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BackgroundWe aimed to explore relations between symptomatic remission and functionality evaluation in schizophrenia patients treated with paliperidone extended-release (ER), as seen in a normal day-to-day practice, using flexible dosing regimens of paliperidone ER. We explored symptomatic remission rate in patients treated with flexibly dosed paliperidone ER by 8 items of Positive and Negative Syndrome Scale (PANSS) and change of Personal and Social Performance (PSP) scale.MethodThis was a 12-week multicenter, open-label, prospective clinical study conducted in in-patient and out-patient populations. Flexible dosing in the range 3-12 mg/day was used throughout the study. All subjects attended clinic visits on weeks 0, 4, 8, and 12 as usual clinical practice for the 12-week observation period. Data were summarized with respect to demographic and baseline characteristics, efficacy measurement with PANSS scale, PSP, and social functioning score, and safety observations. Descriptive statistics were performed to identify the retention rate at each visit as well as the symptomatic remission rate. Summary statistics of average doses the subjects received were based on all subjects participating in the study.ResultsA total of 480 patients were enrolled. Among them, 426 patients (88.8%) had evaluation at week 4 and 350 (72.9%) completed the 12-week evaluation. Patients with at least moderate severity of schizophrenia were evaluated as "mild" or better on PANSS scale by all 8 items after 12 weeks of treatment with paliperidone ER. There was significant improvement in patients' functionality as measured by PSP improvement and score changes. Concerning the other efficacy parameters, PANSS total scale, PSP total scale, and social functioning total scale at the end of study all indicated statistically significant improvement by comparison with baseline. The safety profile also demonstrated that paliperidone ER was well-tolerated without clinically significant changes after treatment administration.ConclusionsAlthough the short-term nature of this study may limit the potential for assessing improvements in function, it is noteworthy that in the present short-term study significant improvements in patient personal and social functioning with paliperidone ER treatment were observed, as assessed by PSP scale.Trial RegistrationClinical Trials. PAL-TWN-MA3

Aripiprazole is a novel atypical antipsychotic drug with neuroprotective properties. As excessive glutamate release is now considered to be part of the pathophysiology of schizophrenia, the objective of this study was to use an in vitro assay system to investigate the effect of aripiprazole and its human metabolite OPC14857 on the release of endogenous glutamate from isolated nerve terminals (synaptosomes), freshly prepared from rat prefrontal cortex. Both aripiprazole and OPC13857 potently inhibited 4-aminopyridine (4-AP)-evoked glutamate release in a concentration-dependent manner. Inhibition of glutamate release by aripiprazole and OPC13857 was associated with a reduction of 4AP-evoked Na+ influx and depolarization, as well as downstream elevation of cytoplasmic free calcium concentration mediated via N- and P/Q-type voltage-dependent Ca2+ channels (VDCCs). Release induced by direct Ca2+ entry with Ca2+ ionophore (ionomycin) was unaffected by aripiprazole or OPC13857, indicating that the inhibitory effect of aripiprazole or OPC13857 is not due to directly interfering with the release process at some point subsequent to Ca2+ influx. In addition, the dopamine D2 receptor antagonist haloperidol and the 5-HT 1A receptor antagonist WAY100635 all effectively blocked the aripiprazole or OPC13857-mediated inhibition of 4-AP-evoked glutamate release. Moreover, aripiprazole or OPC13857 modulation of 4-AP-evoked glutamate release appears to involve a protein kinase A (PKA) signaling cascade, insofar as pretreatment of synaptosomes with the PKA inhibitor H89 suppressed the inhibitory effect of aripiprazole or OPC13857. Together, these results suggest that aripiprazole and its human metabolite OPC14857 inhibit glutamate release from rat prefrontocortical nerve terminals, likely by the activation of dopamine D2 and 5-HT 1A receptors, which subsequently results in the reduction of nerve terminal excitability and downstream VDCC activation through a signaling cascade involving PKA. These actions of aripiprazole may contribute to its neuroprotective effect in excitotoxic injury.