Fosinopril drug interactions

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Amr Marawan, M.D. [2], Ahmed Zaghw, M.D. [3]

Fosinopril

• Fosinopril sodium tablet

Fosinopril and Hydrochlorothiazide

• Fosinopril sodium and Hydrochlorothiazide tablet

Overview

Captopril tablet is an angiontensin converting enzyme inhibitor drug that is FDA approved for the treatment of hypertension, heart failure, left ventricular dysfunction after myocardial infarction, diabetic nephropathy. Adverse reactions include hypotension, rash, hyperkalemia, disorder of taste, cough. hypotension, rash, hyperkalemia, disorder of taste, cough.

Category

Antihypertensive Agents, Angiotensin Converting Enzyme Inhibitors. Editor-In-Chief: C. Michael Gibson, M.S., M.D. [4]; Associate Editor(s)-in-Chief: Amr Marawan, M.D. [5]

Drug Interactions

Diuretics

Patients on diuretics, especially those with intravascular volume depletion, may occasionally experience an excessive reduction of blood pressure after initiation of therapy with fosinopril Na tablets. The possibility of hypotensive effects with fosinopril can be minimized by either discontinuing the diuretic or increasing salt intake prior to initiation of treatment with fosinopril. If this is not possible, the starting dose should be reduced and the patient should be observed closely for several hours following an initial dose and until blood pressure has stabilized.

Potassium supplements and potassium-sparing diuretics

Fosinopril can attenuate potassium loss caused by thiazide diuretics. Potassium-sparing diuretics (spironolactone, amiloride, triamterene, and others) or potassium supplements can increase the risk of hyperkalemia. Therefore, if concomitant use of such agents is indicated, they should be given with caution, and the patient’s serum potassium should be monitored frequently.

Lithium

Increased serum lithium levels and symptoms of lithium toxicity have been reported in patients receiving ACE inhibitors during therapy with lithium. These drugs should be coadministered with caution, and frequent monitoring of serum lithium levels is recommended. If a diuretic is also used, the risk of lithium toxicity may be increased.

Antacids

In a clinical pharmacology study, coadministration of an antacid (aluminum hydroxide, magnesium hydroxide, and simethicone) with fosinopril reduced serum levels and urinary excretion of fosinoprilat as compared with fosinopril administrated alone, suggesting that antacids may impair absorption of fosinopril. Therefore, if concomitant administration of these agents is indicated, dosing should be separated by 2 hours.

Gold

Nitritoid reactions (symptoms include facial flushing, nausea, vomiting, and hypotension) have been reported rarely in patients on therapy with injectable gold (sodium aurothiomalate) and concomitant ACE inhibitor therapy including fosinopril.

Other

Neither fosinopril nor its metabolites have been found to interact with food. In separate single or multiple dose pharmacokinetic interaction studies with chlorthalidone, nifedipine, propranolol, hydrochlorothiazide, cimetidine, metoclopramide, propantheline, digoxin, and warfarin, the bioavailability of fosinoprilat was not altered by coadministration of fosinopril with any one of these drugs. In a study with concomitant administration of aspirin and fosinopril, the bioavailability of unbound fosinoprilat was not altered.

In a pharmacokinetic interaction study with warfarin, bioavailability parameters, the degree of protein binding, and the anticoagulant effect (measured by prothrombin time) of warfarin were not significantly changed.

Drug/Laboratory Test Interaction

Fosinopril may cause a false low measurement of serum digoxin levels with the Digi-Tab® RIA Kit for Digoxin. Other kits, such as the Coat-A-Count® RIA Kit, may be used.

Dual Blockade of the Renin-Angiotensin System (RAS)

Dual blockade of the RAS with angiotensin receptor blockers, ACE inhibitors, or aliskiren is associated with increased risks of hypotension, hyperkalemia, and changes in renal function (including acute renal failure) compared to monotherapy. Closely monitor blood pressure, renal function and electrolytes in patients on fosinopril and other agents that affect the RAS.

Do not co-administer aliskiren with fosinopril in patients with diabetes. Avoid use of aliskiren with fosinopril in patients with renal impairment (GFR<60 mL/min).

Carcinogenesis, Mutagenesis, Impairment of Fertility

No evidence of a carcinogenic effect was found when fosinopril was given in the diet to mice and rats for up to 24 months at doses up to 400 mg/kg/day. On a body weight basis, the highest dose in mice and rats is about 250 times the maximum human dose of 80 mg, assuming a 50 kg subject. On a body surface area basis, in mice, this dose is 20 times the maximum human dose; in rats, this dose is 40 times the maximum human dose. Male rats given the highest dose level had a slightly higher incidence of mesentery/omentum lipomas.

Neither fosinopril nor the active fosinoprilat was mutagenic in the Ames microbial mutagen test, the mouse lymphoma forward mutation assay, or a mitotic gene conversion assay. Fosinopril was also not genotoxic in a mouse micronucleus test in vivo and a mouse bone marrow cytogenetic assay in vivo.

In the Chinese hamster ovary cell cytogenetic assay, fosinopril increased the frequency of chromosomal aberrations when tested without metabolic activation at a concentration that was toxic to the cells. However, there was no increase in chromosomal aberrations at lower drug concentrations without metabolic activation or at any concentration with metabolic activation.

There were no adverse reproductive effects in male and female rats treated with 15 or 60 mg/kg daily. On a body weight basis, the high dose of 60 mg/kg is about 38 times the maximum recommended human dose. On a body surface area basis, this dose is 6 times the maximum recommended human dose. There was no effect on pairing time prior to mating in rats until a daily dose of 240 mg/kg, a toxic dose, was given; at this dose, a slight increase in pairing time was observed. On a body weight basis, this dose is 150 times the maximum recommended human dose. On a body surface area basis, this dose is 24 times the maximum recommended human dose.

References

Adapted from the FDA Package Insert.