Hydrochlorothiazide and Quinapril

Hypertension Quinapril and hydrochlorothiazide tablets are indicated for the treatment of hypertension, to lower blood pressure. Lowering blood pressure reduces the risk of fatal and nonfatal cardiovascular events, primarily strokes and myocardial infarctions. These benefits have been seen in controlled trials of antihypertensive drugs from a wide variety of pharmacologic classes including the class to which this drug principally belongs. There are no controlled trials demonstrating risk reduction with quinapril and hydrochlorothiazide tablets. Control of high blood pressure should be part of comprehensive cardiovascular risk management, including, as appropriate, lipid control, diabetes management, antithrombotic therapy, smoking cessation, exercise, and limited sodium intake. Many patients will require more than one drug to achieve blood pressure goals.

The principal metabolite of quinapril, quinaprilat, is an inhibitor of ACE activity in human subjects and animals. ACE is peptidyl dipeptidase that catalyzes the conversion of angiotensin I to the vasoconstrictor, angiotensin II. The effect of quinapril in hypertension appears to result primarily from the inhibition of circulating and tissue ACE activity, thereby reducing angiotensin II formation. Quinapril inhibits the elevation in blood pressure caused by intravenously administered angiotensin I, but has no effect on the pressor response to angiotensin II, norepinephrine, or epinephrine. Angiotensin II also stimulates the secretion of aldosterone from the adrenal cortex, thereby facilitating renal sodium and fluid reabsorption. Reduced aldosterone secretion by quinapril may result in a small increase in serum potassium.

As individual monotherapy, quinapril is an effective treatment of hypertension in once-daily doses of 10 mg to 80 mg and hydrochlorothiazide is effective in doses of 12.5 mg to 50 mg. In clinical trials of quinapril/hydrochlorothiazide combination therapy using quinapril doses of 2.5 mg to 40 mg and hydrochlorothiazide doses of 6.25 mg to 25 mg, the antihypertensive effects increased with increasing dose of either component. The side effects of quinapril are generally rare and apparently independent of dose, those of hydrochlorothiazide are a mixture of dose-dependent phenomena (primarily hypokalemia) and dose-independent phenomena (e.g., pancreatitis), the former much more common than the latter.

Quinapril and hydrochlorothiazide tablets are contraindicated in patients who are hypersensitive to quinapril or hydrochlorothiazide and in patients with a history of angioedema related to previous treatment with an ACE inhibitor. Quinapril and hydrochlorothiazide tablets are contraindicated in combination with a neprilysin inhibitor (e.g., sacubitril). Do not administer quinapril and hydrochlorothiazide tablets within 36 hours of switching to or from sacubitril/valsartan, a neprilysin inhibitor. Because of the hydrochlorothiazide components, this product is contraindicated in patients with anuria or hypersensitivity to other sulfonamide-derived drugs.

Boxed warning (fetal toxicity): When pregnancy is detected, discontinue quinapril and hydrochlorothiazide as soon as possible. Drugs that act directly on the renin-angiotensin system can cause injury and death to the developing fetus. See WARNINGS: Fetal Toxicity Anaphylactoid and Possibly Related Reactions Presumably because angiotensin converting inhibitors affect the metabolism of eicosanoids and polypeptides, including endogenous bradykinin, patients receiving ACE inhibitors (including quinapril) may be subject to a variety of adverse reactions, some of them serious. Head and Neck Angioedema Angioedema of the face, extremities, lips, tongue, glottis, and larynx has been reported in patients treated with ACE inhibitors and has been seen in 0.1% of patients receiving quinapril.

Quinapril and hydrochlorothiazide has been evaluated for safety in 1571 patients in controlled and uncontrolled studies. Of these, 498 were given quinapril plus hydrochlorothiazide for at least 1 year, with 153 patients extending combination therapy for over 2 years. In clinical trials with quinapril and hydrochlorothiazide, no adverse experience specific to the combination has been observed. Adverse experiences that have occurred have been limited to those that have been previously reported with quinapril or hydrochlorothiazide. Adverse experiences were usually mild and transient, and there was no relationship between side effects and age, sex, race, or duration of therapy. Discontinuation of therapy because of adverse effects was required in 2.1% in patients in controlled studies.

Agents Increasing Serum Potassium Coadministration of quinapril and hydrochlorothiazide with other drugs that raise serum potassium levels may result in hyperkalemia. Monitor serum potassium in such patients. Lithium Increased serum lithium levels and symptoms of lithium toxicity have been reported in patients receiving ACE inhibitors during therapy with lithium. Because renal clearance of lithium is reduced by thiazides, the risk of lithium toxicity is presumably raised further when, as in therapy with quinapril and hydrochlorothiazide, a thiazide diuretic is coadministered with the ACE inhibitor. Quinapril and hydrochlorothiazide and lithium should be coadministered with caution, and frequent monitoring of serum lithium levels is recommended.

Store at 20° to 25°C (68° to 77°F), excursions permitted to 15° to 30°C (59° to 86°F). Protect from light.