Sterility of Non-Preservative Eye Drops
Pinnita Prabhasawat MD*, Suksri Chotikavanich MD*, Amornrut Leelaporn PhD**
Affiliation : * Department of Ophthalmology, Faculty of Medicine, Siriraj Hospital, Mahidol University ** Department of Microbiology, Faculty of Medicine, Siriraj Hospital, Mahidol University
Objectives : To assess microbial contamination of common non-preservative eye drops stored at 4 oC and
non-preservative fortified antibiotic eye drops used in a hospital inpatient setting.
Materials and Methods : A prospective study of the sterility of non-preservative eye drops was examined by
dividing the patients into 2 groups. Group 1 composed of 5 samples of each ophthalmic preparation, which
consisted of fortified antibiotics (vancomycin, cefazolin, gentamicin, and amikacin), non-preservative steroid
eye drops (1% methylprednisolone and 0.01% dexamethasone), and 20% autologous serum stored at 4 oC.
Group 2 was composed of 28 samples of fortified vancomycin and 23 samples of fortified amikacin used in
an inpatient setting for 1 week and kept in 4 oC for 28 days. The contamination was assessed at the day
of preparation and then at day 4, 7, 14, 21, 28 of all medications except autologous serum was done up to
day 84. The sterility was examined by the culturing on tryptic soy broth and thioglycolate broth.
Results : In group 1 and 2, no contamination was detected in any samples within 4 weeks and up to 12 weeks
for autologous serum.
Conclusion : Non- preservative topical eye drops can be safely kept at 4 oC without contamination for 4 weeks
and 12 weeks for 20 % autologous serum drop. For topical antibiotics, under a strict protocol for preparation
and usage might be used without significant risk of bacterial contamination for 4 weeks.
Keywords : Sterility, Non-preservative topical eye drop, Fortified antibiotics, Non-preservative steroid, Autologous serum
