Quinapril
Quinapril
Generic Name
Quinapril
Mechanism
- Inhibition of ACE: Quinapril blocks the conversion of angiotensin‑I to angiotensin‑II, decreasing vasoconstriction and aldosterone release.
- Reduced sympathetic tone: Lower angiotensin‑II levels diminish reflex tachycardia and renin secretion.
- Biotransformation: Oral quinapril is converted in vivo to its active metabolite, enalaprilat, which is responsible for the pharmacologic activity.
- Clinical impact: Resultant vasodilation lowers systemic vascular resistance and reduces afterload, beneficial for heart failure and blood pressure control.
Pharmacokinetics
| Parameter | Typical Values |
| Absorption | Oral bioavailability ~30 %; peak plasma level within 1–2 h. |
| Distribution | Protein binding ~35 %; volume of distribution ~1.5 L/kg. |
| Metabolism | Hepatic conversion to enalaprilat; negligible cytochrome P450 involvement. |
| Elimination | Renally excreted (≈70 %); terminal half‑life 5–10 h for enalaprilat. |
| Food Interaction | Food delays onset slightly; no dose adjustment required. |
| Special Populations | Dosage reduction in severe renal impairment (CrCl < 30 mL/min). |
Indications
- Hypertension – primary or adjunctive therapy.
- Heart failure – symptomatic, reduced ejection fraction; improves morbidity.
- Post‑MI – reduced mortality when combined with β‑blockers.
- Diabetic nephropathy – albuminuria reduction, slows progression.
- Renal protection in CKD – used when other ACEI/ARB strategies indicated.
Contraindications
- Pregnancy – Category X; teratogenic, risk of fetal renal damage.
- Bilateral renal artery stenosis – risk of acute renal failure.
- Hyperkalemia – caution in patients on potassium‑sparing diuretics.
- ACE inhibitor hypersensitivity – rash, angioedema.
- Adrenal insufficiency – may precipitate shock.
- Severe renal dysfunction – dose adjustment essential.
- Acute cardiogenic shock – not recommended.
Dosing
| Condition | Starting Dose | Titration | Max Dose |
| Hypertension | 5 mg once daily | 5 mg increments up to 20 mg/d | 20 mg/d |
| Heart failure | 5 mg daily | Escalate to 10/20 mg/d in 2–4 week intervals | 40 mg/d |
| Post‑MI | 5 mg daily | Similar to heart failure | 40 mg/d |
| Diabetic nephropathy | 5 mg daily | 5–20 mg/d as tolerated | 20 mg/d |
• Administration: Oral gavage or tablet; take with water.
• Spacing: For BID regimens, alternate dosing within 12 h.
Adverse Effects
Common
• Dry cough (10–15 %)
• Dizziness, especially post‑load
• Headache
• GI upset (nausea)
Serious
• Angioedema (0.1 %–0.2 %)
• Severe hyperkalemia (>6 mmol/L)
• Acute renal failure (esp. in volume depletion)
• Severe hypotension
• Elevated creatinine (≥30 % rise)
Monitoring
- Blood pressure: baseline, 1–2 weeks, then quarterly.
- Serum electrolytes: potassium and sodium at baseline and every 3–4 weeks.
- Renal function: serum creatinine and eGFR at baseline, monthly, then quarterly.
- HbA1c: for diabetic patients on ACEi.
- Patient symptom diary: cough frequency, swelling signs.
Clinical Pearls
1. Placental Transfer – Quinapril does not cross the placenta in significant amounts; however, its metabolite, enalaprilat, is teratogenic; always advise women of childbearing potential to use effective contraception.
2. Choice over Other ACEIs – Its active metabolite requires no additional activation by hepatic cytochrome P450; therefore, quinapril provides more consistent pharmacokinetics in hepatic impairment compared to other ACE inhibitors.
3. Cough vs. Angioedema – If a patient develops a dry cough, consider switching to an ARB; but if angioedema appears, discontinue immediately and give epinephrine.
4. Avoid Concomitant P2Y12 Inhibitors – Certain antiplatelet agents (e.g., clopidogrel) may reduce renal perfusion; monitor renal function closely.
5. Dose Adjustment Algorithm – Start at 5 mg/d; assess renal and BP response after 4 weeks; increase to 10 mg/d if tolerated; further titration to 20–40 mg/d only if benefit outweighs risk.
6. Hyperkalemia Prevention – Counsel patients on limiting dietary potassium; caution with potassium‑sparing diuretics and NSAIDs.
7. Monitoring in Diabetes – ACE inhibition slows progression of diabetic nephropathy; but careful monitoring of urinary albumin-to-creatinine ratio is crucial for therapy optimization.
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• *This drug card provides a concise, evidence‑based summary of Quinapril for medical students and clinical practitioners. Use it as a quick reference or a starting point for deeper pharmacokinetic and therapeutic investigations.*