Diuretics
Diuretics
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
