I certainly see your point about a 3-month injectable taking long to get off, if it is the culprit of your syncope. Does your doctor think it would be less likely to cause it than the pill form? I wonder why, if that is his thinking.

I would think that unless your doctor knows something about the injectable being more side effect friendly, there must be other reasons for the injectable. For example, if you tended to miss or skip that medication frequently. Or, if it happened to cost less money.

Obviously, I don't know your doctor's reasons, or if the injectable is a good idea. I will say that I find the extended release (XR) of Seroquel a bit more side effect friendly than the instant release (IR). I attribute that to the "action", as I call it in layman's terms.