Aims: To assess the ocular bioavailability of fluorescein from a novel water free, freeze dried ophthalmic drug delivery system compared to conventional preservativefree fluorescein eye drops. Methods: Sodium fluorescein 0.17% was dissolved in an aqueous solution of hydroxypropylmethyl cellulose 1.0% (HPMC), deposited on sterilised flexible hydrophobic poly-(tetrafluoroethylene) (PTFE) carrier strips and freeze dried under aseptic conditions. The fluorescein dose of the lyophilisate was 68 µg, corresponding to a single conventional drop of 40 µl fluorescein 0.17% solution. In a randomised, open label study 12 healthy volunteers applied the lyophilised fluorescein to one eye and one drop of conventional fluorescein ophthalmic solution to the fellow eye. Fluorophotometry measurements of fluorescein concentrations in the anterior segment were performed with the Fluorotron Master II (Ocumetrics, USA) before and +15, 30, 45, 60, 120, and 180 minutes after application. Results: At all times anterior chamber fluorescein concentration was greater in the lyophysilate treated eye than the solution treated eye. The magnitude of this difference ranged from 2-5.3 times and was statistically significant. Conclusion: The greater intraocular bioavailability of fluorescein from the lyophilisate relative to the solution suggests that it may be a useful method for delivering substances to the eye. C onventional eye drops, used in most medications for ocular treatment, have several disadvantages. Even for experienced users it is difficult to administer a single drop to the right place. Elderly patients or children even without impaired manual skills even injure their eyes and cause bacterial contamination upon contact with the bottle tip. Preservatives are known to cause morphological changes of the cornea, conjunctiva, and Tenon leading to changing in scarring behaviour after glaucoma surgery.1-3 Preservatives cause irritation such as burning, stinging, tearing, hyperaemia, and punctate keratitis and allergies, a common ocular side effect of conventional eye drops. Preservatives and pH adjustments are required to dissolve the drugs (for example, homatropine, pilocarpine, etc) and to maintain their chemical stability. Both are responsible for increased tear flow, thus diluting the applied medication which results in poor pharmacokinetics of conventional eye drops. 4 In the recent past drug delivery devices like the Ocusert and NODS (new ophthalmic drug delivery system) have been demonstrated to be safe and tolerated in the human eye, as well as being efficient delivery systems.5-8 However, none of them has been used therapeutically on a broad scale. Thus, we continue to search for the ideal delivery system which should be constant in its dose delivery, easy to handle, of minimal discomfort and effect on precorneal clarity, pH neutral, sterile, and preservative free.A new ophthalmic drug delivery device (lyophilisate) was developed. The medication is dissolved with a hydrophilic polymer and freeze dried at the tip of a soft hydropho...
