Furosemide
loop diuretic
Third-party optionBy the Layer Nutrition editorial team · How the atlas classifies the 664 molecules
What this medicine is for
Furosemide belongs to the 'loop diuretic' category. Diuretics help the kidneys eliminate water and salt, which lowers blood pressure and relieves oedema.
In the case of Furosemide, this means: Strongly increases the elimination of water and salt (oedema, heart failure). It is generally taken over the long term, within regular monitoring, and is not stopped on your own initiative.
Under which brands it is found
In France, about 15 reimbursable presentations containing Furosemide are recorded. It is found under several brand names and as generics.
- Furosemide Accord
- Furosemide Arrow
- Furosemide Biogaran
- Furosemide Eg
- Furosemide Kalceks
- Furosemide Lavoisier
- Furosemide Renaudin
- Furosemide Sandoz
- and other presentations
Original brand-name products and generics deliver the same active substance; the choice between them is made with your doctor or pharmacist.
On the plate: potassium and magnesium
On furosemide, the body loses more potassium and magnesium through the urine. Food helps rebuild these stores meal after meal.
Potassium is found in many fruits and vegetables. Among fruits: dried apricots, prunes, raisins, orange juice and banana. Among vegetables: potato, spinach, tomato and broccoli. Legumes such as beans and lentils also provide a good share.
Magnesium comes mainly from green leafy vegetables such as spinach, from legumes, nuts and seeds, as well as from whole grains. Several of these foods bring both minerals together, like spinach and lentils: including them in your meals covers a large part of your needs, alongside your treatment.
How furosemide works
Furosemide is a loop diuretic. It acts in the kidney, on the thick ascending limb of the loop of Henle, where it blocks the sodium-potassium-2 chloride co-transporter, known as NKCC2. This transporter is the gateway through which sodium, potassium and chloride pass back from the urinary tubule into the blood. By inhibiting it, furosemide prevents this reabsorption, and both salt and water leave in greater quantity in the urine.
This action is powerful. At the molecular level, the NKCC2 co-transporter is itself regulated, after furosemide administration, by the cyclic GMP pathway and cGMP-dependent protein kinase I. By reducing the volume of water and salt retained by the body, furosemide relieves edema and helps lower blood pressure.
Why furosemide is prescribed
Furosemide is used first of all to clear an excess of fluid. It is indicated in the treatment of edema associated with congestive heart failure, liver cirrhosis and kidney diseases, including nephrotic syndrome. Taken orally, it can also be used in arterial hypertension, when the doctor seeks to reduce blood volume.
Its effect is rapid. After an oral dose, diuresis begins within 30 to 60 minutes, the maximum effect occurs within the first or second hour, and the duration of action is about 6 to 8 hours. The terminal half-life is around 2 hours, which explains a strong but relatively short action, to be repeated as prescribed.
How to take it day to day
Furosemide is usually taken once a day, in the morning. Since a dose acts for about 6 hours and increases urination, it is better not to take it after 4 p.m. or in the evening, otherwise you may have to get up during the night. Its oral absorption is incomplete and variable: in healthy fasting adults, bioavailability is about 64 percent from tablets and 60 percent from the oral solution, compared with intravenous injection.
Food intake can alter this absorption, which makes regularity all the more useful: keeping the same time and the same conditions from one day to the next stabilizes the effect. The treatment should not be stopped on your own, because interrupting the diuretic can allow water retention to return. Any dose change is decided with the doctor, who monitors blood pressure and symptoms.
The effects to know about
By strongly increasing the elimination of salt and water, furosemide also shifts the balance of electrolytes. It can cause electrolyte abnormalities, such as hyponatremia, hypochloremia, hypokalemia and hypomagnesemia. Their frequency and intensity depend on the cumulative dose, which laboratory monitoring makes it possible to control.
Ototoxicity is a rarer effect: hearing disturbances that are most often transient and, exceptionally, permanent. It occurs mainly with high intravenous doses or during a rapid infusion, in cases of kidney failure, or when furosemide is combined with other drugs toxic to the ear such as aminoglycosides. These situations belong to the hospital setting rather than to daily oral use.
What furosemide causes you to lose in minerals and vitamin B1
Beyond sodium, the inhibition of NKCC2 changes the transport of other minerals. By blocking this transporter in the thick ascending limb, furosemide dissipates the transepithelial electrical gradient and causes a marked urinary loss of calcium and magnesium. Magnesium depletion, or hypomagnesemia, is a frequent effect of loop diuretics, which makes magnesium one of the minerals to keep an eye on.
