Carbamazepine and lithium are sometimes used together therapeutically. In some patients, however, adverse CNS reactions occur, despite therapeutic serum concentrations of both agents. Concurrent administration of carbamazepine with colestipol results in a modest reduction in carbamazepine bioavailability. Although the reduction in carbamazepine bioavailability may not be clinically significant, staggering the times of administration of these agents should alleviate any drug interaction. In the same study, cholestyramine did not affect carbamazepine bioavailability.
Hematologic toxicity is possible during therapy with carbamazepine.
Patients should undergo routine monitoring of hematologic function, and any serious indication of bone marrow depression warrants discontinuation of the drug. Early symptoms of toxicity can include fever, pharyngitis, oral ulceration, or unusual bruising or bleeding. Leukopenia, thrombocytopenia, leukocytosis, eosinophilia, agranulocytosis, pancytopenia, or aplastic anemia have been reported with carbamazepine. CNS effects of carbamazepine include dizziness, drowsiness, fatigue, ataxia, blurred vision, diplopia, and hallucinations. Sedation may be seen for the first few days of therapy or following a dosage increase.