Frusax - Diuretic | Precautions | Effects

This article was medically reviewed by M.Pharm, Marko Tanaskovic on August 12, 2018. To read more about an author, click here.

Frusax is a medicine containing an active substance called furosemide (frusemide). It belongs to a group of medicines called loop diuretics. It works by reducing the absorption of water and increasing the excretion of sodium and chlorine, thereby exerting diuretic effect (increases the water excretion from the body). Increasing the excretion of water from the body reduces edema and blood pressure, as the volume of fluid in the blood vessels decreases. Frusax belongs to one of the most potent diuretics.

Frusax is used in the treatment of edema and hypertension.


Frusax is contraindicated in patients with anuria - a condition characterized by exceptionally reduced urinary excretion (less than 100 ml / day) or complete cessation of urinary secretion by the kidneys.

Frusax must be used with extra precaution in patients who have liver damage, as studies in mice have shown that Frusax can cause centrilobular liver necrosis. Frusax is not recommended for use in patients with liver cirrhosis, as it can cause an electrolyte imbalance that can lead to hepatic coma.

If you are experiencing decreased urine output (oliguria) while taking Frusax, you should call your doctor immediately.

Cases of temporary or permanent deafness have been reported in patients who used this medicine. In order to reduce the risk of deafness, it is recommended to maintain Frusax concentration in the blood below 50 mcg / ml. If an appropriate diuretic effect is not achieved in concentrations below 50 mcg / ml, it is recommended to replace Frusax with another diuretic.

Cases of acute pancreatitis have been reported in patients using Frusax. If you are experiencing constant, severe abdominal pain in the upper abdomen, you should contact your doctor immediately.

Keep in mind that Frusax can cause vitamin B1 (thiamine) deficiency, and its use is not recommended in patients who already have a deficiency of this vitamin.

In some patients, Frusax can cause excessive urination that can lead to electrolyte imbalance, dehydration, and circulatory collapse. Frusax can also cause a decrease in potassium levels in the blood (hypokalaemia), which can cause serious cardiac arrhythmias. The risk of hypokalaemia is higher in patients taking corticosteroids, laxatives, or not getting enough potassium through the diet.

Careful monitoring of patients (especially at the beginning of therapy) is recommended in order to detect possible signs of electrolyte imbalance in a timely manner. Tell your doctor if you are experiencing any of the following symptoms: rapid heart rate, irregular heartbeat (arrhythmia), dry mouth, excessive thirst, dizziness, muscle cramps, low blood pressure, nausea or vomiting.

Patients who have prostatic hypertrophy or constriction of the urethra should use Frusax with extra precaution because its use in such patients can aggravate the condition.

Frusax may exhibit somewhat weaker diuretic effect in patients who have increased amounts of protein in the urine.

Frusax increases the blood glucose levels as well as levels of glucose in the urine, so caution should be exercised when Frusax is administered in diabetics.

Frusax is absolutely contraindicated in patients who are allergic to the active substance furosemide or medications belonging to the family of sulfonamides (antibiotics). People who are allergic to sulfonamides are likely to be allergic to Frusax as well.

Frusax, Pregnancy and Breastfeeding

The FDA classifies this drug in group C because animal studies have shown that administration of doses that are 2, 4 or 8 times higher than the maximum recommended doses in humans can cause abortion. For this reason, the use of Frusax during pregnancy is not recommended.

Frusax is excreted in breast milk and its use during breastfeeding is not recommended.


The recommended initial dose in the treatment of edema in adult patients is 20-80 mg once a day. The dose can be gradually increased to a maximum of 600 mg per day (this dose is used only in the treatment of severe edema). Frusax is best taken once a day in the morning or twice a day (e.g. at 9AM and 3PM). Careful monitoring of patients using doses greater than 80 mg daily for a long period of time is required.

The usual initial dose in the treatment of edema in children is 2 mg / kg of body weight once a day. The dose may be increased to a maximum of 6 mg / kg body weight.

The usual dose in the treatment of hypertension in adult patients is 40 mg twice daily (in the morning and at noon). If an appropriate antihypertensive effect is not achieved with this dose, it is recommended to initiate additional antihypertensive medicines.

Frusax can be administered regardless of the meal.


Frusax should not be used concurrently with the following medicines:

  • Aminoglycoside antibiotics, such as: gentamicin, streptomycin, neomycin, tobramycin, kanamycin, and amikacin. These drugs may cause nephrotoxicity and hearing loss, and concurrent use with Frusax increases this risk.
  • Lithium (antipsychotic). Frusax can increase lithium levels in the blood which significantly increases the risk of side effects.
  • Sodium biphosphate - medicine used to clean and empty the bowel prior to colonoscopy. Sodium biphosphate can cause nephrotoxic effects (sometimes months after administration) as well as Frusax, which is why concomitant administration is not recommended.
  • Etecalcetide (brand name Parsabiv) - medicine used to treat secondary hyperparathyroidism. Concurrent use can lead to hypocalcaemia.

Concurrent use with the following medicines can cause severe cardiac arrhythmias:

  • Antiarrhythmic drugs, such as: amiodarone, dronedarone, and dofetilide.
  • Pimozide, haloperidol, droperidol and ziprasidone (antipsychotics).
  • Arsenic trioxide - medicine used in the treatment of leukemia.
  • Cisapride - medicine used in the treatment of gastroesophageal reflux.
  • 5HT-3 receptor antagonists, such as: dolasetron, ondansetron, granisetron, palonosetron, and tropisetron. These drugs are used to treat nausea that occurs due to chemotherapy.

Tell your doctor about all the medicines you are taking.

Side Effects

Frusax can cause the following side effects:

  • Hepatotoxicity.
  • Diarrhea.
  • Acute pancreatitis characterized by severe abdominal pain.
  • Muscle contraction.
  • Nausea.
  • Vomiting.
  • Anemia.
  • Decrease in the number of blood platelets.
  • Decrease in the number of white blood cells.
  • Dizziness.
  • Headache.
  • Stevens-Johnson syndrome.
  • Erythema multiforme.
  • Photosensitivity.
  • Increase in blood glucose levels.
  • Glucose tolerance disorder.
  • Increase in urine glucose levels.
  • Hypotension.
  • Vasculitis.
  • Thrombotic disorders.
  • Fatigue.
  • Fever.
  • Increased amount of sodium excreted in the urine.
  • Urinary retention.
  • Temporary or permanent hearing loss.
  • Increase in creatinine levels in the blood.
  • Increase in triglyceride levels in the blood.

Tell your doctor if you are experiencing any side effects.


  1. NCBI link 1
  2. NCBI link 2
  3. NCBI link 3
  4. NCBI link 4
  5. NCBI link 5

Information on this website are provided for educational purposes only and are not intended for medical advice, diagnosis or treatment.

If you have any concerns or questions about your health, you should always consult with a physician or other health-care professional.

We and our partners use technology such as cookies on our site to personalise content and ads, provide social media features, and analyse our traffic. Click below to consent to the use of this technology across the web. You can change your mind and change your consent choices at anytime by returning to this site.