Zaroxolyn

metolazone

Metenix (UK), Zaroxolyn

Pharmacologic class: Thiazide-like diuretic

Therapeutic class: Diuretic, antihypertensive

Pregnancy risk category B

Action

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

Availability

Tablets: 2.5 mg, 5 mg, 10 mg

Indications and dosages

➣ Hypertension

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

Contraindications

• Hypersensitivity to drug

• Hepatic coma or precoma

• Anuria

Precautions

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).

Administration

• 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.

Adverse reactions

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

Hepatic: hepatitis

Metabolic: dehydration, hypercalcemia, hypomagnesemia, hyponatremia, hypophosphatemia, hypovolemia, hyperglycemia, hyperuricemia, hypokalemia, hypochloremic alkalosis

Musculoskeletal: muscle cramps

Skin: photosensitivity, rashes

Other: chills

Interactions

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

Patient monitoring

• Monitor baseline and periodic electrolyte, blood urea nitrogen, glucose, and uric acid levels.

• Evaluate blood pressure regularly.

See 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.

Patient teaching

• Advise patient to take in morning to avoid frequent nighttime urination.

• Tell patient he may take with food or milk to prevent GI upset.

See 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.

metolazone

(me-tole-a-zone) metolazone,

Zaroxolyn

(trade name)

Classification

Therapeutic: antihypertensives
Pharmacologic: thiazide like diuretics
Pregnancy Category: B

Indications

Mild to moderate hypertension.Edema associated with HF or the nephrotic syndrome.

Action

Increases excretion of sodium and water by inhibiting sodium reabsorption in the distal tubule.Promotes excretion of chloride, potassium, magnesium, and bicarbonate.May produce arteriolar dilation.

Therapeutic effects

Lowering of BP in hypertensive patients.Diuresis with subsequent mobilization of edema. Effect may continue in renal impairment.

Pharmacokinetics

Absorption: Absorption is variable.Distribution: Unknown.Protein Binding: 95%Metabolism and 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–weeks

Contraindications/Precautions

Contraindicated in: Hypersensitivity;Cross-sensitivity with other sulfonamides may exist;Anuria; Lactation: Lactation.Use Cautiously in: Severe hepatic impairment; Obstetric: Safety not established; Geriatric: ↑ sensitivity to drug effects.

Adverse Reactions/Side Effects

Central nervous system

drowsiness
lethargy

Cardiovascular

chest pain
hypotension
palpitations

Gastrointestinal

anorexia
bloating
cramping
drug-induced hepatitis
nausea
pancreatitis
vomiting

Dermatologic

photosensitivity
rashes

Endocrinologic

hyperglycemia

Fluid and Electrolyte

hypokalemia (most frequent)
dehydration
hypercalcemia
hypochloremic alkalosis
hypomagnesemia
hyponatremia
hypophosphatemia
hypovolemia

Hematologic

blood dyscrasias

Metabolic

hyperuricemia (most frequent)

Musculoskeletal

muscle cramps

Interactions

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.

Route/Dosage

Oral (Adults) Hypertension—2.5–5 mg/day; edema—5–20 mg/day.Oral (Children) 0.2–0.4 mg/kg/day divided q 12–24 hr

Availability (generic available)

Tablets: 2.5 mg, 5 mg, 10 mg

Nursing implications

Nursing 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 protein-bound iodine (PBI) concentrations.
- May cause ↑ serum cholesterol, low-density lipoprotein, and triglyceride concentrations.

Potential Nursing Diagnoses

Excess fluid volume (Indications)
Risk for deficient fluid volume (Side Effects)

Implementation

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.

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 ).
- 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.

Evaluation/Desired Outcomes

Decrease in BP.
Increase in urine output.
Decrease in edema.