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Pharmacologic class: Thiazide-like diuretic
Therapeutic class: Diuretic, antihypertensive
Pregnancy risk category B
Inhibits electrolyte reabsorption from ascending loop of Henle and decreases reabsorption of sodium and potassium in distal renal tubules, increasing plasma osmotic pressure and promoting diuresis
Tablets: 2.5 mg, 5 mg, 10 mg
Indications and dosages
Adult: 2.5 to 5 mg P.O. daily.
➣ Edema caused by heart failure or renal disease
Adults: 5 to 20 mg P.O. daily
• Hypersensitivity to drug
• Hepatic coma or precoma
Use cautiously in:
• severe hepatic or renal impairment, gout, hyperparathyroidism, glucose tolerance abnormalities, fluid or electrolyte imbalances, bipolar disorders
• elderly patients
• pregnant or breastfeeding patients
• children (safety not established).
• Give in morning to avoid frequent nighttime urination.
• Discontinue drug before parathyroid function tests are performed.
• Be aware that metolazone is the only thiazide-like diuretic that may cause diuresis in patients with glomerular filtration rates below 20 ml/minute.
CNS: drowsiness, lethargy, vertigo, paresthesia, weakness, headache, fatigue
CV: chest pain, hypotension, palpitations, venous thrombosis, arrhythmias
GI: nausea, vomiting, bloating, cramping, anorexia, pancreatitis
GU: polyuria, nocturia, erectile dysfunction, decreased libido
Hematologic: aplastic anemia, leukopenia, agranulocytosis
Metabolic: dehydration, hypercalcemia, hypomagnesemia, hyponatremia, hypophosphatemia, hypovolemia, hyperglycemia, hyperuricemia, hypokalemia, hypochloremic alkalosis
Musculoskeletal: muscle cramps
Skin: photosensitivity, rashes
Drug-drug. Amphotericin B, corticosteroids, mezlocillin, piperacillin, ticarcillin: additive hypokalemia
Antigout drugs: increased uric acid level
Antihypertensives, nitrates: additive hypotension
Digoxin: increased risk of digoxin toxicity
Lithium: decreased lithium excretion, increased risk of lithium toxicity
Drug-diagnostic tests. Bilirubin, calcium, cholesterol, creatinine, low-density lipoproteins, triglycerides, uric acid: increased levels
Blood glucose, urine glucose: increased levels in diabetic patients
Magnesium, potassium, protein-bound iodine, sodium, urinary calcium: decreased levels
Drug-food. Any food: increased metolazone absorption
Drug-herbs. Aloe, cascara sagrada, senna: increased risk of hypokalemia
Drug-behaviors. Sun exposure: increased risk of photosensitivity
• Monitor baseline and periodic electrolyte, blood urea nitrogen, glucose, and uric acid levels.
• Evaluate blood pressure regularly.
☞ Watch for signs and symptoms of hypokalemia, which may necessitate potassium supplements, potassium-rich diet, or potassium-sparing diuretic. Hypokalemia is particularly dangerous to patients who are on digitalis or have had ventricular arrhythmias.
• Assess patient for fluid and electrolyte imbalances.
• Advise patient to take in morning to avoid frequent nighttime urination.
• Tell patient he may take with food or milk to prevent GI upset.
☞ Instruct patient to report muscle pain, weakness, or cramps; nausea; vomiting; diarrhea; dizziness; restlessness; excessive thirst; fatigue; drowsiness; increased pulse; or irregular heart beats.
• Inform patient that drug may cause gout attacks. Advise him to report sudden joint pain.
• Instruct patient to use sunscreen and protective clothing to avoid photosensitivity.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, foods, herbs, and behaviors mentioned above.