furosemide

General

Pronunciation:
fur-oh-se-mide

Trade Name(s)

• Lasix

Ther. Class.
diuretics

Pharm. Class.
loop diuretics

Indications

• Edema due to heart failure, hepatic impairment, or renal disease.
• Hypertension.

Action

• Inhibits the reabsorption of sodium and chloride from the loop of Henle and distal renal tubule.
• Increases renal excretion of water, sodium, chloride, magnesium, potassium, and calcium.
• Effectiveness persists in impaired renal function.

Therapeutic Effect(s):

• Diuresis and subsequent mobilization of excess fluid (edema, pleural effusions).
• Decreased BP.

Pharmacokinetics

Absorption: 60–67% absorbed after oral administration (↓ in acute HF and in renal failure); also absorbed from IM sites.

Distribution: Crosses placenta, enters breast milk.

Protein Binding: 91–99%.

Metabolism and Excretion: Minimally metabolized by liver, some nonhepatic metabolism, some renal excretion as unchanged drug.

Half-life: 30–60 min (↑ in renal impairment).

TIME/ACTION PROFILE (diuretic effect)

Contraindication/Precautions

Contraindicated in:

• Hypersensitivity;
• Cross-sensitivity with thiazides and sulfonamides may occur;
• Hepatic coma or anuria;
• Some liquid products may contain alcohol, avoid in patients with alcohol intolerance.

Use Cautiously in:

• Severe liver disease (may precipitate hepatic coma; concurrent use with potassium-sparing diuretics may be necessary);
• Electrolyte depletion;
• Diabetes mellitus;
• Hypoproteinemia (↑ risk of ototoxicity);
• Severe renal impairment (↑ risk of ototoxicity);
• OB:  Lactation: Safety not established;
• Pedi:  ↑ risk for renal calculi and patent ductus arteriosis in premature neonates;
• Geri:  May have ↑ risk of side effects, especially hypotension and electrolyte imbalance, at usual doses.

Adverse Reactions/Side Effects

CNS: blurred vision, dizziness, headache, vertigo

CV: hypotension

Derm: ERYTHEMA MULTIFORME, STEVENS-JOHNSON SYNDROME, TOXIC EPIDERMAL NECROLYSIS, photosensitivity, pruritis, rash, urticaria

EENT: hearing loss, tinnitus

Endo: hypercholesterolemia, hyperglycemia, hypertriglyceridemia, hyperuricemia

F and E: dehydration, hypocalcemia, hypochloremia, hypokalemia, hypomagnesemia, hyponatremia, hypovolemia, metabolic alkalosis

GI: anorexia, constipation, diarrhea, dry mouth, dyspepsia, ↑ liver enzymes, nausea, pancreatitis, vomiting

GU: ↑ BUN, excessive urination, nephrocalcinosis

Hemat: APLASTIC ANEMIA, AGRANULOCYTOSIS, hemolytic anemia, leukopenia, thrombocytopenia

MS: muscle cramps

Neuro: paresthesia

Misc: fever

* CAPITALS indicate life-threatening.
Underline indicate most frequent.

Interactions

Drug-Drug

• ↑ risk of hypotension with antihypertensives, nitrates, or acute ingestion of  alcohol.
• ↑ risk of hypokalemia with other diuretics, amphotericin B, stimulant laxatives, and  corticosteroids.
• Hypokalemia may ↑ risk of  digoxin  toxicity and ↑ risk of arrhythmia in patients taking drugs that prolong the QT interval.
• ↓  lithium  excretion, may cause  lithium  toxicity.
• ↑ risk of ototoxicity with  aminoglycosides  or  cisplatin.
• ↑ risk of nephrotoxicity with  cisplatin.
•  NSAIDS  ↓ effects of furosemide.
• May ↑ risk of  methotrexate  toxicity.
• ↓ effects when given at same time as sucralfate, cholestyramine, or  colestipol.
• ↑ risk of  salicylate  toxicity (with use of high-dose  salicylate  therapy).
• Concurrent use with  cyclosporine  may ↑ risk of gouty arthritis.

Route/Dosage

Edema

PO (Adults): 20–80 mg/day as a single dose initially, may repeat in 6–8 hr; may ↑ dose by 20–40 mg every 6–8 hr until desired response. Maintenance doses may be given once or twice daily (doses up to 2.5 g/day have been used in patients with HF or renal disease).  Hypertension– 40 mg twice daily initially (when added to regimen, ↓ dose of other antihypertensives by 50%); adjust further dosing based on response;  Hypercalcemia– 120 mg/day in 1–3 doses.

PO (Children >1 mo): 2 mg/kg as a single dose; may be ↑ by 1–2 mg/kg every 6–8 hr (maximum dose = 6 mg/kg).

PO Neonates: 1–4 mg/kg/dose 1–2 times/day.

