Mode of action | Furosemide

Mode of action

Furosemide inhibits a special transporter that occurs in a specific section of the tubule system. This transporter is a co-transport of sodium, potassium and chloride, which is located in the thick section of the ascending leg of the Henle loop. Due to the inhibition of the transporter, water reabsorption no longer takes place in this part of the tubule system. Thus, an increased amount of water enters the bladder. The drug furosemide has a relatively strong and rapid effect.

Pharmacokinetics and Bioavailability

Pharmacokinetics refers to the absorption, distribution, metabolism and excretion of drugs supplied to the body. Bioavailability describes the proportion of the drug that appears unchanged in the blood and can therefore act. It is a pharmacological parameter and provides information about the extent to which the drug is absorbed.

If furosemide is taken as a tablet, only about half of the substance appears in the blood. The bioavailability is therefore 50 %, sometimes up to 70 %. In the kidney, the largest proportion is filtered and partly also released via the cells of the tubule system.

The breakdown of the substance in the blood is relatively fast. After 30 minutes to 2 hours only half of the substance is still present in the blood (plasma elimination half-life 0.5 – 2 hours). The diuretic effect sets in after 30 – 60 minutes and reaches its maximum after 1 – 2 hours. After about 6 hours, no more effect is to be expected. If furosemide is administered intravenously via a short infusion, the effect sets in after 15 minutes and lasts up to 2 hours.

Application

Furosemide is used to flush out fluid accumulations in tissues (edema). Furosemide is particularly suitable for fluid accumulations caused by heart, kidney or liver disease. The fast and strong effect of this substance is ideal.

It is also of particular importance in the case of oedema, which is a life-threatening condition. This is the case with fluid accumulations in the lungs or brain. Loop diuretics are also used when other diuretic drugs can no longer be used due to severe heart or kidney weakness.

If, for example, the filtration rate of the kidney falls below 50 ml per minute, the use of such a drug is indicated.The normal filtration rate for healthy people is about 120 ml per minute. Another important indication for the use of furosemide or other loop diuretics is acute kidney failure with the threat of lack of excretion (anuria). In this case, an attempt is made to induce me to excrete urine at very high doses.

It is important to note that the amount of filtration cannot be increased. These substances are also sometimes used to treat high blood pressure (hypertension) and cardiac insufficiency. As a rule, however, other diuretics are preferred, as the rapid reduction of the water volume is sometimes not advantageous.

If a patient suffers from a strong increase in calcium level (hypercalcemia), furosemide can be used to lower it. In high doses the drug is administered repeatedly by infusion. Water and electrolyte balance must be constantly monitored and substituted if necessary.

  • Washout of oedemas
  • Heart and kidney weakness
  • Impending kidney failure
  • High blood pressure
  • Derailment of the calcium level