Furosemide is a loop diuretic, commonly known as a “water pill.” This prescription-only medication works by eliminating excess fluid and salt from the body through increased urination. Due to its potency and effects on fluid balance, it must only be taken as directed by a healthcare professional.
Physical Characteristics and Dosage Forms
Furosemide is available as an oral tablet, an oral solution, and an injectable solution. The tablet is typically white or off-white and comes in strengths of 20 milligrams (mg), 40 mg, and 80 mg. Tablet shapes vary between manufacturers, often being round or oval.
Tablets can be identified by imprints unique to the manufacturer and dosage strength, often including the milligram amount or a specific code. Since appearance can change slightly among generic manufacturers, patients should confirm the pill’s identity with a pharmacist.
The oral solution is an alternative for patients who have difficulty swallowing tablets. It is usually a clear, colorless, or slightly yellow liquid, often available in concentrations like 10 mg per milliliter. The injectable form is a sterile, clear solution used in hospitals for rapid action, typically supplied in amber-colored vials to protect it from light.
Conditions Treated by Furosemide
The primary use for furosemide is the treatment of edema, which is the medical term for fluid retention and swelling. This fluid buildup is often associated with serious underlying health conditions. Furosemide is particularly effective at reducing swelling in patients with congestive heart failure (CHF).
In CHF, the heart cannot pump blood efficiently, leading to fluid pooling in the lungs and extremities. The drug is also a standard treatment for edema resulting from chronic kidney disease, including nephrotic syndrome, and cirrhosis of the liver. Liver damage impairs the production of proteins, causing fluid to leak into the abdomen and tissues.
Furosemide is sometimes used to manage high blood pressure (hypertension), often combined with other antihypertensive medications. By helping the kidneys excrete sodium and water, the medication decreases the total fluid volume in the bloodstream, which lowers blood pressure.
Understanding Its Mechanism and Important Warnings
Furosemide is classified as a loop diuretic because its mechanism of action targets the thick ascending limb of the Loop of Henle in the kidney. Within this structure, the drug works by inhibiting the sodium-potassium-chloride cotransporter (NKCC2) protein. This action prevents the reabsorption of sodium, chloride, and potassium back into the blood.
By blocking the reabsorption of these electrolytes, furosemide ensures that a much larger volume of water remains in the urine. This process results in a rapid and significant increase in urine output. The rapid removal of fluid helps to quickly relieve symptoms of fluid overload, such as shortness of breath and swelling. Patients are usually advised to take the medication in the morning to prevent frequent nighttime urination.
Important Warnings
Due to its action, furosemide carries a significant risk of dehydration and electrolyte imbalance. The increased excretion of potassium can lead to hypokalemia, a dangerously low level of potassium in the blood that can affect heart rhythm. Patients are often required to undergo regular blood tests to monitor their potassium, sodium, and kidney function levels.
Another important warning is the potential for ototoxicity, which involves damage to the ear and can manifest as ringing in the ears (tinnitus) or even irreversible hearing loss. This risk is higher with very high doses or when the intravenous form is administered too quickly. Patients must report any signs of hearing changes to their healthcare provider immediately.