The present invention provides a pharmaceutical composition and a method for reducing an infarct region resulting from the ischemic necrosis of cells, especially, a pharmaceutical composition and a method for suppressing ischemia-reperfusion injury in the treatment of ischemic heart disease. The pharmaceutical composition and the method utilize a substance, as an active ingredient, which can increase intracellular cGMP production by acting on a natriuretic peptide receptor, and which has the effect of reducing an infarct region. The substance is preferably a natriuretic peptide. The present invention is particularly useful for the treatment or prophylaxis of ischemic disease.