Hi, I suppose you have been drinking heavily because you are depressed. A lot of people do this.
You should not mix anti-depressants with alcohol. I think this would be difficult in your case.
As above, talk to a professional first.
Your question is a little unclear. You're asking how long you should be abstinent from alcohol before starting Wellbutrin? The answer for someone who drinks occasionally would be a few days.
You then mention concern over having an alcohol withdrawal induced seizure. That either tells me that you have been drinking a lARGE quantity of alcohol daily for an extended period of time, or you have overinflated views on alcohol withdrawal. You have to think of your safety, first and foremost.
The only safe way to approach this is to be 100% honest with your doctor. If you indeed have a substantial drinking problem, you may need to be safely, medically detoxed before starting on the Wellbutrin. The abrupt cessation of alcohol after heavy use over an extended period of time (several months or more, daily) can be dangerous, even deadly in certain circumstances. Don't mess with it.
Also, honesty is important with your doc, because he/she may choose a different medication for you, and would probably like to do some liver studies before starting a new medication. It will also probably be important to more closely monitor your liver function after starting a med. Also, if you approached your doc about being depressed and he Rx'd the Wellbutrin without full knowledge of everything going on, it is limiting the extent of the care you are receiving.
Please do this the right way, and please get help for the drinking, which means aftercare (either in AA, individual therapy, etc). Alcohol is a major depressant. After you get through the w/d's and start to come out of the fog, your mood will start to lift. The Wellbutrin (or other antidepressant) will be helpful with that.
Lastly, we have a couple of great communities here about alcohol abuse. You should check them out! They are full of people who understand and are compassionate. You can even repost this question as well, to get their input. Check them out!
Best of luck, please let us know how you're doing. Take care.