A Sorption Study between Ophthalmic Drugs and Multi Dose Eyedroppers in Simulated Use Conditions

Abstract Preservative free ophthalmic formulations need to be packaged either as single doses, or using specially designed sterility preserving multidose eyedroppers. Our objective was to evaluate potential sorption phenomena between a device with a silicone sterility preserving membrane and the delivered drops of several ophthalmic solutions. Cyclosporine, rifamycin, latanoprost, timolol and norfloxacin were used as model drugs. Quantification of the active substance in delivered drops (1 to 4 drops per day) from low density polyethylene (LDPE) bottles without any sterility preserving device and from LDPE bottles with a sterility preserving silicone membrane (LDPE-Si) was performed for 14 days (n≥3), using validated HPLC methods. For cyclosporine, mean concentrations did not vary by more than 10 % from reference concentrations for either LDPE or LDPE-Si eyedroppers, but for LDPE-Si, the concentrations of the 1 mg.ml-1 cyclosporine micellar solution were found to be significantly lower than for those from LDPE eyedroppers (p=0.0127). For LDPE-Si, rifamycin mean concentrations decreased by 11.2 % throughout the 14 day study period, but didn’t vary by more than 10 % for LDPE and glass eyedroppers. However, rifamycin concentrations from LDPE-Si were not significantly different from those from LDPE eyedroppers. For latanoprost, whilst mean concentrations did not vary by more than 10 % from reference concentration for LDPE eyedroppers, for LDPE-Si eyedroppers concentrations decreased by 76.4 % at their lowest concentration and never returned to their initial level. For timolol and norfloxacin, mean concentrations did not vary by more than 10 % for either LDPE or LDPE-Si eyedroppers and no significant difference was found between the 2 eyedroppers concentrations. Our results are in favor of an absence of significant sorption between LDPE-Si eyedroppers for timolol or norfloxacin ophthalmic solutions. Further studies should be performed on cyclosporine ophthalmic micellar solutions and rifamycin ophthalmic solutions before any definite conclusions can be made. Finally, our results show that latanoprost ophthalmic solutions shouldn’t be used with LDPE-Si eyedroppers as the loss of active substance would cause a sever under-dosing.