Furosemide
Synonyms
Lasix®, diuretics / diuretics, loop diuretics / loop diuretics, water tablets, diuretics
also read:
- Diuretics
- Torem
definition
Furosemide is a chemical substance that, when it enters the body, causes increased urine output. The target of this drug is a specific ion transporter in the kidney.
introduction
Furosemide belongs to the substances of the dehydrating drugs (Diuretics). In the kidney, a transporter ensures that salts are reabsorbed (Sodium, potassium, chloride) and thus causes a resumption of already filtered water. If this transporter is inhibited by furosemide, the salts and, as a result, the water can no longer be reabsorbed and there is an increased urine excretion. Furosemide is the lead substance of the so-called class of active ingredients. Loop diuretics.
Anatomy and Physiology of the Kidney
The large blood vessels leading to the kidney branch out into ever smaller arteries as they progress through the kidney. Inside the kidney are made up of the small afferent ones Blood vessels (Vas afferens) loops formed. Together with a basement membrane and specialized cells (podocytes), the Kidney filter constructed, which is surrounded by a capsule. This filter acts like a sieve and lets liquids, i.e. water, and small blood components through. Here are the day 150 - 200 l of water filtered off. A pipe system is attached to the filter (Tubular system including the collecting tubes), which has the task of concentrating this primary urine from up to 200 l to around 1.5 - 2 l per day by the system reabsorbing water and substances. In addition, these cells are also able to release certain substances into the urine. There are many different channels and transporters on the cells of the tubular system for these purposes. After passing through this system, the so-called. Secondary or terminal urine about the ureter (Urethers) the bladder and can use the urethra (urethra) are eliminated.
The tubule system consists of a proximal and a distal section. In between is the so-called. Henle loop. The collecting tubes are connected to the distal section. These open into the ureters. The different sections indicate different specializations.
Mode of action
Furosemide inhibits a special transporter that occurs in a certain section of the tubular system. This transporter is a manure transport of sodium, potassium and chloridewhich is in the thick section of the ascending leg of the loop of Henle. As a result of the inhibition of the transporter, there is no more water reabsorption in this part of the tubular system. This means that an increased amount of water enters the bladder. The drug furosemide has a relatively strong and quick effect.
Pharmacokinetics and bioavailability
Under Pharmacokinetics one understands the uptake, distribution, metabolism and excretion of drugs supplied to the body.
The Bioavailability describes the proportion of the administered drug that appears unchanged in the blood and can therefore work. It is a pharmacological parameter and makes statements about the amount of drug absorbed.
If furosemide is taken as a tablet, only about half of the substance appears in the blood. The bioavailability is therefore included 50, sometimes at up to 70 %. In the kidney, the largest part is filtered and partly also released via the cells of the tubular system. The breakdown of the substance in the blood is relatively rapid. 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. No effect is to be expected after about 6 hours.
If furosemide is administered intravenously via a short infusion, the effect occurs after 15 minutes and lasts up to 2 hours.
application
- Washout of Edema
- Heart / kidney weakness
- threatening Kidney failure
- high blood pressure
- Derailment of the calcium level
Furosemide is used to flush out fluid build-up in tissues (edema). Furosemide is particularly suitable for the accumulation of fluid that is caused by heart, kidney or liver diseases. The quick and powerful effect of this substance is ideal. This is also of particular importance in the case of edema, which is associated with a threat to life. This is the case when fluid builds up in the lungs or brain. Loop diuretics are also used when other diuretic drugs are no longer used due to severe heart or kidney failure. For example, if the filtration rate of the kidneys falls below 50 ml per minute, the use of such a drug is indicated. The normal filtration rate in healthy people is around 120 ml per minute. Another important indication for the use of furosemide or other loop diuretics is acute kidney failure with the threat of no elimination (anuria). The attempt is made to make me pass urine in very high doses. It must be noted that the amount of filtration cannot be increased.
These substances are sometimes used in high blood pressure (hypertension) and the Heart failure (Heart failure). As a rule, however, other diuretics are preferred because reducing the water volume quickly is sometimes not beneficial.
If a patient has a severe increase in calcium levels (Hypercalcemia), furosemide can be used to lower it. In high doses, the medicine is administered repeatedly by infusion. The water and electrolyte balance must be constantly monitored and, if necessary, substituted.
dosage
Usually the substance furosemide is taken as a tablet. The dose is 20-40 mg and can if necessary after 68 hours be repeated. Furosemide can also be administered as a short infusion in hospitals. The dosage here is also 20 - 40 mg.
Side effects
Due to the washout of the water, the blood becomes thicker (increased viscosity of the blood). This harbors some dangers, because thick blood tends to clot.
Thrombosis or life-threatening Embolisms can be the consequences.
Another consequence of the flooding of water and salt can be a reduced salt content with derailment of the electrolyte balance. In extreme cases, hearing impairment can sometimes be observed. The reason for this is that there is a similar transporter in the hearing aid as that in the kidney.
Furosemide or loop diuretics can Gastrointestinal complaints how diarrhea cause.
Furthermore, the excretion of magnesium is promoted, which leads to a Magnesium deficiency (Hypomagnesaemia). Symptoms are for example Muscle spasms, irritability and fatigue or Palpitations.
In addition, an increased excretion of calcium is induced. Since calcium is important for bone structure, long-term therapy with loop diuretics is not appropriate.
If the use of furosemide causes a sodium deficiency, the effect of the drug is automatically limited.
Treatment with loop diuretics can also cause an increase in Uric acid level accompanied. This can lead to a Attack of gout to lead.
In general, diuretics tend to decrease the amount of filtration. The water excretion is increased, because the filtration capacity and thus the cleaning of the blood of substances that are excreted in the urine is still reduced.
In some cases, reversible hearing impairment can also occur because the drug blocks a transporter that is also found in the inner ear. Usually this only happens with high dosages.
