Real-world effectiveness of antipsychotic treatments in 1011 acutely hospitalized patients with schizophrenia: A one-year follow-up study.

PURPOSE: To compare the real-world effectiveness of antipsychotic treatments focusing on long-acting injectable antipsychotic medications (LAIs) and antipsychotic polytherapies except polytherapy involving clozapine (APEC) for patients with schizophrenia. METHODS: This prospective study was conducted over a 19-month period in 12 psychiatric emergency hospitals in Japan. Patients who were newly admitted to psychiatric emergency wards between September 2019 and March 2020 because of acute onset or exacerbation of Schizophrenia and Other Psychotic Disorders as defined by the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, were included. All patients were followed for one-year after discharge or until March 31, 2021. The primary outcome was the risk of treatment failure defined as psychiatric rehospitalization, discontinuation of medication, death, or continuation of hospitalization for one year. Cox proportional hazards multivariate regression was used for analyses. RESULTS: A total of 1011 patients were enrolled (women, 53.7%; mean [SD] age, 47.5 [14.8] years). During follow-up, 588 patients (58.2%) experienced treatment failure including rehospitalization (513 patients), discontinuation of medication (17 patients), death (11 patients), and continuation of hospitalization for one-year (47 patients). Switching to LAIs (hazard ratio [HR] 0.810, 95%CI 0.659-0.996) and APEC (HR 0.829, 95%CI 0.695-0.990) were significantly associated with a low rate of treatment failure. CONCLUSIONS: Switching to LAIs and APEC in early non-responders seems to be beneficial for the prevention of treatment failure in acutely admitted patients with schizophrenia. The risk of treatment failure was about 19% and 17% lower in patients treated with LAIs and APEC, respectively, than in patients treated without them.

Real-world effectiveness of antipsychotic monotherapy and polytherapy in 1543 patients with acute-phase schizophrenia.

PURPOSE: The effectiveness of antipsychotic treatments in the acute phase of schizophrenia in actual clinical practice remains somewhat unclear. Therefore, the purpose of the present naturalistic, multi-center study conducted from 1 year starting in September 2017 was to examine the response rate to an initial or second antipsychotic in newly admitted patients with acute-phase schizophrenia, as well as the response rate and quality of augmentation with two antipsychotics in patients who failed to respond to both the initial and second antipsychotics. RESULTS: In total, there were 660 (42.8%) and 243 (15.7%) responders to an initial and a second antipsychotic, respectively; thus, 58.5% of all patients were responders to an initial or second antipsychotic. Among 581 nonresponders (37.7%), the initial antipsychotic or a third antipsychotic was added to the second antipsychotic. Among these patients, 89.8% showed a Clinical Global Impression-Improvement score ≤3 (from 'minimally improved' to 'very much improved'). The rates of adverse events such as hyperglycemia, hyper-low-density lipoprotein cholesterolemia, hypertriglyceridemia, hyperprolactinemia, QTc prolongation, and extrapyramidal symptoms were not high in patients receiving augmentation with two antipsychotics compared with all patients, and no serious adverse events were reported. CONCLUSION: Antipsychotic augmentation may be an option in acute-phase treatment for patients who do not respond to either an initial or a second antipsychotic.

A prospective naturalistic multicenter study on choice of parenteral medication in psychiatric emergency settings in Japan.

AIM: To provide information about psychiatric emergency situations in Japan, we examined psychiatrists' preference among parenteral medication since intramuscular (IM)-olanzapine became available and clinical characteristics in patients given IM-olanzapine compared to those given other parenteral medication. METHODS: We conducted a naturalistic study proceeding over a 1-year period in 9 psychiatric emergency departments. RESULTS: Among 197 patients, the distribution of IM-injections (n = 89) was as follows: IM-olanzapine, 66 patients (74.2%), IM-levomepromazine, 17 patients (19.1%), IM-haloperidol, 5 patients (5.6%), and IM-diazepam, 1 patient (1.1%). The distribution of intravenous (IV)-injections (n = 108) was as follows: IV-haloperidol, 78 patients (72.2%), and IV-benzodiazepines (diazepam, flunitrazepam, or midazolam), 30 patients (27.8%). Advantages of IM-olanzapine over other parenteral medications in efficacy were found as follows: less frequent needs of an additional injection despite no difference in duration until a patient became cooperative for oral administration, and less frequent needs of restraint after the injection. Furthermore, advantages of IM-olanzapine over other injections in safety were found as follows: less frequent appearance of extrapyramidal symptoms, no occurrence of ECG abnormality and other serious adverse events except a fall, less frequent needs of an adjunctive anticholinergic drug, and less frequent needs of another kind of drug additionally injected. CONCLUSIONS: Olanzapine has rapidly become the first choice of intramuscular medication in psychiatric emergency situations since it became available in Japan, probably due to the advantages in both efficacy and safety. This study reflecting psychiatric emergency practice in Japan may contribute to periodic international comparison of psychiatric emergency practice.

