At any time during treatment (especially following 1^st^ dose) angioedema may occur rarely with ACEIs (may involve head and neck, or intestine). Use in previous angioedema associated with ACEI therapy contraindicated. Rare toxicity associated with ACEIs includes cholestatic jaundice, which may progress to fulminant hepatic necrosis. A dry, hacking, nonproductive cough usually occurs within first few months of treatment. Hyperkalemia may occur with ACEIs (risk factors include renal dysfunction, diabetes mellitus, concomitant use of potassium-sparing diuretics, potassium supplements, and/or potassium-containing salts). Anaphylactic/anaphylactoid reactions can occur with ACEIs. Severe anaphylactoid reactions may be seen during hemodialysis with high-flux dialysis membranes. Rare cases of anaphylactoid reactions reported in patients undergoing sensitization treatment with hymenoptera (bee, wasp) venom while receiving ACEIs. Symptomatic hypotension with or without syncope can occur (usually with first several doses). Another ACEI, captopril, associated with rare cases of agranulocytosis, neutropenia, or leukopenia with myeloid hypoplasia. Patients with renal impairment at high risk of developing neutropenia. Patients with both renal impairment and collagen vascular disease (e.g. systemic lupus erythematosus) at even higher risk of developing neutropenia. Deterioration may result in oliguria, acute renal failure, and progressive azotemia. Small increases in serum creatinine may occur following initiation. Use with caution in severe aortic stenosis (may reduce coronary perfusion resulting in ischemia), in ischemic heart disease or cerebrovascular disease (due to potential consequences posed by falling blood pressure (e.g. MI, stroke)), and in collagen vascular disease, especially with concomitant renal impairment (may be at increased risk for hematologic toxicity). Use with caution in HCM and outflow tract obstruction since reduction in afterload may worsen symptoms associated with this condition; also in unstented unilateral/bilateral renal artery stenosis. When unstented bilateral renal artery stenosis is present, use is generally avoided, unless possible benefits outweigh risks. Use with caution in pre-existing renal insufficiency. Avoid rapid dosage escalation which may lead to further renal impairment. Use with caution before, during, or immediately after major surgery. Cardiopulmonary bypass, intraoperative blood loss or vasodilating anesthesia increases endogenous renin release. Perioperative use of ACEIs will blunt angiotensin II formation and may result in hypotension.