Ecstasy doesn't drain your spinal fluid, it floods your brain with a neurotransmitter called Serotonin and your brain replenishes itself the days following the use.

Lexapro is an SSRI with a higher binding affinity to 5-HT receptors than MDMA, so it will block much of its effects. The half life of Lexapro is up to 32 hours, so you would have to stop talking them for about a week to be sure. Abruptly stopping the use of such an anti-depressant medication could lead to problems so use caution.

DXM is another story, it is recommended that you don't combine MDMA and DXM within at least 48 hours of each other because of something called serotonin syndrome.