FUROSEMIDE- furosemide_tablet

Investigations into the mode of action of furosemide have utilized micropuncture studies in rats, stop flow experiments in dogs and various clearance studies in both humans and experimental animals. It has been demonstrated that furosemide inhibits primarily the absorption of sodium and chloride not only in the proximal and distal tubules but also in the loop of Henle. The high degree of efficacy is largely due to the unique site of action. The action on the distal tubule is independent of any inhibitory effect on carbonic anhydrase and aldosterone. Recent evidence suggests that furosemide glucuronide is the only or at least the major biotransformation product of furosemide in man. Furosemide is extensively bound to plasma proteins, mainly to albumin. Plasma concentrations ranging from 1 to 400 mcg/mL are 91 to 99% bound in healthy individuals. The unbound fraction averages 2. 1% at therapeutic concentrations. The onset of diuresis following oral administration is within 1 hour. The peak effect occurs within the first or second hour. The duration of diuretic effect is 6 to 8 hours. In fasted normal men, the mean bioavailability of furosemide from furosemide tablets and furosemide oral solution is 64% and 60%, respectively, of that from an intravenous injection of the drug. Although furosemide is more rapidly absorbed from the oral solution (50 minutes) than from the tablet (87 minutes), peak plasma levels and area under the plasma concentration-time curves do not differ significantly. Peak plasma concentrations increase with increasing dose but times-to-peak do not differ among doses. The terminal half-life of furosemide is approximately 2 hours. Significantly more furosemide is excreted in urine following the IV injection than after the tablet or oral solution. There are no significant differences between the two oral formulations in the amount of unchanged drug excreted in urine. Furosemide binding to albumin may be reduced in elderly patients. Furosemide is predominantly excreted unchanged in the urine. The renal clearance of furosemide after intravenous administration in older healthy male subjects (60 to 70 years of age) is statistically significantly smaller than in younger healthy male subjects (20 to 35 years of age). The initial diuretic effect of furosemide in older subjects is decreased relative to younger subjects. ( PRECAUTIONS:Geriatric Use.

INDICATIONS AND USAGE
Furosemide tablets, USP is indicated in adults and pediatric patients for the treatment of edema associated with congestive heart failure, cirrhosis of the liver, and renal disease, including the nephrotic syndrome. Furosemide is particularly useful when an agent with greater diuretic potential is desired. Furosemide tablets, USP may be used in adults for the treatment of hypertension alone or in combination with other antihypertensive agents. Hypertensive patients who cannot be adequately controlled with thiazides will probably also not be adequately controlled with furosemide alone.
Edema
Furosemide tablets, USP is indicated in adults and pediatric patients for the treatment of edema associated with congestive heart failure, cirrhosis of the liver, and renal disease, including the nephrotic syndrome. Furosemide is particularly useful when an agent with greater diuretic potential is desired.
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 -- Edema may be most efficiently and safely mobilized by giving furosemide tablets, USP 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 -- see PRECAUTIONS: Geriatric Use Pediatric patients --

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 -- Edema may be most efficiently and safely mobilized by giving furosemide tablets, USP 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 -- see PRECAUTIONS: Geriatric Use Pediatric patients -- 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 -- Changes in blood pressure must be carefully monitored when furosemide tablets, USP are 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 tablets, USP are added to the regimen. As the blood pressure falls under the potentiating effect of furosemide tablets, USP a further reduction in dosage or even discontinuation of other antihypertensive drugs may be necessary. Geriatric patients -- ( see PRECAUTIONS: Geriatric Use.

ADVERSE REACTIONS
Adverse reactions are categorized below by organ system and listed by decreasing severity. Whenever adverse reactions are moderate or severe, furosemide dosage should be reduced or therapy withdrawn.
Other Reactions
Whenever adverse reactions are moderate or severe, furosemide dosage should be reduced or therapy withdrawn.

