What it's for (Indications)
- Quinapril is indicated for the treatment of hypertension (high blood pressure).
- It can be used as monotherapy or in combination with diuretics, particularly when monotherapy is insufficient.
Dosage Information
| Type | Guideline |
|---|---|
| Standard | For hypertension monotherapy, the recommended initial dosage is 10 or 20 mg once daily. Dosage should be adjusted based on blood pressure response at peak (2-6 hours post-dose) and trough (pre-dose), typically at intervals of at least 2 weeks. Most patients require dosages of 20, 40, or 80 mg/day, administered as a single dose or in two equally divided doses. If the antihypertensive effect diminishes toward the end of the dosing interval with once-daily administration, an increased dosage or twice-daily dosing may be warranted. If blood pressure is not adequately controlled with quinapril monotherapy, a diuretic may be added, and dosage adjustments should be made accordingly. |
Safety & Warnings
Common Side Effects
- Quinapril, as an angiotensin-converting enzyme (ACE) inhibitor, is associated with a spectrum of adverse effects, some of which are common and generally mild, while others are less frequent but potentially serious.
- The most prevalent side effect is a persistent, dry, non-productive cough, which can occur at any point during therapy and may necessitate discontinuation.
- Other commonly reported adverse reactions include dizziness, particularly during the initial phase of treatment or following a dose increase due to its hypotensive effects, as well as headache, fatigue, and nausea.
- Gastrointestinal disturbances such as diarrhea or abdominal pain may also be experienced.
- More serious, though less common, side effects require immediate medical attention.
- Angioedema, a rapid swelling of the face, lips, tongue, and throat, poses a life-threatening risk due to potential airway obstruction and requires urgent medical intervention.
- Patients should be advised to seek emergency care if any signs of angioedema appear.
- Hyperkalemia, an elevation in serum potassium levels, is another important concern, particularly in patients with renal insufficiency, diabetes, or those concurrently using potassium-sparing diuretics or potassium supplements.
- Renal dysfunction, including acute kidney injury, can occur, especially in individuals with pre-existing renal disease or bilateral renal artery stenosis, necessitating careful monitoring of renal function.
- Other rare but significant adverse effects include neutropenia or agranulocytosis (a reduction in white blood cell count), liver enzyme elevations or hepatic dysfunction, and skin rashes.
- Regular monitoring of blood pressure, renal function tests (e.
- g.
- , serum creatinine, BUN), and serum electrolytes (especially potassium) is essential throughout quinapril therapy to detect and manage these potential adverse reactions promptly.
- Patients must be thoroughly counseled on these potential side effects and instructed to report any concerning symptoms to their healthcare provider.
Serious Warnings
- Black Box Warning: USE IN PREGNANCY: When used in pregnancy during the second and third trimesters, ACE inhibitors can cause injury and even death to the developing fetus. When pregnancy is detected, quinapril should be discontinued as soon as possible.
- Quinapril is not recommended during breastfeeding.
- Patients should avoid driving or operating machinery if they experience dizziness or fatigue.
- Alcohol consumption should be avoided.
- Caution is advised in patients undergoing hemodialysis and those with liver impairments.
- Monitoring of serum potassium levels may be necessary due to the potential for a small increase.
How it Works (Mechanism of Action)
Quinapril is a prodrug that is deesterified to its active metabolite, quinaprilat, which is an angiotensin-converting enzyme (ACE) inhibitor. ACE catalyzes the conversion of angiotensin I to angiotensin II, a potent vasoconstrictor. By inhibiting ACE, quinaprilat reduces angiotensin II formation, leading to vasodilation and decreased blood pressure. This action also reduces aldosterone secretion, which may result in a small increase in serum potassium.