Physicochemical characterization of a reverse micellar solution after loading with different drugs

Area of Science:

• Physical Chemistry
• Materials Science
• Pharmaceutical Sciences

Background:

• Reverse micellar solutions (RMS) are crucial for drug solubilization and delivery.
• Understanding drug-solubilizer interactions is vital for optimizing formulation stability and efficacy.
• Lecithin and middle-chain triglycerides (MCT) form versatile RMS for pharmaceutical applications.

Purpose of the Study:

• To investigate the impact of diclofenac sodium (DS), timolol maleate (TM), and pilocarpine hydrochloride (PHCl) on the physicochemical properties of lecithin-MCT RMS.
• To evaluate how these drugs affect the structural transitions of RMS upon hydration.
• To compare the behavior of MCT-based RMS with those using isopropylmyristate (IPM).

Main Methods:

• Solubilization of DS, TM, and PHCl in lecithin-MCT RMS.
• Analysis of physicochemical parameters including micellar size and shape.
• Investigation of RMS transformation into lamellar mesophases upon water contact.
• Characterization of liquid crystal defect structures and interlayer distances.

Main Results:

• None of the drugs significantly altered the size of the reverse micellar associates.
• Diclofenac sodium and pilocarpine hydrochloride increased micellar anisometry, while timolol maleate resulted in spherical micelles.
• All drugs facilitated the transformation into lamellar mesophases but increased defect structures; higher DS content reduced interlayer distance.

Conclusions:

• Diclofenac sodium, timolol maleate, and pilocarpine hydrochloride modulate the structural characteristics of lecithin-MCT RMS.
• The presence of these drugs influences the liquid crystalline phase behavior, potentially affecting drug release profiles.
• Formulation strategies for drug delivery systems utilizing RMS should consider these drug-induced structural modifications.