ALDACTAZIDE

ALDACTAZIDE- spironolactone and hydrochlorothiazide tablet, film coated
Pfizer Laboratories Div Pfizer Inc

DESCRIPTION

ALDACTAZIDE oral tablets contain:

spironolactone . . . . . . . . . . . . . . . . . . . . 25 mg
hydrochlorothiazide . . . . . . . . . . . . . . . . 25 mg

or

spironolactone . . . . . . . . . . . . . . . . . . . . 50 mg
hydrochlorothiazide . . . . . . . . . . . . . . . . 50 mg

Spironolactone (ALDACTONE®), an aldosterone antagonist, is 17-hydroxy-7α-mercapto-3-oxo-17α-pregn-4-ene-21-carboxylic acid γ-lactone acetate and has the following structural formula:

Chemical Structure

Spironolactone is practically insoluble in water, soluble in alcohol, and freely soluble in benzene and in chloroform.

Hydrochlorothiazide, a diuretic and antihypertensive, is 6-chloro-3,4-dihydro-2H-1,2,4-benzothiadiazine-7-sulfonamide 1,1-dioxide and has the following structural formula:

Chemical Structure

Hydrochlorothiazide is slightly soluble in water and freely soluble in sodium hydroxide solution.

Inactive ingredients include calcium sulfate, corn starch, flavor, hydroxypropyl cellulose, hypromellose, iron oxide, magnesium stearate, polyethylene glycol, povidone, and titanium dioxide.

ACTIONS / CLINICAL PHARMACOLOGY

Mechanism of action

ALDACTAZIDE is a combination of two diuretic agents with different but complementary mechanisms and sites of action, thereby providing additive diuretic and antihypertensive effects. Additionally, the spironolactone component helps to minimize the potassium loss characteristically induced by the thiazide component.

The diuretic effect of spironolactone is mediated through its action as a specific pharmacologic antagonist of aldosterone, primarily by competitive binding of receptors at the aldosterone-dependent sodium-potassium exchange site in the distal convoluted renal tubule. Hydrochlorothiazide promotes the excretion of sodium and water primarily by inhibiting their reabsorption in the cortical diluting segment of the distal renal tubule.

ALDACTAZIDE is effective in significantly lowering the systolic and diastolic blood pressure in many patients with essential hypertension, even when aldosterone secretion is within normal limits.

Both spironolactone and hydrochlorothiazide reduce exchangeable sodium, plasma volume, body weight, and blood pressure. The diuretic and antihypertensive effects of the individual components are potentiated when spironolactone and hydrochlorothiazide are given concurrently.

Pharmacokinetics

Spironolactone is rapidly and extensively metabolized. Sulfur-containing products are the predominant metabolites and are thought to be primarily responsible, together with spironolactone, for the therapeutic effects of the drug. The following pharmacokinetic data were obtained from 12 healthy volunteers following the administration of 100 mg of spironolactone (ALDACTONE film-coated tablets) daily for 15 days. On the 15th day, spironolactone was given immediately after a low fat breakfast and blood was drawn thereafter.

Accumulation Factor:
AUC (0–24 hr, day 15)/AUC (0–24 hr, day 1) Mean Peak Serum Concentration Mean (SD) Post-Steady State Half-Life
7-α-(thiomethyl) spirolactone (TMS) 1.25 391 ng/mL at 3.2 hr 13.8 hr (6.4) (terminal)
6-β-hydroxy-7-α-(thiomethyl) spirolactone (HTMS) 1.50 125 ng/mL at 5.1 hr 15.0 hr (4.0) (terminal)
Canrenone (C) 1.41 181 ng/mL at 4.3 hr 16.5 hr (6.3) (terminal)
Spironolactone 1.30 80 ng/mL at 2.6 hr Approximately 1.4 hr (0.5) (β half-life)

The pharmacological activity of spironolactone metabolites in man is not known. However, in the adrenalectomized rat the antimineralocorticoid activities of the metabolites C, TMS, and HTMS, relative to spironolactone, were 1.10, 1.28, and 0.32, respectively. Relative to spironolactone, their binding affinities to the aldosterone receptors in rat kidney slices were 0.19, 0.86, and 0.06, respectively.

