Furosemide (Page 3 of 4)

Nursing Mothers

Because it appears in breast milk, caution should be exercised when furosemide is administered to a nursing mother.

Furosemide may inhibit lactation.

Pediatric Use

In premature infants, furosemide may precipitate nephrocalcinosis/nephrolithiasis. Nephrocalcinosis/nephrolithiasis has also been observed in children under 4 years of age with no history of prematurity who have been treated chronically with furosemide. Monitor renal function, and renal ultrasonography should be considered, in pediatric patients receiving furosemide.

If furosemide is administered to premature infants during the first weeks of life, it may increase the risk of persistence of patent ductus arteriosus.

Geriatric Use

Controlled clinical studies of furosemide did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for the elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal or cardiac function, and of concomitant disease or other drug therapy.

This drug is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection and it may be useful to monitor renal function. (See PRECAUTIONS: General and DOSAGE AND ADMINISTRATION.)

ADVERSE REACTIONS

Adverse reactions are categorized below by organ system and listed by decreasing severity.

Gastrointestinal System Reactions

  • hepatic encephalopathy in patients with hepatocellular insufficiency
  • pancreatitis
  • jaundice (intrahepatic cholestatic jaundice)
  • increased liver enzymes
  • anorexia
  • oral and gastric irritation
  • cramping
  • diarrhea
  • constipation
  • nausea
  • vomiting

Systemic Hypersensitivity Reactions

  • severe anaphylactic or anaphylactoid reactions (e.g., with shock)
  • systemic vasculitis
  • interstitial nephritis
  • necrotizing angiitis

Central Nervous System Reactions

  • tinnitus and hearing loss
  • paresthesias
  • vertigo
  • dizziness
  • headache
  • blurred vision
  • xanthopsia

Hematologic Reactions

  • aplastic anemia
  • thrombocytopenia
  • agranulocytosis
  • hemolytic anemia
  • leukopenia
  • anemia
  • eosinophilia

Dermatologic-Hypersensitivity Reactions

  • toxic epidermal necrolysis
  • Stevens-Johnson Syndrome
  • erythema multiforme
  • drug rash with eosinophilia and systemic symptoms
  • acute generalized exanthematous pustulosis
  • exfoliative dermatitis
  • bullous pemphigoid
  • purpura
  • photosensitivity
  • rash
  • pruritus
  • urticaria

Cardiovascular Reaction

  • Orthostatic hypotension may occur and be aggravated by alcohol, barbiturates or narcotics.
  • Increase in cholesterol and triglyceride serum levels.

Other Reactions

  • hyperglycemia
  • glycosuria
  • hyperuricemia
  • muscle spasm
  • weakness
  • restlessness
  • urinary bladder spasm
  • thrombophlebitis
  • fever

Whenever adverse reactions are moderate or severe, furosemide dosage should be reduced or therapy withdrawn.

OVERDOSAGE

The principal signs and symptoms of overdosage with furosemide are dehydration, blood volume reduction, hypotension, electrolyte imbalance, hypokalemia and hypochloremic alkalosis, and are extensions of its diuretic action.

The acute toxicity of furosemide has been determined in mice, rats and dogs. In all three, the oral LD 50 exceeded 1000 mg/kg body weight, while the intravenous LD 50 ranged from 300 to 680 mg/kg. The acute intragastric toxicity in neonatal rats is 7 to 10 times that of adult rats.

The concentration of furosemide in biological fluids associated with toxicity or death is not known.

Treatment of overdosage is supportive and consists of replacement of excessive fluid and electrolyte losses. Serum electrolytes, carbon dioxide level and blood pressure should be determined frequently. Adequate drainage must be assured in patients with urinary bladder outlet obstruction (such as prostatic hypertrophy).

Hemodialysis does not accelerate furosemide elimination.

DOSAGE AND ADMINISTRATION

Edema

Therapy should be individualized according to patient response to gain maximal therapeutic response and to determine the minimal dose needed to maintain that response.

Adults

The usual initial dose of furosemide is 20 mg to 80 mg given as a single dose. Ordinarily a prompt diuresis ensues. If needed, the same dose can be administered 6 to 8 hours later or the dose may be increased. The dose may be raised by 20 mg to 40 mg and given not sooner than 6 to 8 hours after the previous dose until the desired diuretic effect has been obtained. The individually determined single dose should then be given once or twice daily (e.g., at 8 am and 2 pm). The dose of furosemide may be carefully titrated up to 600 mg/day in patients with clinically severe edematous states.

Edema may be most efficiently and safely mobilized by giving furosemide on 2 to 4 consecutive days each week.

When doses exceeding 80 mg/day are given for prolonged periods, careful clinical observation and laboratory monitoring are particularly advisable. (See PRECAUTIONS: Laboratory Tests.)

Geriatric Patients

In general, dose selection for the elderly patient should be cautious, usually starting at the low end of the dosing range (see PRECAUTIONS: Geriatric Use).

Pediatric Patients

The usual initial dose of oral furosemide in pediatric patients is 2 mg/kg body weight, given as a single dose. If the diuretic response is not satisfactory after the initial dose, dosage may be increased by 1 or 2 mg/kg no sooner than 6 to 8 hours after the previous dose. Doses greater than 6 mg/kg body weight are not recommended. For maintenance therapy in pediatric patients, the dose should be adjusted to the minimum effective level.

Hypertension

Therapy should be individualized according to the patient’s response to gain maximal therapeutic response and to determine the minimal dose needed to maintain the therapeutic response.

Adults

The usual initial dose of furosemide for hypertension is 80 mg, usually divided into 40 mg twice a day. Dosage should then be adjusted according to response. If response is not satisfactory, add other antihypertensive agents.

Changes in blood pressure must be carefully monitored when furosemide is used with other antihypertensive drugs, especially during initial therapy. To prevent excessive drop in blood pressure, the dosage of other agents should be reduced by at least 50 percent when furosemide is added to the regimen. As the blood pressure falls under the potentiating effect of furosemide, a further reduction in dosage or even discontinuation of other antihypertensive drugs may be necessary.

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