Hydralazine is a potent arteriolar dilator and markedly increases cardiac output in patients with congestive heart failure. However, as a single agent, it has not been shown to improve symptoms or exercise tolerance during chronic treatment. The combination of hydralazine and isosorbide dinitrate is an alternative therapy when ACE inhibitors are contraindicated or cannot be tolerated. Daily doses of hydralazine up to 300 mg in combination with isosorbide dinitrate 160 mg in the presence of cardiac glycosides and diuretics have some effect in reducing mortality. 

Side effect: Gastrointestinal distress, headaches, tachycardia, and hypotension.