I have experiance a seratonin crisis. If one likes being totally out of control of their body while they experiance siezures, out of contol heartrates, life threatening heart rhythms, loss of bowel/bladder control and hallucination not to mention the fun of being in intensive care. Then have fun...... I would not do anything ever again that could even REMOTELY cause this again. And the worse part of the whole thing is they cannot give you anything to counter act all of the above except for keeping IV fluids running, because some meds that will help with the sypmtoms will actually kill you during this time.
Also every person is different in how long it takes their body to totally "clear" AD's so it is a total guessing game. I know you cannot stop your "friend" but maybe this info will help.

PS my crises was cause by ULTRAM and a SSRI which were both perscibed by the same doc who did not know that this could happen!!!!