Antipsychotic switching versus augmentation among early non-responders to risperidone or olanzapine in acute-phase schizophrenia.

PURPOSE: We examined whether augmentation with olanzapine would be superior to switching to olanzapine among early non-responders (ENRs) to risperidone, and whether augmentation with risperidone would be superior to switching to risperidone among ENRs to olanzapine. We performed a rater-blinded, randomized clinical trial at psychiatric emergency sites. Eligible patients were newly admitted patients with acute schizophrenia. ENRs to the initial antipsychotic (Clinical Global Impressions-Improvement Scale: ≥ 4 at 2 weeks) were allocated to receive either augmentation with or switching to the other antipsychotic (RIS+OLZ vs. RIS-OLZ; OLZ+RIS vs. OLZ-RIS) RESULTS: Sixty patients who completed 2 weeks of risperidone treatment were divided into 33 early responders (RIS-ER) and 27 ENRs (RIS+OLZ, n=14; RIS-OLZ, n=13). Although time to treatment discontinuation for any cause was significantly shorter in RIS+OLZ group (54.1 days [95% confidence interval, 41.3-67.0]) than in RIS-ER group (68.7 [61.2-76.2]; P=0.050), it was not significantly shorter in RIS-OLZ group (58.5 [43.1-73.9]) than in RIS-ER group (P=0.19). Sixty patients who completed 2 weeks of olanzapine treatment were divided into 36 early responders (OLZ-ER) and 24 ENRs (OLZ+RIS, n=11; OLZ-RIS, n=13). Although time to treatment discontinuation for any cause was significantly shorter in OLZ-RIS group (56.1days [40.7-71.5]) than in OLZ-ER group (74.9 [68.5-81.3]; P=0.008), it was not significantly shorter in OLZ+RIS group (64.6 [49.6-79.6]) than in OLZ-ER group (P=0.20). CONCLUSION: Despite the lack of pharmacokinetic investigation of dose adequacy in this study, it is possible that switching to olanzapine among ENRs to risperidone might have a small advantage over augmentation with olanzapine, while augmentation with risperidone might have a small advantage over switching to risperidone among ENRs to olanzapine. Further research is required before it would be appropriate to modify routine practice in the direction of these findings.

The possibility that requiring high-dose olanzapine cannot be explained by pharmacokinetics in the treatment of acute-phase schizophrenia.

We examined clinical characteristics including serum olanzapine concentrations for acute schizophrenia patients who required above conventional doses. We performed a rater-blinded, randomized clinical trial in 12 psychiatric emergency sites. Eligible patients were 18-64 years old and met diagnostic criteria for schizophrenia, acute schizophrenia-like psychotic disorder, or schizoaffective disorder. A total of 42 patients were randomly assigned by means of sealed envelopes to receive risperidone (3-12 mg/day; n=20) and olanzapine (10-40 mg/day; n=22), with follow-up at 8 weeks. The Negative score of the Positive and Negative Syndrome Scale was significantly higher in patients who required high doses than in patients who responded to conventional doses. Serum olanzapine concentrations at the time of oral 20mg/day could be obtained from 5 out of 7 patients who subsequently required high-dose olanzapine. All values were more than 30 ng/mL after 11-16 h from dosing to sample collection, and the mean value was 47.876 (S.D. 21.546) ng/mL. Such concentrations are appropriate with respect to a therapeutic range of 20-50 ng/mL. The present study has shown evidence that the reason for requiring high-dose olanzapine cannot be explained by pharmacokinetics in the treatment of acute-phase schizophrenia.

Volume reductions in frontopolar and left perisylvian cortices in methamphetamine induced psychosis.