Hypertension
Furosemide tablets, USP may be used in adults for the treatment of hypertension alone or in combination with other antihypertensive agents. Hypertensive patients who cannot be adequately controlled with thiazides will probably also not be adequately controlled with furosemide alone.
CONTRAINDICATIONS
Furosemide tablets are contraindicated in patients with anuria and in patients with a history of hypersensitivity to furosemide.
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 -- Changes in blood pressure must be carefully monitored when furosemide tablets, USP are 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 tablets, USP are added to the regimen. As the blood pressure falls under the potentiating effect of furosemide tablets, USP a further reduction in dosage or even discontinuation of other antihypertensive drugs may be necessary. Geriatric patients -- ( see PRECAUTIONS: Geriatric Use

Geriatric Population
Furosemide binding to albumin may be reduced in elderly patients. Furosemide is predominantly excreted unchanged in the urine. The renal clearance of furosemide after intravenous administration in older healthy male subjects (60 to 70 years of age) is statistically significantly smaller than in younger healthy male subjects (20 to 35 years of age). The initial diuretic effect of furosemide in older subjects is decreased relative to younger subjects. ( PRECAUTIONS:Geriatric Use
Pregnancy
PREGNANCY CATEGORY C - Furosemide has been shown to cause unexplained maternal deaths and abortions in rabbits at 2, 4 and 8 times the maximal recommended human dose. There are no adequate and well-controlled studies in pregnant women. Furosemide tablets should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Treatment during pregnancy requires monitoring of fetal growth because of the potential for higher birth weights. The effects of furosemide on embryonic and fetal development and on pregnant dams were studied in mice, rats and rabbits. Furosemide caused unexplained maternal deaths and abortions in the rabbit at the lowest dose of 25 mg/kg (2 times the maximal recommended human dose of 600 mg/day). In another study, a dose of 50 mg/kg (4 times the maximal recommended human dose of 600 mg/day) also caused maternal deaths and abortions when administered to rabbits between Days 12 and 17 of gestation. In a third study, none of the pregnant rabbits survived a dose of 100 mg/kg. Data from the above studies indicate fetal lethality that can precede maternal deaths. The results of the mouse study and one of the three rabbit studies also showed an increased incidence and severity of hydronephrosis (distention of the renal pelvis and, in some cases, of the ureters) in fetuses derived from the treated dams as compared with the incidence in fetuses from the control group.
Nursing Mothers
Because it appears in breast milk, caution should be exercised when furosemide tablets are administered to a nursing mother. Furosemide tablets may inhibit lactation.
Pediatric Use
In premature infants furosemide tablets 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 tablets. Monitor renal function, and renal ultrasonography should be considered, in pediatric patients receiving furosemide tablets. If furosemide tablets are 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 DOSAGE AND ADMINISTRATION

