Classifications: electrolyte & water balance agent; diuretic; antihypertensive; Therapeutic: diuretic; antihypertensive
Pregnancy Category: B first and second trimester; D third trimester
15 mg, 25 mg, 50 mg, 100 mg tablets
Sulfonamide derivative that differs chemically from thiazides but shares similar actions. Increases excretion of sodium
and chloride by inhibiting their reabsorption in the cortical diluting segment of the ascending loop of Henle.
Antihypertensive effect is correlated to the decrease in extracellular and intracellular volumes. Decreased volume results
in reduced cardiac output with subsequent decrease in peripheral resistance.
Edema associated with CHF, renal decompensation, hepatic cirrhosis, corticosteroid and estrogen therapy; as sole agent or
with other antihypertensives to treat hypertension.
Hypersensitivity to sulfonamide or thiazide derivatives; anuria, hypokalemia; pregnancy (category B in first and second
trimester, and category D in third trimester), neonates with jaundice.
History of renal and hepatic disease, gout, SLE, diabetes mellitus.
Route & Dosage
Adult: PO 12.525 mg/d, may be increased to 100 mg/d if needed
Child: PO 2 mg/kg 3 times/wk
Adult: PO 50100 mg/d, may be increased to 200 mg/d if needed
- Administer as single dose in a.m. to reduce potential for interrupted sleep because of diuresis.
- Consult physician when chlorthalidone is used as a diuretic; an intermittent dose schedule may reduce incidence of adverse
- Store tablets in tightly closed container at 15°30° C (59°86° F) unless otherwise advised.
Adverse Effects (≥1%)CV:
Orthostatic hypotension. GI:
Anorexia, nausea, vomiting, diarrhea
, cramping, jaundice
. Hematologic: Agranulocytosis, thrombocytopenia
, aplastic anemia. CNS:
Dizziness, vertigo, paresthesias, headache. Metabolic: Hypokalemia,
hyponatremia, hypochloremia, hypercalcemia, glycosuria, hyperglycemia, exacerbation of gout
Rash, urticaria, photosensitivity, vasculitis. Urogenital:
Increased risk of digoxin toxicity
because of hypokalemia; corticosteroids
, amphotericin B
increases hypokalemia; decreases lithium
elimination; may antagonize the hypoglycemic effects of sulfonylureas
s may attenuate diuretic effects; cholestyramine
decreases thiazide absorption.
Readily from GI tract. Onset:
2 h. Peak:
36 h. Duration:
2472 h. Distribution:
Crosses placenta; appears in breast milk. Elimination:
3060% in urine in 24 h. Half-Life:
Assessment & Drug Effects
- Establish baseline BP measurements and check at regular intervals during period of dosage adjustment when chlorthalidone
is used for hypertension.
- Be alert to signs of hypokalemia (see Appendix F). Older adult patients are more sensitive to adverse effects of drug-induced
diuresis because of age-related changes in the cardiovascular and renal systems.
- Lab tests: Baseline and periodic: serum electrolytes (particularly K, Mg, Ca), serum uric acid, creatinine, BUN, and uric
acid and blood glucose (especially in patients with diabetes).
- Monitor lithium and digoxin levels closely when either of these drugs is used concurrently.
Patient & Family Education
- Maintain adequate potassium intake, monitor weight, and make a daily estimate of I&O ratio.