Objective: Azilsartan medoxomil is considered as a prodrug of the active metabolite, azilsartan which is an angiotensin II receptor blocker that can be utilized for the treatment of mild to moderate essential hypertension. Azilsartan medoxomil is classified as class II according to the biopharmaceutical classification. This study aims to prepare nanosuspension of azilsartan medoxomil to improve its solubility.
Method: Solvent anti-solvent precipitation with ultrasonication method was utilized to prepare azilsartan medoxomil nanosuspension. Different stabilizers (TPGS, and PEG6000) alone at a different drug: stabilizer ratio or in combination with other co-stabilizer (Tween80 or SLS) are used in formulations. Effect of other parameters such as stirring speed of the antisolvent and using of ultrasonication power also was investigated. Azilsartan medoxomil nanosuspension were characterized for particle size analysis, the percentage of drug entrapment efficiency, atomic force microscope and in vitro dissolution study. Also to develop stable and suitable oral dosage form, the optimized formulation was freeze-dried into self-dispersible dry nanosuspension and then evaluated.
Results: The best formula (F13) has a particle size of 48.7 nm containing PEG6000 as the main stabilizer and Tween80 as co-stabilizer at a drug: stabilizer:co-stabilizer ratio 1:0.75:0.25 with stirring speed of antisolvent system at 3500 rpm. % entrapment efficiency was ranged from 80% ± 1 to 97% ± 1. For self-dispersible dry nanosuspension, the selected formula (F13m) when using mannitol as cryoprotectant showed fast dispersibility in 1 minute in dissolution media and complete in-vitro dissolution in less than 30 minutes in both media (0.1 N HCl and phosphate buffer solution (pH 6.8)).
Conclusions: from the study we conclude antisolvent-precipitation with ultrasonication method is an efficient method to formulate azilsartan medoxomil nanosuspension and easy to formulate azilsartan medoxomil self-dispersible dry nanosuspension with high solubility and dissolution rate.