You bought carbamazepine, or a doctor prescribed it for you? It is a Rx (prescription only) medication.

Either way, you did research- okay good and you know that it can substitute as a mood stabilizer for bipolar/schizoaffective.

Yes, there are researchers showing a correlation, and therefore possible direct relation between lithium use and renal impairment.

www.ncbi.nlm.nih.gov says that: "Unfortunately the potential side effects of lithium have always been an issue, and among these the possible impact of long-term lithium treatment on renal function has given rise to considerable concern. Lithium is known to affect renal concentrating ability, and lithium-induced polyuria is not uncommon, estimated to affect approximately 20% of patients, but this is rarely clinically significant. It is less clear, however, whether or not the protracted use of lithium can cause progressive deterioration in renal function, culminating in renal failure. Results of several long-term studies suggest that this is not the case, and the consensus of literature has been that in the absence of lithium toxicity, long-term sequelae are rare. On the other hand there are a number of case reports which describe instances of renal insufficiency in lithium treated patients with no other obvious cause. At the present time regular monitoring of renal function is still recommended."

Therefore, I would not stray from the lithium unless you specifically were directed to do so by a doctor with sufficient knowledge of the two drugs at hand, and their effects. I have been there, had some issues with lithium and tried to fix it on my own. Like many other plans, could either go really well or prove to be a significant issue.