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Keywords:

  • Anti-serotonin 5-HT2A activity/anti-dopamine D2 activity ratio;
  • blonanserin;
  • DIEPSS;
  • drug-induced extrapyramidal symptoms;
  • plasma concentration

Aims:  Blonanserin is a second-generation antipsychotic that was developed in Japan. We investigated the relationships between plasma concentration, the plasma anti-5-HT2A activity/anti-D2 activity (S/D) ratio and extrapyramidal symptoms (EPS) in blonanserin dosing.

Methods:  The subjects were 29 outpatients with schizophrenia. We assessed EPS using the Drug-Induced Extrapyramidal Symptoms Scale (DIEPSS). The plasma concentrations were measured by high performance liquid chromatography, and the plasma anti-D2 and anti-5-HT2A activities were measured by [3H]-spiperone and [3H]-ketanserin radioreceptor assays.

Results:  The results revealed that there were significant correlations between both the plasma concentration and the DIEPSS total score (P < 0.05). A negative correlative tendency was found between the S/D ratio and the DIEPSS total score. Furthermore, the plasma concentrations were divided into a low plasma concentration group and a high plasma concentration group, and the S/D ratios were divided into a low S/D ratio group and a high S/D ratio group. We then compared each group based on the DIEPSS total scores. The score in the high plasma concentration-low S/D ratio group was significantly higher than in the high plasma concentration-high S/D ratio, low plasma concentration-high S/D ratio and low plasma concentration-low S/D ratio groups (P < 0.05 for all).

Conclusions:  These findings indicate that the incidence of EPS during treatment with blonanserin is mainly determined by plasma concentration, but the incidence of EPS may be inhibited when anti-5HT2A activity is predominant over anti-D2 activity.