provided herein are drug delivery systems comprising nanosuspension formulations suitable for parenteral delivery to a subject . the nanosuspension formulations may comprise a benzimidazole derivative , e . g ., mebendazole , and surface stabilizers , such as block copolymer , e . g ., pluronic f108 , and surfactant , e . g ., tween 80 , and , optionally , water . provided are methods for defining nanosuspensions of a benzimidazole derivative as having maximum therapeutic efficacy for a treatment regimen by adjusting and / or selecting particles size based on pharmacokinetic parameters of the derivative in the tissue . also provided are methods for improving the bioavailability of a benzimidazole derivative during treatment of a pathophysiological condition and for treating a cancer by using formulation combining particle diameters whereby the retention of the benzimidazole derivative within the particles increases as the diameter increases such that , upon administration , release of the benzimidazole derivative from the particles into tissue is continuous over a range of time as determined by the particle diameters .