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Published on: October 13, 2010
A novel emulsifier, labrasol, enhances gastrointestinal absorption of gentamicin
1Department of Pharmacokinetics, Kyoto Pharmaceutical University, Japan. takada@mb.kyoto-phu.ac.jp
Abstract:
Gentamicin (GM) is an important aminoglycoside antibiotic for the treatment of infections caused by a wide spectrum of aerobic gram-negative bacilli and gram-positive cocci. As a class, the aminoglycosides are poorly absorbed from the gastrointestinal (GI) tract and are commonly used as injectable and topical preparations. This study was aimed at finding the effect of a novel emulsifier, Labrasol, on the absorption of GM from the GI tract of rats. GM formulations were prepared, either as saline solution or as Labrasol microemulsions, and were administrated to rat small intestine and colon. Plasma GM levels following intestinal application were compared to those obtained with intravenous (i.v.) administration. A 5 mg/kg dose of GM preparation containing Labrasol, 1 ml/kg, administrated into colon resulted in the mean AUC of 21.179+/-1.374 microg x h/ml, compared to 7.813+/-0.105 microg x h /ml obtained with i.v. administration of GM, 1 mg/kg. The absolute bioavailability (BA) of the Labrasol preparation was 54.2%. Labrasol facilitates the transmucosal delivery of GM from rat colon by forming microemulsions, and the BA obtained with Labrasol microemulsion was higher than with other surfactants (8.4% for Tween 80 and 3.4% for Transcutol P). Additionally, in vitro permeation studies demonstrated that Labrasol also inhibited the intestinal secretory transport. The effect of Labrasol is ascribed to both (1) enhanced GM absorption from the GI lumen into the systemic circulation and (2) inhibition of efflux of GM from the enterocytes to the GI lumen.
Insights
Labrasol, a novel emulsifier, significantly enhances gentamicin absorption from the rat gastrointestinal tract. This microemulsion formulation achieved 54.2% bioavailability, surpassing other surfactants and offering a promising alternative for drug delivery.
Area of Science:
- Pharmacology
- Drug Delivery Systems
- Gastrointestinal Absorption
Background:
- Gentamicin (GM) is a crucial aminoglycoside antibiotic for treating aerobic gram-negative and gram-positive bacterial infections.
- Aminoglycosides exhibit poor oral absorption, necessitating injectable or topical administration routes.
- Novel delivery systems are needed to improve gastrointestinal absorption of antibiotics like gentamicin.
Purpose of the Study:
- To investigate the effect of Labrasol, a novel emulsifier, on the gastrointestinal absorption of gentamicin in rats.
- To compare the bioavailability of gentamicin formulated with Labrasol microemulsions against conventional administration.
- To explore the mechanisms by which Labrasol influences gentamicin transmucosal delivery.
Main Methods:
- Preparation of gentamicin formulations as saline solutions and Labrasol microemulsions.
- Administration of formulations into the rat small intestine and colon.
- Measurement of plasma gentamicin levels and calculation of area under the curve (AUC) and absolute bioavailability (BA).
- In vitro permeation studies to assess Labrasol's effect on intestinal transport.
Main Results:
- Labrasol microemulsion administration into the rat colon resulted in significantly higher plasma gentamicin levels (AUC: 21.179 µg*h/mL) compared to intravenous administration (AUC: 7.813 µg*h/mL).
- The absolute bioavailability of gentamicin with Labrasol reached 54.2%, substantially higher than with Tween 80 (8.4%) or Transcutol P (3.4%).
- In vitro studies indicated Labrasol inhibits intestinal secretory transport and enhances transmucosal absorption of gentamicin.
Conclusions:
- Labrasol effectively facilitates the transmucosal delivery of gentamicin from the rat colon via microemulsion formation.
- The enhanced bioavailability is attributed to both increased absorption into circulation and inhibition of drug efflux from enterocytes.
- Labrasol represents a promising excipient for improving oral or localized gastrointestinal delivery of gentamicin.
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