metolazone

Absorption: Absorption is variable.

Distribution: Extensively distributed to tissues.

Protein Binding: 95%.

Metabolism/Excretion: Excreted mainly unchanged by the kidneys.

Half-Life: 6–20 hr.

Time/Action Profile ⬆ ⬇

(diuretic effect‡)

ROUTE	ONSET	PEAK	DURATION
PO	1 hr	2 hr	12–24 hr

‡Full antihypertensive effect may take days–wk.

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity;
Cross-sensitivity with other sulfonamides may exist;
Anuria;
Lactation: Lactation.

Use Cautiously in:

Severe hepatic impairment;
OB: Use during pregnancy only if potential maternal benefit justifies potential fetal risk; may ↑ risk of hypoglycemia, hypokalemia, hyponatremia, jaundice, and thrombocytopenia in fetus;
Geri: Older adults may have ↑ sensitivity to drug effects.

Adv. Reactions/Side Effects ⬆ ⬇

CV: chest pain, hypotension, palpitations

Derm: photosensitivity, rash

Endo: hyperglycemia

F and E: hypokalemia, dehydration, hypercalcemia, hypochloremic alkalosis, hypomagnesemia, hyponatremia, hypophosphatemia, hypovolemia

GI: anorexia, bloating, cramping, drug-induced hepatitis, nausea, pancreatitis, vomiting

Hemat: blood dyscrasias

Metab: hyperuricemia

MS: muscle cramps

Neuro: drowsiness, lethargy

Interactions ⬆ ⬇

Drug-drug:

↑risk of hypotension with nitrates, acute ingestion of alcohol, or other antihypertensives.
↑risk of hypokalemia with corticosteroids, amphotericin B, or piperacillin/tazobactam.
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.

Drug-Food:

Food may ↑ extent of absorption.

Route/Dosage ⬆ ⬇

PO (Adults ): Hypertension: 2.5–5 mg/day; edema: 5–20 mg/day.
PO (Children ): 0.2–0.4 mg/kg/day divided every 12–24 hr.

Availability ⬆ ⬇

(Generic available)

Tablets: 2.5 mg; 5 mg; 10 mg

Assessment ⬆ ⬇

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 cholesterol, low-density lipoprotein cholesterol, and triglyceride concentrations.

Implementation ⬆ ⬇

Do not confuse metolazone with methimazole, methazolamide, methadone, or methotrexate.
Administer in the morning to prevent disruption of sleep cycle.
- Intermittent dose schedule may be used for continued control of edema.
PO: May give with food or milk to minimize GI irritation.

Patient/Family Teaching ⬆ ⬇

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 Food Sources for Specific Nutrients).
- 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.
- Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected, and to avoid breastfeeding during therapy. Monitor for hypoglycemia, hypokalemia, hyponatremia, jaundice, and thrombocytopenia in the fetus or newborn following maternal use.
- 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.

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇

Action ⬆ ⬇

Pharmacokinetics ⬆ ⬇