Adult: Adjunct: Initially, 40 mg via slow inj over 1-2 minutes, may be increased to 80 mg given via slow inj if satisfactory response is not achieved within 1 hour.
Oral Hypertension
Adult: Alone or in combination with other antihypertensives: 40-80 mg daily, adjusted according to patient response. Alternatively, usual maintenance dose of 20-40 mg daily may be given. Elderly: Initiate at lower doses.
Oral Oliguria in acute or chronic renal failure
Adult: In patients with chronic renal insufficiency: Initially, 250 mg, may be increased in increments of 250 mg every 4-6 hours if satisfactory response is not achieved. Max: 1,500 mg 24 hourly. Elderly: Initiate at lower doses.
Oral Oedema
Adult: Cases associated with CHF, liver cirrhosis, and renal disease, including nephrotic syndrome: Initially, 40 mg daily preferably in the morning, adjusted as necessary according to patient response. Mild cases may respond to 20 mg daily or 40 mg on alternate days. In some cases, 80 mg or more daily in 1 or 2 divided doses may be required. Child: Usual dose: 1-3 mg/kg daily. Max: 40 mg daily. Elderly: Initiate at lower doses.
Parenteral Oedema
Adult: Initially, 20-50 mg via slow IV or IM inj, may be increased in increments of 20 mg every 2 hours if necessary. Doses >50 mg must be given via slow IV infusion at a Max rate of 4 mg/minute. Max: 1,500 mg daily. Child: 0.5-1.5 mg/kg daily. Max: 20 mg daily. Elderly: Initiate at lower doses.
Renal Impairment
Parenteral: Oedema: Severe: Max IV infusion rate: 2.5 mg/minute.
Administration
oral soln: May be taken with or without food. May be taken w/o meals for better absorption. May be taken w/ meals to reduce GI discomfort.
Reconstitution
IV infusion: Dilute with 0.9% NaCl, lactated Ringer’s, and 5% dextrose infusion solutions, adjusting the pH to more than 5.5 when necessary.
Incompatibility
Incompatible with injections of amrinone, ciprofloxacin, diazepam, diltiazem hydrochloride, dobutamine hydrochloride, dopamine hydrochloride, droperidol, doxorubicin, gentamicin, isoprenaline, labetalol hydrochloride, lidocaine, metoclopramide, midazolam hydrochloride, milrinone lactate, morphine, pethidine, nicardipine hydrochloride, vecuronium bromide, parenteral nutrient solutions, cisatracurium besilate, levofloxacin, phenylephrine, vasopressin, vincristine. May be precipitated with strongly acidic solutions such as infusions with ascorbic acid, epinephrine, norepinephrine, and tetracycline.
Contraindications
Hypersensitivity to furosemide and sulfonamides. Anuria, renal failure with anuria not responding to furosemide; renal failure due to poisoning by nephrotoxic or hepatotoxic agents; renal failure associated with hepatic coma, electrolyte disturbances (e.g. severe hyponatraemia, severe hypokalaemia), hypovolaemia, dehydration, hypotension; comatose or pre-comatose states associated with liver cirrhosis or encephalopathy; Addison’s disease, porphyria, digitalis intoxication. Lactation.
Special Precautions
Patient with prediabetes or diabetes mellitus; prostatic hyperplasia, urinary stricture, impaired micturition, gout, hepatorenal syndrome, hypoproteinaemia (e.g. nephrotic syndrome), cirrhosis, acute hypercalcaemia; at risk from a pronounced fall in blood pressure (e.g. significant coronary or cerebral artery stenosis). Not recommended in patients at high risk for radiocontrast nephropathy. Renal and hepatic impairment. Children and elderly. Pregnancy.
Adverse Reactions
Significant: Fluid and electrolyte depletion, symptomatic hypotension, asymptomatic hyperuricaemia, nephrotoxicity, ototoxicity (e.g. hearing disorders, tinnitus, deafness [sometimes irreversible]), photosensitivity, sulfonamide allergy, urinary retention, SLE exacerbation or activation; nephrocalcinosis or nephrolithiasis (in premature infants), decreased glucose tolerance, transient increase in free thyroid hormones. Blood and lymphatic system disorders: Haemoconcentration. Rarely, agranulocytosis, thrombocytopenia, leucopenia. Eye disorders: Blurred vision. Gastrointestinal disorders: Nausea, vomiting, diarrhoea, constipation. General disorders and administration site conditions: Fatigue, pain at inj site (IM). Investigations: Increased creatinine, serum cholesterol and triglycerides; increased blood urea and urine volume. Immune system disorders: Rarely, severe anaphylactic or anaphylactoid reactions. Metabolism and nutrition disorders: Dehydration, hyponatraemia, hypokalaemia, hypochloraemia, metabolic alkalosis, hypocalcaemia, hypomagnesaemia, hypovolaemia, gout. Musculoskeletal and connective tissue disorders: Muscle spasms. Nervous system disorders: Headache, dizziness, hepatic encephalopathy (in patient with hepatic insufficiency), paraesthesia. Skin and subcutaneous tissue disorders: Rash, pruritus, urticaria, erythema multiforme. Vascular disorders: Orthostatic hypotension.
