furosemide

Brand Name

Apo-Furosemide (CAN), Furoside (CAN),\ Lasix, Lasix Special (CAN), Myrosemide, Novosemide (CAN), Uritol (CAN)

Class and Category

Chemical class: Sulfonamide

Therapeutic class: Antihypertensive, diuretic

Pregnancy category: C

Indications and Dosages

To reduce edema caused by cirrhosis, heart failure, and renal disease, including nephrotic syndrome

ORAL SOLUTION, TABLETS

Adults. 20 to 80 mg as a single dose, increased by 20 to 40 mg every 6 to 8 hr until desired response occurs. Maximum: 600 mg daily.

Children. 2 mg/kg as a single dose, increased by 1 to 2 mg/kg every 6 to 8 hr until desired response occurs.Maximum: 6 mg/kg/dose.

I.V. INFUSION, I.V. OR I.M. INJECTION

Adults. 20 to 40 mg as a single dose, increased by 20 mg every 2 hr until desired response occurs.

Children. 1 mg/kg as a single dose, increased by 1 mg/kg every 2 hr until desired response occurs. Maximum: 6 mg/kg/dose.

DOSAGE ADJUSTMENT

Initial single dose limited to 20 mg for elderly patients.

To manage mild to moderate hypertension, as adjunct to treat acute pulmonary edema and hypertensive crisis

ORAL SOLUTION, TABLETS

Adults. Initial: 40 mg b.i.d., adjusted until desired response occurs. Maximum: 600 mg daily.

I.V. INFUSION OR INJECTION

Adults with normal renal function. 40 to 80 mg as a single dose over several minutes.

Adults with acute renal failure or pulmonary edema. 100 to 200 mg as a single dose over several minutes.

DOSAGE ADJUSTMENT

For patients with acute pulmonary edema without hypertensive crisis, dosage reduced to 40 mg followed by 80 mg 1 hr later if therapeutic response doesn’t occur.

Route                     Onset                     Peak                       Duration

P.O.                         20–60 min                1–2 hr                      6–8 hr

I.V.                           5 min                        In 30 min                  2 hr

I.M.                           30 min                      Unknown                 2 hr

Mechanism of Action

Inhibits sodium and water reabsorption in the loop of Henle and increases urine formation. As the body’s plasma volume decreases, aldosterone production increases, which promotes sodium reabsorption and the loss of potassium and hydrogen ions. Furosemide also increases the excretion of calcium, magnesium, bicarbonate, ammonium, and phosphate. By reducing intracellular and extracellular fluid volume, the drug reduces blood pressure and decreases cardiac output. Over time, cardiac output returns to normal.

Incompatibilities

Don’t mix furosemide (a milky, buffered alkaline solution) with highly acidic solutions.

Contraindications

Anuria unresponsive to furosemide; hypersensitivity to furosemide, sulfonamides, or their components

Interactions

DRUGS

ACE inhibitors: Possibly first-dose hypotension

aminoglycosides, cisplatin: Increased risk of ototoxicity

amiodarone: Increased risk of arrhythmias from hypokalemia

chloral hydrate: Possibly diaphoresis, hot flashes, and hypertension

digoxin: Increased risk of digitalis toxicity related to hypokalemia

insulin, oral antidiabetic drugs: Increased blood glucose level

lithium: Increased risk of lithium toxicity

NSAIDs: Possibly decreased diuresis

phenytoin, probenecid: Possibly decreased therapeutic effects of furosemide

propranolol: Possibly increased blood propranolol level

thiazide diuretics: Possibly profound dieresis and electrolyte imbalances

ACTIVITIES

alcohol use: Possibly increased hypotensive and diuretic effects of furosemide

Adverse Reactions

CNS: Dizziness, fever, headache, paresthesia, restlessness, vertigo, weakness

CV: Orthostatic hypotension, shock, thromboembolism, thrombophlebitis

EENT: Blurred vision, oral irritation, ototoxicity, stomatitis, tinnitus, transient hearing loss (rapid I.V. injection), yellow vision

ENDO: Hyperglycemia

GI: Abdominal cramps, anorexia, constipation, diarrhea, gastric irritation, hepatocellular insufficiency, indigestion, jaundice, nausea, pancreatitis, vomiting

GU: Bladder spasms, glycosuria

HEME: Agranulocytosis (rare), anemia, aplastic anemia (rare), azotemia, hemolytic anemia, leukopenia, thrombocytopenia

MS: Muscle spasms

SKIN: Bullous pemphigoid, erythema multiforme, exfoliative dermatitis, photosensitivity, pruritus, purpura, rash, urticaria

Other: Allergic reaction (interstitial nephritis, necrotizing vasculitis, systemic vasculitis), dehydration, hyperuricemia, hypochloremia, hypokalemia, hyponatremia, hypovolemia

Nursing Considerations

WARNING Use furosemide cautiously in patients with advanced hepatic cirrhosis, especially those who also have a history of electrolyte imbalance or hepatic encephalopathy; drug may lead to lethal hepatic coma.

•Obtain patient’s weight before and periodically during furosemide therapy to monitor fluid loss.

• For once-a-day dosing, give drug in the morning so patient’s sleep won’t be interrupted by increased need to urinate.

• Prepare drug for infusion with normal saline solution, lactated Ringer’s solution, or D5W.

• Administer drug slowly I.V. over 1 to 2 minutes to prevent ototoxicity.

• Expect patient to have periodic hearing tests during prolonged or high-dose I.V. therapy.

•Monitor blood pressure and hepatic and renal function as well as BUN, blood glucose, and serum creatinine, electrolyte, and uric acid levels, as appropriate.

• Be aware that elderly patients are more susceptible to hypotensive and electrolytealtering effects and thus are at greater risk for shock and thromboembolism.

• If patient is at high risk for hypokalemia, give potassium supplements along with furosemide, as prescribed.

• Expect to discontinue furosemide at maximum dosage if oliguria persists for more than 24 hours.

• Be aware that furosemide may worsen left ventricular hypertrophy and adversely affect glucose tolerance and lipid metabolism.

• Notify prescriber if patient experiences hearing loss, vertigo, or ringing, buzzing, or sense of fullness in her ears. Drug may need to be discontinued.

PATIENT TEACHING

• Instruct patient to take furosemide at the same time each day to maintain therapeutic effects. Urge her to take it as prescribed, even if she feels well.

• Instruct patient to take the last dose of furosemide several hours before bedtime to avoid sleep interruption from diuresis. If patient receives once-daily dosing, advise her to take the dose in the morning to avoid sleep disturbance caused by nocturia.

• Advise patient to change position slowly to minimize effects of orthostatic hypotension and to take furosemide with food or milk to reduce GI distress.

• Caution patient about drinking alcoholic beverages, standing for prolonged periods, and exercising in hot weather because these actions increase the hypotensive effect of furosemide.

• Emphasize the importance of weight and diet control, especially limiting sodium intake.

• Unless contraindicated, urge patient to eat more high-potassium foods and to take a potassium supplement, if prescribed, to prevent hypokalemia.

• Instruct patient to keep follow-up appointments with prescriber to monitor progress. Urge her to notify prescriber about persistent, severe nausea, vomiting, and diarrhea because they may cause dehydration.

• Inform diabetic patient that furosemide may increase blood glucose level, and advise her to check her blood glucose level frequently.