Compositions and methods for treating systemic diseases by intravenous administration of formulations of synthesized curcumin (diferuloylmethane) and concomitantly a calcium channel blocker to human subjects with neoplastic and neurodegenerative diseases are disclosed herein. The diseases are treated by prolonged administration of sub-optimal doses of liposomal curcumin or polymeric nanocurcumin or the sustained release curcumin from PLGA nanocurcumin at dosages below systemic hemolytic thresholds concomitantly with or without calcium channel blockers.