The findings of an extension study presented at the 18th European Congress of Psychiatry in Munich on 28 February suggest that asenapine has comparable efficacy and tolerability to olanzapine (Zyprexa).
Asenapine is currently awaiting European approval for the treatment of schizophrenia and manic episodes associated with bipolar disorder. It has antagonist activity at a range of serotonin, alpha-adrenergic, dopamine and histamine receptors.
The extension study enrolled 218 patients with manic or mixed episodes associated with bipolar I disorder, who had previously completed one of two short-term efficacy studies.
In the original trials, investigators randomised patients to receive 5mg or 10mg asenapine twice daily (as sublingual tablets), 5–20 mg olanzapine once daily, or placebo. Individuals who were randomised to active treatment continued their assigned regimen for the extension study; those randomised to the placebo group switched to asenapine.
After a total of 52 weeks of treatment, manic symptoms had declined to a similar extent with asenapine and olanzapine. The mean reduction in Young Mania Rating Scale score was 28.6 in the asenapine-treated patients and 28.2 in the patients who received olanzapine.
Within the group that received active treatment (rather than placebo) throughout the 52-week period, treatment-emergent adverse events occurred in 86.1% of patients who received asenapine and in 79.4% of olanzapine-treated patients. The most frequent adverse events were insomnia, sedation, and depression in the asenapine group and weight gain, somnolence, and sedation in the olanzapine group.