Medication Update

Christy L. Collard, PharmD, Department of Primary Care, Ralph H. Johnson VA Medical Center, Charleston, SC.

South Med J. 2001;94(11) 

In This Article

Thiazide Diuretics

Mode of Action

Inhibition of sodium and chloride reabsorption in the distal tubule of the kidney, resulting in increased urinary excretion of sodium and water. Direct arteriolar vasodilation.

Contraindications

Known hypersensitivity to thiazides or other sulfonamides. Anuria.

Adverse Effects

Electrolyte abnormalities, including hypokalemia, hypomagnesemia, hyponatremia, and hypercalemia may occur. Elevated blood glucose levels have also been reported. Hyperuricemia is possible, therefore use with caution in patients who suffer from gout. Arrhythmias may be precipitated secondary to electrolyte abnormalities. Hyperlipidemia (increase in total cholesterol, triglycerides, and LDL cholesterol) has occurred. Dermatologic side effects include photosensitivity and an SLE-like syndrome.

Drug-Drug Interactions

Hypotension may occur when used in combination with ACE inhibitors. Patients taking carbamazepine may experience symptomatic hyponatremia with thiazide use. Corticosteroids may have a synergistic effect on potassium levels, resulting in hypokalemia. Concomitant use of cholestyramine may result in drug binding. Decreased clearance of lithium may result in an increased risk of lithium toxicity. There is a potential for digitalis toxicity due to a hypokalemia-induced proarrhythmic state. Methotrexate used in combination with thiazides may result in myelosuppression. Concomitant use of NSAIDS may result in decreased diuretic effectiveness and increased potassium levels secondary to decreased synthesis of renal prostaglandins. Propranolol may exacerbate hyperglycemia and hypertriglyceridemia.

Drug-Food Interactions

Food may result in a small (15%) decrease in hydrochlorothiazide efficacy.

Available Agents

hydrochlorothiazide (HCTZ): Esidrix, Hydrodiuril, Oretic.

chlorothiazide: Diuril.

chlorthalidone: Hygronton, Thalitone.

indapamide: Lozol.

metolazone: Zaroxolyn.

Recommended Dose

Depends on the agent chosen.

Dosage Forms Available

Available in many different dosage strengths.

Manufacturer

Various.

References

  1. DRUGDEX System. Hutchison TA, Shahan DR (ed). MICROMEDEX Inc., Greenwood Village, Colo (Edition expires 2001)

  2. Martindale: The Complete Drug Reference. Sweetman S (ed). London, Pharmaceutical Press. Electronic version.

 

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