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Quinapril Hydrochloride / Hydrochlorothiazide

Pronunciation: KWIN-uh-PRILL HIGH-droe-KLOR-ide/high-droe-klor-THIGH-uh-zide
Class: Antihypertensive combination

Trade Names

- Tablets 10 mg quinapril/12.5 mg hydrochlorothiazide
- Tablets 20 mg quinapril/12.5 mg hydrochlorothiazide
- Tablets 20 mg quinapril/25 mg hydrochlorothiazide



Competitively inhibits angiotensin I-converting enzyme, resulting in the prevention of angiotensin I conversion to angiotensin II, a potent vasoconstrictor that stimulates aldosterone secretion. This action results in a decrease in sodium and fluid retention, an increase in diuresis, and a decrease in BP.

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Increases chloride, sodium, and water excretion by interfering with transport of sodium ions across renal tubular epithelium.

Indications and Usage

Treatment of hypertension.


Patients with a history of angioedema related to previous treatment with an ACE inhibitor; patients with anuria; hypersensitivity to sulfonamide-derived drugs or any component of the product.

Dosage and Administration

The fixed combination is not indicated for initial therapy. The combination may be substituted for the titrated components.


PO Quinapril monotherapy is an effective treatment of hypertension over a dose range of 10 to 80 mg/day administered every day. Hydrochlorothiazide is effective in doses of 12.5 to 50 mg every day. Patients whose BP is not adequately controlled with quinapril monotherapy may be given quinapril/hydrochlorothiazide (10/12.5 or 20/12.5). Further increases in dose of either or both components depend on the clinical response. Generally, the dose of hydrochlorothiazide should not be increased until 2 to 3 wk have elapsed.

Renal Function Impairment

No adjustment required as long as CrCl is greater than 30 mL/min; in severe renal function impairment, loop diuretics are preferred to thiazides.


Store tablets at controlled room temperature (68° to 77°F). Keep container tightly closed.

Drug Interactions

ACTH, corticosteroids

Electrolyte depletion may be intensified, especially hypokalemia.

Alcohol, barbiturates (eg, phenobarbital), narcotics

Orthostatic hypotension may be potentiated.

Anticoagulants (eg, warfarin)

Anticoagulant effect may be decreased.

Antidiabetic agents (eg, insulin, sulfonylureas), antigout agents (eg, probenecid)

Dosage adjustment may be necessary because of possible hydrochlorothiazide-induced elevation in blood glucose levels.

Cardiac glycosides (eg, digoxin)

Possible digitalis toxicity associated with hypokalemia.

Cholestyramine, colestipol

May impair the absorption of hydrochlorothiazide.


In diabetic patients, requirements of insulin may be increased, decreased, or unchanged.


Plasma levels of lithium may be elevated, increasing the risk of toxicity.


May reduce the natriuretic and antihypertensive effect of hydrochlorothiazide.

Potassium supplements, potassium-sparing diuretics (eg, spironolactone)

Increased risk of hyperkalemia.

Nondepolarizing muscle relaxants (eg, tubocurarine)

Effects may be increased.

Pressor amines (eg, norepinephrine)

Response to pressor amines may be decreased.

Tetracycline and other drugs that interact with magnesium

Because of the magnesium content in quinapril, absorption of tetracycline may be reduced, decreasing the therapeutic effect.

Laboratory Test Interactions


May decrease serum protein-bound iodine levels without signs of thyroid disturbances.

Adverse Reactions


Bradycardia; cor pulmonale; vasculitis; deep thrombosis; vasodilatation; chest pain.




Orthostatic hypotension.


Dizziness; somnolence; paralysis; hemiplegia; speech disorder; abnormal gait; meningism; amnesia; headache; fatigue; insomnia; vertigo; asthenia.




Lightheadedness; paresthesia; weakness; restlessness.


Urticaria; macropapular rash; petechiases.


Esophagitis; abnormal vision; rhinitis.




Transient blurred vision; xanthopsia.


GI carcinoma; vomiting; diarrhea; nausea; abdominal pain; constipation; dyspepsia.


Pancreatitis; sialadenitis; diarrhea; cramping; gastric irritation; anorexia.


Abnormal kidney function; albuminuria; pyuria; hematuria; nephrosis.


Renal failure; renal function impairment; interstitial nephritis.




Aplastic anemia; agranulocytosis; leukopenia; thrombocytopenia; hemolytic anemia.


Cholestatic jaundice; hepatitis.


Jaundice (intrahepatic cholestatic).


Weight loss.


Hyperglycemia; glucosuria; hyperuricemia; hypokalemia; hyponatremia; hypochloremic alkalosis.


