citalopram has a half-life of 35h, so it's going to take a while until it is out of your body. a good amount of time would probably be 5-7 days. but keep in mind that ssris can effect long lasting changes in your serotonin system that also dampen or kill mdma's effects. how long you took the citalopram and in which dose (and of course how you react to it) will influence how long it takes for mdma to work normally again. some people report that having the ssri out of their body is enough, others report a timescale of months or even years.