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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.
Pharmacologic: thiazide like diuretics
Time/action profile (diuretic effect†)
|PO||1 hr||2 hr||12–24 hr|
Adverse Reactions/Side Effects
Central nervous system
- chest pain
- drug-induced hepatitis
Fluid and Electrolyte
- hypokalemia (most frequent)
- hypochloremic alkalosis
- blood dyscrasias
- hyperuricemia (most frequent)
- muscle cramps
Drug-Drug interaction↑ risk of hypotension with nitrates, acute ingestion of alcohol, or other antihypertensives.↑ risk of hypokalemia with corticosteroids, amphotericin B, piperacillin, or ticarcillin.May ↑ the risk of digoxin toxicity.↓ the excretion of lithium ; may cause toxicity.May ↓ the effectiveness of methenamine.Stimulant laxatives (including aloe, senna) may ↑ risk of potassium depletion.Food may ↑ extent of absorption.
Availability (generic available)
- Monitor BP, intake and output, and daily weight, and assess feet, legs, and sacral area for edema daily.
- Assess patient, especially if taking digoxin, for anorexia, nausea, vomiting, muscle cramps, paresthesia, and confusion. Notify health care professional if these signs of electrolyte imbalance occur. Patients taking digoxin are at risk of digoxin toxicity because of the potassium-depleting effect of the diuretic.
- Assess patient for allergy to sulfonamides.
- Hypertension: Monitor BP before and periodically during therapy.
- Monitor frequency of prescription refills to determine compliance.
- Lab Test Considerations: Monitor electrolytes (especially potassium), blood glucose, BUN, and serum creatinine and uric acid levels before and periodically during therapy.
- May cause ↑ in serum and urine glucose in diabetic patients.
- May cause an ↑ in serum bilirubin, calcium, creatinine, and uric acid, and a ↓ in serum magnesium, potassium, and sodium and urinary calcium concentrations.
- May cause ↓ serum protein-bound iodine (PBI) concentrations.
- May cause ↑ serum cholesterol, low-density lipoprotein, and triglyceride concentrations.
Potential Nursing DiagnosesExcess fluid volume (Indications)
Risk for deficient fluid volume (Side Effects)
- Do not confuse metolazone with methimazole.
- Administer in the morning to prevent disruption of sleep cycle.
- Intermittent dose schedule may be used for continued control of edema.
- Oral: May give with food or milk to minimize GI irritation.
- Instruct patient to take metolazone at the same time each day. Take missed doses as soon as remembered but not just before next dose is due. Do not double doses.
- Instruct patient to monitor weight biweekly and notify health care professional of significant changes.
- Caution patient to change positions slowly to minimize orthostatic hypotension; may be potentiated by alcohol.
- Advise patient to use sunscreen and protective clothing in the sun to prevent photosensitivity reactions.
- Instruct patient to discuss dietary potassium requirements with health care professional (see ).
- Instruct patient to notify health care professional of medication regimen before treatment or surgery.
- Advise patient to report muscle weakness, cramps, nausea, vomiting, diarrhea, or dizziness to health care professional.
- Emphasize the importance of routine follow-up exams.
- Hypertension: Advise patient to continue taking the medication even if feeling better. Medication controls but does not cure hypertension.
- Encourage patient to comply with additional interventions for hypertension (weight reduction, low-sodium diet, regular exercise, smoking cessation, moderation of alcohol consumption, and stress management).
- Instruct patient and family in correct technique for monitoring weekly BP.
- Advise patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and to consult with health care professional before taking other medications, especially cough or cold preparations, concurrently with this therapy.
- Decrease in BP.
- Increase in urine output.
- Decrease in edema.