Quinapril - Drug Monograph

Introduction

Quinapril is an angiotensin-converting enzyme (ACE) inhibitor used primarily in the management of hypertension and heart failure. As a prodrug, it undergoes hydrolysis to its active metabolite quinaprilat, which exerts potent vasodilatory effects through the renin-angiotensin-aldosterone system (RAAS) inhibition.

Mechanism of Action

Quinapril competitively inhibits angiotensin-converting enzyme, preventing the conversion of angiotensin I to angiotensin II—a potent vasoconstrictor. This results in:

• Decreased peripheral vascular resistance
• Reduced aldosterone secretion
• Increased bradykinin levels contributing to vasodilation
• Diminished sodium and water retention

Indications

• Hypertension (monotherapy or combination therapy)
• Heart failure (as adjunctive therapy)
• Post-myocardial infarction management (to reduce cardiovascular mortality)
• Diabetic nephropathy (renoprotective effects in patients with type 1 diabetes)

Dosage and Administration

• Initial dose: 10-20 mg once daily
• Maintenance: 20-80 mg daily in 1-2 divided doses

• Initial: 5 mg twice daily
• Titration: May increase to 10-20 mg twice daily

• Renal impairment: Adjust based on creatinine clearance
• Hepatic impairment: Use with caution
• Elderly: Start with lower initial doses
• Pediatric: Safety not established

Pharmacokinetics

Contraindications

• History of angioedema related to previous ACE inhibitor therapy
• Concomitant use with aliskiren in patients with diabetes
• Hypersensitivity to quinapril or other ACE inhibitors
• Second/third trimester pregnancy

Warnings and Precautions

• Angioedema: May occur at any time during therapy
• Hypotension: Particularly in volume-depleted patients
• Renal impairment: Monitor renal function, risk of acute renal failure
• Hyperkalemia: Especially with renal impairment or diabetes
• Cough: Persistent dry cough may develop
• Neutropenia/agranulocytosis: Rare but serious
• Hepatic effects: Monitor liver function tests

Drug Interactions

• Diuretics: Enhanced hypotensive effect
• NSAIDs: Reduced antihypertensive effect, increased renal risk
• Potassium-sparing diuretics/potassium supplements: Increased hyperkalemia risk
• Lithium: Increased lithium levels
• Antidiabetic agents: Enhanced hypoglycemic effects
• Gold injections: Nitritoid reactions reported

Adverse Effects

• Headache (12%)
• Dizziness (7-12%)
• Fatigue (5-10%)
• Cough (2-13%)

• Angioedema
• Acute renal failure
• Hyperkalemia
• Neutropenia/agranulocytosis
• Hepatic failure
• Hypotension

Monitoring Parameters

• Blood pressure (standing and supine)
• Renal function (serum creatinine, BUN)
• Electrolytes (potassium levels)
• Complete blood count (baseline and periodically)
• Liver function tests
• Signs of angioedema
• Pregnancy testing in women of childbearing potential

Patient Education

• Take medication at same time each day
• Report any swelling of face, lips, or tongue immediately
• Notify provider of persistent dry cough
• Rise slowly from sitting/lying position to prevent dizziness
• Avoid potassium supplements unless prescribed
• Maintain adequate hydration
• Use effective contraception during treatment
• Regular blood pressure monitoring
• Do not discontinue abruptly without medical guidance

References

1. FDA Prescribing Information: Quinapril Hydrochloride Tablets 2. Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 8) 3. ACC/AHA Heart Failure Guidelines (2022) 4. Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th Edition 5. Micromedex® Drug Information: Quinapril 6. Clinical Pharmacology [database online]. Tampa, FL: Elsevier 7. KDIGO Clinical Practice Guideline for the Management of Blood Pressure in Chronic Kidney Disease (2021)