Disclosed herein is the use of an active agent comprising a peptide derived from atrial natriuretic peptide (ANP) prohormone or a mimetic thereof in the manufacture of a medicament for treating a disease in a subject. The medicament is administered subcutaneously in a multimodal dosage regime comprising at least an initial dosage stage and at least one maintenance dosage stage. The initial dosage stage comprises infusing the active agent at an initial dosage rate for an initial period to achieve a target steady state blood plasma concentration of the active agent or metabolite thereof. The maintenance dosage stage(s) comprise(s) adjusting the dosage rate to a maintenance dosage rate for a maintenance period to substantially maintain said target steady state blood plasma concentration of the active agent or metabolite thereof.