Consumption of methamphetamine disturbs dopaminergic transmission and sometimes provokes schizophrenia-like-psychosis, named methamphetamine-associated psychosis (MAP). While previous studies have repeatedly reported regional volume reductions in the frontal and temporal areas as neuroanatomical substrates for psychotic symptoms, no study has examined whether such neuroanatomical substrates exist or not in patients with MAP. Magnetic resonance images obtained from twenty patients with MAP and 20 demographically-matched healthy controls (HC) were processed for voxel-based morphometry (VBM) using Diffeomorphic Anatomical Registration using Exponentiated Lie Algebra. An analysis of covariance model was adopted to identify volume differences between subjects with MAP and HC, treating intracranial volume as a confounding covariate. The VBM analyses showed significant gray matter volume reductions in the left perisylvian structures, such as the posterior inferior frontal gyrus and the anterior superior temporal gyrus, and the frontopolar cortices, including its dorsomedial, ventromedial, dorsolateral, and ventrolateral portions, and white matter volume reduction in the orbitofrontal area in the patients with MAP compared with the HC subjects. The smaller regional gray matter volume in the medial portion of the frontopolar cortex was significantly correlated with the severe positive symptoms in the individuals with MAP. The volume reductions in the left perisylvian structure suggest that patients with MAP have a similar pathophysiology to schizophrenia, whereas those in the frontopolar cortices and orbitofrontal area suggest an association with antisocial traits or vulnerability to substance dependence.

A comparison between augmentation with olanzapine and increased risperidone dose in acute schizophrenia patients showing early non-response to risperidone.

We examined whether augmentation with olanzapine would be superior to increased risperidone dose among acute schizophrenia patients showing early non-response to risperidone. We performed a rater-blinded, randomized controlled trial at psychiatric emergency sites. Eligible patients were newly admitted patients with acute schizophrenia. Early response was defined as Clinical Global Impressions-Improvement Scale score ≤3 following 2 weeks of treatment. Early non-responders were allocated to receive either augmentation with olanzapine (RIS+OLZ group) or increased risperidone dose (RIS+RIS group). The 78 patients who completed 2 weeks of treatment were divided into 52 early responders to risperidone and 26 early non-responders to risperidone (RIS+OLZ group, n=13; RIS+RIS group, n=13). No difference in the achievement of ≥50% improvement in Positive and Negative Syndrome Scale total score was observed between RIS+OLZ and RIS+RIS groups. Although time to treatment discontinuation for any cause was significantly shorter in the RIS+RIS group (6.8 weeks [95% confidence interval, 5.2-8.4]) than in early responders to risperidone (8.6 weeks [7.9-9.3]; P=0.018), there was no significant difference between the RIS+OLZ group (7.9 weeks [6.3-9.5]) and early responders to risperidone. Secondary outcomes justify the inclusion of augmentation arms in additional, larger studies comparing strategies for early non-responders.

Reduced amygdala and hippocampal volumes in patients with methamphetamine psychosis.

The similarity between psychotic symptoms in patients with schizophrenia such as hallucinations and delusions and those caused by administration of methamphetamine has been accepted. While the etiology of schizophrenia remains unclear, methamphetamine induced psychosis, which is obviously occurred by methamphetamine administration, had been widely considered as a human pharmaceutical model of exogenous psychosis. Although volume reductions in medial temporal lobe structure in patients with schizophrenia have repeatedly been reported, those in patients with methamphetamine psychosis have not yet been clarified. Magnetic resonance images (MRI) were obtained from 20 patients with methamphetamine psychosis and 20 age, sex, parental socio-economic background, and IQ matched healthy controls. A reliable manual tracing methodology was employed to measure the gray matter volume of the amygdala and the hippocampus from MRIs. Significant gray matter volume reductions of both the amygdala and hippocampus were found bilaterally in the subjects with methamphetamine psychosis compared with the controls. The degree of volume reduction was significantly greater in the amygdala than in hippocampus. While the total gray, white matter and intracranial volumes were also significantly smaller-than-normal in the patients; the regional gray matter volume reductions in these medial temporal structures remained statistically significant even after these global brain volumes being controlled. The prominent volume reduction in amygdala rather than that in hippocampus could be relatively specific characteristics of methamphetamine psychosis, since previous studies have shown significant volume reductions less frequently in amygdala than in hippocampus of the other psychosis such as schizophrenia.

Difference in early prediction of antipsychotic non-response between risperidone and olanzapine in the treatment of acute-phase schizophrenia.

