Chlorthalidone

INDICATIONS AND USAGE Diuretics such as chlorthalidone are indicated in the management of hypertension either as the sole therapeutic agent or to enhance the effect of other antihypertensive drugs in the more severe forms of hypertension. Chlorthalidone is indicated as adjunctive therapy in edema associated with congestive heart failure, hepatic cirrhosis, and corticosteroid and estrogen therapy. Chlorthalidone has also been found useful in edema due to various forms of renal dysfunction, such as nephrotic syndrome, acute glomerulonephritis, and chronic renal failure.Chlorthalidone has also been found useful in edema due to various forms of renal dysfunction, such as nephrotic syndrome, acute glomerulonephritis, and chronic renal failure. Usage in Pregnancy The routine use of diuretics in an otherwise healthy woman is inappropriate and exposes mother and fetus to unnecessary hazard. Diuretics do not prevent development of toxemia of pregnancy, and there is no satisfactory evidence that they are useful in the treatment of developed toxemia. Edema during pregnancy may arise from pathologic causes or from the physiologic and mechanical consequences of pregnancy. Chlorthalidone is indicated in pregnancy when edema is due to pathologic causes, just as it is in the absence of pregnancy (however, see PRECAUTIONS , below). Dependent edema in pregnancy, resulting from restriction of venous return by the expanded uterus, is properly treated through elevation of the lower extremities and use of support hose; use of diuretics to lower intravascular volume in this case is illogical and unnecessary. There is hypervolemia during normal pregnancy that is harmful to neither the fetus nor the mother (in the absence of cardiovascular disease), but that is associated with edema, including generalized edema, in the majority of pregnant women. If this edema produces discomfort, increased recumbency will often provide relief. In rare instances, this edema may cause extreme discomfort that is not relieved by rest. In these cases, a short course of diuretics may provide relief and be appropriate.

DOSAGE AND ADMINISTRATION Therapy should be initiated with the lowest possible dose. This dose should be titrated according to individual patient response to gain maximal therapeutic benefit while maintaining lowest dosage possible. A single dose given in the morning with food is recommended; divided daily doses are unnecessary. Hypertension Initiation Therapy, in most patients, should be initiated with a single daily dose of 25 mg. If the response is insufficient after a suitable trial, the dosage may be increased to a single daily dose of 50 mg. If additional control is required, the dosage of chlorthalidone tablets may be increased to 100 mg once daily or a second antihypertensive drug (step 2 therapy) may be added. Dosage above 100 mg daily usually does not increase effectiveness. Increases in serum uric acid and decreases in serum potassium are dose-related over the 25 mg/day to 100 mg/day range. Maintenance Maintenance doses may be lower than initial doses and should be adjusted according to individual patient response. Effectiveness is well sustained during continued use. Edema Initiation Adults, initially 50 mg to 100 mg daily, or 100 mg on alternate days. Some patients may require 150 mg to 200 mg at these intervals or up to 200 mg daily. Dosages above this level, however, do not usually produce a greater response. Maintenance Maintenance doses may often be lower than initial doses and should be adjusted according to individual patient response. Effectiveness is well sustained during continued use.

CONTRAINDICATIONS Anuria Known hypersensitivity to chlorthalidone tablets or other sulfonamide-derived drugs.

ADVERSE REACTIONS The following adverse reactions have been observed, but there is not enough systematic collection of data to support an estimate of their frequency. Gastrointestinal System Reactions: anorexia, gastric irritation, nausea, vomiting, cramping, diarrhea, constipation, jaundice (intrahepatic cholestatic jaundice), pancreatitis. Central Nervous System Reactions: dizziness, vertigo, paresthesias, headache, xanthopsia. Hematologic Reactions: leukopenia, agranulocytosis, thrombocytopenia, aplastic anemia. Dermatologic-Hypersensitivity Reactions: purpura, photosensitivity, rash, urticaria, necrotizing angiitis (vasculitis, cutaneous vasculitis), Lyell’s syndrome (toxic epidermal necrolysis). Cardiovascular Reactions: orthostatic hypotension may occur and may be aggravated by alcohol, barbiturates, or narcotics. Other Adverse Reactions: hyperglycemia, glycosuria, hyperuricemia, muscle spasm, weakness, restlessness, impotence. Whenever adverse reactions are moderate or severe, chlorthalidone dosage should be reduced or therapy withdrawn. To report SUSPECTED ADVERSE REACTIONS, contact Macleods Pharma USA, Inc. at 1-888-943-3210 or 1-855-926-3384 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

