Origin Determination of Impurities Occurring During the Preparation of Fortified Vancomycin Eye Drop

Introduction
Dunkirk Pharmacy prepare fortified eye drops for the treatment of eye infections. They are packaged in tinted glass vials washed and sterilized in our sterilization unit. During a preparation session, we noticed flocculation when filling the vials with the reconstituted Vancomycin solution. This reaction seems to be caused by a deposit on the wall of the vials. The flocculation disappears after a few seconds in solution. Flocculation does not occur with other molecules (Gentamicin, Amphotericin B and Ceftazidime), we asked ourselves about the cause of this anomaly.

Objective
To identify the origin of the impurities and to fix it.

Materials and Methods
We investigated washing and sterilization methods. After an unsuccessful bibliographic search, we carried out 3 series of preparations packaged in vials undergoing different treatments in order to identify the source of the problem: washed (W+) unwashed (W-), sterilized (S+), unsterilized (S-), with lubricant during washing (Lu+) or without (Lu-).
Series 1: 5 collectively W+/S+ vials, 5 individual W+/S+ vials, 5 W-/S- vials.
Series 2: 5 collectively W+/S+ vials, 5 individual W+/S+ vials, 5 W+/Lu+/S- vials, 5 W+/Lu-/S- vials
Series 3: 5 collectively W+/S+ vials, 5 individual W+/S+ vials, 5 W-/S+ vials.

Results
Among 15 W+S bottles collectively sterilized, 6 contained flocculation (40%). Among 15 W+S bottles individually sterilized, 2 presented flocculation (13%). Among 5 bottles sterilized without washing, 4 displayed flocculation (80%). No flocculation was found in the 10 vials washed without sterilization process (with or without lubricant) or in the 5 vials neither washed nor sterilized.

Discussion-Conclusion
Given the results, trend is emerging whereby the impurities found on the bottles come from the sterilization process. We supposed that they derive from the condensation of salts contained in the sterilization water. It would be interesting to carry the analysis further by increasing the number of vials tested and try to identify the nature of these impurities to ensure their harmlessness for the patient. Alternatively, we could opt for a ready-to-use, already sterile container.

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