The drug, which is often referred to as Ecstasy or Molly in its street form, has been involved in eight clinical trials by the Multidisciplinary Association for Psychedelic Studies (MAPS) in the US. The organisation is interested in using MDMA to treat post-traumatic stress disorder (PTSD) and hopes it will be approved for use as a medicine in 2021.

If MDMA is accepted as a prescription in the US, this could then lead to it being stocked at pharmacies in the UK.

Scientists working for MAPS have now treated 136 people using MDMA and another phase of clinical trials is due to start next year.

Brad Burge of MAPS said: “Phase 3 starts around 2017, and it will take four to five years to finish. So that will put it at early 2021 for FDA approval.”

U.S. psychiatrist Michael Mithoefer has been leading the clinical trials into the use of MDMA as a treatment for PTSD. His team initially worked with people who had been living with PTSD for an average of 20 years, mostly as a result of sexual abuse, and had found conventional anti-depressants were not effective.

In one trial, 12 patients were given a dose of MDMA on two or three occasions as part of an eight-hour psychotherapy session with two therapists. Meanwhile eight other patients were given a placebo instead of the MDMA.

The Pure form of Ecstasy is thought to help PTSD

The research found that 83% of those who had taken the MDMA showed significant improvement with their PTSD, compared to 25% of those taking the placebo.

Research is also being carried out into whether MDMA could help people with autism to feel less anxious in social situations. And scientists are looking into the use of the drug to relieve anxiety in terminally ill people.

If MDMA is approved as a medication, it will not be in the same form as drug users take on a night out. Ecstasy sold by drug dealers is often mixed with other substances, which could make it more dangerous.

Ecstasy is often seen as a party drug and became popular with users during the 1980s and 1990s. People who take it often get a surge of energy and feelings of warmth and affection.

However, there can be serious risks and 670 people have died after taking the drug in England and Wales between 1996 and 2014. It is particularly dangerous if taken by anyone with asthma, a heart condition, high or low blood pressure or epilepsy.

Users can also experience paranoia, confusion, anxiety and panic attacks.