Furosemide for Edema

Furosemide works as a diuretic to help the kidneys excrete excess fluid and salt from your body. It can help reduce swelling and water retention. 

There are several causes for edema, and it’s important to consult with your doctor to identify the cause of your edema and determine which medication would help to alleviate the symptoms. 

There are basically three classes of diuretics, namely potassium-sparing diuretics, loop diuretics, and thiazide diuretics. Furosemide is a type of loop diuretic, which is commonly used to treat edema and congestive heart failure. 

You may identify Furosemide by Lasix, which is one of the brand names Furosemide is sold under. Lasix is the popular brand for this diuretic. 

What Is Furosemide?

Furosemide is recommended for treating edema especially when the edema does not respond to thiazide diuretics. It is especially effective for edema associated with heart failure, liver cirrhosis, renal impairment, and nephrotic conditions.

It is available as tablets of different strengths (20 mg, 40 mg, and 80 mg). It is also sold as oral solutions in the following concentrations (10 mg/mL and 8 mg/mL) as well as an injectable 10 mg/mL solution.

Although there are many brand names for furosemide now, Lasix remains the most popular. The name is derived from the last six hours, which is the duration of action of injectable furosemide (intramuscular injection since oral and intravenous Lasix last between two and four hours).

Furosemide is the diuretic of choice when other types of diuretics do not effectively treat a patient’s edema.

However, when the edema is resistant to all diuretics especially when the dose of the administered diuretic is already increased to its therapeutic limit, furosemide is combined with human albumin to provide immediate relief. Human albumin helps improve the efficacy of the diuretic.

Injectable forms of furosemide are also extensively used in veterinary medicine.

How Furosemide Works

The site of action of furosemide is the thick ascending limb of the loop of Henle in the nephrons of the kidneys. It specifically inhibits a symporter (a transporter responsible for the movement of multiple ions across membranes) which transports sodium, potassium, and chloride ions. This symporter is designated NKCC2.

When furosemide blocks this symporter, it prevents the reabsorption of sodium and chloride ions. Since the same symporter controls potassium reabsorption, potassium ions are also prevented from returning to the blood.

This inhibition reduces the electric potential of the lumen of the nephron at the site of action of furosemide.

By preventing the reabsorption of potassium ions, the reabsorption of divalent ions (such as calcium and magnesium) at the loop of Henle is also affected.

However, calcium reabsorption still proceeds at the distal convoluted tubule of the nephron. This is why long-term administration of furosemide can cause hypomagnesemia but rarely hypocalcemia.

By inhibiting the return of sodium, chloride, and potassium into the blood, furosemide reduces the osmotic pressure of water passing through the nephron. This means that it is not pumped back into the blood.

In this way, furosemide promotes increased urine production and fluid loss from the body. Since water is not returned to the blood, the overall blood volume falls and with it, the blood pressure also falls.

This is why furosemide is used to treat edema and hypertension.

Furosemide needs to be transported to the loop of Henle in the kidney. However, in patients with renal insufficiency, blood flow to the kidney is restricted. This affects the distribution of furosemide to its site of action.

To overcome this limitation, the dose of furosemide is increased so that a sufficient amount of the drug is made available to the kidney. Alternatively, furosemide can be paired with a thiazide diuretic to effectively manage edema.

NSAIDs such as ibuprofen and aspirin also produce a similar effect. They reduce the glomerular filtration rate (GFR) and interfere with the distribution of furosemide to the kidney nephron. Therefore, patients placed on furosemide should avoid concurrent use of NSAIDs.

What Are The Benefits? 

Furosemide is one of the medications that has been approved by the US Food and Drug Administration (FDA) to treat edema. This means that the FDA considers it effective and safe enough to be prescribed for edema. 

Loop diuretics have been used effectively and successfully for several decades. They are commonly prescribed to treat edema. Furosemide is particularly helpful for people who have kidney problems. 

Are There Any Side Effects? 

You may experience frequent urination for up to 6 hours after a dose and this should decrease after using furosemide for a few weeks. 

In some cases, the medication might cause some mild side effects such as muscle cramps, confusion, thirst, upset stomach, weakness, dizziness, vomiting, headache, blurred vision, and restlessness. 

Serious side effects include fever, sore throat, unusual bleeding or bruising, ringing in the ears, difficulty breathing or swallowing loss of hearing, and excessive weight loss. If any of these symptoms worsen or do not go away after some time, call your doctor immediately. 

Furosemide is considered ototoxic (damaging to the ear and harmful to the sense of hearing) especially when a large dose of the diuretic is injected too rapidly in edema patients with renal impairment.

The drug also promotes the accumulation of uric acid. Therefore, it should not be used in people who also suffer from gout.

Furosemide can cause hyperglycemia. For this reason, care should be taken when administered to diabetics since glucose control can become difficult to monitor and maintain.

Like all loop diuretics, furosemide can lead to significant loss of potassium from the body. Because of this tendency to cause hypokalemia, it is sometimes sold as a combination product.

Lasix-K, for example, is a formulation of furosemide and potassium.  The potassium included in the medication is meant to replace the ones lost to the diuretic action of furosemide.

Alternatively, furosemide can also be formulated alongside a potassium-sparing diuretic such as amiloride. A common co-formulation of both diuretics is co-amilofruse.

Are There Any Drug Interactions?

Furosemide might interact with the following medications: Aminoglycoside antibiotics such as Gentamicin; Aspirin and other salicylates; Indomethacin; Lithium and antihypertensives. 

The drug might also interact with aloe, celery seed, creatine, calcium, ephedra, coenzyme q10, glucosamine, licorice, melatonin, potassium, magnesium, vitamin b1 (thiamine), and vitamin c. 

Are There Any Contraindications? 

This medication may not be safe for all. You should consult your doctor if you are already on any medication or have a pre-existing condition. Please work with your doctor to find a treatment program that suits you and your lifestyle. 

You should avoid furosemide if you are pregnant or nursing. Tell your doctor if you are pregnant or plan to become pregnant. You should also tell your doctor if you are allergic to sulfa medications or have any other drug allergies. 

Although furosemide may be beneficial for those who have kidney disease, inform your doctor if you have ever had kidney complications. You should also tell your doctor if you have ever had gout, diabetes, or liver disease. 

For more information about edema, and its treatment methods, read these articles: Drugs For Edema, Edema Home Remedies, and Edema Products.