Add-On Mirtazapine Enhances Effects on Cognition in Schizophrenic Patients Under Stabilized Treatment With Clozapine

The development of therapeutic strategies for cognitive dysfunction remains one of the primary goals in the treatment of schizophrenia. The pharmacodynamic profile of mirtazapine, an antidepressant that enhances noradrenergic and serotonergic transmission, is based on a presynaptic α2 antagonism and postsynaptic 5-HT2 and 5-HT3 antagonism. Mirtazapine shares some pharmacological similarities with that of clozapine. This 8-week open label trial aimed to discover whether the addition of 30 mg mirtazapine could potentiate the effects on cognition of an ongoing stabilized clozapine therapy in 15 persons who met the criteria for chronic schizophrenia in the Diagnostic and Statistical Manual of Mental Disorders (4th ed., text rev.; American Psychiatric Association, 2000). Mirtazapine adjunction was well tolerated and induced a significant improvement in cognitive performance, as measured by the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS; Randolph, 1998) total score and by the subscales for immediate and delayed memory (p < .01). Since Hamilton Depression Rating Scale (HAM-D; Hamilton, 1967), Brief Psychiatric Rating Scale (BPRS; Overall & Gorham, 1962), and Scale for the Assessment of Negative Symptoms (SANS; Andreasen, 1989) scores at Week 8 did not show significant differences from baseline, the improvements in the effects of clozapine on cognition observed after the addition of mirtazapine seemed to be a direct rather than an indirect action of this drug (e.g., via mood or other psychopathological symptoms). These findings suggest a potential role for mirtazapine as a useful strategy to augment the efficacy of clozapine in the treatment of cognitive dysfunctions in chronic schizophrenia. © 2007 American Psychological Association.