Furosemide

furosemide (fur oh' se mide) Apo-Furosemide (CAN), Furoside (CAN), Lasix, Myrosemide (CAN) Pregnancy Category C Drug class

Loop diuretic Therapeutic actions

Inhibits the reabsorption of sodium and chloride from the ascending limb of the loop of Henle, leading to a sodium-rich diuresis. Indications

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Oral, IV: Edema associated with CHF, cirrhosis, renal disease IV: Acute pulmonary edema Oral: Hypertension

Contraindications and cautions

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Contraindicated with allergy to furosemide, sulfonamides; allergy to tartrazine (in oral solution); anuria, severe renal failure; hepatic coma; pregnancy; lactation. Use cautiously with SLE, gout, diabetes mellitus.

Available forms

Tablets—20, 40, 80 mg; oral solution—10 mg/mL, 40 mg/5 mL; injection—10 mg/mL Dosages ADULTS

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Edema: Initially, 20–80 mg/day PO as a single dose. If needed, a second dose may be given in 6–8 hr. If response is unsatisfactory, dose may be increased in 20to 40-mg increments at 6- to 8-hr intervals. Up to 600 mg/day may be given. Intermittent dosage schedule (2–4 consecutive days/wk) is preferred for maintenance, or 20–40 mg IM or IV (slow IV injection over 1–2 min). May increase dose in increments of 20 mg in 2 hr. High-dose therapy should be given as infusion at rate not exceeding 4 mg/min. Acute pulmonary edema: 40 mg IV over 1–2 min. May be increased to 80 mg IV given over 1–2 min if response is unsatisfactory after 1 hr. Hypertension: 40 mg bid PO. If needed, additional antihypertensive agents may be added.

PEDIATRIC PATIENTS

Avoid use in premature infants: stimulates PGE2 synthesis and may increase incidence of patent ductus arteriosus and complicate respiratory distress syndrome. • Edema: Initially, 2 mg/kg/day PO. If needed, increase by 1–2 mg/kg in 6–8 hr. Do not exceed 6 mg/kg. Adjust maintenance dose to lowest effective level. • Pulmonary edema: 1 mg/kg IV or IM. May increase by 1 mg/kg in 2 hr until the desired effect is seen. Do not exceed 6 mg/kg.

PATIENTS WITH RENAL IMPAIRMENT

Up to 4 g/day has been tolerated. IV bolus injection should not exceed 1 g/day given over 30 min. Pharmacokinetics Route Oral IV, IM

Onset 60 min 5 min

Peak 60–120 min 30 min

Duration 6–8 hr 2 hr

Metabolism: Hepatic; T1/2: 30–60 min Distribution: Crosses placenta; enters breast milk Excretion: Urine, feces IV facts

Preparation: Store at room temperature; exposure to light may slightly discolor solution. Infusion: Inject directly or into tubing of actively running IV; inject slowly over 1–2 min. Incompatibilities: Do not mix with acidic solutions. Isotonic saline, lactated Ringer's injection, and 5% dextrose injection may be used after pH has been adjusted (if necessary); precipitates form with gentamicin, netilimicin, milrinone in 5% dextrose, 0.9% sodium chloride. Adverse effects

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CNS: Dizziness, vertigo, paresthesias, xanthopsia, weakness, headache, drowsiness, fatigue, blurred vision, tinnitus, irreversible hearing loss CV: Orthostatic hypotension, volume depletion, cardiac arrhythmias, thrombophlebitis Dermatologic: Photosensitivity, rash, pruritus, urticaria, purpura, exfoliative dermatitis, erythema multiforme GI: Nausea, anorexia, vomiting, oral and gastric irritation, constipation, diarrhea, acute pancreatitis, jaundice GU: Polyuria, nocturia, glycosuria, urinary bladder spasm Hematologic: Leukopenia, anemia, thrombocytopenia, fluid and electrolyte imbalances Other: Muscle cramps and muscle spasms

Interactions

Drug-drug • Increased risk of cardiac arrhythmias with digitalis glycosides (due to electrolyte imbalance) • Increased risk of ototoxicity with aminoglycoside antibiotics, cisplatin • Decreased absorption of furosemide with phenytoin • Decreased natriuretic and antihypertensive effects with indomethacin, ibuprofen, other NSAIDs • Decreased GI absorption with charcoal

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May reduce effect of insulin or oral antidiabetic agents because blood glucose levels can become elevated

Nursing considerations CLINICAL ALERT!

Name confusion has occurred between furosemide and torsemide; use extreme caution. Assessment

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History: Allergy to furosemide, sulfonamides, tartrazine; electrolyte depletion anuria, severe renal failure; hepatic coma; SLE; gout; diabetes mellitus; lactation, pregnancy Physical: Skin color, lesions, edema; orientation, reflexes, hearing; pulses, baseline ECG, BP, orthostatic BP, perfusion; R, pattern, adventitious sounds; liver evaluation, bowel sounds; urinary output patterns; CBC, serum electrolytes (including calcium), blood sugar, liver and renal function tests, uric acid, urinalysis, weight

Interventions

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Administer with food or milk to prevent GI upset. Reduce dosage if given with other antihypertensives; readjust dosage gradually as BP responds. Give early in the day so that increased urination will not disturb sleep. Avoid IV use if oral use is at all possible. Do not mix parenteral solution with highly acidic solutions with pH below 3.5. Do not expose to light, may discolor tablets or solution; do not use discolored drug or solutions. Discard diluted solution after 24 hr. Refrigerate oral solution. Measure and record weight to monitor fluid changes. Arrange to monitor serum electrolytes, hydration, liver function. Arrange for potassium-rich diet or supplemental potassium as needed.

Teaching points

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Record intermittent therapy on a calendar or dated envelopes. When possible, take the drug early so increased urination will not disturb sleep. Take with food or meals to prevent GI upset. Weigh yourself on a regular basis, at the same time and in the same clothing, and record the weight on your calendar. These side effects may occur: Increased volume and frequency of urination; dizziness, feeling faint on arising, drowsiness (avoid rapid position changes; hazardous activities, like driving; and consumption of alcohol); sensitivity to sunlight (use sunglasses, wear protective clothing, or use a sunscreen); increased thirst (suck on sugarless lozenges; use frequent mouth care); loss of body potassium (a potassium-rich diet or potassium supplement will be needed).

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Report loss or gain of more than 3 lb in 1 day, swelling in your ankles or fingers, unusual bleeding or bruising, dizziness, trembling, numbness, fatigue, muscle weakness or cramps.

Adverse effects in Italic are most common; those in Bold are life-threatening.