In humans, the potencies of TMS and 7-α-thiospirolactone in reversing the effects of the synthetic mineralocorticoid, fludrocortisone, on urinary electrolyte composition were 0.33 and 0.26, respectively, relative to spironolactone. However, since the serum concentrations of these steroids were not determined, their incomplete absorption and/or first-pass metabolism could not be ruled out as a reason for their reduced in vivo activities.

Spironolactone and its metabolites are more than 90% bound to plasma proteins. The metabolites are excreted primarily in the urine and secondarily in bile.

The effect of food on spironolactone absorption (two 100 mg ALDACTONE tablets) was assessed in a single dose study of 9 healthy, drug-free volunteers. Food increased the bioavailability of unmetabolized spironolactone by almost 100%. The clinical importance of this finding is not known.

Hydrochlorothiazide is rapidly absorbed following oral administration. Onset of action of hydrochlorothiazide is observed within one hour and persists for 6 to 12 hours. Hydrochlorothiazide plasma concentrations attain peak levels at one to two hours and decline with a half-life of four to five hours. Hydrochlorothiazide undergoes only slight metabolic alteration and is excreted in urine. It is distributed throughout the extracellular space, with essentially no tissue accumulation except in the kidney.

INDICATIONS AND USAGE

Spironolactone, an ingredient of ALDACTAZIDE, has been shown to be a tumorigen in chronic toxicity studies in rats (see Precautions section). ALDACTAZIDE should be used only in those conditions described below. Unnecessary use of this drug should be avoided.

ALDACTAZIDE is indicated for:

Edematous conditions for patients with:

Congestive heart failure:

  • For the management of edema and sodium retention when the patient is only partially responsive to, or is intolerant of, other therapeutic measures;
  • The treatment of diuretic-induced hypokalemia in patients with congestive heart failure when other measures are considered inappropriate;
  • The treatment of patients with congestive heart failure taking digitalis when other therapies are considered inadequate or inappropriate.

Cirrhosis of the liver accompanied by edema and/or ascites:

  • Aldosterone levels may be exceptionally high in this condition. ALDACTAZIDE is indicated for maintenance therapy together with bed rest and the restriction of fluid and sodium.

The nephrotic syndrome:

  • For nephrotic patients when treatment of the underlying disease, restriction of fluid and sodium intake, and the use of other diuretics do not provide an adequate response.

Essential hypertension:

  • For patients with essential hypertension in whom other measures are considered inadequate or inappropriate;
  • In hypertensive patients for the treatment of a diuretic-induced hypokalemia when other measures are considered inappropriate;
  • ALDACTAZIDE is 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 classes to which this drug principally belongs. There are no controlled trials demonstrating risk reduction with ALDACTAZIDE.

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. For specific advice on goals and management, see published guidelines, such as those of the National High Blood Pressure Education Program’s Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC).

Numerous antihypertensive drugs, from a variety of pharmacologic classes and with different mechanisms of action, have been shown in randomized controlled trials to reduce cardiovascular morbidity and mortality, and it can be concluded that it is blood pressure reduction, and not some other pharmacologic property of the drugs, that is largely responsible for those benefits. The largest and most consistent cardiovascular outcome benefit has been a reduction in the risk of stroke, but reductions in myocardial infarction and cardiovascular mortality also have been seen regularly.

Elevated systolic or diastolic pressure causes increased cardiovascular risk, and the absolute risk increase per mmHg is greater at higher blood pressures, so that even modest reductions of severe hypertension can provide substantial benefit. Relative risk reduction from blood pressure reduction is similar across populations with varying absolute risk, so the absolute benefit is greater in patients who are at higher risk independent of their hypertension (for example, patients with diabetes or hyperlipidemia), and such patients would be expected to benefit from more aggressive treatment to a lower blood pressure goal.

Some antihypertensive drugs have smaller blood pressure effects (as monotherapy) in black patients, and many antihypertensive drugs have additional approved indications and effects (e.g., on angina, heart failure, or diabetic kidney disease). These considerations may guide selection of therapy.

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