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Purpose: Ophthalmic preparations can cause toxic ocular reactions, often associated with the use of preservatives. The aim of this study was to compare the ocular tolerance of three ophthalmic preparations based on timolol: a preservative free ophthalmic preparation (Timabak) and two other commercially available preserved preparations (Timoptol) and Timoptol LP)., Methods: The effect of repeatedly instilling eye drops for 28 days on rabbit eyes was assessed in vivo by mean of a confocal laser scanning ophthalmoscope. The corneal microlesions were selectively marked by fluorescein., Results and Conclusion: The overall results show the good ocular tolerance of the three tested products. However, a closer comparison between the products brought out differences in the extent of lesions among the tested products depending on their composition. Indeed the preservative free eye drops appeared better tolerated than the two preserved preparations.

The present review describes work done over the past twenty years on the controlled release of drugs using iontophoresis or electrophoresis techniques. Following a description of therapeutic applications, in vivo and in vitro studies have been discussed with emphasis on the potentials of such techniques to control drug release. Different mathematical models have been reviewed and an attempt has been made to combine them to explain the various configurations of systems currently used.