. The objective of this study was to investigate the microbiological stability of a 10 µg/mL clonidine solution in order to determine its shelf life.

Methods
Microbiological control of non-sterile oral products was carried out in accordance with the acceptance criteria set by the European Pharmacopoeia (Ph. Eur. 5.1.4) : microbial enumeration test (Ph. Eur. 2.6.12) and test for specified microorganisms (MO) (Ph. Eur 2.6.13). To this end, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus spizizenii, Aspergillus brasiliensis, Candida albicans and Escherichia coli (Vitroids™ discs, Millipore) were thawed and then resuspended according to their CFU levels and laboratory specifications.
The fertility of the culture media and the applicability of the method (enumeration by membrane filtration - EZFit^® pump, Millipore^® - and detection of specified MOs) were verified. Different dilutions in phosphate buffer (Millipore^®) were tested to neutralise the preservative (potassium sorbate).
The study was conducted over 1 month with controls on days 0, 7, 14 and 28. Once the vials were opened, the stability study was continued with repeated openings and sampling on days 7, 14 and 28. Samples were stored at 4 ± 2°C.

Results
To neutralize the preservative, a 10-fold dilution was used for microbial enumeration, while a 20-fold dilution was chosen for the E.coli test. During the 2-month study, no yeast or mould growth was observed and the E. coli test remained negative. The count of aerobic germs revealed a maximum of 30 CFU/mL, below the limit of 100 CFU/mL set by the Ph. Eur.

Conclusion
The microbiological quality of the clonidine 10 µg/mL solution complies Ph. Eur. criteria. These results validate a shelf-life of 2 months at 4 ± 2°C. After opening, the solution remains stable for 1 month. The study is continuing with additional testing planned at M3 and M6.

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