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Buccal penetration enhancers--how do they really work?
Joseph A Nicolazzo1, Barry L Reed, Barrie C Finnin
1Department of Pharmaceutics, Monash University, 381 Royal Parade, Parkville, Victoria 3052, Australia.
Summary
Penetration enhancers for buccal drug delivery do not work by disrupting lipids like they do for skin. Instead, they enhance drug absorption through partitioning, extraction, protein interaction, or retention on the mucosal surface.
Area of Science:
- Pharmacology
- Drug Delivery
- Biomaterials
Background:
- Agents enhancing skin drug delivery, such as surfactants and fatty acids, are assumed to act similarly on the buccal mucosa.
- This assumption is based on the disruption of intercellular lipids in the stratum corneum, a mechanism potentially misapplied to the nonkeratinized buccal mucosa.
Purpose of the Study:
- To delineate the distinct structural and chemical properties of the buccal mucosa and skin permeability barriers.
- To elucidate the precise mechanisms by which buccal penetration enhancers facilitate drug delivery.
- To identify limitations in current models used for evaluating buccal penetration enhancers.
Main Methods:
- Literature review and comparative analysis of the intercellular lipid composition of skin and buccal mucosa.
- Examination of existing data on the mechanisms of action of buccal penetration enhancers.
- Critical assessment of predictive models for buccal drug delivery.
Main Results:
- The lipid composition of the buccal mucosa differs significantly from the stratum corneum, challenging the direct extrapolation of skin penetration enhancer mechanisms.
- Buccal penetration enhancement appears to involve mechanisms beyond lipid disruption, including increased drug partitioning, lipid extraction, interaction with epithelial proteins, and enhanced drug retention.
- Current models may inaccurately predict buccal enhancer efficacy due to overlooking these distinct mechanisms.
Conclusions:
- The mechanisms of buccal and skin penetration enhancement are fundamentally different, primarily due to variations in tissue lipid structure and composition.
- Buccal penetration enhancers likely act through a combination of increasing drug partitioning, extracting lipids without disruption, interacting with proteins, and improving drug retention.
- Relying on skin penetration models for buccal drug delivery assessment is likely to be misleading and may result in incorrect predictions.