PURPOSE: We examined whether early response/non-response to risperidone according to the Clinical Global Impressions-improvement scale (CGI-I) at 2 weeks could predict subsequent response. This prediction was also applied to olanzapine. We then investigated whether early non-responders (ENRs) to risperidone or olanzapine who switched to the other showed significantly greater improvement, compared with those staying on the initial antipsychotic. We performed a rater-blinded, randomized controlled trial in 18 psychiatric emergency sites. Eligible patients were newly admitted patients with acute schizophrenia. Early response was defined as CGI-I ≤ 3 following 2 weeks of treatment. The primary outcome measure was achievement of remission and ≥ 50% improvement in the Positive and Negative Syndrome Scale at 4 weeks. RESULTS: At 4 weeks, 53% of risperidone early responders (ERs) went into remission, whereas only 9% of ENRs staying on risperidone (n=11) did (P=0.016). Similarly, at 4 weeks, 81% of risperidone ERs achieved ≥ 50% response, whereas only 9% of ENRs staying on risperidone achieved ≥ 50% response (P < 0.0001). In contrast, 58% of olanzapine ERs (n=33) went into remission, whereas 38% of ENRs staying on olanzapine (n=8) did at 4 weeks (P=0.44). Similarly, 61% of olanzapine ERs achieved ≥ 50% response, whereas 25% of ENRs staying on olanzapine achieved ≥ 50% response (P=0.12). The negative likelihood ratio for the prediction of ≥ 50% response at 4 weeks by early response status to risperidone at 2 weeks was 0.057. CONCLUSION: In newly admitted patients with acute schizophrenia, non-response to risperidone using CGI-I at 2 weeks can predict subsequent response. It looks like there is significant response to olanzapine that doesn't occur until 4 weeks. Thus, clinicians may want to switch to another drug earlier when risperidone is the first drug, and later when olanzapine is the first drug.

Effectiveness of second-generation antipsychotics with acute-phase schizophrenia.

PURPOSE: Although olanzapine may have advantages over other second-generation antipsychotics (SGAs) regarding longer time to treatment discontinuation among chronically ill patients, little evidence has been provided for the comparative effectiveness of SGAs in the acute phase. We aimed to determine if any of four SGAs were more effective in treating newly admitted acute schizophrenic patients. We performed a rater-blinded, randomized controlled trial of four SGAs in 15 psychiatric emergency sites. Eligible patients were 18-64 years old and met diagnostic criteria for schizophrenia, acute schizophrenia-like psychotic disorder, or schizoaffective disorder. A final total of 78 patients were randomly assigned by means of sealed envelopes to receive risperidone (3-12 mg/day; n=20), olanzapine (10-20 mg/day; n=17), quetiapine (300-750 mg/day; n=20), or aripiprazole (12-30 mg/day; n=21), with follow-up at 8 weeks. The primary outcome measure was all-cause treatment discontinuation. RESULTS: Overall, 37% (29/78) of patients discontinued the study medication before 8 weeks: 25% for risperidone; 12% for olanzapine; 55% for quetiapine; and 52% for aripiprazole. Time to treatment discontinuation for any cause was significantly longer in the olanzapine group than in the quetiapine (p=0.006) or aripiprazole (p=0.008) groups, but not compared to the risperidone group (p=0.32). Time to treatment discontinuation was significantly longer in the risperidone group than in the quetiapine group (p=0.048), but not compared to the aripiprazole group (p=0.062). However, the rate of p.r.n. intramuscular haloperidol use was significantly higher in the aripiprazole group than in other groups (p=0.029). CONCLUSION: Olanzapine and risperidone are superior to quetiapine and aripiprazole for the acute treatment of psychosis in hospitalized patients.

Effects of smoking on the lung accumulation of [11C]McN5652.

OBJECTIVE: The lung is one of the key organs for determining the distribution of drugs in the human body. Various factors influence the accumulation of drugs. In this study, we investigated the effects of smoking on drug distribution to the lung using radiolabeled drugs. METHODS: We measured the lung uptake of [11C](+)McN5652, a radioligand for serotonin transporter (5-HTT), and inactive enantiomer [11C](-)McN5652 in 19 healthy men (12 nonsmokers and 7 smokers) using positron emission tomography. Pretreatment study was performed by the administration of clomipramine (50 mg), a potent 5-HTT inhibitor. RESULTS: The mean lung uptake of [11C](+)McN5652 and [11C](-)McN5652 was significantly higher in smokers than in nonsmokers. The lung uptake of [11C](+)McN5652 decreased after pretreatment with clomipramine, whereas that of [11C](-)McN5652 was not affected by clomipramine. CONCLUSIONS: Lung uptake of [11C](-)McN5652 was influenced by smoking, possibly because the probable nonspecific binding accumulation was changed as [11C](-)McN5652 was reported to have negligible affinity to 5-HTT. Smoking might be one of the important factors when distribution of radioligands is considered.

