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Look Up > Drugs > Chlorthalidone
Chlorthalidone
Pronunciation
U.S. Brand Names
Generic Available
Canadian Brand Names
Pharmacological Index
Use
Pregnancy Risk Factor
Contraindications
Warnings/Precautions
Adverse Reactions
Overdosage/Toxicology
Drug Interactions
Mechanism of Action
Pharmacodynamics/Kinetics
Usual Dosage
Dietary Considerations
Monitoring Parameters
Test Interactions
Cardiovascular Considerations
Mental Health: Effects on Mental Status
Mental Health: Effects on Psychiatric Treatment
Dental Health: Local Anesthetic/Vasoconstrictor Precautions
Dental Health: Effects on Dental Treatment
Patient Information
Nursing Implications
Dosage Forms
References

Pronunciation
(klor THAL i done)

U.S. Brand Names
Hygroton®; Thalitone®

Generic Available

Yes


Canadian Brand Names
Apo®-Chlorthalidone; Novo-Thalidone; Uridon®

Pharmacological Index

Diuretic, Thiazide


Use

Management of mild to moderate hypertension when used alone or in combination with other agents; treatment of edema associated with congestive heart failure, nephrotic syndrome, or pregnancy. Recent studies have found chlorthalidone effective in the treatment of isolated systolic hypertension in the elderly.


Pregnancy Risk Factor

B (per manufacturer); D (based on expert analysis)


Contraindications

Hypersensitivity to chlorthalidone or any component; cross-sensitivity with other thiazides or sulfonamides; anuria; renal decompensation; pregnancy


Warnings/Precautions

Use with caution in patients with hypokalemia, renal disease, hepatic disease, gout, lupus erythematosus, or diabetes mellitus. Use with caution in severe renal diseases. Correct hypokalemia before initiating therapy.


Adverse Reactions

1% to 10%:

Endocrine & metabolic: Hypokalemia

Dermatologic: Photosensitivity

Gastrointestinal: Anorexia, epigastric distress

<1% (Limited to important or life-threatening symptoms): Dizziness, headache, weakness, restlessness, insomnia, purpura, rash, urticaria, necrotizing angiitis, vasculitis, cutaneous vasculitis, hyperuricemia or gout, hyponatremia, sexual ability (decreased), hyperglycemia, glycosuria, nausea, vomiting, cholecystitis, pancreatitis, diarrhea or constipation, polyuria, aplastic anemia, leukopenia, agranulocytosis, thrombocytopenia, hepatic function impairment, paresthesia, muscle cramps or spasm


Overdosage/Toxicology

Symptoms of overdose include hypermotility, diuresis, lethargy, confusion, muscle weakness, coma

Following GI decontamination, therapy is supportive with I.V. fluids, electrolytes, and I.V. pressors if needed


Drug Interactions

Angiotensin-converting enzyme inhibitors: Increased hypotension if aggressively diuresed with a thiazide diuretic.

Beta-blockers increase hyperglycemic effects in Type 2 diabetes mellitus.

Cyclosporine and thiazides can increase the risk of gout or renal toxicity; avoid concurrent use.

Digoxin toxicity can be exacerbated if a thiazide induces hypokalemia or hypomagnesemia.

Lithium toxicity can occur by reducing renal excretion of lithium; monitor lithium concentration and adjust as needed.

Neuromuscular blocking agents can prolong blockade; monitor serum potassium and neuromuscular status.

NSAIDs can decrease the efficacy of thiazides reducing the diuretic and antihypertensive effects.


