furosemide

furosemide

(fur oh' se mide)

Apo-Furosemide (CAN), Furosemide Special (CAN), Lasix

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

·        Oral, IV: Edema associated with CHF, cirrhosis, renal disease

·        IV: Acute pulmonary edema

·        Oral: Hypertension

Contraindications and cautions

·        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

·        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 20- to 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 prostaglandin E₂ 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	Onset	Peak	Duration
Oral	60 min	60–120 min	6–8 hr
IV, IM	5 min	30 min	2 hr

Metabolism: Hepatic; T_1/2: 30–60 min

Distribution: Crosses placenta; enters breast milk

Excretion: Feces, urine

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

·        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, hyperglycemia, hyperuricemia

·        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

·        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

·        History: Allergy to furosemide, sulfonamides, tartrazine; electrolyte depletion anuria, severe 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, LFTs, renal function tests, uric acid, urinalysis, weight

Interventions

·        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.

·        WARNING: 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 and renal function.

·        Arrange for potassium-rich diet or supplemental potassium as needed.

Teaching points

·        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.

·        Blood glucose levels may become temporarily elevated in patients with diabetes after starting this drug.

·        You may experience these side effects: 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).

·        Report loss or gain of more than 3 pounds 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.