Image caption Dr Hans Geyer is deputy director of the WADA laboratory in Cologne

The deputy director of the World Anti Doping Laboratory in Cologne says that painkillers fulfil all the requirements of a doping substance.

Dr Hans Geyer has been evaluating doping control forms and urine samples for a decade looking for evidence of pain medication.

He found that athletes in many fields are taking large quantities of these drugs both in and out of competition.

He says that controlling these drugs in sport is impossible.

Dr Geyer says that as well as the analytical data he has been told directly by players that abuse of medications is widespread.

Painkillers really enhance performance but they have negative effects on body tissues, maybe irreversible effects. Dr Hans Geyer, WADA Cologne

"In a world championship in handball I have an original citation from one of the best players who said 50% of the team that won the championship took diclofenac - therefore we have to ask what is going wrong? Is the training too hard? Can a normal person not do these sports without painkillers? This is very alarming.

"It's well known that Andreas Erm who won a bronze medal in the 50km walk in the 2003 world athletic championship in Paris received pain killers several times during the walk - can you tell me this is not performance enhancing?

"His body was not able to walk 50km on this day in such a speed but he won the bronze medal because he was treated with pain killing medications!"

Doping grey zone

Dr Geyer says that competitors like Erm were not doing anything wrong. There is obviously a need to treat competitors in an event if they are in pain. But out of competition he is worried that about the use of medicines. Athletes may be able to improve their training performance because they don't need such a long recovery time after a hard session.

"It is a grey zone. In my opinion pain killers fulfil all requirements of a doping substance because normally pain is a protection mechanism of the body and with pain killers you switch of this protection system, like if you switch off fatigue, which is also a protection mechanism of the body.

Image caption Should doping labs also test for pain medications?

"Painkillers really enhance performance but they have negative effects on body tissues, maybe irreversible effects."

But while pain killing medications may have performance enhancing effects, Dr Geyer believes it will not be possible to limit their use in sport.

"I think the control of these substances is impossible, as they are easily available in society. Therefore it is not possible to treat the use of painkillers in the same way as other doping substances."

Who is responsible?

There are issues relating to the supply of these medications as many of the most powerful pain killing drugs are available only on prescription.

Dr Geyer argues that the medical community often has no choice but to give in to the demands of high profile athletes.

"Doctors know that there may be problems with tissues and bones and the knees and they also know that if they allow the athlete to continue his training and competing with pain killing medications there will most probably be irreversible or long-term effects.

"This should be discussed. There a question of ethical responsibility and the motivation of sports medicine.

"But you know if an athlete doesn't receive the medication from one doctor he goes to the next and if he is a famous athlete he will receive everything. This is also a question that should be discussed."