A new method for continuous intraocular drug delivery.

A novel device for the continuous intraocular delivery of drugs is described. The active intraocular component of the device is made from hollow haemodialysis fibres. During operation, the drug to be administered diffuses from a small extraocular reservoir to the intraocular fibres, where it passes through the semipermeable walls and into the vitreous body. The delivery of gentamicin by the device into the vitreous body of the cat is compared with direct intraocular injection techniques. Characteristics of the process of drug delivery were influenced by the geometry and design of the device. A reservoir concentration of 10 g/L gentamicin sulphate in a device with four fibres, each 5 mm long, resulted in stable vitreal gentamicin levels of 104 to 128 mg/L at 10 hours. Intravitreal injection of 0.1 ml of a 10 g/L solution of gentamicin caused localised peaks of intravitreal gentamicin concentration in the range 1180 to 3296 mg/L, before falling to 356 to 665 mg/L at 10 hours. The device provides the opportunity of a more controlled and continuous drug delivery, thus avoiding the high localised concentrations that may occur with direct injection techniques in which the required dose is delivered as a bolus. Refinement of a device of this type may result in a clinically useful method of intraocular drug delivery for drugs which present a risk of localised retinal toxicity or require repetitive administration with conventional intraocular injection techniques.