Try and see if you can download the package insert from the
manufacturer. It should have typical clearance rates for it.
I had to do this for another drug.

I think most drugs clear in 3-5 days.

Carbamazepine (Tegretol) has an average half-life-time of 8.5 hours,
with broad intraindividual variances (1.7 to 12 hours).
So, in the worst case (12 hours), after 3 days there is 1/64 of the
initial concentration left, which is a value well below threshold.
(Source: medical informations of the manufacturer Novartis)