This drug may cause reduced mental alertness, dizziness, and blurred vision, if affected, do not drive or operate machinery.
Monitoring Parameters
Correct hypovolaemia, hypotension, and severe electrolyte disturbances prior to treatment initiation. Monitor blood pressure, serum electrolytes (e.g. serum Na, K), renal function, and blood glucose levels periodically; orthostasis, hearing (on high doses or rapid IV administration).
Overdosage
Symptoms: Profound diuresis resulting in dehydration, blood volume reduction, hypotension, electrolyte imbalance, hypokalaemia, hypotension, tachycardia, and hypochloraemic alkalosis. Management: Symptomatic and supportive treatment. Replacement of excessive fluid and electrolyte losses. May consider giving activated charcoal within 1 hour of ingesting toxic doses. Ensure adequate drainage in patients with urinary bladder outlet obstruction (e.g. prostatic hypertrophy). Treat dehydration and hypotension with appropriate IV fluids.
Drug Interactions
Increased risk of hyperkalaemia with K-sparing diuretics (e.g. amiloride, spironolactone) and K salts. Diuretic effects may be antagonised by NSAIDs (e.g. indometacin, ketorolac), and reduced by phenytoin, probenecid, methotrexate. May cause severe hypotension with ACE inhibitors or angiotensin II receptor antagonists. Increased risk of cardiotoxicity with cardiac glycosides, antihistamines, antipsychotics (e.g. pimozide, risperidone). May enhance the nephrotoxic effects of aminoglycosides, cisplatin, cephalosporins. May increase the risk of ototoxicity with aminoglycosides, polymyxin, vancomycin, cisplatin, ethacrynic acid, and other ototoxic drugs. Reduced serum level with aliskiren. May increase the serum levels of lithium. May antagonise the hypoglycaemic effects of antidiabetics. Enhanced hypotensive effect with MAOIs. Increased risk of hyponatraemia with carbamazepine. Gastrointestinal absorption may be decreased by sucralfate. May potentiate the effects of salicylates causing toxicity. Increased risk of gouty arthritis with ciclosporin.
Food Interaction
Hypotensive effect may be enhanced by alcohol.
Lab Interference
May result in false-negative aldosterone/renin ratio (ARR).
Action
Description: Furosemide is an anthranilic acid derivative and a potent diuretic. It mainly inhibits the reabsorption of Na and chloride in the ascending loop of Henle and in both the proximal and the distal renal tubules. It also interferes with the chloride-binding cotransport system, thereby causing its natriuretic effect.
Synonym: frusemide. Onset: Diuresis: 30-60 minutes (oral); approx 5 minutes (IV). Symptomatic improvement in acute pulmonary oedema: Within 15-20 minutes prior to diuretic effect. Duration: 6-8 hours (oral); 2 hours (IV). Pharmacokinetics: Absorption: Incompletely but rapidly absorbed from the gastrointestinal tract. Bioavailability: 47-64% (oral tab); 50% (oral solution). Time to peak plasma concentration: 1-2 hours (oral); 30 minutes (IV). Distribution: Crosses the placenta and enters breast milk. Volume of distribution: 0.1-0.2 L/kg; may be higher based on the disease. Plasma protein binding: 91- 99%, mainly to albumin. Metabolism: Undergoes minimal hepatic metabolism. Excretion: Mainly via urine (oral: 50%, IV: 80%) within 24 hours; faeces (as unchanged drug). Elimination half-life: 0.5-2 hours (normal renal function); 9 hours (ESRD).
Chemical Structure
Furosemide Source: National Center for Biotechnology Information. PubChem Database. Furosemide, CID=3440, https://pubchem.ncbi.nlm.nih.gov/compound/Furosemide (accessed on Jan. 21, 2020)
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