FUROSEMIDE

(fur-oh'se-mide)
Fumide

, Furomide

, Lasix, Luramide

Classifications: electrolytic and water balance agent; loop diuretic
Pregnancy Category: C

Availability

20 mg, 40 mg, 80 mg tablets; 10 mg/mL, 40 mg/5 mL oral solution; 10 mg/mL injection

Actions

Rapid-acting potent sulfonamide "loop" diuretic and antihypertensive with pharmacologic effects and uses almost identical to those of ethacrynic acid. Exact mode of action not clearly defined; decreases renal vascular resistance and may increase renal blood flow.

Therapeutic Effects

Inhibits reabsorption of sodium and chloride primarily in loop of Henle and also in proximal and distal renal tubules; an antihypertensive that decreases edema and intravascular volume. Reportedly less ototoxic than ethacrynic acid.

Uses

Treatment of edema associated with CHF, cirrhosis of liver, and kidney disease, including nephrotic syndrome. May be used for management of hypertension, alone or in combination with other antihypertensive agents, and for treatment of hypercalcemia. Has been used concomitantly with mannitol for treatment of severe cerebral edema, particularly in meningitis.

Contraindications

History of hypersensitivity to furosemide or sulfonamides; increasing oliguria, anuria, fluid and electrolyte depletion states; hepatic coma; pregnancy (category C), lactation.

Cautious Use

Infants, older adults; hepatic cirrhosis, nephrotic syndrome; cardiogenic shock associated with acute MI; history of SLE, history of gout; patients receiving digitalis glycosides or potassium-depleting steroids.

Route & Dosage

Edema
Adult: PO 20–80 mg in 1 or more divided doses up to 600 mg/d if needed IV/IM 20–40 mg in 1 or more divided doses up to 600 mg/d
Child: PO 2 mg/kg, may be increased by 1–2 mg/kg q6–8h (max: 6 mg/kg/dose) IV/IM 1 mg/kg, may be increased by 1 mg/kg q2h if needed (max: mg/kg/dose)
Neonate: PO 1–4 mg/kg q12–24h IV/IM 1–2 mg/kg q12–24h

Hypertension
Adult: PO 10–40 mg b.i.d. (max: 480 mg/d)

Administration

Oral

Give with food or milk to reduce possibility of gastric irritation.
Schedule doses to avoid sleep disturbance (e.g., a single dose is generally given in the morning; twice-a-day doses at 8 a.m. and 2 p.m.).
Note: Slight discoloration of tablets reportedly does not alter potency.
Store tablets at controlled room temperature, preferably at 15°–30° C (59°–86° F) unless otherwise directed. Protect from light.
Store oral solution in refrigerator, preferably at 2°–8° C (36°–46° F). Protect from light and freezing.

Intramuscular

Protect syringes from light once they are removed from package.
Discard yellow or otherwise discolored injection solutions.

Intravenous

Note: Verify correct IV concentration and rate of infusion/injection with physician before administration to infants or children.

PREPARE: Direct: Give undiluted.

ADMINISTER: Direct: Give undiluted at a rate of 20 mg or a fraction thereof over 1 min. With high doses a rate of 4 mg/min is recommended to decrease risk of ototoxicity.

INCOMPATIBILITIES Solution/additive: Buprenorphine, chlorpromazine, ciprofloxacin, diazepam, diphenhydramine, dobutamine, doxapram, doxorubicin, droperidol, erythromycin, gentamicin, isoproterenol, labetalol, meperidine, metoclopramide, milrinone, netilmicin, pancuronium, prochlorperazine, promethazine, quinidine, thiamine vinblastine, vincristine. Y-site: Amrinone, amsacrine, azithromycin, ciprofloxacin, diazepam, diltiazem, dobutamine, diphenhydramine, dopamine, doxorubicin, droperidol, esmolol, filgrastim, fluconazole, gemcitabine, gentamicin, hydralazine, idarubicin, methocarbamol, metoclopramide, midazolam, milrinone, morphine, netilmicin, nicardipine, ondansetron, quinidine, thiopental, tobramycin, vecuronium, vinblastine, vincristine, vinorelbine, TPN.

