Mixed micelles of sodium cholate and Brij30: Their rheological behaviour and capability towards solubilization and stabilization of rifampicin

• NaC aggregates showed micellar growth upon addition of Brij30.
• The solubility of rifampicin was higher in NaC micellar systems.
• The solubilization capacity of NaC decreased with increase in Brij30.
• The mixed micelles are more protective for oxidation of drug.
• The formulation enhances solubility, stability and bioavailability of the drug.

Rifampicin is wide-spectrum antibiotic but being poorly water soluble and unstable towards oxidation, it requires high dose in order to reach therapeutic plasma concentrations thereby making its adverse effects like hepatotoxicity more prominent. Sodium cholate (NaC), Brij30 and their mixed micellar systems were evaluated for their solubilization and stabilization capability towards rifampicin. NaC aggregates showed micellar growth upon addition of Brij30 surfactant inferred by characterization using rheology and were found to form both wormlike micelles and vesicles. The solubility of rifampicin was found to be higher in NaC micellar systems due to an appreciable interfacial solubilization favoured by electrostatic interactions. The solubilization capacity of mixed micellar systems decreased with increase in Brij30 surfactant concentration. A comparative study of stability of rifampicin against oxidation with H2O2 showed that the micelles were able to stabilize the drug. The mixed micellar systems possessed much more solubilization efficiency than Brij30 micellar systems and at the same time proved markedly more protective against oxidation of rifampicin when compared to NaC besides being stable to large stress and having the desirable characteristics of their viscoelasticity, thus proving to be the ideal systems for solubilization and stabilization of rifampicin. These experimental results are expected to be important for enhancing the solubility, stability and hence bioavailability of rifampicin.

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