Atypical antipsychotic properties of AD-6048, a primary metabolite of blonanserin

Long-term oral blonanserin treatment for schizophrenia: a review of Japanese long-term studies

In general, the course of schizophrenia is chronic accompanied not only by positive and negative symptoms but also by cognitive dysfunction associated with psychosocial disability, and thus treatment combining antipsychotics and psychological therapy is considered promising. This review focused on two prospective, open-label, multicenter, phase 3 long-term studies for approval of oral blonanserin for the treatment of schizophrenia. These two studies included both inpatients and outpatients with variable disease duration or symptom prominence according to the Positive and Negative Syndrome Scale (PANSS). The selected two studies consisted of almost the same study schedule and eligibility criteria but different protocols regarding prior medications and concomitant antipsychotics. The proportion of patients who had a baseline PANSS negative score higher than the positive score was 82.2 and 67.2% in the two studies. In both studies, patients with an illness duration of ≥ 10 years were the most common. Based on the clinical symptoms at baseline, the physician determined the treatment: blonanserin monotherapy, blonanserin in combination with the existing antipsychotic medication, or therapy simplified to haloperidol together with blonanserin. The 28-week completion rate for long-term blonanserin treatment was high in both studies (82.2 and 78.7%). The types of adverse events in both studies were similar to those in the preceding 8-week randomized, active-controlled studies in Japan, which were included in the application package for the approval of oral blonanserin for patients with schizophrenia. Long-term blonanserin use did not increase the risk of extrapyramidal symptoms but reduced the dose of antiparkinsonian drugs, minimally affecting functioning. In both studies, the PANSS total score, positive score, and negative score were improved at the last observation carried forward compared with those at baseline. In conclusion, blonanserin is useful for long-term treatment of chronic schizophrenic patients when the appropriate management of clinical symptoms and adverse drug reactions are applied. Blonanserin might represent a promising treatment option that partially or completely relieves patients with chronic schizophrenia of polypharmacy. Blonanserin may possibly fit both the current real-world clinical setting and the currently recommended approach to antipsychotic medication.

Effects of food and grapefruit juice on single-dose pharmacokinetics of blonanserin in healthy Chinese subjects

PURPOSE

The purpose of this study was to investigate the potential effects of a meal and grapefruit juice on the pharmacokinetics of blonanserin and its metabolite N-desethyl blonanserin in healthy Chinese volunteers.

METHODS

This was a single-centre, open-label, fixed-sequence study, where 12 healthy Chinese volunteers received a single dose of 8 mg blonanserin after an overnight fast in period 1 (reference), a high-fat meal during period 2 and with co-administration of 250 mL of grapefruit juice in period 3. The washout period was 7 days. Series of plasma samples were collected after each dose to determine concentrations of blonanserin and its metabolite N-desethyl blonanserin using liquid chromatography-tandem mass spectrometry. Pharmacokinetic parameters were estimated by non-compartmental analysis and compared between periods by standard average bioequivalence ANOVA. Adverse events were monitored throughout the study.

RESULTS

All subjects completed the study. High-fat meals significantly increased blonanserin exposure (AUC_t) 2.58-fold (90% CI 2.21, 3.02), relative to the reference period. Co-administration of blonanserin with grapefruit juice remarkably prolonged elimination half-life of blonanserin (from 9.7 to 21.4 h) and significantly increased exposures to blonanserin and N-desethyl blonanserin by 5.82-fold (90% CI 4.57, 7.42) and 1.81-fold (90% CI 1.65, 1.98), respectively.

CONCLUSIONS

These results suggested that blonanserin was largely metabolised in the intestinal tract before becoming systemically available, and both food and grapefruit juice enhanced exposure to blonanserin and N-desethyl blonanserin. Grapefruit juice increased bioavailability and may have reduced systemic clearance of blonanserin. Further intestinal CYP3A4 and hepatic CYP3A4 might be postulated to explain the delayed elimination of blonanserin. Dose adjustment of blonanserin is needed on the basis of co-intake of known strong CYP3A4 inhibitor. Patients taking high-dose blonanserin also need to be cautious about the ingestion of grapefruit juice.

Glycine-Binding Site Stimulants of NMDA Receptors Alleviate Extrapyramidal Motor Disorders by Activating the Nigrostriatal Dopaminergic Pathway

Dysfunction of the N-methyl-d-aspartate (NMDA) receptor has been implicated in the pathogenesis of schizophrenia. Although agonists for the glycine-binding sites of NMDA receptors have potential as new medication for schizophrenia, their modulation of antipsychotic-induced extrapyramidal side effects (EPS) has not yet been clarified. We herein evaluated the effects of glycine-binding site stimulants of NMDA receptors on antipsychotic-induced EPS in mice and rats. d-cycloserine (DCS) and d-serine significantly improved haloperidol (HAL)-induced bradykinesia in mice, whereas glycine showed no effects. Sodium benzoate, a d-amino acid oxidase inhibitor, also attenuated HAL-induced bradykinesia. Improvements in HAL-induced bradykinesia by DCS were antagonized by the NMDA antagonist dizocilpine or nitric oxide synthase inhibitor L-N^G-Nitro-l-arginine methyl ester. In addition, DCS significantly reduced HAL-induced Fos expression in the dorsolateral striatum without affecting that in the nucleus accumbens. Furthermore, a microinjection of DCS into the substantia nigra pars compacta significantly inhibited HAL-induced EPS concomitant with elevations in dopamine release in the striatum. The present results demonstrated for the first time that stimulating the glycine-binding sites of NMDA receptors alleviates antipsychotic-induced EPS by activating the nigrostriatal dopaminergic pathway, suggesting that glycine-binding site stimulants are beneficial not only for efficacy, but also for side-effect management.

Nicotine Elicits Convulsive Seizures by Activating Amygdalar Neurons

Nicotinic acetylcholine (nACh) receptors are implicated in the pathogenesis of epileptic disorders; however, the mechanisms of nACh receptors in seizure generation remain unknown. Here, we performed behavioral and immunohistochemical studies in mice and rats to clarify the mechanisms underlying nicotine-induced seizures. Treatment of animals with nicotine (1–4 mg/kg, i.p.) produced motor excitement in a dose-dependent manner and elicited convulsive seizures at 3 and 4 mg/kg. The nicotine-induced seizures were abolished by a subtype non-selective nACh antagonist, mecamylamine (MEC). An α7 nACh antagonist, methyllycaconitine, also significantly inhibited nicotine-induced seizures whereas an α4β2 nACh antagonist, dihydro-β-erythroidine, affected only weakly. Topographical analysis of Fos protein expression, a biological marker of neural excitation, revealed that a convulsive dose (4 mg/kg) of nicotine region-specifically activated neurons in the piriform cortex, amygdala, medial habenula, paratenial thalamus, anterior hypothalamus and solitary nucleus among 48 brain regions examined, and this was also suppressed by MEC. In addition, electric lesioning of the amygdala, but not the piriform cortex, medial habenula and thalamus, specifically inhibited nicotine-induced seizures. Furthermore, microinjection of nicotine (100 and 300 μg/side) into the amygdala elicited convulsive seizures in a dose-related manner. The present results suggest that nicotine elicits convulsive seizures by activating amygdalar neurons mainly via α7 nACh receptors.