Hydrochlorothiazide (HCTZ) is the primary drug in the class of thiazide diuretic agents. Although HCTZ is marketed under many brand names and in combination with numerous blood pressure medications, it is usually prescribed as a generic alone or in these combination. HCTZ is used to treat conditions of water retention (called edema) and cardiac conditions like high blood pressure or congestive heart failure. HCTZ is approved for use at doses of 12.5 to 100 mg each day, and water-removal effects (diuresis) occurs within two hours of a dose.
Gout
HCTZ can increased uric acid levels in the blood (called hyperuricemia). When uric acid builds up in the body, it can settle into joint areas, such as around the big toe or elbows. Uric acid crystals at the joints cause swelling, heat and pain, symptoms of gout. Gout caused by HCTZ or by other nondrug causes is treated with pain relievers and drugs to remove the uric acid from the body.
Hypergylcemia
HCTZ can increase glucose levels in the body as well. This hyperglycemia effect is of most concern for patients who are diabetic, since their bodies cannot regulate glucose levels without added insulin and medications. Diabetes that has not been diagnosed in a person yet may be revealed when the person begins HCTZ treatment if the body cannot adequately react the the high glucose side effect. In either case, glucose levels should be measured more often during treatment with HCTZ.
Electrolyte Changes
One of the most common types of side effects from HCTZ is a change in electrolyte levels, especially sodium, potassium, chloride and magnesium. These changes occur in part because of the rapid fluid level changes, because HCTZ removes excess fluid from the body quickly. Electrolytes may be removed with the fluid or may be imbalanced between the blood and tissues. Low potassium may cause heart rhythm changes, and low levels of any of these electrolytes can cause dry mouth, irritability, tiredness, muscle pain and stomach cramps.
Cardiac Symptoms
HCTZ is used to remove extra fluid that stresses the heart and vessels in congestive heart failure and high blood pressure, but it may also cause cardiac side effects. Low blood pressure (hypotension) is the most likely cardiac effect; noticeable symptoms of hypotension include general dizziness and particularly dizziness when changing from sitting to standing positions.
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