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Furosemide

Pronunciation

Pronunciation: fyu-ROH-se-mide
Class: Loop diuretic

Trade Names

Lasix
- Tablets 20 mg
- Tablets 40 mg
- Tablets 80 mg
- Oral solution 8 mg/mL
- Oral solution 10 mg/mL
- Injection 10 mg/mL

Apo-Furosemide (Canada)
Furosemide Special (Canada)
Lasix Special (Canada)

Pharmacology

Inhibits reabsorption of sodium and chloride in proximal and distal tubules and loop of Henle.

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Pharmacokinetics

Absorption

Mean bioavailability is 64% with the tablet and 60% with the oral solution.

Distribution

Protein binding is 91% to 99% (albumin).

Metabolism

The major metabolite is furosemide glucuronide.

Elimination

The t 1/ 2 is about 2 h; furosemide is excreted in urine.

Onset

PO 1 h, IV 5 min.

Peak

PO 1 to 2 h, IV 30 min.

Duration

PO 6 to 8 h, IV 2 h.

Indications and Usage

Adjunctive therapy in acute pulmonary edema, edema associated with CHF, hepatic cirrhosis, and renal disease ( IV only); hypertension ( PO only).

Contraindications

Hypersensitivity to any component of the product; anuria.

Dosage and Administration

Acute Pulmonary Edema
Adults

IV 40 mg (over 1 to 2 min). If response not satisfactory within 1 h, increase to 80 mg.

Infants and Children

IV/IM Usual initial dose: 1 mg/kg. If response not satisfactory, may increase by 1 mg/kg not sooner than 2 h after previous dose. Max dose: 6 mg/kg. Premature infant's max dose: 1 mg/kg/day.

Edema
Adults

PO Usual initial dose: 20 to 80 mg/day as a single dose may repeat 6 to 8 h later if needed; may titrate up to 600 mg/day. Maintenance: Give determined single dose once or twice daily (8 AM and 2 PM). IV/IM 20 to 40 mg over 1 to 2 min. Repeat 2 h later if needed.

Children

PO Usual initial dose: 2 mg/kg as a single dose. May increase by 1 or 2 mg/kg 6 to 8 h later if needed. Max dose: 6 mg/kg.

Hypertension
Adults

PO 40 mg twice daily.

General Advice

  • Tablets and oral solution
  • Administer without regard to meals. Administer with food if GI upset occurs.
  • Do not use tablets that are discolored.
  • Measure and administer prescribed dose of oral solution using supplied dosing cup, calibrated dosing syringe, or calibrated dosing spoon.
  • Injection
  • For IM or IV administration only. Not for intradermal, subcutaneous, or intra-arterial administration.
  • Administer IV injection of usual doses (eg, 20 to 80 mg) over 1 to 2 min.
  • For high-dose IV therapy, dilute prescribed dose of furosemide in sodium chloride 0.9% injection, Ringers lactate injection, or dextrose 5% injection (after adjusting pH to more than 5.5) and administer at controlled infusion rate not more than 4 mg/min.
  • Furosemide injection precipitates at pH values less than 7. Ensure that pH of prepared infusion solution is in neutral to weakly alkaline range. Do not administer furosemide through infusion line containing acidic solution or acidic drugs.
  • Do not administer if particulate matter, cloudiness, or discoloration is noted.

Storage/Stability

Store tablets, oral solution, and injection at controlled room temperature (59° to 86°F). Protect from light. Protect tablets from moisture. Protect injection from freezing.

Drug Interactions

Aminoglycosides, ethacrynic acid

May increase auditory toxicity. Avoid coadministration.

Antihypertensive agents

Antihypertensive effects may be potentiated. Reduce dose by at least 50% when furosemide is coadministered.

Charcoal

May reduce absorption of furosemide.

Cisplatin

May cause additive ototoxicity.

Digitalis glycosides

Electrolyte disturbances may predispose to digitalis-induced arrhythmias.

Lithium

May increase plasma lithium levels and toxicity. Avoid coadministration.

Norepinephrine

Arterial responsiveness to norepinephrine may be decreased.

NSAIDs

May decrease effects of furosemide.

Phenytoin

May reduce diuretic effects of furosemide.

Salicylates

Because of competition for renal excretion, patients may experience salicylate toxicity. Salicylates may impair diuretic response in patients with cirrhosis and ascites.

Succinylcholine

The effects may be potentiated by furosemide.

Sucralfate

Natriuretic and antihypertensive effects of furosemide may be decreased; separate the administration times by at least 2 h.

Thiazide diuretics

Synergistic effects that may result in profound diuresis and serious electrolyte abnormalities.

Tubocurarine

The skeletal muscle relaxant effect may be antagonized by furosemide.

Incompatibility

Acid solutions including other parenteral medications (eg, labetalol, ciprofloxacin, amrinone, milrinone): do not add to furosemide solution; precipitate forms.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Cardiovascular

Chronic aortitis; orthostatic hypotension; thrombophlebitis.