Mechanism of Action

Sulfonamide-derived diuretic that inhibits sodium and chloride reabsorption in the cortical-diluting segment of the ascending loop of Henle


Pharmacodynamics/Kinetics

Peak effect: 2-6 hours

Absorption: Oral: 65%

Distribution: Crosses placenta; appears in breast milk

Metabolism: In the liver

Half-life: 35-55 hours; may be prolonged with renal impairment, with anuria: 81 hours

Elimination: ~50% to 65% excreted unchanged in urine


Usual Dosage

Oral:

Adults: 25-100 mg/day or 100 mg 3 times/week

Elderly: Initial: 12.5-25 mg/day or every other day; there is little advantage to using doses >25 mg/day

Dosage adjustment in renal impairment: Clcr <10 mL/minute: Administer every 48 hours


Dietary Considerations

This product may cause a potassium loss; your physician may prescribe a potassium supplement, another medication to help prevent the potassium loss, or recommend that you eat foods high in potassium, especially citrus fruits; do not change your diet on your own while taking this medication, especially if you are taking potassium supplements or medications to reduce potassium loss; too much potassium can be as harmful as too little


Monitoring Parameters

Assess weight, I & O records daily to determine fluid loss; blood pressure, serum electrolytes, renal function


Test Interactions

creatine phosphokinase [CPK] (S), ammonia (B), amylase (S), calcium (S), chloride (S), cholesterol (S), glucose, acid (S), chloride (S), magnesium, potassium (S), sodium (S)


Cardiovascular Considerations

Thiazide diuretics are effective first-line therapeutic agents in the management of hypertension and have proven to be of benefit in terms of cardiovascular outcome. They may act synergistically to lower blood pressure when combined with an ACE inhibitor or beta-blocker. The initial concern about thiazide diuretic-induced hypokalemia, glucose intolerance, and lipid profiles does not appear to be of substantial clinical consequence in the treatment of hypertension. The benefits of this class of agents in the treatment of hypertension is established and compares well with other first-line therapeutic agents.


Mental Health: Effects on Mental Status

None reported


Mental Health: Effects on Psychiatric Treatment

Rare reports of blood dyscrasias; use caution with clozapine and carbamazepine; thiazides decrease lithium clearance resulting in elevated serum lithium levels and potential toxicity; monitor serum lithium levels


Dental Health: Local Anesthetic/Vasoconstrictor Precautions

No information available to require special precautions


Dental Health: Effects on Dental Treatment

No effects or complications reported


Patient Information

Take prescribed dose with food early in the day. Include orange juice or bananas in your diet, but do not take potassium supplements without consulting prescriber. You may experience postural hypotension (use caution when rising from lying or sitting position, when climbing stairs, or when driving); photosensitivity (use sunblock, wear protective clothing and eyewear, and avoid direct sunlight); decreased accommodation to heat (avoid excessive exercise in hot weather). Report muscle weakness, tremors, or cramping; persistent nausea or vomiting; swelling of extremities; significant increase in weight; respiratory difficulty; rash; unusual weakness or fatigue; or easy bruising or bleeding. Pregnancy/breast-feeding precautions: Do not get pregnant while taking this medication; use appropriate barrier contraceptive measures. Consult prescriber if breast-feeding.


Nursing Implications

Take blood pressure with patient lying down and standing


Dosage Forms

Tablet: 25 mg, 50 mg, 100 mg

Hygroton®: 25 mg, 50 mg, 100 mg

Thalitone®: 15 mg, 25 mg


References

Freis ED, "The Efficacy and Safety of Diuretics in Treating Hypertension," Ann Intern Med, 1995, 122(3):223-6.

Hulley SB, Furberg CD, Gurland B, et al, "Systolic Hypertension in the Elderly Program (SHEP): Antihypertensive Efficacy of Chlorthalidone," Am J Cardiol, 1985, 56(15):913-20.

Mulley BA, Parr GD, Pau WK, et al, "Placental Transfer of Chlorthalidone and its Elimination in Maternal Milk," Eur J Clin Pharmacol, 1978, 13:129-31.

SHEP Cooperative Research Group, "Prevention of Stroke by Antihypertensive Drug Treatment in Older Persons With Isolated Systolic Hypertension," JAMA, 1991, 265(24):3255-64.


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