Abstract
Purpose: :
The demographical development will lead to an increase of patients wearing rigid gaspermeable (RGP) contact lenses, who apply ophthalmic drugs regularly due to age related ocular disorders. Up to now it is unclear, if RGP lenses can or can not absorb locally applied eye drops, perhaps leading to side effects in case of drug release. In order to evaluate possible absorption rates, we initiate an in vitro pilot study for measuring the amount of drug release via the desorption rate.
Methods: :
Two different types of RGP lenses (fluor-silicone-methacrylate (FSM)- and cellulose-acetate-butyrate (CAB)-copolymers were examined after soaking for 8h in eye drop solutions. These solutions consisted of three antiglaucomatous drugs (brimonidine, metipranolol, timolol), one antibiotic eye drop (ofloxacine), one antiallergic drug (acelastine), one non-steroidal-antiinflammatory eye drop (flurbiprofene) and one preservative (benzalconiumchloride (BAC)). A polymeric hydrogel contact lens (methyl-methacrylate/VP) was used as control. For each eye drop solution and each lens type 50 lenses were measured for drug release with the UV/VIS spectral photometer (Lambda 14 Perkin Elmer).
Results: :
In the FSM lens type group we achieved relatively high desorption rates in the lenses soaked with metipranolol, ofloxacine, flurbiprofene, and BAC in between 0.79µg/ml/lens (ofloxacine) to 1.15µg/ml/lens (flurbiprofene). Desorption rates lower than 0.20µg/ml/lens were present in the remaining drug measurements. We could achieve similar results in the CAB lens type group, except the metipranolol soaked lenses in which an amount of 1.60µg/ml/lens could be evaluated. In comparison, the polymeric hydrogel contact lenses presented drug releases from 19 to 383 ng/ml/lens.
Conclusions: :
All of the RGP lenses soaked in different eye drops can release measurable amounts of the used drug solutions, but these amounts were up to 100 to 1000 times lower than these obtained in hydrogel lenses. So, regarding to the well known occurrence of ocular side effects due to drug release in hydrogel lens wear, also side effects during RGP lens wear could be expected particularily with regard to drug accumulation in long term treatment. Further studies are necessary to evaluate these considerations.
Keywords: contact lens • drug toxicity/drug effects • imaging/image analysis: non-clinical