Diuretics are divided into several subgroups. Thiazide and thiazide-related diuretics inhibit reabsorption of sodium and chloride in the distal renal tubule, increasing the excretion of sodium, chloride, and water by the kidneys. Loop diuretics inhibit the reabsorption of sodium and chloride in the loop of Henle and in the distal renal tubule; because of this added effect, loop diuretics are more potent. Potassium-sparing diuretics block the effect of aldosterone on the renal tubule, leading to a loss of sodium and water and the retention of potassium; their overall effect is much weaker. Osmotic diuretics pull fluid out of the tissues with a hypertonic effect. Overall effect of diuretics is a loss of water and electrolytes from the body.

Indications

Adjunctive therapy in edema associated with heart failure, cirrhosis, corticosteroid and estrogen therapy, renal impairment

Treatment of hypertension, alone or in combination with other antihypertensives

Reduction of intracranial pressure before and during neurosurgery

Reduction of intraocular pressure in acute episodes of glaucoma when other therapies are not successful

Unlabeled uses: Treatment of diabetes insipidus, especially nephrogenic diabetes insipidus, reduction of incidence of osteoporosis in postmenopausal women

Contraindications and cautions

Contraindicated with fluid or electrolyte imbalances, renal or hepatic disease, gout, SLE, glucose tolerance abnormalities, hyperparathyroidism, manic-depressive disorders, or lactation.

Adverse effects

CNS: Dizziness, vertigo,paresthesias, weakness, headache, drowsiness, fatigue

CV: Orthostatic hypotension, venous thrombosis, volume depletion, cardiac arrhyth- mias, chest pain

Dermatologic: Photosensitivity, rash, purpura, exfoliative dermatitis

GI: Nausea, anorexia, vomiting, dry mouth, diarrhea, constipation,jaundice, hepatitis, pancreatitis

GU: Polyuria, nocturia, impotence, loss of libido

Hematologic: Leukopenia, thrombocytopenia, agranulocytosis, aplastic anemia, neutropenia, fluid and electrolyte imbalances

Other: Muscle cramps and muscle spasms, fever, hives, gouty attacks, flushing, weight loss, rhinorrhea, electrolyte imbalance

Interactions

Drug-drug

Increased thiazide effects and possible acute hyperglycemia with diazoxide

Decreased absorption with cholestyramine, colestipol

Increased risk of cardiac glycoside toxicity if hypokalemia occurs

Increased risk of lithium toxicity

Increased dosage of antidiabetics may be needed

Risk of hyperkalemia if potassium-sparing diuretics are given with potassium preparations or ACE inhibitors

Increased risk of ototoxicity if loop diuretics are taken with aminoglycosides or cisplatin ?Drug-lab test

Monitor for decreased PBI levels without clinical signs of thyroid disturbances

Nursing considerations

Assessment

History: Fluid or electrolyte imbalances, renal or liver disease, gout, SLE, glucose tol- erance abnormalities, hyperparathyroidism, bipolar disorders, lactation

Physical: Orientation, reflexes, muscle strength; pulses, BP, orthostatic BP, perfusion, edema, baseline ECG; R, adventitious sounds; liver evaluation, bowel sounds; CBC, serum electrolytes, blood glucose; LFTs, renal function tests; serum uric acid, urinalysis

Interventions

Administer with food or milk if GI upset occurs.

Administer early in the day so increased urination will not disturb sleep.

Ensure ready access to bathroom.

Establish safety precautions if CNS effects, orthostatic hypotension occur.

Adverse effects

in italics are most common; those in bold are life-threatening. U Do not crush.

Measure and record regular body weights to monitor fluid changes.

Provide mouth care and frequent small meals as needed.

Monitor IV sites for any sign of extravasation.

Monitor electrolytes frequently with parenteral use, periodically with chronic use.

Teaching points

Take these drugs early in the day so sleep will not be disturbed by increased urination.

Weigh yourself daily and record weights.

Protect your skin from exposure to the sun or bright lights.

If taking a potassium-sparing diuretic, avoid foods high in potassium and avoid using salt substitutes.

Take prescribed potassium replacement, and eat foods high in potassium if taking a thiazide or loop diuretic.

Increased urination will occur (stay close to bathroom facilities).

Use caution if dizziness, drowsiness, or faintness occurs.

Report rapid weight gain or loss, swelling in ankles or fingers, unusual bleeding or bruising, muscle cramps.

Representative drugs

Carbonic anhydrase inhibitors acetazolamide methazolamide

Thiazide and related diuretics chlorothiazide chlorthalidone hydrochlorothiazide indapamide methyclothiazide metolazone

Loop diuretics bumetanide ethacrynic acid furosemide torsemide

Potassium-sparing diuretics amiloride spironolactone triamterene

Osmotic diuretic mannitol