Furosemide And Its Diuretic Action In Our Body

Furosemide is a highly effective diuretic that belongs to the classification of loop diuretics. These drugs are capable of altering ion transport throughout the nephron, which is the anatomical and physiological unit of the kidney.

By altering this transport, they increase the volume of urine since they stimulate the renal excretion of water and electrolytes. All of this causes a decrease in the volume of extracellular fluids.

It is a drug that is indicated alone or in combination when the patient suffers from high blood pressure. However, it can also be used to treat edema (due to fluid retention) caused by various medical problems such as liver or heart disease.

To better understand how furosemide works in our body, we must understand how our kidney works. Read on to receive all the information about it.

Ion transport mechanism in the kidney

The kidneys are the main organs of the urinary system. They are responsible for the excretion of waste substances through the formation of urine and for maintaining the balance of the internal environment of the body, that is, homeostasis.

Its anatomical and physiological unit is the nephron, and it consists of 4 parts: the proximal convoluted tubule, the loop of Henle, the distal convoluted tubule, and the collecting tubule.

The fluid to be purified reaches the proximal convoluted tubule passing through the glomerulus. This tube is very permeable to water and is where most drugs are actively secreted so that they are eliminated in the urine. Afterwards, the remaining liquid passes to the loop of Henle, which consists of two parts, the descending and the ascending.

The descending part is also permeable to water but is totally impermeable to solutes. Therefore, due to these characteristics, a hypertonic urine will form, that is, with a high concentration of solutes.

As for the ascending part, it has the opposite characteristics, it is impermeable to water and permeable to solutes, originating hypotonic urine. This urine passes to the distal convoluted tubule, which is impermeable to water and hypotonic urine is formed.

Finally, the liquid reaches the collecting tubule, where the permeability to water is variable. The control of the processes at this level is mediated by the hormone aldosterone and the antidiuretic hormone (ADH).

When urine is formed, it reaches the bladder through the ureters, which upon reaching a certain level of filling, sends a signal to the brain that creates the need to urinate.

Mechanism of action of furosemide

This drug acts from within the loop of Henle, that is, in the tubular lumen. To get here, it is secreted into the proximal convoluted tubule by active transport or passive diffusion .

Once in the loop of Henle, it inhibits the sodium, potassium, and chloride counterscarrier and, to a lesser extent, the calcium and magnesium carrier. This action is carried out in the ascending handle, which is the diluting part, since it is permeable to water.

By blocking these cotranspotators, it prevents these electrolytes from being reabsorbed causing more water to be released to try to dilute it. The effects of furosemide are rapid and short-lived. By eliminating more water, it reduces its volume in the body, due to this phenomenon its antihypertensive effects.

Pharmacokinetics

Furosemide can be administered both orally and intravenously . If the first option is chosen, the effects last between 4 and 8 hours, observing the action after 10-30 minutes. If the second option is chosen, the effects can be observed after 5 minutes and last approximately 2 hours.

It has a bioavailability of 90% and has a partial metabolism in the liver, where 4-chloro-5-sulfamoyl-anthralinic acid is formed which, with the rest of the drug, will be eliminated in the urine.

It is important to note that it is highly bound to plasma proteins, a fact to take into account if furosemide is being administered with some other drug that has the same characteristic, since they can interact and cause undesirable effects.

Adverse reactions

The different adverse effects that furosemide can trigger are due to its diuretic effects. Among them we can point out:

• Hypokalemia When the doses are high, they can greatly decrease the potassium levels in the blood and can trigger arrhythmias.
• Hypochloremic alkalosis.
• Hypovolaemia, hyponatraemia, hyperuricemia, and hyperglycemia.
• Ototoxicity (ear problems).