Should clenbuterol still be banned?

Two cyclists, Rudi van Houts and Phillip Nielsen, failed doping tests last year, including the testing of B-samples, but were recently cleared of any wrongdoing, based on their defence that the drug clenbuterol entered their system as a result of contaminated meat. Dr Ross Tucker looks at the implications of this ruling on the future of clenbuterol.

Both failed the tests after racing or training in Mexico (where, admittedly, it has been alleged that almost 20% of meat is treated and thus contaminated with clenbuterol). These cases, most of you will realise, are the same as that presented by Tour de France champion Alberto Contador, with the same outcome (for now).

Much has been written on the Contador case already, but the most recent exonerations reinforce the struggle that doping control has when a positive finding is not enforceable as a result of an explanation that can neither be proven, nor disproven.

Plausible explanation and "impossible" proof

The bottom line is that in terms of the implications for doping control, it actually doesn't even matter if the cyclists are guilty or not.  Just like Contador, they present an explanation that is plausible.  The problem is that neither party (cycling or the cyclist) can currently prove its argument.

Strict liability has always held that the athlete who has failed a doping control must explain how an illegal substance entered their system - the burden of proof lies with the athlete (but only once they've failed the test - this is an important distinction.  It's not simply a case "guilty until proven innocent"). 

The Contador verdict effectively spun strict liability around 180 degrees, so that rightly or wrongly, it now seems to lie with the governing bodies to prove that the positive test was in fact the result of deliberate doping. 
Proving the case: limits and hair samples

This seems impossible in cases like these. The only way to overcome this is to do detailed studies on the drugs to investigate levels expected in urine/blood/hair as a result of doping compared to contamination - both Contador and van Houts had incredibly small amounts in their bodies (50 and 30 pg/ml respectively, it's been reported). 

If one knew the amounts that occurred due to contamination, and if they were routinely this small, then it might be possible to classify clenbuterol as a "threshold" drug, which is allowed up to a certain limit, set by knowledge that doping produces a value of at least "X".  That's currently not the case, and any clenbuterol is an adverse analytical finding, or "strike".

The problem with using the amount detected in the sample is that you never know the ingested (or doped) amount, and nor do you know the timing of ingestion (or use) relative to the test. 

These are clearly crucial as to what eventually gets detected, and without knowing this, setting thresholds is largely meaningless.  And so the athletes will be cleared more and more, particularly as a result of the precedent created by the Contador case.  This was one of the major implications of that verdict. 

There is another option - a hair test. 

A German table tennis player, Dimitrij Ovtcharov, was exonerated after he provided a negative hair sample.  Apparently, clenbuterol "sticks to hair" and so a negative hair test suggests contamination, since the drug would not be present in large enough amounts to remain in the hair. 

Strangely, this happens more with dark hair than blonde hair, so a light-haired person would produce a "vague" finding, according to one expert, Detlef Thieme.  WADA are challenging Ovtcharov's exoneration, incidentally. Clearly, this is not yet a conclusive method of separating contamination from doping, but may be a prospect for the future.

Reconsidering clenbuterol

Clenbuterol therefore has three successive strikes next to its name - time to reclassify it on the list, or remove it altogether.  Unless an alternative method of testing, or better understanding of the levels as a result of ingestion can be obtained, it seems to be unlikely that a positive test for this particular drug is not going to be challenged on the grounds of contamination. 

And when that happens, it seems unlikely that a case can be resolved in favour of the authorities. 

So until such time that the authorities are able to disprove contamination, or prove deliberate doping, they are powerless to enforce test results. Time to retire clenbuterol, and save the athletes of having to present this argument and go through hearings that will ultimately produce a similar outcome.

The remaining alternative, and this is tongue in cheek, is that sports bodies will have to start insisting that athletes please submit a sample of all ingested meat for testing at every event. Urine in flask A, blood in vial B, and meat in container C, please...

(April 2011)

Dr Ross Tucker, is Health24’s FitnessDoc and has a Ph.D. in Exercise Physiology from the University of Cape Town and a Post-Graduate degree in Sports Management from the UCT's Faculty of Commerce. He is currently employed at the University of Cape Town and Sports Science Institute of South Africa, and works as a consultant to various sporting teams, including South African Sevens, Canoeing, Rowing and Triathlon SA. He also blogs on


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