Materials and Methods: Ophthalmic solution bottles of preservative-free brimonidine 0.15% (D1), benzalkonium chloride-containing (BAK) brimonidine 0.15% (D2), purite-containing brimonidine 0.15% (D3) and BAK-containing timolol maleate dorzolamide fi xed combination (D4) were included in this study in terms of microbial contamination risk. Moreover, microbial contamination of the two bottles [preservative-free brimonidine 0.15% (D7) and BAK-containing brimonidine 0.15% (D8)] was investigated after contacting their tips with the lower eyelid edge of a researcher. Every day twice a day for 60 days; the caps of the bottles were opened and they were closed after waiting for 20 sec. One drop was added from these six bottles 11 times during the study period (60 days) to the six separate and renewed blood-agar mediums. Microbial contamination was evaluated every visit by examining the blood agar mediums by the same microbiologist. In terms of antimicrobial effi cacy; D1, D2, D3 and D4 were compared with the antibiotic containing ophthalmic solutions; moxifl oxacin (D5) and tobramycin (D6) by using agar well diffusion method.

Results: No bacterial growth was observed in the mediums of D1, D2, D3, D4 and D8 bottles. The bacterial growth of methicillin-susceptible and resistant coagulase-negative staphylococci was observed in the medium of D7 bottle on some days. A large inhibition zone was seen around D5 and D6, whereas a smaller inhibition zone was detected around D2 and D4. No inhibition zone was detected around the D1 and D3 bottles.

Conclusions: Multi-dose preservative-free antiglaucomatous ophthalmic solutions have not any risk of bacterial contamination unless the tip of the bottle is contaminated. Keywords : Benzalkonium chloride, Brimonidine, Glaucoma, Purite, Multi-dose non-preservative ophthalmic solutions