Furosemide tablets may increase the ototoxic potential of aminoglycoside antibiotics, especially in the presence of impaired renal function. Except in life-threatening situations, avoid this combination. Furosemide tablets should not be used concomitantly with ethacrynic acid because of the possibility of ototoxicity. Patients receiving high doses of salicylates concomitantly with furosemide, as in rheumatic disease, may experience salicylate toxicity at lower doses because of competitive renal excretory sites. There is a risk of ototoxic effects if cisplatin and furosemide tablets are given concomitantly. In addition, nephrotoxicity of nephrotoxic drugs such as cisplatin may be enhanced if furosemide tablet is not given in lower doses and with positive fluid balance when used to achieve forced diuresis during cisplatin treatment. Furosemide tablets have a tendency to antagonize the skeletal muscle relaxing effect of tubocurarine and may potentiate the action of succinylcholine. Lithium generally should not be given with diuretics because they reduce lithium’s renal clearance and add a high risk of lithium toxicity. Furosemide tablets combined with angiotensin converting enzyme inhibitors or angiotensin II receptor blockers may lead to severe hypotension and deterioration in renal function, including renal failure. An interruption or reduction in the dosage of furosemide tablets, angiotensin converting enzyme inhibitors, or angiotensin receptor blockers may be necessary. Potentiation occurs with ganglionic or peripheral adrenergic blocking drugs. Furosemide may decrease arterial responsiveness to norepinephrine. However, norepinephrine may still be used effectively. Simultaneous administration of sucralfate and furosemide tablets may reduce the natriuretic and antihypertensive effects of furosemide. Patients receiving both drugs should be observed closely to determine if the desired diuretic and/or antihypertensive effect of furosemide is achieved. The intake of furosemide and sucralfate should be separated by at least two hours. In isolated cases, intravenous administration of furosemide within 24 hours of taking chloral hydrate may lead to flushing, sweating attacks, restlessness, nausea, increase in blood pressure, and tachycardia. Use of furosemide concomitantly with chloral hydrate is therefore not recommended. Phenytoin interferes directly with renal action of furosemide tablets. There is evidence that treatment with phenytoin leads to decrease intestinal absorption of furosemide tablets, and consequently to lower peak serum furosemide concentrations. Methotrexate and other drugs that, like furosemide tablets, undergo significant renal tubular secretion may reduce the effect of furosemide tablets. Conversely, furosemide tablets may decrease renal elimination of other drugs that undergo tubular secretion. High- dose treatment of both furosemide tablets and these other drugs may result in elevated serum levels of these drugs and may potentiate their toxicity as well as the toxicity of furosemide tablets. Furosemide tablets can increase the risk of cephalosporin-induced nephrotoxicity even in the setting of minor or transient renal impairment. Concomitant use of cyclosporine and furosemide is associated with increased risk of gouty arthritis secondary to furosemide-induced hyperurecemia and cyclosporine impairment of renal urate excretion. One study in six subjects demonstrated that the combination of furosemide and acetylsalicylic acid temporarily reduced creatinine clearance in patients with chronic renal insufficiency. There are case reports of patients who developed increased BUN, serum creatinine and serum potassium levels, and weight gain when furosemide was used in conjunction with NSAIDs. Literature reports indicate that coadministration of indomethacin may reduce the natriuretic and antihypertensive effects of furosemide in some patients by inhibiting prostaglandin synthesis. Indomethacin may also affect plasma renin levels, aldosterone excretion, and renin profile evaluation. Patients receiving both indomethacin and furosemide should be observed closely to determine if the desired diuretic and/or antihypertensive effect of furosemide is achieved.

WARNINGS
In patients with hepatic cirrhosis and ascites, furosemide tablets therapy is best initiated in the hospital. In hepatic coma and in states of electrolyte depletion, therapy should not be instituted until the basic condition is improved. Sudden alterations of fluid and electrolyte balance in patients with cirrhosis may precipitate hepatic coma; therefore, strict observation is necessary during the period of diuresis. Supplemental potassium chloride and, if required, an aldosterone antagonist are helpful in preventing hypokalemia and metabolic alkalosis. If increasing azotemia and oliguria occur during treatment of severe progressive renal disease, furosemide tablets should be discontinued. Cases of tinnitus and reversible or irreversible hearing impairment and deafness have been reported. Reports usually indicate that furosemide ototoxicity is associated with rapid injection, severe renal impairment, the use of higher than recommended doses, hypoproteinemia or concomitant therapy with aminoglycoside antibiotics, ethacrynic acid, or other ototoxic drugs. If the physician elects to use high dose parenteral therapy, controlled intravenous infusion is advisable (for adults, an infusion rate not exceeding 4 mg furosemide per minute has been used) (See PRECAUTIONS: Drug Interactions ).
Carcinogenesis,Mutagenesis, Impairment of Fertility
Furosemide was tested for carcinogenicity by oral administration in one strain of mice and one strain of rats. A small but significantly increased incidence of mammary gland carcinomas occurred in female mice at a dose 17.5 times the maximum human dose of 600 mg. There were marginal increases in uncommon tumors in male rats at a dose of 15 mg/kg (slightly greater than the maximum human dose) but not at 30 mg/kg. Furosemide was devoid of mutagenic activity in various strains of Salmonella typhimurium in vitro in vitro Saccharomyces cerevisiae. Furosemide produced no impairment of fertility in male or female rats, at 100 mg/kg/day (the maximum effective diuretic dose in the rat and 8 times the maximal human dose of 600 mg/day).
OVERDOSAGE
The principal signs and symptoms of overdose 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 50 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.

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