Bioavailability of vitamin B using a small-volume nebulizer ophthalmic drug delivery system

BACKGROUND: To determine the intraocular bioavailability of a novel embodiment for vitamin B(12) delivered to the ocular surface by a piezo-electric ultrasonic nebulizer. METHODS: The semisolid embodiment contained 0.02% (w/w) vitamin B(12) in 1 g of ointment, which was immiscible and insoluble in 5 mL sterilized warm water. To confirm in vitro functionality, nebulized mist particles of the embodiment were collected and analysed for vitamin B(12) content. The in vivo arm of the study was designed as randomization of 23 patients who were scheduled to undergo cataract surgery in hospital. Fourteen patients were treated with nebulized vitamin B(12), five patients had one drop of 0.02% vitamin B(12) instilled in the conjunctival cul de sac, and four control patients had no medication. Twelve hours after the vitamin was delivered, the patients underwent the cataract procedure and a sample of aqueous humour was collected from each. High performance liquid chromatography was used for detection of vitamin B(12) in all samples. RESULTS: The in vitro analysis of mist particles showed increasing concentrations of vitamin B(12). In the patient tests, analysis of the aqueous humour samples showed that none of the controls or those receiving eye drops had detectable vitamin B(12) in the aqueous humour. However, 4 of 14 in the nebulizer group had vitamin B(12) detected in the aqueous humour in the amount of 10(-7) mol. CONCLUSIONS: The small-volume nebulizer system might provide another method of ophthalmic drug delivery.