Albendazole solution formulation via vesicle-to-micelle transition of phospholipid-surfactant aggregates

<p><b>Objective:</b> To reveal the physicochemical mechanisms governing the solubilization of albendazole in surfactant and phospholipid-surfactant solutions and, on this basis, to formulate clinically relevant dose of albendazole in solution suitable for parenteral delivery.</p> <p><b>Significance:</b> (1) A new drug delivery system for parenteral delivery of albendazole is proposed, offering high drug solubility and low toxicity of the materials used; (2) New insights on the role of surface curvature on albendazole solubilization in surfactant and surfactant-phospholipid aggregates are provided.</p> <p><b>Methods:</b> The effect of 17 surfactants and 6 surfactant-phospholipid mixtures on albendazole solubility was studied. The size of the colloidal aggregates was determined by light-scattering. The dilution stability of the proposed formulation was assessed by experiments with model human serum.</p> <p><b>Results:</b> Anionic surfactants increased very strongly drug solubility at pH = 3 (up to 4 mg/mL) due to strong electrostatic attraction between the oppositely charged (at this pH) drug and surfactant molecules. This effect was observed with all anionic surfactants studied, including sodium dodecyl sulfate, double chain sodium dioctylsulfosuccinate (AOT), and the bile salt sodium taurodeoxycholate. The phospholipid-surfactant mixture of 40% sodium dipalmitoyl-phosphatidylglycerol +60% AOT provided highest albendazole solubilization (4.4 mg/mL), smallest colloidal aggregate size (11 nm) and was stable to dilution with model human serum at (and above) 1:12 ratio.</p> <p><b>Conclusions:</b> A new albendazole delivery system with high drug load and low toxicity of the materials used was developed. The high solubility of albendazole was explained with vesicle-to-micelle transition due to the larger interfacial curvature preferred for albendazole solubilization locus.