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19. 4. 2012.

Masking agences

In the group of masking agences are the substances that use various mechanisms to influent the time and amount of excreted doping and disable doping control.
Masking agences are thought to be the following substances: diuretics, epitestosterone, probenecid and plasma expanders.


Diuretics are drugs that stop natrium tubular resorption and increase the volume of excreted urine. In therapy also osmotic diuretics are used, that connect for themselves bigger amount of water and lead to increasing of urine excreted.
Diuretics share is done according to their effect:
  • Fast and hard action diuretics: furosemide, ethacrynic acid
  • Diuretics that spare potassium: aldosterone antagonists and triamterene
  • Osmotic diuretics
  • Anhydrase inhibitors
  • Other diuretics: mercury rimifons, ammonium chloride…

According to their strength, three groups are found:
  • Strong: furosemide and ethacrynic acid( action comes very quick, and lasts 4-8 hours)
  • Moderate: thiazides( action goes slower than in fast diuretics, but lasts longer – 6-12-24 hours)
  • Weak: triamterene, amiloride, spironolactone

Mutual features of strong and weak diuretics are increased excretion of potassium and natrium. Weak diuretics have advantage compared to this two groups, cause their diuretic effect is not followed by hard potassium loss.
Tiazides are the group of diuretics that is very widespread today in therapy(hypertension, edems…). These substances decrease natrium reabsorption in distal tubules of kidneys, causing that way increased fluid secretion, and in the same time potassium loss. The most important unwished effects are hypocalemia and hyperuricaemia.
Furosemide and ethacrynic acid manifest diuretics effect by decreasing natrium reabsorption on the level of Henle’s loop, which creates strong and fast diuretics effect. These rimifons cause dehydration, potassium loss, temporary deafness and some other disorders.
Spironolactone is the rimifon that, by antagonizing effects of aldosterone, causes increased natrium excretion, with, at the same time, potassium retention. Its effect comes slowly, reaching its maximum in 2-3 days.
Triamterene and amiloride have same effects like spironolactone, but their effect mechanism is different.
Mannitol is the most significant representor of osmotic diuretics. It is applied only through infusions in special medical indications.

List of most often used diuretics: acetazolomid, hydrochlorothiazide, bumetanide, mannitol, chlorthalidone, mersalil, ethacrynic acid, spironolactone, furosemide, triamterene and  similar substances.

Appliance in sport

Athletes that have categories most often use this methods, in order to reduce body mass fast.
Increased urine excretion and following dilution effect of other illegal substances in urine is the important reason for diuretics abuse.

Harmful effects

There is a risk of hypocalemia and dehydration. Fluid loss from the organism absolutely negatively influences of psychophysical abilities of the athletes. The hardest consequences are: heart arrhythmia, muscle weakness, parestesia…


Diuretics can be detected by methods of gas chromatography-mass spectrometry.


Epitestosterone is applied as a try to change relation testosterone/epitestosterone in urine, and mask illegal amount of testosterone. Finding of epitestosterone that is bigger than 200ng/ml is thought to be doping.

Plasma expanders

These substances belong to the group of plasma substitutors. Today there is no device that can fulfill all demands of plasma substitutors. Dextrans represent the group of substances that has advantage comparing to all other devices.
Dextrans are glycopolysaccharides in which molecules of glucose are connected with glycoside connections.
Most often used are dextran 70(molecule mass 70000) and dextran 40(molecule mass 40000) in combination with 5% glucose solution or 0,9% natrium-chloride solution.
One gram of dextrane can contain in circulation 20-25ml of water or to pull the same amount of water from tissues into blood vessels.
After the infusion of dextrane following effects come very fast: increased heart minute volume, hypervolemia, diuresis. Dextranes are used in medicine in various types of shock.

Appliance in sport

Through increase of plasma volume and diuresis, plasma expanders decrease concentration of doping substance in urine and blood.

Harmful effects

Dextrans can cause allergic reactions and anafilactic shock.


Dextranes are mostly excreted through kidneys, half-time of holding in plasma for dextrane 40 is about 6 hours, and for dextrane 70 over 24 hours.

“Doping in sport”, Marina Djordjevic Nikic

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