• Depressants (e.g. 2M2B, alcohol, barbiturates, benzodiazepines, GHB/GBL, methaqualone, opioids) - This combination potentiates the muscle relaxation, amnesia, sedation, and respiratory depression caused by one another and at higher doses, can lead to a sudden, unexpected loss of consciousness along with dangerously depressed respiration. There is also an increased risk of vomiting while unconsciousness and dying from the resulting suffocation. If nausea or vomiting occurs before consciousness is lost, users should attempt to fall asleep in the recovery position or have a friend move them into it.
• Stimulants (e.g. amphetamine, cocaine, methylphenidate, MDMA) - This combination can potentiate the anxiety-inducing, manic, delusional and disinhibiting effects of dissociatives, particularly those without pronounced motor suppressing components such as ketamine. The sum of these effects can increase the likelihood of an anxiety attack, delusions or a psychotic episode. There is also evidence that suggests that combining these two increases their neurotoxicity. Anecdotally, worsened comedowns are also commonly reported when these two classes of substances are combined.
• Dissociatives (e.g. dextromethorphan, ketamine, methoxetamine, PCP) - Combination can unpredictably potentiate amnesia, sedation, motor control loss and delusions. It may also result in a sudden loss of consciousness along with a dangerous amount of respiratory depression. If nausea or vomiting occurs before consciousness is lost, users should attempt to fall asleep in the recovery position or have a friend move them into it.