Furosemide is a monosulphonyl diuretic. It is an effective diuretic that retains its activity even in low glomerular filtration rate (GFR). Furosemide has a distinctive action on renal tubular function. It affects a peak diuresis far greater than that observed with other agents. Other features are (I) prompt onset of action (II) inhibition of sodium and chloride transport in the ascending limb of the loop of Henle and (III) independence of their action from acid-base balance changes. Furosemide acts primarily to inhibit electrolyte reabsorption in the thick ascending limb of the loop of Henle. Furosemide is readily absorbed from the gastrointestinal tract and considerable proportions are bound to plasma proteins. It is rapidly excreted in the urine. With an hour after intravenous injection, its effect is evident in about 5 minutes and last for about 2 hours.

Furosemide is indicated in-

• Fluid retention associated with chronic congestive cardiac failure (if diuretic treatment is required).
• Fluid retention associated with acute congestive cardiac failure.
• Fluid retention associated with chronic renal failure.
• Maintenance of fluid excretion in acute renal failure, including that due to pregnancy or burns.
• Fluid retention associated with nephrotic syndrome (if diuretic treatment is required).
• Fluid retention associated with liver disease (if necessary to supplement treatment with aldosterone antagonists).
• Hypertension.
• Hypertensive crisis (as a supportive measure).
• Support of forced diuresis.

Furosemide 40 mg Tablet-

Edema:

• Adults: The initial adult dose is 40 mg daily, reduced to 20 mg daily or 40mg on alternate days. In some patients daily doses of 80mg or higher (given in divided doses) may be required. The individually determined single dose should then be given once or twice daily (eg, at 8 am and 2 pm). For resistant edema, 80-120 mg daily. In patients with clinically severe edematous states the dose of furosemide may be carefully titrated up to 600 mg/day. When doses exceeding 80 mg/day are given for prolonged periods, careful clinical observation and laboratory monitoring are particularly advisable.
• Children: Neonate: 0.5-2 mg/kg every 12-24 hours (every 24 hours if postmenstrual age under 31 weeks).
• Child 1 month-12 years: 0.5-2 mg/kg 2-3 times daily (every 24 hours if postmenstrual age less than 31 weeks); higher doses may be required in resistant edema; max. 12 mg/kg daily, not to exceed 80 mg daily.
• Child 12-18 years:20-40 mg daily, increased in resistant edema to 80-120 mg daily.
• Elderly: In the elderly furosemide is generally eliminated more slowly. Dosage should be titrated until the required response is achieved.

Hypertension:

• 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.
• Children: The usual dose is 1 - 3 mg/kg body weight daily up to a maximum dose of 40mg/day.
• Elderly: In the elderly furosemide is generally eliminated more slowly. Dosage should be titrated until the required response is achieved.

Furosemide 250 mg Tablet: For selected patients with advanced chronic renal failure, diuretic therapy may be started with Furosemide orally. If conventional doses (80 to 160 mg orally) fail to produce an adequate diuresis, a single dose of 250 mg is given as a starting dose. If a satisfactory diuresis does not ensue within 4-6 hours, the initial dose may be doubled to 500 mg. The criterion of optimal dosage is a urinary output of at least 2.5 liters per day. A maximum daily dose of 1000 mg should not be exceeded.

Furosemide Syrup: Furosemide Liquid has an exceptionally wide therapeutic range, the effect being proportional to the dosage. Furosemide Liquid is best given as a single dose either daily or on alternate days. The usual initial daily dose is 40 mg. This may require adjustment until the effective dose is achieved as a maintenance dose. In mild cases, 20 mg daily or 40 mg on alternate days may be sufficient, whereas in cases of resistant edema, daily doses of 80 mg and above may be used as one or two daily, or intermittently. Severe cases may require gradual titration of the furosemide dosage up to 600 mg daily. The recommended maximum daily dose of furosemide administration is 1,500 mg.

Furosemide Injection-

Edema:

Adults: Doses of 20-50 mg intramuscularly or intravenously may be given initially. If larger doses are required, they should be given increasing by 20 mg increments and not given more often than every two hours. If doses greater than 50 mg are required it is recommended that they should be given by slow intravenous infusion. The recommended maximum daily dose of furosemide administration is 1,500 mg.

By slow intravenous injection:

• Neonate: 0.5-1 mg/kg every 12-24 hours (every 24 hours if postmenstrual age under 31 weeks).
• Child 1 month-12 years: 0.5-1 mg/kg repeated every 8 hours as necessary;maximum 2 mg/kg (max. 40 mg) every 8 hours.
• Child 12-18 years: 20-40 mg repeated every 8 hours as necessary; higher doses may be required in resistant cases.

By continuous intravenous infusion:

• Child 1 month-18 years: 0.1-2 mg/kg/hour (following cardiac surgery, initially 100 micrograms/kg/hour, doubled every 2 hours until urine output exceeds 1 mL/kg/hour).
• Elderly: In the elderly furosemide is generally eliminated more slowly. Dosage should be titrated until the required response is achieved.

Hypertension:

• Adults: Doses of 20 to 50 mg intramuscularly or intravenously may be given initially. If larger doses are required, they should be given increasing by 20 mg increments and not given more often than every two hours. If doses greater than 50 mg are required it is recommended that they should be given by slow intravenous infusion. The recommended maximum daily dose of furosemide administration is 1,500 mg. Children: Parenteral doses for children range from 0.5-1.5 mg/kg body weight daily up to a maximum total daily dose of 20 mg.
• Elderly: In the elderly furosemide is generally eliminated more slowly. Dosage should be titrated until the required response is achieved.

Furosemide is contraindicated in anuria, electrolyte deficiency and pre-comatose states associated with liver cirrhosis. Hypersensitivity to furosemide or sulphonamides.

As with other diuretics, electrolytes and water balance may be disturbed as a result of diuresis of prolonged therapy. Prolonged use can produce alkalosis. It may also cause uric acid retention and may rarely produce acute gout. Furosemide may provoke hyperglycemia and glycosuria.

Overdose Effects

Signs and symptoms: The clinical picture in acute or chronic overdose depends primarily on the extent and consequences of electrolyte and fluid loss, e.g. hypovolaemia, dehydration, haemoconcentration, cardiac arrhythmias (including AV block and ventricular fibrillation).

Management: No specific antidote to furosemide is known. If ingestion has only just taken place, attempts may be made to limit further systemic absorption of the active ingredient by measures such as gastric lavage or those designed to reduce absorption (e.g. activated charcoal).

Patients with prostatic hypertrophy or impairment of micturition have an increased risk of developing acute retention. A marked fall in blood pressure may be seen when ACE inhibitors are added to furosemide therapy. The toxic effects of nephrotoxic antibiotics may be increased by concomitant administration of potent diuretics such furosemide.

Driving a vehicle or performing other hazardous tasks: Some adverse effects (e.g. an undesirably pronounced fall in blood pressure) may impair the patient's ability to concentrate and react, and, therefore, constitute a risk in situations where these abilities are of special importance (e.g. operating a vehicle or machinery).

Pregnancy & Lactation

Pregnancy category C. Furosemide should be cautiously used in cardiogenic shock complicated by pulmonary oedema and in the first trimester of pregnancy. Blood pressure and pulse during rapid diuresis should be monitored. Caution should be observed in patients liable to electrolyte deficiency. In case of nursing mother, furosemide may inhibit lactation or may pass into breast milk. In that case it should be used with caution.