Sustanon Depot 400 mg/mL is a high-concentration injectable formulation combining testosterone esters with different release characteristics. The multi-ester structure is designed to provide staged availability of the active compound, combining comparatively shorter and longer release phases.

Following ester hydrolysis, testosterone interacts with intracellular androgen receptors and influences androgen-responsive cellular processes associated with protein metabolism and nitrogen balance. The 400 mg/mL concentration provides a reduced formulation volume compared with lower-strength presentations containing an equivalent total amount of testosterone esters.