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Frank Schleck, the Tour de France and doping: so what’s xipamide?

The Radioshack-Nissan-Trek rider has retired from this year’s Tour de France. Nicolas Bouvy/EPA

After the recent re-ignition of allegations against seven-time Tour de France winner Lance Armstrong, many in professional cycling had hoped for a quiet year on the doping front. But, it seems, the Tour de France always delivers.

In 2006, it was Floyd Landis (testosterone). In 2008, it was Bernhard Kohl (EPO receptor activator). In 2010, it was Alberto Contador (clenbuterol). Now, we may have a scalp for this year. Luxembourg’s Frank Schleck, last year’s third-place finisher, has returned an A-sample showing positive for the banned diuretic xipamide.

Diuretics – what’s the point?

You might think a diuretic - a drug that increases urine and sodium excretion - would be a strange choice for performance enhancement in a sport where dehydration is a clear and present danger. And you’d be right.

Diuretics are not at all performance-enhancing by themselves, but have two related functions which places them on the banned-substance list:

1) People who are trying to rapidly lose weight to achieve a lower weight class (think any combat or power sport) will use diuretics to temporarily dehydrate themselves below their weight category limit, “weigh in”, and then rehydrate for competition. An enormous advantage can be gained this way, as athletes frequently compete several kilos above their scale weight.

2) Somewhat more sinisterly, diuretics are used as “masking agents” to hide the presence of other drugs in a urine test. The main method of action for masking is simple. A diuretic increases the amount of urine produced so if an athlete keeps their hydration high and manages their electrolyte balance, they can produce drastically diluted urine which is less likely to show the presence of any other banned performance-enhancing substance.

Frank Schleck. Yorick Jansens/EPA

What is xipamide?

Xipamide is about 40 years old and quite an uncommon diuretic - the World Anti-Doping Authority reported no positive tests for it in 2010, and don’t mention it at all on their website (although it is most assuredly considered a “substance … with a similar chemical structure or similar biological effect” to other diuretics).

Typically, xipamide would be used for the treatment of oedema (fluid retention) or related conditions and has no therapeutic exemption. That is, there is no condition under which you are allowed to test positive to it.

In cases such as Frank Schleck’s, there are several possible explanations apart from laboratory error, which is unlikely:

1) It was taken in the manner described above, as a masking agent.

2) It was ingested as a contaminant (from a food product, medication or athletic supplement). This is increasingly unlikely, given the increasing amount of attention afforded to this problem in professional cycling teams. It also seems that Schleck’s team have categorically ruled this out.

3) To add a layer of intrigue, it’s possible the substance remained as a contaminant from blood doping - that blood was drawn out and contaminated at an earlier time and then recently re-injected.

It may be possible to determine more precisely what is going on from the level of xipamide present, or other related factors.

But as is customary in these cases, the UCI cannot comment any further due to privacy concerns, so all we are left with in the meantime is speculation and another year’s worth of recrimination.

One thing is for certain though: Frank Schleck’s Tour 2012 is over.

Further reading:
Tour de France: the science of hill climbing
Suffer score: how demanding is Le Tour de France?
Le Tour de France is set to roll, so what makes a perfect bike wheel?
High-end bikes for sale … but what are you really buying?
Cadel Evans and other machines: the science of the Tour de France time trial
Science of elite cycling: Tour de France (stage 1 to 11)
Science of elite cycling: Tour de France (stage 12 to 21)

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