IM IV (Adults): 20–40 mg, may repeat in 1–2 hr and ↑ by 20 mg every 1–2 hr until response is obtained, maintenance dose may be given every 6–12 hr;  Continuous infusion– Bolus 0.1 mg/kg followed by 0.1 mg/kg/hr, double every 2 hr to a maximum of 0.4 mg/kg/hr.

IM IV Children: 1–2 mg/kg/dose every 6–12 hr;  Continuous infusion– 0.05 mg/kg/hr, titrate to clinical effect.

IM IV Neonates: 1–2 mg/kg/dose every 12–24 hr.

Hypertension

PO (Adults): 40 twice daily initially (when added to regimen, ↓ dose of other antihypertensives by 50%); adjust further dosing based on response.

Availability (generic available)

Oral solution (10 mg/mL–orange flavor, 8 mg/mL–pineapple–peach flavor): 8 mg/mL, 10 mg/mL

Cost:

Generic: 10 mg/mL $10.40/60 mL

Tablets: 20 mg, 40 mg, 80 mg, 500 mg 

Cost:

Generic: 20 mg $6.50/100, 40 mg $7.11/100, 80 mg $10.83/100

Solution for injection: 10 mg/mL

Assessment

• Assess fluid status. Monitor daily weight, intake and output ratios, amount and location of edema, lung sounds, skin turgor, and mucous membranes. Notify health care professional if thirst, dry mouth, lethargy, weakness, hypotension, or oliguria occurs.
• Monitor BP and pulse before and during administration. Monitor frequency of prescription refills to determine compliance in patients treated for hypertension.
• Geri:  Diuretic use is associated with increased risk for falls in older adults. Assess falls risk and implement fall prevention strategies.
• Assess patients receiving digoxin for anorexia, nausea, vomiting, muscle cramps, paresthesia, and confusion. Patients taking digoxin are at increased risk of digoxin toxicity because of the potassium-depleting effect of the diuretic. Potassium supplements or potassium-sparing diuretics may be used concurrently to prevent hypokalemia.
• Assess patient for tinnitus and hearing loss. Audiometry is recommended for patients receiving prolonged high-dose IV therapy. Hearing loss is most common after rapid or high-dose IV administration in patients with decreased renal function or those taking other ototoxic drugs.
• Assess for allergy to sulfonamides.
• Assess patient for skin rash frequently during therapy. Discontinue furosemide at first sign of rash; may be life-threatening. Stevens-Johnson syndrome, toxic epidermal necrolysis, or erythema multiforme may develop. Treat symptomatically; may recur once treatment is stopped.

Lab Test Considerations:

Monitor electrolytes, renal and hepatic function, serum glucose, and uric acid levels before and periodically throughout therapy. Commonly ↓ serum potassium. May cause ↓ serum sodium, calcium, and magnesium concentrations. May also cause ↑ BUN, serum glucose, creatinine, and uric acid levels.

Potential Diagnoses

• Excess fluid volume (Indications) 
• Deficient fluid volume (Side Effects) 

Implementation

• Do not confuse Lasix (furosemide) with Luvox (fluvoxamine).
  • If administering twice daily, give last dose no later than 5 pm to minimize disruption of sleep cycle.
  • IV route is preferred over IM route for parenteral administration.
• PO May be taken with food or milk to minimize gastric irritation. Tablets may be crushed if patient has difficulty swallowing.
  • Do not administer discolored solution or tablets.

Patient/Family Teaching

• Instruct patient to take furosemide as directed. Take missed doses as soon as possible; do not double doses.
  • Caution patient to change positions slowly to minimize orthostatic hypotension. Caution patient that the use of alcohol, exercise during hot weather, or standing for long periods during therapy may enhance orthostatic hypotension.
  • Instruct patient to consult health care professional regarding a diet high in potassium (see food sources for specific nutrients).
  • Advise patient to contact health care professional if weight gain more than 3 lbs in 1 day.
  • Instruct patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and to consult health care professional before taking any OTC medications concurrently with this therapy.
  • Instruct patient to notify health care professional of medication regimen before treatment or surgery.
  • Caution patient to use sunscreen and protective clothing to prevent photosensitivity reactions.
  • Advise patient to contact health care professional immediately if rash, muscle weakness, cramps, nausea, dizziness, numbness, or tingling of extremities occurs.
  • Advise diabetic patients to monitor blood glucose closely; may cause increased blood glucose levels.
  • Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected, or if breast feeding. Monitor fetal growth during pregnancy; increased risk for higher birth weights.
  • Emphasize the importance of routine follow-up examinations.
  • Geri:  Caution older patients or their caregivers about increased risk for falls. Suggest strategies for fall prevention.
• Hypertension: Advise patients on antihypertensive regimen to continue taking medication even if feeling better. Furosemide controls but does not cure hypertension.
  • Reinforce the need to continue additional therapies for hypertension (weight loss, exercise, restricted sodium intake, stress reduction, regular exercise, moderation of alcohol consumption, cessation of smoking).

Evaluation/Desired Outcomes

• Decrease in edema.
  • Decrease in abdominal girth and weight.
  • Increase in urinary output.
• Decrease in BP.