Adverse event load in bipolar participants receiving either carbamazepine immediate-release or extended-release capsules: a blinded, randomized study

In epilepsy, slow-release formulations of carbamazepine (CBZ) have fewer adverse events (AEs) compared with immediate-release (IR) formulations. As CBZ is used for mania, it is important to determine whether a similar pattern exists for bipolar patients. This was a 3-month, blinded, random-assignment study to an IR formulation or extended-release carbamazepine capsules (ERCC, Equetro) in type I or type II bipolar patients already on CBZ or clinically determined to benefit from it. Dosages were titrated to patients' clinical needs. Mood and AE ratings were performed at baseline and monthly for 3 months. There was no difference in mood ratings or in the total level of AEs in patients receiving IR or ERCC. However, autonomic AEs (5.0+/-1.1 vs. 2.0+/-0.7, P = 0.02) and gastrointestinal AEs (1.6+/-0.4 vs. 0.6+/-0.3, P = 0.05) were significantly less in participants receiving ERCC. CBZ level in patients receiving ERCC were higher (9.2+/-1.7 vs. IR 7.2+/-1.3 microg/ml, P = 0.005). Total AE load was directly related to CBZ level only in participants receiving the IR formulation. In conclusion, ERCC is better tolerated than IR CBZ in bipolar patients.