Impaired Renal Function: As a consequence of inhibiting the renin-angiotensin-aldosterone system, changes in renal function may be anticipated in susceptible individuals. In patients with severe congestive heart failure whose renal function may depend on the activity of the renin-angiotensin-aldosterone system, treatment with angiotensin-converting enzyme inhibitors, including fosinopril sodium, may be associated with oliguria and/or progressive azotemia and (rarely) with acute renal failure and/or death.

In hypertensive patients with renal artery stenosis in a solitary kidney or bilateral renal artery stenosis, increases in blood urea nitrogen and serum creatinine may occur. Experience with another angiotensin converting enzyme inhibitor suggests that these increases are usually reversible upon discontinuation of ACE inhibitor and/or diuretic therapy. In such patients, renal function should be monitored during the first few weeks of therapy. Some hypertensive patients with no apparent pre-existing renal vascular disease have developed increases in blood urea nitrogen and serum creatinine, usually minor and transient, especially when fosinopril sodium has been given concomitantly with a diuretic. This is more likely to occur in patients with pre-existing renal impairment. Dosage reduction of fosinopril sodium and/or discontinuation of the diuretic may be required.

Evaluation of patients with hypertension or heart failure should always include assessment of renal function (see DOSAGE AND ADMINISTRATION).

Impaired renal function decreases total clearance of fosinoprilat and approximately doubles AUC. In general, no adjustment of dosing is needed. However, patients with heart failure and severely reduced renal function may be more sensitive to the hemodynamic effects (e.g., hypotension) of ACE inhibition (see CLINICAL PHARMACOLOGY).

Hyperkalemia: In clinical trials, hyperkalemia (serum potassium greater than 10% above the upper limit of normal) has occurred in approximately 2.6% of hypertensive patients receiving fosinopril sodium. In most cases, these were isolated values which resolved despite continued therapy. In clinical trials, 0.1% of patients (two patients) were discontinued from therapy due to an elevated serum potassium. Risk factors for the development of hyperkalemia include renal insufficiency, diabetes mellitus, and the concomitant use of potassium-sparing diuretics, potassium supplements, and/or potassium-containing salt substitutes, which should be used cautiously, if at all, with fosinopril sodium (see PRECAUTIONS: Drug Interactions).

Cough: Presumably due to the inhibition of the degradation of endogenous bradykinin, persistent nonproductive cough has been reported with all ACE inhibitors, always resolving after discontinuation of therapy. ACE inhibitor-induced cough should be considered in the differential diagnosis of cough.

Impaired Liver Function: Since fosinopril is primarily metabolized by hepatic and gut wall esterases to its active moiety, fosinoprilat, patients with impaired liver function could develop elevated plasma levels of unchanged fosinopril. In a study in patients with alcoholic or biliary cirrhosis, the extent of hydrolysis was unaffected, although the rate was slowed. In these patients, the apparent total body clearance of fosinoprilat was decreased and the plasma AUC approximately doubled.

Surgery/Anesthesia: In patients undergoing surgery or during anesthesia with agents that produce hypotension, fosinopril will block the angiotensin II formation that could otherwise occur secondary to compensatory renin release. Hypotension that occurs as a result of this mechanism can be corrected by volume expansion.

Hemodialysis

Recent clinical observations have shown an association of hypersensitivity-like (anaphylactoid) reactions during hemodialysis with high-flux dialysis membranes (e.g., AN69) in patients receiving ACE inhibitors as medication. In these patients, consideration should be given to using a different type of dialysis membrane or a different class of medication. (See WARNINGS: Anaphylactoid reactions during membrane exposure.)