Perilymph Pharmacokinetics of Markers and Dexamethasone Applied and Sampled at the Lateral Semi-Circular Canal
Open Access
- 12 September 2012
- journal article
- Published by Springer Science and Business Media LLC in Journal of the Association for Research in Otolaryngology
- Vol. 13 (6), 771-783
- https://doi.org/10.1007/s10162-012-0347-y
Abstract
Perilymph pharmacokinetics was investigated by a novel approach, in which solutions containing drug or marker were injected from a pipette sealed into the perilymphatic space of the lateral semi-circular canal (LSCC). The cochlear aqueduct provides the outlet for fluid flow so this procedure allows almost the entire perilymph to be exchanged. After wait times of up to 4 h the injection pipette was removed and multiple, sequential samples of perilymph were collected from the LSCC. Fluid efflux at this site results from cerebrospinal fluid (CSF) entry into the basal turn of scala tympani (ST) so the samples allow drug levels from different locations in the ear to be defined. This method allows the rate of elimination of substances from the inner ear to be determined more reliably than with other delivery methods in which drug may only be applied to part of the ear. Results were compared for the markers trimethylphenylammonium (TMPA) and fluorescein and for the drug dexamethasone (Dex). For each substance, the concentration in fluid samples showed a progressive decrease as the delay time between injection and sampling was increased. This is consistent with the elimination of substance from the ear with time. The decline with time was slowest for fluorescein, was fastest for Dex, with TMPA at an intermediate rate. Simulations of the experiments showed that elimination occurred more rapidly from scala tympani (ST) than from scala vestibuli (SV). Calculated elimination half-times from ST averaged 54.1, 24.5 and 22.5 min for fluorescein, TMPA and Dex respectively and from SV 1730, 229 and 111 min respectively. The elimination of Dex from ST occurred considerably faster than previously appreciated. These pharmacokinetic parameters provide an important foundation for understanding of drug treatments of the inner ear.This publication has 47 references indexed in Scilit:
- Dexamethasone Levels and Base-to-Apex Concentration Gradients in the Scala Tympani Perilymph After Intracochlear Delivery in the Guinea PigOtology & Neurotology, 2012
- Marker entry into vestibular perilymph via the stapes following applications to the round window niche of guinea pigsHearing Research, 2012
- Direct Entry of Gadolinium into the Vestibule Following Intratympanic Applications in Guinea Pigs and the Influence of Cochlear ImplantationJournal of the Association for Research in Otolaryngology, 2011
- Distribution of Dexamethasone and Preservation of Inner Ear Function following Intratympanic Delivery of a Gel-Based FormulationAudiology and Neurotology, 2010
- Principles of Local Drug Delivery to the Inner EarAudiology and Neurotology, 2009
- Dose-Dependent Sustained Release of Dexamethasone in Inner Ear Cochlear Fluids Using a Novel Local Delivery ApproachAudiology and Neurotology, 2009
- RAPID CLEARANCE OF METHYLPREDNISOLONE AFTER INTRATYMPANIC APPLICATION IN HUMANS. COMMENT ON: BIRD PA, BEGG EJ, ZHANG M, ET AL. INTRATYMPANIC VERSUS INTRAVENOUS DELIVERY OF METHYLPREDNISOLONE TO COCHLEAR PERILYMPH. OTOL NEUROTOL 2007;28:1124-30Otology & Neurotology, 2008
- Dexamethasone Concentration Gradients Along Scala Tympani After Application to the Round Window MembraneOtology & Neurotology, 2008
- Concentration Gradient Along the Scala Tympani After Local Application of Gentamicin to the Round Window MembraneThe Laryngoscope, 2007
- Demonstration of a Longitudinal Concentration Gradient Along Scala Tympani by Sequential Sampling of Perilymph from the Cochlear ApexJournal of the Association for Research in Otolaryngology, 2006