Furosemide also affects a water-soluble vitamin, thiamine, or vitamin B1. It increases its urinary excretion in a dose-dependent way: a study in healthy volunteers showed that low doses, given intravenously, already increase this loss. In heart failure patients treated over the long term, several works report varying degrees of thiamine deficiency, especially at high doses; the main mechanism is the increased urine output, with a possible direct inhibition of the cellular uptake of the vitamin.
Interactions and monitoring
Furosemide is involved in several interactions worth knowing. Non-steroidal anti-inflammatory drugs reduce its effectiveness and increase the renal risk. Its combination with aminoglycosides raises the risk of damage to the ear and kidney. It increases lithium levels, with a risk of lithium toxicity. Finally, the hypokalemia and hypomagnesemia it induces increase the toxicity of digoxin, which calls for particular vigilance in patients treated with this drug.
Monitoring therefore accompanies the treatment from start to finish. It relies on checking serum electrolytes, namely sodium, potassium, chloride, magnesium and calcium, on monitoring kidney function, blood pressure and symptoms, including hearing. This follow-up makes it possible to adjust the dose and to spot an imbalance early, in order to get the best from the diuretic while limiting its risks.
Sources
- Furosemide
- Regulation of the Na+-K+-2Cl- cotransporter by cGMP/cGMP-dependent protein kinase I after furosemide administration
- Furosemide tablet
- How and when to take furosemide
- Cumulative doses predict the risk of furosemide-induced electrolyte abnormalities
- Loop Diuretics
- Molecular mechanisms of loop diuretics on renal calcium and magnesium transport
- Urinary loss of thiamine is increased by low doses of furosemide in healthy volunteers
- Does Long-Term Furosemide Therapy Cause Thiamine Deficiency in Patients with Heart Failure? A Focused Review
- A Comprehensive Review of the Pharmacologic Perspective on Loop Diuretic Drug Interactions with Therapeutically Used Drugs
- Potassium Fact Sheet for Consumers
- Magnesium Fact Sheet for Consumers
Related molecules
To explore in the « Heart and blood pressure » family and its neighbours.
See the whole « Heart and blood pressure » family · Back to the atlas
Supplements to consider
Beyond the plate, a single isolated nutrient can be worth discussing, to confirm with your doctor or pharmacist. Here is which one and in which form.
Magnesium
Magnesium is a mineral involved in many enzymatic reactions. Supplements differ mainly by their salt: organic forms such as bisglycinate and citrate are better tolerated digestively and better absorbed than oxide.
Preferred form bisglycinate or citrate rather than oxide
Potassium
Potassium is an electrolyte mineral. As a supplement, potassium citrate is a well-tolerated and bioavailable form; the elemental potassium content per capsule remains moderate owing to regulatory limits.
Preferred form potassium citrate
Frequently asked questions
What is furosemide used for?
Furosemide is a loop diuretic: it increases the urinary elimination of water and salt, in situations such as fluid retention or high blood pressure. It is a prescription medicine. For your specific indication, refer to the leaflet and to your doctor or pharmacist.
What are the side effects of furosemide?
The leaflet notably mentions increased urination and electrolyte imbalances, in particular a drop in potassium. Possible effects vary from one person to another: read the leaflet and report any symptom to your doctor or pharmacist.
Does furosemide interact with other medications?
Yes, the leaflet flags interactions, for example with lithium, certain aminoglycoside antibiotics and anti-inflammatory drugs (NSAIDs). Do not combine anything without confirmation: tell your doctor or pharmacist about all of your treatments and check the leaflet.
Can furosemide affect magnesium levels?
The literature on loop diuretics describes an increased urinary elimination of magnesium and potassium. A blood test, ordered and interpreted by your doctor, helps assess your situation.
Which form of magnesium to consider while taking a loop diuretic?
If magnesium intake is relevant for you, magnesium in the bisglycinate form is generally well tolerated by the digestive system. Raise the question with your doctor, who will place it within your follow-up.
What about potassium, should you take it as a supplement?
Potassium is strictly the doctor's domain when on a diuretic: it is monitored with a blood test and is never added over the counter. Note that research links a magnesium deficiency to hypokalemia that is harder to correct, which makes medical follow-up all the more important.
Ces réponses portent sur le volet nutritionnel. Pour toute question sur votre médicament, la notice et votre médecin ou pharmacien font foi.