Under the World Anti-Doping Agency (WADA) Prohibited List, there is a category of prohibited substances called Diuretics and Masking Agents, which are prohibited at all times. And while many people understand that substances that clear the body of excess fluid faster are prohibited under this category, the Diuretics and Masking Agents category also includes substances that are used for a variety of other purposes, including spironolactone for acne treatment and acetazolamide for altitude sickness.
Keep reading to better understand this category of prohibited substances and avoid inadvertent use of diuretics or masking agents.
What are diuretics and masking agents?
A diuretic is a drug that makes the body, specifically the kidneys, produce and pass more urine. Sometimes called “water pills”, diuretics help the body get rid of excess fluid more quickly. Medically, diuretics have many important uses, such as reducing fluid levels associated with high blood pressure, congestive heart failure, or kidney disease and declines in kidney function. However, some medications with diuretic or masking actions are prescribed for other reasons, such as to treat seizure disorders, reduce elevated pressure in the eye, and treat altitude sickness or even skin conditions like acne. In this way, diuretics can be taken orally, dermally as skin creams, or as eye drops.
Why are diuretics and masking agents prohibited?
From an anti-doping perspective, diuretics can interfere with the detection of prohibited substances by influencing the speed and manner in which prohibited substances are broken down and excreted from the body.
Anything that alters urine volume and concentration can affect how substances or their metabolites appear in a urine sample. In other words, some substances act as “masking agents” even though they do not necessarily increase urine production. This category is more than just “medications that make you urinate”.
On the WADA Prohibited List, the S5 category of prohibited Diuretics and Masing Agents includes:
- Conventional diuretics, which may be misused for rapid weight loss or urine dilution
- Vaptans, which promote excretion of relatively electrolyte-free water, sometimes used to help the body hold onto important salts and electrolytes while still getting rid of some fluid
- Plasma expanders administered intravenously, which can alter blood-volume-related testing
- Other substances with potential masking effects, including desmopressin and probenecid
See the table below for a few examples of medications prohibited in this category that people might not realize have diuretic or masking actions:
| Substance | Sometimes prescribed to treat |
| Acetazolamide | Glaucoma; elevation sickness (altitude sickness or “mountain sickness”); certain seizure disorders |
| Hydrochlorothiazide, Chlorothiazide or Lisinopril/Hydrochlorothiazide combination | High blood pressure and fluid retention. HCTZ is often paired with Lisinopril. |
| Conivaptan/Mozavaptan | Hyponatremia or “low blood sodium” |
| Desmopressin | Excessive urination/thirst related to diabetes (anti-diuretic). |
| Furosemide | Fluid retention caused by heart failure, liver cirrhosis, or kidney disease |
| Mannitol | Emergency reduction of pressure in the brain or eye |
| Probenecid | Prevention of gout or high uric acid levels; increase blood levels of certain antibiotics |
| Spironolactone | Prescribed off-label for acne or excess hair growth related to androgen sensitivity |
| Sultiame | Certain focal seizure disorders in some countries where available |
What are the side effects of diuretics?
Using a diuretic without appropriate medical supervision may lead to adverse health effects, such as dehydration, dizziness, cramps, low blood pressure, electrolyte disturbances like low sodium and potassium levels, heat illness, kidney function problems, and abnormal heart rhythms (arrythmias). These risks can be especially serious for athletes who are training or competing, particularly in hot conditions.
Can I get a TUE for a substance in the category of diuretics or masking agents?
Any athlete in the Registered Testing Pool (RTP), Clean Athlete Program (CAP), or Education Pool (EP) who needs to use a diuretic or masking agent must apply for a Therapeutic Use Exemption (TUE). It’s also important to remember that use of a diuretic or masking agent in combination with substances that have a permitted dose limit (e.g. inhalers containing salbutamol or formoterol, cathine, ephedrine, methylephedrine, or pseudoephedrine) requires a TUE for both the diuretic and the other substance. All other athletes should submit a TUE Pre-Check Form to determine if a TUE is necessary.
If you’re unsure if you are an RTP, CAP, or EP athlete, please submit a TUE Pre-Check Form.
More questions?
For questions about specific products, substances, and methods, contact USADA’s Drug Reference Line at DrugReference@USADA.org or call (719) 785-2000, option 2.
