Quinapril

Quinapril tablets are approved for two main uses:

• High blood pressure (hypertension): Quinapril tablets lower blood pressure, reducing the risk of stroke and heart attack. They can be used alone or combined with a thiazide diuretic when blood pressure isn't controlled with one medication.
• Heart failure: Quinapril tablets are used as adjunctive (add-on) therapy in heart failure, alongside conventional treatments such as diuretics and/or digitalis.

Quinapril is converted in the body to its active form, quinaprilat, which blocks an enzyme called ACE (angiotensin-converting enzyme). ACE normally produces angiotensin II — a chemical that constricts blood vessels and raises blood pressure. By blocking this step, quinapril keeps blood vessels relaxed, reduces blood pressure, and eases the heart's workload. It also lowers aldosterone, a hormone that makes the kidneys hold onto salt and water, which can modestly raise potassium levels.

Quinapril works in people with both high- and low-renin hypertension, although it tends to be somewhat less effective as a single agent in Black patients compared to non-Black patients.

Quinapril tablets are taken by mouth. For high blood pressure, they are typically taken once daily, though twice-daily dosing may be used if needed for better blood pressure control throughout the day. For heart failure, dosing generally starts twice daily and is increased gradually over weeks under medical supervision.

• High-fat meals can moderately reduce absorption — try to be consistent with when and how you take the tablet
• Your doctor will adjust the dose based on your blood pressure response and kidney function
• If you miss a dose, take it as soon as you remember — but skip it if it's almost time for the next dose. Never double up.

Most side effects with quinapril are mild and temporary. Common ones include:

• Dizziness or lightheadedness (especially when standing up quickly)
• Headache
• Dry, persistent cough — a well-known effect of ACE inhibitors
• Fatigue
• Nausea or vomiting
• Low blood pressure (more common in heart failure)
• Chest pain (in heart failure patients)
• Diarrhea

More serious reactions — including severe swelling of the face, lips, tongue, or throat (angioedema), sudden sharp drop in blood pressure, or signs of kidney or liver problems — require immediate medical attention. Stop quinapril and seek emergency care if swelling affects your throat or breathing.

• Fetal harm: Quinapril must not be used during the second or third trimester of pregnancy. It can cause serious injury or death to an unborn baby. Stop it immediately if you become pregnant and contact your doctor.
• Angioedema (dangerous swelling): Swelling of the face, lips, tongue, throat, or intestines can occur. Throat swelling can block the airway — this is a medical emergency. Black patients have a higher reported rate of this reaction with ACE inhibitors.
• Low blood pressure: Risk is highest in people who are dehydrated, on diuretics, or have heart failure. Dizziness or fainting — especially when standing — should be reported to your doctor.
• Kidney function changes: Quinapril can reduce kidney function, especially in people already on diuretics. Blood and urine tests are recommended during treatment.
• High potassium (hyperkalemia): Quinapril can raise potassium levels, which can affect heart rhythm. Avoid potassium supplements or salt substitutes without your doctor's guidance.
• Rare liver reaction: A syndrome of jaundice progressing to serious liver damage has been reported rarely with ACE inhibitors. Contact your doctor immediately if you develop yellowing of the skin or eyes.

Quinapril can interact with several medications and substances — always tell your prescriber and pharmacist everything you take:

• Diuretics (water pills): Can cause a sharp drop in blood pressure when starting quinapril — your doctor may adjust or pause the diuretic first
• Potassium-sparing diuretics or potassium supplements: Combined with quinapril, these can raise potassium to dangerous levels
• Lithium: Quinapril can cause lithium to build up in the blood, increasing toxicity risk — close monitoring required
• NSAIDs (ibuprofen, naproxen, COX-2 inhibitors): Can blunt quinapril's blood pressure effect and increase risk of kidney problems
• Aliskiren: Should not be combined with quinapril in people with diabetes; avoid in kidney impairment
• Sacubitril/valsartan (Entresto): Do not take within 36 hours of switching to or from this drug — risk of serious angioedema
• mTOR inhibitors (e.g., temsirolimus): May increase the risk of angioedema
• Injectable gold (sodium aurothiomalate): Rare flushing, nausea, and low blood pressure reactions reported
• Tetracycline antibiotics: Quinapril's magnesium content can reduce tetracycline absorption by up to 37% — take them apart in time

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

• Tell your doctor if you have ever had angioedema (severe swelling), from any cause — your risk may be higher
• Tell your doctor if you have kidney disease — quinapril is cleared through the kidneys, and doses are adjusted based on kidney function
• Tell your doctor if you have alcoholic cirrhosis or liver disease — quinapril may not be converted to its active form as effectively
• Older adults (65 and older) may have reduced kidney clearance of quinapril and typically start on a lower dose
• Do not use during pregnancy — particularly the second and third trimesters; can cause serious fetal harm or death
• Patients with collagen vascular diseases (such as lupus or scleroderma) and kidney disease may need periodic white blood cell monitoring
• People with heart failure, low sodium levels, or those on high-dose diuretics need close monitoring when starting quinapril
• Do not use if you are allergic to quinapril or have had angioedema from any ACE inhibitor

Taking too much quinapril would most likely cause a serious drop in blood pressure, leading to dizziness, weakness, or fainting. There is no specific antidote, but the main treatment is supportive — lying flat and, if needed, receiving intravenous fluids (salt solution) to stabilize blood pressure. Hemodialysis does not significantly remove quinapril from the body.

Quinapril begins lowering blood pressure within about 1 hour of taking a dose, with peak effects typically reached within 2 to 4 hours. With regular use, most of the blood pressure benefit for a given dose is seen within 1 to 2 weeks. The medication lowers both sitting and standing blood pressure without significantly affecting heart rate. In heart failure, quinapril reduces the resistance the heart pumps against and improves cardiac output, while also improving exercise capacity and reducing symptoms like breathlessness, fatigue, and swelling.

After swallowing a quinapril tablet, peak blood levels appear within about 1 hour. The body converts quinapril into its active form, quinaprilat, which reaches peak levels roughly 2 hours after the dose. Absorption can be reduced by about 25–30% if taken with a high-fat meal. Quinaprilat is cleared mainly through the kidneys, and its removal slows significantly in people with reduced kidney function or in older adults — which is why dose adjustments are needed in those groups. About 97% of the drug circulates bound to proteins in the blood.

Dispense in well-closed containers as defined in the USP. Store at 20° to 25°C (68° to 77°F) . Protect from light.