What are thiazide diuretics? Thiazide diuretics are a type of diuretic (a drug that increases urine flow). They act directly on the kidney and promote diuresis (urine flow) by inhibiting the sodium/chloride cotransporter located in the distal tubule of the nephron (a functional unit of the kidney). Thiazides reduce sodium reabsorption, which increases urinary fluid loss, which in turn reduces extracellular fluid and plasma volume. This reduces cardiac output (how hard the heart has to work to pump blood through the body) and lowers blood pressure. Thiazides also work in other ways to lower blood pressure. Thiazides also cause a loss of potassium while retaining calcium. Thiazides are typically used to lower blood pressure because their diuretic effect is relatively weak compared to other types of diuretics (such as loop diuretics). Examples of thiazide diuretics taken orally include:

• Chlorothiazide
• Chlorthalidone
• Hydrochlorothiazide
• Indapamide
• Metolazone

Are thiazide diuretics safe? After 60 years of use, thiazide diuretics remain an effective and safe therapeutic choice for the treatment of hypertension and edema. In addition, their ability to enhance the efficacy of many other classes of hypertension drugs makes them a valuable therapeutic option in the treatment of hypertension. However, the following drugs may interact with thiazide diuretics: Lithium in combination with thiazide diuretics may increase the risk of lithium toxicity and is not recommended. Alcohol and other CNS depressants may increase the likelihood of thiazide diuretics causing orthostatic hypotension (dizziness or fainting due to low blood pressure when standing up quickly from a sitting or lying position). Concurrently administered antidiabetic drugs may require dose adjustments. Other hypertension drugs may have additive effects in lowering blood pressure. Corticosteroids can increase electrolyte loss, importantly causing hypokalemia (low blood calcium). Side effects Diuretics are generally safe. Side effects include increased urination and sodium loss. Diuretics can also affect blood potassium levels. If you are taking a thiazide diuretic, your potassium levels may drop too low (hypokalemia), which can cause life-threatening heartbeat problems. If you are taking a potassium-sparing diuretic, you may have too much potassium in your blood. Inn Inn

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I What are the trade names of thiazide diuretics? Three thiazide diuretics are most commonly used: hydrochlorothiazide (HCTZ), chlortalidone and indapamide. HCTZ and chlortalidone are FDA-approved for clinical use in the treatment of primary hypertension. Which thiazide diuretic is best? Chlortalidone is the preferred diuretic for initial and continuing therapy of hypertension, starting at a dose of 12.5 mg/d and increasing to ≤25.0 mg/d with or without other antihypertensive drugs. What medications should not be taken with thiazide diuretics? Drug other comments Most thiazide diuretics are taken once a day, in the morning. Any reduction in blood pressure is maintained for 24 hours with this once-a-day dose. However, the effect of the extra urine is used up within 12 hours. So you won't have to get up at night to make extra trips to the toilet. The dose used to treat high blood pressure (hypertension) is quite low and many people hardly notice the increase in urine output.