Simulation of application strategies for local drug delivery to the inner ear.

Local, rather than systemic, drug delivery to the inner ear is becoming more widely used to treat inner ear disorders. While many substances are undergoing preclinical and clinical studies, it is equally important to develop appropriate drug delivery systems. Pharmacokinetic studies are technically demanding in animals and almost impossible in humans. Computer simulations have helped establish the basic principles of drug distribution in the inner ear. The distribution of methylprednisolone in the guinea pig cochlea has been simulated for different drug delivery systems based on kinetic parameters established in prior studies. Results were compared for different rates of drug clearance from the middle ear. Absolute and relative drug levels in the perilymph were highly dependent on how long the drug remained in the middle ear. For a brief (30 min) application, the basal to apical drug gradient was higher than for longer delivery times. These findings show that controlling middle ear drug clearance is of critical importance.