MDMA, otherwise known as ecstasy, is being given to patients suffering from post-traumatic stress disorder (PTSD) as part of a clinical study in Switzerland.
It is the first time that the illegal drug, which has been linked to a number of deaths, has been approved for research on a group of patients by the Swiss authorities.
A dozen trauma victims are expected to take part in the study, which began in October last year and is due to finish in 2008.
One patient has completed the treatment; two more have been enrolled and will receive MDMA-assisted psychotherapy shortly.
The Swiss trial is running parallel to a similar study being carried out by researchers in the United States.
"They have had favourable results in easing PTSD and I am expecting a similar response," Peter Oehen, the psychiatrist and psychotherapist leading the study, told swissinfo.
It took over a year for Oehen to gain approval from Swissmedic, the Swiss Agency for Therapeutic Products, an ethics committee and the Federal Health Office. Clearance finally came through in August last year. Oehen said the process had gone "very smoothly" and with few delays.
Those selected for the trial must be over 18, they must have been diagnosed with PTSD and they must not have used ecstasy more than five times or within the previous six months. They also have to speak German.
Eight of them will get a full dose of MDMA – 125mg with a booster after two-and-a-half hours of 62.5mg – and four will receive a smaller dose during the three experimental sessions that each patient will undergo. The effects of the drug last several hours.
"[The full dose] will produce a change of consciousness, a feeling of wellbeing, reduction of fear and help them face up to the very difficult feelings associated with trauma, such as anxiety," Oehen explained.
The trial is being sponsored by the Multidisciplinary Association for Psychedelic Studies (MAPS) and will cost more than $150,000 (SFr190,000).
The US non-profit organisation has a five-year goal to make MDMA into a prescription medicine for the treatment of PTSD.
Oehen admitted that researchers faced a tough task in gaining respectability for the drug after a considerable number of negative headlines over the past two decades.
Question marks have been raised over the effects of MDMA on the nervous system and whether it damages cognitive function among heavy users.
Oehen said this was hard to investigate because of a number of confounding factors: heavy users usually combine ecstasy with other drugs and have irregular lifestyles including repeated sleep and fluid deprivation.
"There are a small number of carefully designed studies which indicate that in a clinical setting it probably won't cause any cognitive damage," he said.
"In Switzerland we had a period between 1989 and 1993 when several psychiatrists in private practice had a licence to do this kind of therapy using MDMA and LSD. They had quite favourable results but it was not in a clinical scientific setting."
Marta Kunz, a scientific officer at the Federal Health Office, confirmed to swissinfo that this was the first study of its kind in Switzerland.
She said that while the authorities recognised the risks associated with MDMA, the law allowed the possibility of research under strict conditions.
swissinfo, Adam Beaumont
Methylenedioxymethamphetamine (MDMA) was patented by the German drug company Merck in 1914.
It was used therapeutically by the chemist Alexander Shulgin in the late 1970s.
Dubbed ecstasy, it became a global party drug in the 1990s.
It is banned in most countries including Switzerland.
The drug is being provided by a Swiss pharmaceutical company and is administered at Oehen's practice in canton Solothurn, northern Switzerland.
Participants are also undergoing tests before and after MDMA-assisted therapy to see which areas of the brain are affected by PTSD and whether the therapy improves brain function.
The next step, once the US and Swiss trials are completed, will be for a global study of up to 500 patients.