Evaluation of contamination in preservative-free multi-dose Brimonidine eye drops: a comparative study

To investigate the effectiveness of preservative-free multi-dose eye drop technology in preventing contamination.

Prospective study METHODS: In this study, the caps, first and second drops of preservative-free multidose brimonidine (PF-MDB) and multidose brimonidine with purite preservative (P-MDB) used by 54 glaucoma patients were analysed on both chocolate and sheep blood agar. The patients used the drops at 3-week intervals. The contents of the eye droppers were examined for contamination by piercing the bottom of the eye dropper in accordance with aseptic techniques.

The contamination levels detected using chocolate agar in the caps and the first drops of PF-MDBs were significantly higher than in P-MDBs (p=0.006 and p<0.001, respectively). The contamination levels detected using blood sheep agar in the caps and the first and second drops of PF-MDBs were significantly higher than in P-MDBs (p=0.001, ‹0.001, 0.006, respectively). No growth was found inside the eye dropper bottles of either PF-MDB or P-MDB drops. There was a significantly higher level of contamination in the first drops of PF-MDB compared to the second drops (p<0.001).

PF-MDB bottle technology effectively prevents microbial contamination in the bottle without preservatives. However, due to the lack of a preservative, there is increased bacterial and fungal growth associated with contamination on the cap, as well as in the first and second drops, compared to P-MDB.