First of all, if your doctor insists that taking an Anti-Depressant will "cure" your anxiety problems, then quite frankly he's full of shit. It definitely is true that Anti-Depressants are quite frequently very effective in treating anxiety. But no doctor should ever give their patient any sort of "guarantee" that a certain medication or type of medication will successfully treat any problem, & considering how the statistics on the success rate of Anti-Depressants are all over the place & therefore inconclusive by nature, your doctor really, REALLY shouldn't guarantee that an Anti-Depressant will successfully treat your anxiety.
I've never even heard of the medication your doctor wants to put you on, & I've never heard of anybody who's taken it either. & I've been prescribed a lot of different types of meds for Depression in my lifetime, as well as a lot for anxiety.
Why your doctor wants you on that medication, I really don't know. SSRIs -- medications like Zoloft, Prozac, & Lexapro, that effect your Serotonin levels only -- are thought to be the most effective Anti-Depressants for treating anxiety.
Also, according to my current psychiatrist, while Anti-Depressants that only increase Serotonin levels are often effective at treating anxiety, Anti-Depressants that focus on increasing Norepinephrine (sp?) levels not only aren't helpful for treating anxiety, but can make anxiety worse. My doctor explained to me the science behind it, but all I remember is that because of certain things about the differences in how Serotonin effects your brain & how Norepinephrine & Dopamine [Norepenephrine in your brain is "converted into" Dopamine, to put it in very simple terms], SNRIs (Serotonin-Norepenephrine Reuptake Inhibitors) ideally should only be prescribed for Depression when anxiety isn't present, or when other types of Anti-Depressants have been tried & found unsuccessful. I haven't heard anything about TeCAs in particular from any doctor -- I'm pretty sure those are really "old-school" meds -- but I know they effect Norepeneprhine [why do I even bother trying to spell that?] levels more intensely than SNRIs.
I have extreme anxiety problems & I've had absolutely horrible reactions to Anti-Depressants that effect Norepinephrine levels. However, my mom was recently prescribed Cymbalta (an SNRI) for her Depression & Anxiety problems, & she swears it helps her anxiety issues a lot, so obviously there are exceptions.
I'm not telling you to tell your doctor that you don't want to try the medications he suggests because of what I or anybody else on an internet forum said; I'm just saying there are definitely some questions you might want to raise with him about why he wants you on that medication.
&, considering how little TeCAs effect Serotonin levels, you actually still will be able to do MDMA. It will effect you a bit less, but it won't decrease the potency to the point where taking it is just pointless.