Uptake of gadolinium and dexamethasone in rat inner ear and facial nerve using different administrations.

Abstract

The pathway by which drugs are injected subcutaneously behind the ear to act on the inner ear has not been fully elucidated. To compare the uptake of gadopentetate dimeglumine (Gd-DTPA) and dexamethasone (Dex) in the cochlea and facial nerve of rats following different administrations. Magnetic resonance imaging was applied to observe the distribution of Gd-DTPA in the facial nerve and inner ear. We observed the uptake of Dex after it was injected with different methods. Images of the intravenous (IV) and intramuscular (IM) groups showed that the bilateral cochlea of the rat was visualized almost simultaneously. While in the left post-auricular (PA) injection group, it was asynchronous. The maximum accumulation (Cmax) of the Gd in the left facial nerve of the PA group (35.406±5.32) was substantially higher than that of the IV group (16.765±3.7542) (p<.01). Compared with systemic administration, PA has the advantages of long Gd and Dex action time and high accumulation concentration to treat facial nerve diseases. The distribution of Gd and Dex in the inner ear and facial nerve of rats following PA injection might be unique.