Although the combined use of 
lithium and 
carbamazepine is beneficial in many patients, mild to severe neurotoxicity is reported to have developed in some, and possibly sinus node dysfunction in others. 
 Monitor the outcome of concurrent use carefully, but note that signs of 
toxicity have developed even with 
lithium levels within the normal range. Risk factors appear to be a history of neurotoxicity with 
lithium therapies and compromised medical or neurological functioning.