Drug Interactions Chlorthalidone may add to or potentiate the action of other antihypertensive drugs. Potentiation occurs with ganglionic peripheral adrenergic blocking drugs. Medication such as digitalis may also influence serum electrolytes. Warning signs, irrespective of cause, are: dryness of mouth, thirst, weakness, lethargy, drowsiness, restlessness, muscle pains or cramps, muscular fatigue, hypotension, oliguria, tachycardia, and gastrointestinal disturbances such as nausea and vomiting. Insulin requirements in diabetic patients may be increased, decreased, or unchanged. Higher dosage of oral hypoglycemic agents may be required. Latent diabetes mellitus may become manifest during chlorthalidone administration. Chlorthalidone and related drugs may increase the responsiveness to tubocurarine. Chlorthalidone and related drugs may decrease arterial responsiveness to norepinephrine. This diminution is not sufficient to preclude effectiveness of the pressor agent for therapeutic use. Drug /Laboratory Test Interactions Chlorthalidone and related drugs may decrease serum PBI levels without signs of thyroid disturbance. Carcinogenesis, Mutagenesis, Impairment of Fertility No information is available. Pregnancy Teratogenic Effects. Pregnancy Category B Reproduction studies have been performed in the rat and the rabbit at doses up to 420 times the human dose and have revealed no evidence of harm to the fetus due to chlorthalidone. There are, however, no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed. Nonteratogenic Effects Thiazides cross the placental barrier and appear in cord blood. The use of chlorthalidone and related drugs in pregnant women requires that the anticipated benefits of the drug be weighed against possible hazards to the fetus. These hazards include fetal or neonatal jaundice, thrombocytopenia, and possibly other adverse reactions that have occurred in the adult. Nursing Mothers Thiazides are excreted in human milk. Because of the potential for serious adverse reactions in nursing infants from chlorthalidone, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother. Pediatric Use Safety and effectiveness in children have not been established. Geriatric Use Clinical studies of the 15 mg chlorthalidone tablets did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience with 15 mg chlorthalidone tablets has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal or cardiac function, and of concomitant disease or other drug therapy. This drug is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function.

DESCRIPTION Chlorthalidone is an oral antihypertensive/diuretic. It is a monosulfamyl diuretic that differs chemically from thiazide diuretics in that a double-ring system is incorporated in its structure. It is 2-chloro-5-(1-hydroxy-3-oxo-1- isoindolinyl) benzenesulfonamide with the following structural formula: chlorthalidone-strecture Molecular Formula: C 14 H 11 ClN 2 O 4 S Molecular weight: 338.776 Chlorthalidone, USP is practically insoluble in water, in ether, and in chloroform; soluble in methanol; slightly soluble in alcohol. Chlorthalidone tablets are available containing either 25 mg or 50 mg of chlorthalidone USP and the following inactive ingredients: microcrystalline cellulose, partially pregelatinized maize starch, sodium starch glycolate, colloidal silicon dioxide, magnesium stearate, ingredients of aquadry blend yellow like iron oxide yellow, lactose monohydrate, Ferrosoferric Oxide for 25 mg and ingredients of aquadry blend green like D & C Yellow #10 aluminum lake, FD & C blue #1/ Brilliant Blue FCF Aluminum Lake for 50 mg.

OVERDOSAGE Symptoms of acute over dosage include nausea, weakness, dizziness, and disturbances of electrolyte balance. The oral LD 50 of the drug in the mouse and the rat is more than 25,000 mg/kg body weight. The minimum lethal dose (MLD) in humans has not been established. There is no specific antidote, but gastric lavage is recommended, followed by supportive treatment. Where necessary, this may include intravenous dextrose-saline with potassium, administered with caution.

HOW SUPPLIED Chlorthalidone Tablets, USP are available containing 25 mg or 50 mg of Chlorthalidone, USP. 25 mg Tablets are Light yellow colour, round, unscored tablet, debossed with "N" on one side and plain on other side. 25 mg Tablets are supplied as follows: Bottles of 100 tablets NDC # 75834-109-01 Bottles of 1000 tablets NDC # 75834-109-10 50 mg Tablets are Light green colour, round tablet, debossed with "N" and score line on one side and plain on other side. 50 mg Tablets are supplied as follows: Bottles of 100 tablets NDC # 75834-110-01 Bottles of 1000 tablets NDC # 75834-110-10 Store at 20° to 25°C (68° to 77°F). [See USP for Controlled Room Temperature.] Protect from light. Dispense in a tight, light-resistant container as defined in the USP using a child-resistant closure. ANIMAL PHARMACOLOGY Biochemical studies in animals have suggested reasons for the prolonged effect of chlorthalidone. Absorption from the gastrointestinal tract is slow due to its low solubility. After passage to the liver, some of the drug enters the general circulation, while some is excreted in the bile, to be reabsorbed later. In the general circulation, it is distributed widely to the tissues, but is taken up in highest concentrations by the kidneys, where amounts have been found 72 hours after ingestion, long after it has disappeared from other tissues. The drug is excreted unchanged in the urine. Manufactured for: Nivagen Pharmaceuticals, Inc. Sacramento, CA 95827 USA Toll free number: 1-877-977-0687 Manufactured by: Umedica Laboratories Pvt. Ltd. Plot No.221 and 221/1, GIDC, II nd Phase, Vapi, Gujarat 396195, India (IND) Manufactured by: Square Pharmaceuticals Limited Dhaka Unit, Kaliakoir, Gazipur – 1750, Bangladesh. Revised July 2023, V-03