Long term in vivo release profile of dexamethasone loaded silicone rods implanted into the cochlea of guinea pigs

Glucocorticosteroids are used intra-operative in cochlear implant surgery to dampen inflammatory reactions. As a result of the fast clearance of glucocorticoids from the inner ear, sustained application should be more effective in suppressing tissue reaction. The embedding of the glucocorticoid dexamethasone into the cochlear implant electrode carrier and its continuous release may solve this problem. The aim of the present study was to examine how perilymph drug levels are influenced by the dexamethasone concentration in the electrode carrier at different time points.

Silicone rods were implanted into the basal turn of the scala tympani of guinea pigs. The silicone rods were loaded either homogeneously with dexamethasone or loaded with a vertical stripe. After implantation, dexamethasone concentrations in perilymph and tissue were measured at several time points over a period of up to 12 weeks.

Following an initial burst release phase, stable dexamethasone levels were detected in scala tympani perilymph for several weeks. Rods with vertical stripes had a faster release termination than in homogeneously loaded rods. The tissue drug concentration over time shows a similar dynamic as perilymph drug concentration but only reaches about 0.005 – 0.05% of the perilymph drug concentration.

The data shows that dexamethasone can be released from silicone rods in a controlled and sustained way over a period of several weeks leading to constant drug concentrations in the scala tympani perilymph. There occurs no accumulation of dexamethasone in cochlear tissue.

Publication History

Publication Date:
23 April 2019 (online)