Pluronic–cationic surfactant mixed micelles: Solubilization and release of the drug hydrochlorothiazide

Moderately hydrophobic poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers [Pluronics® with 20 > % PEO < 80] form micelles in water with a hydrodynamic diameter of about 20 nm. The aqueous mixed systems of Pluronics® P103, P104 and P105 [Pluronics® with molecular weight of PPO = 3250, and % of PEO 30, 40 and 50 respectively] with cationic surfactants of the type alkyltrimethylammonium bromide (CnTAB, n = 10, 12, 14 and 16) were studied in water and salt solution. It is apparent that the presence of trace amounts of cationic surfactant induces a charge on nonionic Pluronics® micelles and leads to a decrease in their size. The efficiency of surfactants to decrease micellar size depends on the alkyl chain length of the surfactants. A representative system, P103-C14TAB was chosen to investigate and the feasibility of using Pluronic®–surfactants systems compared with pure Pluronic® micelle as an in vitro release vehicle for hydrochlorothiazide (HCT); a hydrophobic diuretic drug with poor aqueous solubility. Pluronic®–surfactant systems were found to be more efficient for HCT loading; their loading capacity can be tuned by changing the surfactant concentration and pH. Drug release profiles were established for P103 and P103-C14TAB mixed systems. The rate of controlled release of HCT from micelles was explained by employing different kinetic models to examine the in vitro release profile.