Chlorthalidone is a diuretic medication used to treat hypertension (high blood pressure). It is described as a thiazide diuretic (or, rather, a diuretic similar to thiazide because it acts similarly to thiazides but does not exactly contain the molecular structure). In comparison with other drugs of the thiazide class, chlorthalidone has the longest action time but a diuretic effect similar to the maximum therapeutic doses. It is often used in the treatment of hypertension and swelling due to fluid retention (edema).
In terms of activity, chlorothalidone is very similar to hydrochlorothiazide and is used as an independent medicine or in combination with other antihypertensive agents to reduce blood pressure, and also as an adjuvant medication to treat edema caused by heart failure and kidney disorders, like the nephrotic syndrome.
Chlorthalidone prevents the reabsorption of sodium and chloride by inhibiting the sodium/chloride cotransporter channel in the distal nephritic convoluted tubule.
Initially, diuretics reduce blood pressure by decreasing cardiac output and reducing the volume of extracellular and plasma fluid. Finally, the cardiac output returns to normal, and the volume of extracellular fluid and plasma becomes slightly lower than normal, but a reduction in peripheral vascular resistance is maintained, which results in a lower overall blood pressure.
Chlorthalidone is contraindicated in the following cases: Hypersensitivity to chlorthalidone or sulphonamides. Anuria. Renal insufficiency or severe hepatic insufficiency, hypokalemia and refractory hyponatremia, hypercalcemia and symptomatic hyperuricemia.
Caution should be exercised when prescribing chlorthalidone in patients treated with digitalis, elderly patients, patients with nephrosis, cirrhosis, gout, diabetes, hyperlipidemia (discontinue treatment if serum lipids increase). The electrolytes must be controlled during the treatment since the intake of chlorthalidone can cause hypercalcemia, hypokalemia, hyponatremia, hypomagnesemia and hypochloraemic alkalosis.
During pregnancy do not prescribe chlorthalidone since it can decrease the uteroplacental irrigation and crosses the placental barrier. It should also not be taken during breastfeeding since chlorthalidone passes into the milk or, if it is to be taken, breastfeeding will be discontinued.
Intake of chlorthalidone increases lithium levels.
Chlorthalidone potentiates the action of: derivatives of curare and other antihypertensive agents.
The hypokalemic effect of chlorthalidone is increased by: corticosteroids, ACTH, amphotericin, carbenoxolone.
Chlorthalidone increases the toxicity of digitalis.
The effect of chlorthalidone may be diminished by NSAIDs (non-steroidal anti-inflammatory drugs).
When taking chlorthalidone the dose of antidiabetic drugs should be adjusted.
Electrolyte alterations, rash, orthostatic hypotension, arrhythmias, gastrointestinal disorders, hyperuricemia, hyperglycemia, increased blood lipids, thrombocytopenia.
Chlorthalidone is unlikely to affect the ability to drive or use machines. However, like other antihypertensive medications, chlorthalidone may cause dizziness or drowsiness in some people, especially at the beginning of treatment, when changing doses or if alcohol is consumed. Patients receiving chlorthalidone should be warned to not drive or operate machines if they experience dizziness or drowsiness.
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