CNS

Dizziness; fever; headache; paresthesia; restlessness; vertigo.

Dermatologic

Erythema multiforme; exfoliative dermatitis; local irritation and pain with parenteral use; necrotizing angiitis; photosensitivity; pruritus; purpura; rash; systemic vasculitis; urticaria.

EENT

Blurred vision; hearing impairment; tinnitus; xanthopsia (yellow vision).

GI

Anorexia; constipation; cramping; diarrhea; nausea; oral and gastric irritation; pancreatitis; vomiting.

Genitourinary

Glycosuria; interstitial nephritis; urinary bladder spasm.

Hematologic

Anemia, hemolytic anemia, leukopenia, thrombocytopenia; aplastic anemia, agranulocytosis (rare).

Hepatic

Jaundice.

Metabolic

Hyperglycemia; hyperuricemia; hypokalemia; metabolic alkalosis.

Miscellaneous

Muscle spasm; weakness.

Precautions

Monitor

Monitor for possible occurrence of blood dyscrasia and liver damage. Monitor urine and blood glucose in diabetes. Frequently monitor serum electrolytes, magnesium, calcium, CO 2 , uric acid, and renal function early in therapy and periodically thereafter during active diuresis. Assess patients for signs or symptoms of fluid or electrolyte imbalance.


Pregnancy

Category C .

Lactation

Excreted in breast milk.

Children

May increase incidence of patent ductus arteriosus in premature infants with respiratory distress syndrome, especially in first few weeks of life.

Hypersensitivity

Patients with known sulfonamide sensitivity may show allergic reactions to furosemide.

Renal Function

Discontinue if increasing azotemia and oliguria occur during treatment of severe progressive renal disease.

Photosensitivity

May occur.

Dehydration

Excessive diuresis may cause dehydration and decreased blood volume with circulatory collapse and possible vascular thrombosis and embolism, especially in elderly cardiac patients.

Diarrhea

Furosemide solution vehicle contains sorbitol and may induce diarrhea, especially in children.

Glucose intolerance

May increase blood glucose; precipitation of diabetes mellitus has been reported rarely.

Hepatic cirrhosis

Sudden alterations of electrolyte balance may precipitate hepatic and coma; monitor carefully.

Hyperuricemia/gout

Asymptomatic hyperuricemia can occur; gout may rarely be precipitated.

Ototoxicity (deafness, tinnitus, vertigo)

Associated with rapid injection, severe renal impairment, very large doses, or concurrent use of other ototoxic drugs. Usually reversible within 1 to 24 h, but may be permanent in some patients. Infusion rates not exceeding 4 mg/min may reduce risk.

Systemic lupus erythematosus

May be exacerbated or activated.

Overdosage

Symptoms

Dehydration, electrolyte imbalance, hypochloremic alkalosis, hypokalemia, hypotension, reduction of blood volume.

Patient Information

  • Injection
  • Advise patient or caregiver that injection is used when a rapid onset of diuresis is needed, when GI absorption is impaired, or when taking oral medications is not practical, and that conversion to oral therapy will be made as soon as possible.
  • Tablets and oral solution
  • Advise patient to take prescribed dose without regard to meals but to take with food if stomach upset occurs.
  • Advise patient or caregiver using oral solution to measure and administer prescribed dose using supplied dosing cup, calibrated dosing syringe, or calibrated dosing spoon.
  • Advise patient that medication will increase urination and not to take before bedtime or before activities in which increased urination would be a problem. Instruct patient that if dose is delayed to take the dose later in the day to prevent interference with activities. Caution patient not to skip doses.
  • Caution patient not to change the dose or stop taking unless advised by health care provider.
  • Ensure patient understands how to implement fluid and salt restriction if prescribed as part of therapeutic regimen.
  • Instruct patient to lie or sit down if they experience dizziness or lightheadedness when standing.
  • Caution patient that inadequate fluid intake, excessive perspiration, diarrhea, or vomiting can lead to excessive fall in BP resulting in lightheadedness or fainting.
  • Instruct diabetic patient to monitor blood glucose more frequently when drug is started or dose is changed and to inform health care provider of significant changes in readings.
  • Caution patient to avoid unnecessary exposure to UV light (sunlight, tanning booths) and to use sunscreen and wear protective clothing when exposed to UV light until tolerance is determined.
  • Advise women to notify health care provider if pregnant, planning to become pregnant, or breastfeeding.
  • Instruct patient to inform health care provider if any of the following occur: muscle pain, weakness, or cramps; persistent nausea or vomiting; diarrhea; excessive thirst; unexplained tiredness; drowsiness; dizziness or feeling of the room spinning; ringing in the ears or decreased hearing; confusion or changes in thinking; increased heart rate; unexplained joint pain; abnormal skin sensations.

Copyright © 2009 Wolters Kluwer Health.

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