furosemide

Absorption: 60–67% absorbed after oral administration (↓ in acute HF and in renal failure); also absorbed from IM sites; IV administration results in complete availability; 99.6% absorbed after SUBQ administration.

Distribution: Crosses placenta, enters breast milk.

Protein Binding: 91–99%.

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

Half-Life: 30–120 min (↑ in renal impairment).

Time/Action Profile ⬆ ⬇

(diuretic effect)

ROUTE	ONSET	PEAK	DURATION
PO	30–60 min	1–2 hr	6–8 hr
IM	10–30 min	unknown	4–8 hr
IV	5 min	30 min	2 hr
Subcut	unknown	unknown	8 hr

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity;
Cross-sensitivity with thiazides and sulfonamides may occur;
Hepatic coma;
Anuria;
Hepatic cirrhosis or ascites (SUBQ only);
Acute pulmonary edema (SUBQ only);
Some liquid products may contain alcohol, avoid in patients with alcohol intolerance.

Use Cautiously in:

Severe hepatic impairment (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: Use during pregnancy only if potential maternal benefit justifies potential fetal risk;
Lactation: Use while breastfeeding only if potential maternal benefit justifies potential risk to infant;
Pedi: risk for renal calculi and patent ductus arteriosis in premature neonates;
Geri: Appears on Beers list. May worsen or cause hyponatremia in older adults. Use with caution in older adults and monitor sodium concentrations closely when initiating therapy or the dose.

Adv. Reactions/Side Effects ⬆ ⬇

CV: hypotension

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

EENT: hearing loss, tinnitus

Endo: hypercholesterolemia, hyperglycemia, hypertriglyceridemia, hyperuricemia

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

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

GU: ↑BUN, excessive urination, nephrocalcinosis

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

MS: muscle cramps

Neuro: blurred vision, dizziness, headache, paresthesia, vertigo

Misc: fever

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.
SC (Adults ): 30 mg over the 1st hr, then 12.5 mg per hr over the next 4 hr with the single-use on-body Infusor. Replace with oral diuretic therapy as soon as possible.

Hypertension

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

Availability ⬆ ⬇

(Generic available)

Tablets: 20 mg; 40 mg; 80 mg; 500 mg
Oral solution10 mg/mL—orange flavor, 8 mg/mL—pineapple—peach flavor: 8 mg/mL; 10 mg/mL
Solution for intravenous/intramuscular injection: 10 mg/mL
Solution for SUBQ injection (Furoscix) (prefilled cartridges): 80 mg/10 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, serum creatinine, and uric acid levels.

Implementation ⬆ ⬇

If administering twice daily, give last dose no later than 5 pm to minimize disruption of sleep cycle. Do not confuse Lasix with Wakix.
- 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.
SC: The single-use, on-body Infusor with prefilled cartridge is pre-programed to deliver 30 mg of furosemide over the first hr followed by 12.5 mg per hr for the subsequent 4 hrs. Inspect fluid in prefilled cartridge; solution is clear to slightly yellow; do not administer solutions that are discolored or cloudy. Load prefilled cartridge into the on-body infusor and close cartridge holder. Peel away adhesive liner on on-body infusor and apply onto a clean, dry area of the abdomen between top of beltline and bottom of ribcage (at least 2 ½ inches from beltline or bottom of ribcage) that is not tender, bruised, red or indurated. Start injection by firmly pressing and releasing the blue start button. Do not remove until the injection is complete (signaled by the solid green status light, beeping sound, and the white plunger rod filling the cartridge window). Rotate the site of each subcutaneous administration. Patient must limit activity during administration. On-body infusor is not compatible with use in an MRI setting. SUBQ route is not for chronic use; replace with oral diuretics as soon as practical.

IV Administration:

Diluent: Administer undiluted (larger doses may be diluted and administered as intermittent infusion [see below]).Concentration: 10 mg/mL.
Rate: Administer at a rate of 20 mg/min. Pedi: Administer at a maximum rate of 0.5–1 mg/kg/min (for doses 120 mg) with infusion not exceeding 10 min.
Intermittent Infusion: Diluent: Dilute larger doses in 50 mL of D5W, D10W, D20W, D5/0.9% NaCl, D5/LR, 0.9% NaCl, 3% NaCl, or LR. Infusion stable for 24 hr at room temperature. Do not refrigerate. Protect from light.Concentration: 1 mg/mL.
Rate: Administer at a rate not to exceed 4 mg/min (for doses >120 mg) in adults to prevent ototoxicity. Pedi: not to exceed 1 mg/kg/min with infusion not exceeding 10 min. Use an infusion pump to ensure accurate dose.

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 breastfeeding. Monitor fetal growth during pregnancy; increased risk for higher birth weights.
- Emphasize the importance of routine follow-up examinations.
- 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).

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇

Action ⬆ ⬇

Pharmacokinetics ⬆ ⬇