STUDY ON THE INFLUENCE OF COSOLVENT AND SURFACTANT ON SOLUBILIZATION OF EFAVIRENZ
Mbah Chika, Omeje Edwin* and Ugodi Gerald.
ABSTRACT
The very poor aqueous solubility of drugs, give rise to difficulties in the design of pharmaceutical formulations and very often lead to variable oral bioavailability. Cosolvency and micellar solubilization are widely used alternative for the solubilization of poorly soluble drugs. Efavirenz has very poor aqueous solubility and belongs to Class II drugs under Biopharmaceutical Classification Systems. The purpose of this work was to investigate the effect of some solubilizing agents on the aqueous solubility of efavirenz and invariably its bioavailability. Determination of aqueous solubility of efavirenz was in aqueous mixture of cosolvents (glycerol, propylene glycol, polyethylene glycol 400) and surfactants (tween 20, tween 80, sodium lauryl sulfate, cetrimide). Excess of efavirenz was added into each of the mixed solvent at 25 ±1oC. Equilibrium method (shake-flask technique) was utilized. Following equilibrium, the solutions were filtered and analyzed using ultraviolet absorption spectroscopic technique. The results indicate logarithm linear relationships between efavirenz solubility in water-cosolvent mixtures and cosolvent fraction volume. The solubilization power (σ) or the slope is used to describe the drug-cosolvent-water system. Linear relationships between the solubility of efavirenz in water-surfactant mixtures and surfactant concentration were observed. The solubilization capacity (k) or the slope is used to describe the drug-surfactant-water system. The free energy of solubilization was found to be linearly related to micellar partition coefficients of efavirenz. The results of the study show that cosolvency and micellization significantly improved aqueous solubility of efavirenz.
Keywords: Efavirenz, aqueous solubility, cosolvency, micellization.
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