Fosinopril

Fosinopril is an oral ACE inhibitor approved for the following conditions:

• High blood pressure (hypertension) — Fosinopril Sodium tablets can be used alone or combined with a thiazide diuretic when additional blood pressure lowering is needed
• Heart failure — Fosinopril Sodium tablets are used as add-on therapy alongside diuretics, with or without digitalis, to help manage symptoms and improve exercise tolerance

Fosinopril is a prodrug — after you swallow it, your body converts it into the active form, fosinoprilat. Fosinoprilat blocks ACE (angiotensin-converting enzyme), which normally helps produce angiotensin II, a chemical that tightens blood vessels and raises blood pressure. By blocking this process, fosinopril allows blood vessels to relax, lowers blood pressure, and also reduces the amount of aldosterone (a hormone that causes the body to retain salt and water). In heart failure, this dual effect reduces both the pressure the heart pumps against (afterload) and the volume it must handle (preload), easing its overall workload.

Because fosinopril is cleared through both the liver and kidneys, it can generally be used at standard doses even in patients with significant kidney disease — an advantage compared with some other ACE inhibitors. However, ACE inhibitors as a class tend to have a smaller blood-pressure-lowering effect in Black patients compared to non-Black patients.

Fosinopril Sodium tablets are taken by mouth, typically once a day. Food may slow absorption slightly but does not reduce the total amount absorbed, so it can be taken with or without food. For heart failure, patients are usually observed closely after the first dose for signs of low blood pressure.

• If you are on a diuretic (water pill), your doctor may adjust or pause it before starting fosinopril to reduce the chance of a blood pressure drop
• Do not use potassium supplements or potassium-containing salt substitutes unless your doctor directs you to — they can raise potassium to unsafe levels
• Never stop taking fosinopril on your own; always check with your prescriber first

Most side effects with fosinopril are mild and temporary, but there are a few important ones to know about:

• Dry, nagging cough — a well-known ACE inhibitor side effect; talk to your doctor if it becomes bothersome
• Dizziness or lightheadedness — especially when standing up quickly (orthostatic hypotension)
• Nausea or vomiting
• Diarrhea
• Fatigue or weakness
• Headache
• Elevated potassium levels (hyperkalemia) — may cause muscle weakness or heart rhythm changes

Seek emergency care immediately for sudden swelling of the face, lips, tongue, or throat (angioedema) — this is rare but can be life-threatening. Also contact your doctor right away if you develop yellowing of the skin or eyes, significant drop in urination, or signs of low blood pressure such as fainting.

• Fetal toxicity (most critical): Fosinopril can cause fetal injury or death, especially in the second and third trimesters. Stop the medication as soon as pregnancy is detected and contact your doctor immediately.
• Angioedema (severe swelling): Rare but potentially fatal swelling of the face, tongue, throat, or intestines can occur. Throat swelling is a medical emergency. Black patients and those taking mTOR inhibitors (e.g., temsirolimus) are at higher risk.
• Low blood pressure (hypotension): Most likely in patients who are dehydrated, on high-dose diuretics, have low sodium, or have heart failure. The first dose requires close monitoring in heart failure patients.
• Kidney function changes: Fosinopril can worsen kidney function, particularly in people with heart failure or severe kidney disease. Blood and urine tests may be needed regularly.
• High potassium (hyperkalemia): Risk increases when combined with potassium supplements, potassium-sparing diuretics, or salt substitutes containing potassium.
• Liver failure: Rarely reported with ACE inhibitors. Stop fosinopril and seek care if jaundice or markedly abnormal liver tests develop.
• Blood count changes: Rare risk of low white blood cell counts (agranulocytosis), particularly in patients with kidney disease or connective-tissue diseases such as lupus.