Coughing; pneumonia; asthma; respiratory infiltration; lung disorder; upper respiratory tract infection; bronchitis.


Shock; accidental injury; neoplasm; cellulitis; ascites; generalized edema; hernia; myopathy; myositis; arthritis; myalgia; viral infection; angioedema.


Back pain; anaphylactoid reactions.


Muscle spasm; hypersensitivity (including necrotizing angiitis, Stevens-Johnson syndrome, respiratory distress [including pneumonia and pulmonary edema], purpura, urticaria, rash, and photosensitivity).



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, discontinue therapy as soon as possible.


Monitor blood sugar in diabetic patient when drug is started or dose is changed.


Category D (second and third trimester); Category C (first trimester). ACE inhibitors (eg, quinapril) can cause injury or death to fetus if used during second or third trimester. When pregnancy is detected, discontinue as soon as possible.


Excreted in breast milk.


Safety and efficacy not established.


Select dose with caution, reflecting greater frequency of decreased hepatic, renal, or cardiac function and comorbidity.

Renal Function

Use with caution.

Hepatic Function

Use with caution.

Anaphylactoid reactions

Reported in patients with a history of angioedema, undergoing desensitizing treatment with Hymenoptera venom, and in patients dialyzed with high-flux membranes.


Use with extreme caution in patients with a history of angioedema. Angioedema associated with laryngeal edema may be fatal. Angioedema may occur more frequently in black patients receiving an ACE inhibitor compared with non-black patients.


Chronic cough may occur during treatment.

Electrolyte imbalance

Treatment with thiazide diuretics has been associated with hypokalemia, hyponatremia, hypochloremic alkalosis, hypercalcemia, and hypomagnesemia. Do not initiate therapy prior to correction of imbalance.

Hepatic failure

Rarely, ACE inhibitors have been associated with a syndrome that starts with cholestatic jaundice and progresses to fulminant hepatic necrosis and death.


Decreases in BP may occur, especially in salt- or volume-depleted patients as a result of dialysis, prolonged diuretic therapy, dietary salt restriction, diarrhea, or vomiting. Volume and salt depletion should be corrected before initiating therapy with quinapril/hydrochlorothiazide.

Metabolic disturbances

Thiazide diuretics tend to reduce glucose tolerance, raise cholesterol, triglycerides, and uric acid levels.


Has occurred with other ACE inhibitors.


In patients undergoing surgery or during anesthesia with agents that produce hypotension, angiotensin II formation, secondary to compensatory renal release, may be blocked.

Systemic Lupus Erythematosus (SLE)

Hydrochlorothiazide may exacerbate or activate SLE.



Dehydration, electrolyte imbalance (hypokalemia [which may accentuate cardiac arrhythmias in patients receiving digitalis], hypochloremia, hyponatremia), hypotension.

Patient Information

  • Advise patient to take prescribed dose every day without regard to meals.
  • Advise patient to try to take each dose at about the same time every day.
  • Inform patient that drug controls, but does not cure, hypertension and to continue taking drug as prescribed even when BP is not elevated.
  • Caution patient not to change the dose or stop taking unless advised by health care provider.
  • Instruct patient to continue taking other BP medications as prescribed by health care provider.
  • Instruct patient in BP and pulse measurement skills.
  • Advise patient to monitor and record BP and pulse at home and to inform health care provider if abnormal measurements are noted. Also, advise patient to take record of BP and pulse to each follow-up visit.
  • Caution patient to avoid sudden position changes to prevent orthostatic hypotension.
  • Instruct patient to lie or sit down if experiencing dizziness or lightheadedness when standing.
  • Caution patient that inadequate fluid intake, excessive perspiration, diarrhea, or vomiting can lead to excessive fall in BP resulting in lightheadedness or fainting.
  • Instruct diabetic patient to monitor blood glucose more frequently when drug is started or dose is changed and to inform health care provider of significant changes in readings.
  • Caution patient to avoid unnecessary exposure to UV light (sunlight, tanning booths) and to use sunscreen and wear protective clothing when exposed to UV light to avoid photosensitivity reaction.
  • Emphasize to hypertensive patient importance of other modalities on BP: weight control, regular exercise, smoking cessation, and moderate intake of alcohol and salt.
  • Instruct patient to stop taking drug and immediately report any of the following symptoms to health care provider: fainting, swelling of the face, lips, eyelids or tongue, difficulty breathing.
  • Instruct patient to inform health care provider if a persistent cough develops while taking this medication.
  • Caution patient not to take any prescription or OTC medications, potassium-containing salt substitutes, potassium supplements, or dietary supplements unless advised by health care provider.

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