Nevertheless, research groups reported that 2.3% of patients with bipolar disorder who received asenapine monotherapy had PRL levels ≥ 4 times the upper limit of the normal range, compared with those who received a placebo (332, 342), In contrast, 9% of patients with schizophrenia who received asenapine (5 and 10 mg twice daily) had PRL levels over 2-fold the upper limit of the normal range compared with those who received a placebo (343). Here, PRL is linked to schizophrenia.