Undesirable effects can occur with the following frequencies: Very common (≥1/10), Common (≥1/100 to <1/10), Uncommon (≥1/1,000 to <1/100), Rare (≥1/10,000 to <1/1,000), Very rare (<1/10,000, including isolated reports), not known (cannot be estimated from the available data).
Blood and lymphatic system disorders:
Uncommon: thrombocytopenia.
Rare: eosinophilia, leukopenia, bone marrow depression which necessitates withdrawal of treatment. The hematopoietic status should be therefore regularly monitored.
Very rare: agranulocytosis, aplastic anaemia, haemolytic anaemia.
Immune system disorders:
Severe anaphylactic or anaphylactoid reactions (e.g. with shock) occur rarely.
The incidence of allergic reactions, such as skin rashes, photosensitivity, vasculitis, fever, interstitial nephritis or shock is very low, but when these occur treatment should be withdrawn.
Metabolism and nutrition disorders:
Electrolyte and water balance may be disturbed as a result of diuresis. Furosemide causes increased excretion of sodium and chloride and consequently water, and hyponatraemia may occur. The diuretic action of furosemide may lead to or contribute towards hypovolaemia and dehydration, especially in elderly patients. Severe fluid depletion may lead to haemoconcentration with a tendency for thromboses to develop.
Excretion of other electrolytes is increased, and hypokalaemia, serum calcium depletion and hypomagnesaemia may occur. Symptomatic electrolyte disturbances and metabolic alkalosis may develop following gradual electrolyte depletion or acute severe electrolyte losses during higher dose therapy administered to patients with normal renal function.
Pre-existing metabolic alkalosis (e.g. in decompensated cirrhosis of the liver) may be aggravated by furosemide treatment.
Warning signs of electrolyte disturbances depend on the type of disturbances.
Sodium deficiency can manifest itself as: confusion, muscle cramps, muscle weakness, loss of appetite, dizziness, drowsiness and vomiting.
Potassium deficiency can manifest itself as: muscular weakness, paralysis, gastrointestinal symptoms (vomiting, constipation and meteorism), renal symptoms (polyuria) or cardiac symptoms. Severe potassium depletion can result in paralytic ileus or confusion, which can result in coma.
Magnesium and calcium deficiency result very rarely in tetany and heart rate disturbances.
Metabolic acidosis can also occur. The risk of this abnormality increases at higher doses and is influenced by the underlying disorder (e.g. liver cirrhosis, heart failure), concomitant medications (see section 4.5) and diet.
Serum cholesterol (reduction of serum HDL-cholesterol, elevation of serum LDL-cholesterol) and triglyceride levels may rise during furosemide treatment. During long-term therapy they will usually return to normal within six months.
As with other diuretics, treatment with furosemide may lead to transitory increase in blood creatinine and urea levels. Furosemide may increase the levels of uric acid and precipitate gout.
Endocrine disorders:
Furosemide may provoke hyperglycaemia and glycosuria but less so than thiazide diuretics. Glucose tolerance may decrease with furosemide. In patients with diabetes mellitus, this may lead to a deterioration of control; latent diabetes mellitus may become manifest and insulin requirements of diabetic patients may increase (see section 4.4).
Psychiatric/Nervous system disorders:
Rarely paraesthesia and hyperosmolar coma may occur.
Not known: dizziness, fainting and loss of consciousness (caused by symptomatic hypotension).
Symptoms of hypotension may also include dizziness, light-headedness, sensation of pressure in the head, headache, drowsiness, concentration impairment and slowed reactions. Headache, lethargy or confusion may be warning signs of electrolyte disturbances.
Eye disorders:
Uncommon: visual disturbances, blurred vision.
Ear and labyrinth disorders:
Hearing disorders, including deafness and tinnitus, may occur in rare cases, particularly in patients with renal failure, hypoproteinaemia (e.g. nephritic syndrome) and/or when intravenous furosemide has been given too rapidly. Although symptoms are usually transient, deafness (sometimes irreversible) (uncommon) may occur, especially in patients treated with other ototoxic medications (see section 4.4 and section 4.5).
Cardiac disorders:
Cardiac rhythm disturbances (uncommon) may occur as a consequence of electrolyte imbalance.
If furosemide is administered to premature infants during the first weeks of life, it may increase the risk of persistence of patent ductus arteriosus.
Vascular disorders:
Hypotension and orthostatic hypotension may occur, especially in patients taking other medications which lower blood pressure.
Allergic vasculitis has been reported very rarely.
Gastrointestinal disorders:
Nausea, vomiting, diarrhoea, constipation, dry mouth, thirst, bowel motility disturbances are uncommon but are not usually severe enough to necessitate withdrawal of treatment.
Hepatobiliary disorders:
Hepatic encephalopathy in patients with hepatocellular insufficiency may occur (see section 4.3).
In isolated cases, intrahepatic cholestasis, an increase in liver transaminases or acute pancreatitis (rare) may develop.
Skin and subcutaneous tissue disorders:
Uncommon: photosensitivity
Rare: skin and mucous membrane reactions may occasionally occur eg pruritis, urticaria, other rashes or bullous lesions, hypersensitivity to light, erythema multiforme, bullous pemphigoid, Stevens-Johnson syndrome, toxic epidermal necrolysis (Lyell's Syndrome), exfoliative dermatitis, purpura, acute generalised exanthematous pustulosis (AGEP) and drug rash with eosinophilia and systemic symptoms (DRESS).
Not known: Lichenoid reactions.
Musculoskeletal and connective tissue disorders:
Serum calcium levels may be reduced, muscle spasms or muscle weakness may indicate electrolyte disturbances. In very rare cases tetany has been observed.
Renal and urinary disorders:
Treatment with furosemide may lead to transient increases in blood creatinine and urea levels (uncommon). Renal failure may occur (rarely) as a consequence of fluid and electrolyte depletion, especially during concurrent treatment with NSAIDs or nephrotoxic medications.
Increased production of urine may provoke or aggravate complaints in patients with an obstruction of urinary outflow. Acute retention of urine with possible secondary complications may occur, for example, in patients with bladder emptying disorders, prostatic hyperplasia or narrowing of the urethra (see section 4.4).
Nephrocalcinosis/nephrolithiasis has been reported in premature infants and in adults, generally after long-term therapy.
There have been rare reports of interstitial nephritis.
General disorders and administration site conditions:
Uncommon: asthenia.
Rare: malaise, fever.
Following intramuscular injection, local reactions such as pain may occur.
Pregnancy, puerperium and perinatal conditions:
In premature infants with respiratory distress syndrome, administration of furosemide during the first weeks of life may increase the risk of persistence of patent ductus arteriosus.
In premature infants, furosemide can be precipitated as nephrocalcinosis/ kidney stones.
Rare complications may include minor psychiatric disturbances.
Reporting of suspected adverse reactions
Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via Yellow Card Scheme, Website: www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store.