Use infusion solutions within 24 h.
Store parenteral solution at controlled room temperature, preferably at 15°–30° C (59°–86° F) unless otherwise directed. Protect from light.

Adverse Effects (1%)

CV: Postural hypotension, dizziness with excessive diuresis, acute hypotensive episodes, circulatory collapse. Metabolic: Hypovolemia, dehydration, hyponatremia hypokalemia, hypochloremia metabolic alkalosis, hypomagnesemia, hypocalcemia (tetany), hyperglycemia, glycosuria, elevated BUN, hyperuricemia. GI: Nausea, vomiting, oral and gastric burning, anorexia, diarrhea, constipation, abdominal cramping, acute pancreatitis, jaundice. Urogenital: Allergic interstitial nephritis, irreversible renal failure, urinary frequency. Hematologic: Anemia, leukopenia, thrombocytopenic purpura; aplastic anemia, agranulocytosis (rare). Special Senses: Tinnitus, vertigo, feeling of fullness in ears, hearing loss (rarely permanent), blurred vision. Skin: Pruritus, urticaria, exfoliative dermatitis, purpura, photosensitivity, porphyria cutanea tarde, necrotizing angiitis (vasculitis). Body as a Whole: Increased perspiration; paresthesias; activation of SLE, muscle spasms, weakness; thrombophlebitis, pain at IM injection site.

Diagnostic Test Interference

Furosemide may cause elevations in BUN, serum amylase, cholesterol, triglycerides, uric acid and blood glucose levels, and may decrease serum calcium, magnesium, potassium, and sodium levels.

Interactions

Drug: other diuretics enhance diuretic effects; with digoxin increased risk of toxicity because of hypokalemia; nondepolarizing neuromuscular blocking agents (e.g., tubocurarine) prolong neuromuscular blockage; corticosteroids, amphotericin B potentiate hypokalemia; decreased lithium elimination and increased toxicity; sulfonylureas, insulin blunt hypoglycemic effects; nsaids may attenuate diuretic effects.

Pharmacokinetics

Absorption: 60 of oral dose absorbed from GI tract. Peak: 60–70 min PO; 20–60 min IV. Onset: 30–60 min PO; 5 min IV. Duration: 2 h. Distribution: Crosses placenta. Metabolism: Small amount metabolized in liver. Elimination: Rapidly excreted in urine; 50% of oral dose and 80% of IV dose excreted within 24 h; excreted in breast milk. Half-Life: 30 min.

Nursing Implications

Assessment & Drug Effects

Observe patients receiving parenteral drug carefully; closely monitor BP and vital signs. Sudden death from cardiac arrest has been reported.
Monitor for S&S of hypokalemia (see Appendix F).
Monitor BP during periods of diuresis and through period of dosage adjustment.
Observe older adults closely during period of brisk diuresis. Sudden alteration in fluid and electrolyte balance may precipitate significant adverse reactions. Report symptoms to physician.
Lab tests: Obtain frequent blood count, serum and urine electrolytes, CO₂, BUN, blood sugar, and uric acid values during first few months of therapy and periodically thereafter.
Monitor I&O ratio and pattern. Report decrease or unusual increase in output. Excessive diuresis can result in dehydration and hypovolemia, circulatory collapse, and hypotension. Weigh patient daily under standard conditions.
Monitor urine and blood glucose & HbA_1C closely in diabetics and patients with decompensated hepatic cirrhosis. Drug may cause hyperglycemia.
Note: Excessive dehydration is most likely to occur in older adults, those with chronic cardiac disease on prolonged salt restriction, or those receiving sympatholytic agents.

Patient & Family Education

Consult physician regarding allowable salt and fluid intake.
Ingest potassium-rich foods daily (e.g., bananas, oranges, peaches, dried dates) to reduce or prevent potassium depletion.
Learn S&S of hypokalemia (see Appendix F). Report muscle cramps or weakness to physician.
Make position changes slowly because high doses of antihypertensive drugs taken concurrently may produce episodes of dizziness or imbalance.
Avoid replacing fluid losses with large amounts of water.
Avoid prolonged exposure to direct sun.
Do not breast feed while taking this drug.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug