First direct comparison of MDMA and MDA reveals distinct psychedelic differences

Researchers have directly compared the physical and psychological effects of the psychoactive drug MDMA with its chemical cousin MDA in human volunteers for the first time. The results show that MDA produces a longer lasting therapeutic experience with more visual distortions and adverse reactions. These outcomes suggest MDA may be less suited than standard MDMA for therapeutic uses. The study was published in the journal Neuropsychopharmacology.

MDMA is a widely known synthetic compound that promotes strong feelings of empathy, trust, and interpersonal connection. Because it reliably induces these emotional states, medical professionals are investigating the substance as a medication for psychotherapy in patients suffering from post-traumatic stress disorder. When a person consumes MDMA, their body breaks the molecule down into several secondary chemicals.

One of these breakdown products is a molecule called MDA. MDA is psychoactive in its own right and has a history of limited psychiatric exploration. Both substances fall into a broad category of drugs known as entactogens, which roughly translates to touching within.

Pharmacologically, both drugs work by releasing signaling chemicals in the brain, including serotonin and dopamine. Laboratory models show that MDA targets dopamine slightly more aggressively than MDMA does. It also exhibits a ten-fold higher activation of a specific serotonin receptor known to drive the subjective effects of classic psychedelics.

Despite these known molecular differences, researchers had never evaluated the two drugs side by side in a controlled human setting. Clinical pharmacologist Isabelle Straumann at the University Hospital Basel in Switzerland and her colleagues sought to map these distinctions. Clarifying how these chemicals operate in the body could guide future clinical decisions.

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The research team also wanted to test a new method for delivering these drugs. Fast-acting stimulants carry a high risk of abuse because they cause a rapid rush of euphoria. To slow the absorption of the drugs, the researchers created specialized versions by chemically attaching an amino acid called lysine to the standard MDMA and MDA molecules.

These combined molecules act as inactive carriers, known as prodrugs, which the body must metabolize before the active drug can enter the bloodstream. This slow-release strategy is already used in prescription medications for attention deficit hyperactivity disorder to lower their abuse potential.

To carry out the investigation, Straumann and her colleagues recruited 23 healthy adult volunteers. The group consisted of 12 women and 11 men. Each participant attended five different 13-hour testing sessions separated by at least two weeks.

During these sessions, the participants received one of five identical-looking capsules. The options included a placebo, a standard recreational dose of MDMA, a chemically equivalent dose of MDA, the lysine-attached version of MDMA, or the lysine-attached version of MDA. The trial used a double-blind design, meaning neither the participants nor the observing researchers knew which capsule was administered on any given day.

After taking the pill, each volunteer stayed in a quiet hospital room. Throughout the day, the research team repeatedly measured the participants’ blood pressure, pupil size, heart rate, and body temperature. The researchers also asked the volunteers to rate their subjective emotional and physical experiences on numbered visual scales.

Additionally, the team drew blood to track drug concentrations and hormone levels. They specifically looked for oxytocin, a hormone heavily associated with social bonding and trust. MDMA is known to trigger a massive release of oxytocin, which scientists suspect plays a role in its therapeutic benefit. Because oxytocin can be volatile to measure, the researchers also tracked a stable carrier protein called neurophysin I.

The gathered data showed that MDA produced a longer and subjectively more intense experience than MDMA. While the psychological effects of MDMA lasted about four hours for the average participant, the MDA effects lingered for more than six hours. MDA reached its peak effect in the body at the same two-hour mark as MDMA.

Participants reported that MDA caused stronger stimulant effects and provoked more visual distortions than its famous counterpart. The volunteers also experienced more fear and bad drug experiences while under the influence of MDA. Subacute adverse effects in the days following the session, such as headaches, exhaustion, and a lack of appetite, were slightly more prevalent after MDA use.

Both chemicals produced comparable increases in body temperature, heart rate, pupil size, and blood pressure. As expected, MDMA triggered a heavy release of oxytocin. The researchers found that MDA also increased circulating levels of oxytocin and its carrier protein, doing so slightly more intensely than MDMA.

When testing the slow-release prodrug versions, the researchers encountered a partial success. The lysine-attached MDA pill functioned exactly as intended. It delayed the onset of the drug’s effects by roughly an hour and pushed the peak subjective experience further out in time while keeping physiological responses similar to standard MDA.

The lysine-attached MDMA pill produced absolutely no physical or psychological effects. Blood tests confirmed that the participants’ bodies were completely unable to separate the active MDMA from the lysine molecule. The researchers suspect the highly specific chemical shape of the MDMA compound prevented digestive enzymes from completing the process.

Because the researchers expected the lysine-attached MDMA to work, this biological failure accidentally created a second placebo session for the participants. The volunteers reported greater subjective drug experiences during this second unexpected placebo day than they did during their scheduled placebo session. They reported feeling elevated and stimulated simply because they anticipated taking a mind-altering substance.

This observation highlights the enormous power of expectation in psychiatric research. The physical and emotional shifts caused by expectant belief can easily cross over into the interpretation of clinical results. The researchers noted that knowing a placebo might be administered may limit the scientific utility of a control group in psychedelic trials.

The researchers also observed minor differences in how certain groups processed the drugs. Female participants reported slightly more extreme visual and time alterations than male participants. Women also reported more subacute adverse effects in the days following the MDA sessions.

Participant genetics also played a role in drug clearance rates. Individuals with a specific variation of the CYP2D6 liver enzyme cleared the active chemicals from their systems at a slower rate. These poor metabolizers experienced a longer elimination half-life for the drugs and reported more exhaustion in the days following the study than participants with typical liver enzymes.

The specific trial features a few limitations that warrant attention in future studies. The researchers only tested a single dose of each substance. It remains entirely unclear how higher or lower amounts might shift the balance of prosocial and adverse effects.

The study also took place in a sterile clinical environment using healthy volunteers. People experiencing active psychiatric conditions might respond to the visual and emotional shifts of these substances in very different ways. Additionally, the trial used chemical mixtures rather than isolated drug variants, which can sometimes produce slightly distinct outcomes based on how they bind to brain receptors.

Future research will likely focus on tweaking the chemical structure of these molecules to maximize therapeutic benefits while minimizing adverse physical reactions. For now, the clinical data point to standard MDMA holding a more favorable psychological profile than its longer-acting chemical cousin.

The study, “Acute effects of MDMA, MDA, lysine-MDMA, and lysine-MDA in a randomized, double-blind, placebo-controlled, crossover trial in healthy participants,” was authored by Isabelle Straumann, Patrick Vizeli, Isidora Avedisian, Livio Erne, Diana Noorshams, Ina Vukalovic, Anne Eckert, Dino Luethi, Deborah Rudin, and Matthias E. Liechti.