It would be effective, but since it is an extract, you have to be extra careful with dosing. The difference between not enough and too much could be a matter of milligrams. It's a lot easier to microdose with rootbark, because you're working with more material. Plus I think it's better, since you really get ALL of the active constituents of the rootbark, not just what came through in the extraction.
It'll work, but you gotta start reeeeally small, because doing more iboga than you intended to can be really stressful.