Fosinopril can interact with several medications and substances — tell your doctor and pharmacist about everything you take:

• Potassium supplements, potassium-sparing diuretics, or potassium-containing salt substitutes — can raise potassium to dangerous levels when combined with fosinopril
• Diuretics (water pills) — increase the risk of a blood pressure drop, especially with the first dose of fosinopril
• Lithium — fosinopril can raise lithium blood levels, increasing the risk of lithium toxicity; frequent monitoring is needed
• Antacids (aluminum/magnesium-based) — may reduce fosinopril absorption; separate doses by at least 2 hours
• NSAIDs (ibuprofen, naproxen) and COX-2 inhibitors — can blunt fosinopril's blood-pressure effect and may impair kidney function, especially in older or dehydrated patients
• Injectable gold (sodium aurothiomalate) — rarely causes flushing, nausea, and low blood pressure when combined with ACE inhibitors
• mTOR inhibitors (e.g., temsirolimus) — increase the risk of angioedema (dangerous swelling)
• Aliskiren — must not be combined with fosinopril in patients with diabetes; avoid in those with kidney disease due to risk of low blood pressure, high potassium, and kidney failure
• Other ACE inhibitors or angiotensin receptor blockers (ARBs) — combining two drugs that block the same system raises risk of low blood pressure, high potassium, and kidney damage

This is not a complete list of interactions. Always talk with your doctor or pharmacist before starting, stopping, or changing any medication.

• Pregnancy: Do not take fosinopril if you are pregnant. Stop immediately and contact your doctor if you become pregnant while taking it — the drug can seriously harm the baby.
• Prior angioedema with any ACE inhibitor: You must not take fosinopril if you have had dangerous swelling reactions with any ACE inhibitor.
• Hypersensitivity: Do not take fosinopril if you are allergic to it or any other ACE inhibitor.
• Diabetes + aliskiren use: Do not combine fosinopril with aliskiren if you have diabetes.
• Kidney disease: Fosinopril can be used in kidney impairment at standard doses due to its dual liver/kidney elimination route, but kidney function and potassium should be monitored.
• Liver disease: Fosinopril clearance is reduced in patients with liver cirrhosis; your doctor may adjust monitoring or dosing.
• Collagen-vascular diseases (e.g., lupus, scleroderma): Higher risk of blood count problems; white blood cell monitoring may be needed.
• Black patients: ACE inhibitors tend to lower blood pressure less effectively and carry a higher rate of angioedema in this population — discuss all options with your prescriber.
• Children under 50 kg: An appropriate tablet strength is not available for children weighing less than 50 kg.
• Older adults: Side effect rates in patients 65 and older were similar to younger patients in clinical trials, but close monitoring is still appropriate.
• Dialysis patients: Fosinopril is not well removed by dialysis; anaphylactoid (severe allergic-like) reactions have been reported with certain high-flux dialysis membranes.

The most likely effect of taking too much fosinopril is a significant drop in blood pressure (hypotension), which can cause dizziness, fainting, or weakness. Fosinopril is not well removed by dialysis, so standard supportive care — such as intravenous fluids to restore blood pressure — is the primary approach. If you suspect an overdose, seek emergency medical help immediately.

Fosinopril begins to significantly suppress ACE activity within 2 hours of a dose. A single dose of fosinopril suppresses the ACE enzyme by 90% or more for up to 12 hours, and meaningful suppression (over 85%) is still measurable at 24 hours — helping explain why once-daily dosing is effective for most patients. In the blood, fosinopril also causes small increases in potassium levels over time, which is worth monitoring, especially in patients on other medications that raise potassium.

After swallowing a fosinopril tablet, the drug is absorbed through the upper small intestine — food may slow this slightly but does not reduce how much is absorbed overall. The body converts fosinopril into its active form (fosinoprilat) within hours, with peak blood levels reached in about 3 hours. Fosinoprilat is cleared about equally by the liver and kidneys — a dual elimination pathway that is unusual among ACE inhibitors and means that even patients with severe kidney disease typically do not require dose adjustments. The effective half-life (how long the drug stays active) is roughly 11 to 14 hours in most patients.

Store at 20° to 25°C (68° to 77°F); excursions permitted to 15° to 30°C (59° to 86°F) . Protect from moisture by keeping bottle tightly closed.