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Mannitol and the blood-labyrinth barrier
Trung N Le1,2, Brian W Blakley3
1Department of Otolaryngology - Head & Neck Surgery, Sunnybrook Research Institute, University of Toronto, 2075 Bay view Ave., Room M1.102, Toronto, ON, M4N 3M5, Canada. trungngocle@gmail.com.
Summary
Mannitol transiently increases the permeability of the blood labyrinth barrier (BLB), aiding gentamicin entry and exit. This finding suggests potential clinical benefits for drug delivery to the inner ear.
Area of Science:
- Pharmacology
- Neuroscience
- Otolaryngology
Background:
- Characterizing the blood labyrinth barrier (BLB) is crucial for pharmacological manipulation.
- Investigating the BLB is technically challenging.
- This study introduces a novel method for BLB control and pharmacokinetic analysis.
Purpose of the Study:
- To establish the pharmacokinetics of gentamicin in perilymph, cerebrospinal fluid (CSF), and blood.
- To evaluate the effect of mannitol on BLB and blood-brain barrier (BBB) permeability to gentamicin.
Main Methods:
- A controlled animal research project involving 44 guinea pigs.
- Measurement of gentamicin concentrations in blood, perilymph, and CSF with and without mannitol administration.
- Pharmacokinetic analysis of 175 samples collected over 17.5 hours post-infusion.
Main Results:
- Mannitol significantly increased gentamicin's entry and egress through the BLB (p=0.0044).
- Mannitol's effect on the blood-brain barrier (BBB) was not statistically significant (p=0.581).
- Gentamicin concentrations in perilymph and CSF remained lower than in blood.
Conclusions:
- Mannitol administration temporarily enhances BLB permeability.
- Strategic timing of mannitol may improve drug delivery (e.g., gentamicin) into the perilymph.
- Findings suggest potential clinical applications for osmotic agents in modulating inner ear drug concentrations.
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