Effect of oil phase lipophilicity on in vitro drug release from o/w microemulsions with low surfactant content

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Lucia Montenegro1, Claudia Carbone, Gabriele Condorelli

  • 1Department of Pharmaceutical Sciences, University of Catania, Viale A. Doria 6, 95125 Catania, Italy. lmontene@unict.it

Drug Development and Industrial Pharmacy
|May 25, 2006
PubMed

Insights

This study shows that oil phase lipophilicity in topical microemulsions (MEs) influences drug release rates. Higher drug lipophilicity led to slower release, suggesting tailored MEs for controlled drug delivery.

Area of Science:

  • Pharmaceutical Sciences
  • Colloid and Surface Chemistry
  • Drug Delivery Systems

Background:

  • Topical drug delivery often utilizes oil-in-water (o/w) microemulsions (MEs) for enhanced efficacy.
  • Controlling drug release from MEs is crucial for optimizing therapeutic outcomes.
  • Low emulsifier content in MEs is desirable for formulation stability and reduced irritation.

Purpose of the Study:

  • To investigate the impact of oil phase lipophilicity on the in vitro drug release kinetics from o/w microemulsions (MEs).
  • To evaluate the influence of different lipophilic oils and model drugs on ME properties and drug release profiles.
  • To explore the potential of low-emulsifier o/w MEs for controlled topical drug delivery.

Main Methods:

  • Preparation of o/w MEs using the phase inversion temperature (PIT) method with varying oil phases (isopropyl myristate, isopropyl palmitate, isopropyl stearate).
  • Incorporation of three model drugs with different lipophilicities: Naproxen (NAP), Idebenone (IDE), and Butylmethoxydibenzoylmethane (BMBM).
  • Evaluation of ME droplet size and in vitro drug release using Franz-type diffusion cells.

Main Results:

  • MEs exhibited small droplet sizes (28-44 nm) with stable size distribution.
  • Drug release rates were dependent on both ME composition and the incorporated drug's lipophilicity.
  • Higher drug lipophilicity resulted in slower release rates, with no release observed for BMBM within 6 hours.
  • Drug release followed pseudo-first order kinetics for NAP in certain MEs, while IDE showed a biphasic release pattern.

Conclusions:

  • Oil phase lipophilicity significantly modulates drug release from low-emulsifier o/w MEs.
  • Drug solubility in the oil phase appears to be a key factor influencing thermodynamic activity and release rate.
  • Careful selection of oil phase lipids and emulsifiers can enable controlled drug delivery from topical microemulsions.

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