Angioedema might occur (especially following first dose), and may involve the head and neck (potentially compromising airway) or the intestine (presenting with abdominal pain)(higher risk in African-Americans and idiopathic or hereditary angioedema). May cause cholestatic jaundice (risk of fulminant hepatic necrosis). A dry, hacking, nonproductive cough might occur. Hyperkalemia is possible (risk factors: renal dysfunction, diabetes mellitus, concomitant use of potassium-sparing diuretics, potassium supplements, and/or potassium-containing salts). Anaphylactic/anaphylactoid reactions might occur. Symptomatic hypotension with or without syncope may also occur. Captopril has been associated with rare cases of agranulocytosis, neutropenia, or leukopenia with myeloid hypoplasia (higher risk in renal impairment and collagen vascular disease). May be associated with deterioration of renal function and/or increases in serum creatinine, particularly in low renal blood flow. Use with caution in the following situations: severe aortic stenosis (may reduce coronary perfusion resulting in ischemia), in ischemic heart disease or cerebrovascular disease (potential consequences posed by falling blood pressure), in hypertrophic cardiomyopathy and outflow tract obstruction (may worsen symptoms associated with reduction in afterload), in unstented unilateral/bilateral renal artery stenosis (risk of deterioration in renal function), and before, during, or immediately after major surgery (cardiopulmonary bypass, intraoperative blood loss or vasodilating anesthesia increases endogenous renin release). May cause drowsiness or insomnia. A syndrome which may include fever, myalgia, arthralgia, interstitial nephritis, vasculitis, rash, eosinophilia, and elevated ESR has been reported for captopril and other ACE inhibitors.