HYDROCHLOROTHIAZIDE

Hydrochlorothiazide is a diuretic and antihypertensive. It is the 3,4-dihydro derivative of chlorothiazide. Its chemical name is 6-chloro-3,4-dihyrdo-2 H -1,2,4-benzothiadiazine-7-sulfonamide1,1-dioxide, and its structural formula is Hydrochlorothiazide is a white, or practically white, crystalline powder, which is slightly soluble in water, but freely soluble in sodium hydroxide solution. Each tablet, for oral administration, contains 25 mg or 50 mg hydrochlorothiazide. In addition. each tablet contains the following inactive ingredients: Anhydrous Lactose, Pregelatinized Starch from Corn, Magnesium Stearate, Microcrystalline Cellulose, and FD&C Yellow #6. structural formula

Hydrochlorothiazide tablets are indicated as adjunctive therapy in edema associated with congestive heart failure, hepatic cirrhosis, and corticosteroid and estrogen therapy. Hydrochlorothiazide has also been found useful in edema due to various forms of renal dysfunction such as the nephrotic syndrome, acute glomerulonephritis, and chronic renal failure. Hydrochlorothiazide is indicated in the management of hypertension either as the sole therapeutic agent or to enhance the effectiveness of other antihypertensive drugs in the more severe forms of hypertension.

Therapy should be individualized according to patient response. Use the smallest dosage necessary to achieve the required response. Adults For Edema - The usual adult dosage is 25 to 100 mg daily as a single or divided dose. Many patients with edema respond to intermittent therapy, i.e., administration on alternate days or on three to five days each week. With an intermittent schedule, excessive response and the resulting undesirable electrolyte imbalance are less likely to occur. For Control of Hypertension - The usual initial dose in adults is 25 mg daily given as a single dose. The dose may be increased to 50 mg daily, given as a single or two divided doses. Doses above 50 mg are often associated with marked reductions in serum potassium (see also PRECAUTIONS ). Patients usually do not require doses in excess of 50 mg of hydrochlorothiazide daily when used concomitantly with other antihypertensive agents. Infants and Children For Diuresis and For Control of Hypertension - The usual pediatric dosage is 0.5 to 1 mg per pound (1 lo 2 mg/kg) per day in single or two divided doses, not to exceed 37.5 mg per day in infants up to 2 years of age or 100 mg per day in children 2 to 12 years of age. In infants less than 6 months of age, doses up to 1.5 mg per pound (3 mg/kg) per day in two divided doses may be required (see PRECAUTIONS, Pediatric Use ).

Anuria. Hypersensitivity to this product or to other sulfonamide-derived drugs

The following adverse reactions have been reported and, within each category, are listed in order of decreasing severity. Body As A Whole : Weakness. Cardiovascular : Hypotension including orthostatic hypotension (may be aggravated by alcohol, barbiturates, narcotics or antihypertensive drugs). Digestive : Pancreatitis, jaundice (intrahepatic cholestatic jaundice), diarrhea, vomiting. sialadenitis, cramping, constipation, gastric irritation, nausea, anorexia. Hematologic : Aplastic anemia, agranulocytosis, leukopenia, hemolytic anemia, thrombocytopenia. Hypersensitivity : Anaphylactic reactions, necrotizing angiitis (vasculitis and cutaneous vasculitis), respiratory distress including pneumonitis and pulmonary edema, photosensitivity, fever, urticaria, rash, purpura. Metabolic: Electrolyte imbalance {see PRECAUTIONS ), hyperglycemia, glycosuria, hyperuricemia. Musculoskeletal : Muscle spasm. Nervous System/Psychiatric: Vertigo, paresthesias, dizziness, headache, restlessness. Renal : Renal failure, renal dysfunction, interstitial nephritis. (See WARNINGS .) Skin : Erythema multiforme including Stevens-Johnson syndrome, exfoliative dermatitis including toxic epidermal necrolysis, alopecia. Special Senses : Transient blurred vision, xanthopsia. Urogenital : Impotence. Postmarketing Experience Non-melanoma Skin Cancer : Hydrochlorothiazide is associated with an increased risk of non-melanoma skin cancer. In a study conducted in the Sentinel System, increased risk was predominantly for squamous cell carcinoma (SCC) and in white patients taking large cumulative doses. The increased risk for SCC in the overall population was approximately 1 additional case per 16,000 patients per year, and for white patients taking a cumulative dose of ≥50,000 mg the risk increase was approximately 1 additional SCC case for every 6,700 patients per year. Whenever adverse reactions are moderate or severe, thiazide dosage should be reduced or therapy withdrawn.

When given concurrently the following drugs may interact with thiazide diuretics. Alcohol, Barbiturates, or Narcotics -potentiation of orthostatic hypotension may occur. Antidiabetic Drugs· (oral agents and insulin) - dosage adjustment of the antidiabetic drug may be required. Other Antihypertensive Drugs - additive effect or potentiation. Cholestyramine and Colestipol Resins - Absorption of hydrochlorothiazide is impaired in the presence of anionic exchange resins. Single doses of cholestyramine and colestipol resins bind the hydrochlorothiazide and reduce its absorption in the gastrointestinal tract by up to 85 and 43 percent, respectively. Corticosteroids, ACTH - intensified electrolyte depletion, particularly hypokalemia. Pressor Amines (e.g., Norepinephrine) - possible decreased response to pressor amines but not sufficient to preclude their use. Skeletal Muscle Relaxants, Nondepolarizing (e.g., Tubocurarine) - possible increased responsiveness to the muscle relaxant. Lithium - generally should not be given with diuretics. Diuretic agents reduce the renal clearance of lithium and add a high risk of lithium toxicity. Refer to the package insert for lithium preparations before use of such preparations with hydrochlorothiazide. Nonsteroidal Anti-Inflammatory Drugs - In some patients, the administration of a nonsteroidal anti-inflammatory agent can reduce the diuretic, natriuretic, and antihypertensive effects of loop, potassium-sparing and thiazide diuretics. Therefore, when hydrochlorothiazide and nonsteroidal anti-inflammatory agents are used concomitantly, the patient should be observed closely to determine if the desired effect of the diuretic is obtained.