Abstract
Background. Predictors of response to psychoactive drugs are valuable in providing practical guidance and in optimizing a treatment regimen. Here we used linear regression analysis to identify treatment-specific predictors of response to therapy with beaded extended-release carbamazepine capsules (CBZ-ERC) (Shire, Wayne, PA, USA) in 600 outpatients with bipolar disorder.
Methods. Data were obtained from medical charts of subjects who received CBZ-ERC in a private practice setting. Illness severity and improvement were assessed using the Clinical Global Impression–Severity (CGI-S) and Clinical Global Impression–Improvement (CGI-I) scales.
Results. We found that increasing baseline CGI-S scores correlated with lower CGI-I scores (R2 = 0.01, p = 0.009); that is, the higher the baseline CGI-S score, the greater the expected degree of improvement. There was also a correlation between increasing CBZ-ERC dose and improvement in CGI-I scores (R2 = 0.02; p = 0.0004). Moreover, we found that increasing carbamazepine (CBZ) blood concentration correlated with decreases in CGI-I scores (R2 = 0.12; p = 0.025), and that there was a correlation between higher total daily CBZ-ERC dose in mg/kg of body weight and decreases in CGI-I scores (R2 = 0.01; p = 0.038).
Conclusions. These findings suggest that bipolar patients with more severe baseline symptoms, on higher CBZ-ERC doses, and with higher CBZ blood levels were more likely to respond to CBZ-ERC treatment.
Notes
aDose at best office visit.
bMeasured at or near best.
aData points may contain data from more than one office visit per patient or when both variables were available at the same office visit.