Time course of dopamine D2 receptor occupancy by clozapine with medium and high plasma concentrations.

Most antipsychotics were thought to induce antipsychotic action at an excess of 70% striatal dopamine D2 receptor occupancy, while the clinical dose of clozapine was reported to show less than 60% occupancy. High-dose clozapine could occupy as high as 80% of striatal dopamine D2 receptor in monkey PET studies. Although the time course of dopamine D2 receptor occupancy is an important property of antipsychotics, that by clozapine has not been investigated in a clinical setting. We measured the time course of extrastriatal dopamine D2 receptor occupancy with different doses of clozapine and evaluated whether the measured occupancies fitted the binding theory. Three consecutive PET scans with [11C]FLB 457 were performed for two patients with schizophrenia, chronically taking 600 mg/day and 200 mg/day of clozapine, respectively. Series of occupancies were also measured in combination with fluvoxamine or paroxetine in one patient. Dopamine D2 receptor occupancies were also simulated using individual clozapine plasma data and previously determined in vivo ED50 value. The occupancy of one patient with high plasma concentration (1207 ng/ml at peak time) was around 75% at peak and around 60% after 26 h. Another patient with medium plasma concentration (649 ng/ml at peak time) showed less than 50% occupancy at peak, decreasing to 15% after 25 h. The measured occupancy values fitted well with the simulated occupancy values. At high plasma concentration, clozapine can induce high extrastriatal dopamine D2 receptor occupancy in the human brain, and this finding fitted well with the theoretical estimation.

Abnormal effective connectivity of dopamine D2 receptor binding in schizophrenia.

Receptor binding has been examined region by region in both in vitro and in vivo studies, but less attention has been paid to the connectivity of regional receptor binding despite the fact that neurophysiological studies have indicated an extensive inter-regional connectivity. In this study, we investigated the connectivity of regional dopamine D2 receptor binding in positron emission tomography data from 10 drug-naive patients with schizophrenia and 19 healthy controls. We applied a structural equation method to regional receptor binding. The results indicated that the network models of the patients and normal subjects were significantly different. As to the individual path coefficients, (a) connectivity between cortical regions was different between groups; (b) connectivity from the prefrontal cortex, parietal cortex, and thalamus to the anterior cingulate differed from that in controls; and (c) connectivity from the prefrontal cortex to the anterior cingulate and thalamus via the hippocampus was observed in normal subjects but not in patients. These results suggest that a systems-level change reflected in the connectivity of D2 receptor binding is present in schizophrenia.

In vivo evaluation of [11C]N-(2-chloro-5-thiomethylphenyl)-N'-(3-methoxy-phenyl)-N'-methylguanidine ([11C]GMOM) as a potential PET radiotracer for the PCP/NMDA receptor.

The development of imaging methods to measure changes in NMDA ion channel activation would provide a powerful means to probe the mechanisms of drugs and device based treatments (e.g., ECT) thought to alter glutamate neurotransmission. To provide a potential NMDA/PCP receptor PET tracer, we synthesized the radioligand [11C]GMOM (ki = 5.2 +/-0.3 nM; log P = 2.34) and evaluated this ligand in vivo in awake male rats and isoflurane anesthetized baboons. In rats, the regional brain uptake of [11C]GMOM ranged from 0.75+/-0.13% ID/g in the medulla and pons to 1.15+/-0.17% ID/g in the occipital cortex. MK801 (1 mg/kg i.v.) significantly reduced (24-28%) [11C]GMOM uptake in all regions. D-serine (10 mg/kg i.v.) increased [11C]GMOM %ID/g values in all regions (10-24%) reaching significance in the frontal cortex and cerebellum only. The NR2B ligand RO 25-6981 (10 mg/kg i.v.) reduced [11C]GMOM uptake significantly (24-38%) in all regions except for the cerebellum and striatum. Blood activity was 0.11+/-0.03 %ID/g in the controls group and did not vary significantly across groups. PET imaging in isoflurane-anesthetized baboons with high specific activity [11C]GMOM provided fairly uniform regional brain distribution volume (VT) values (12.8-17.1 ml g(-1)). MK801 (0.5 mg/kg, i.v., n = 1, and 1.0 mg/kg, i.v., n = 1) did not significantly alter regional VT values, indicating a lack of saturable binding. However, the potential confounding effects associated with ketamine induction of anesthesia along with isoflurane maintenance must be considered because both agents are known to reduce NMDA ion channel activation. Future and carefully designed studies, presumably utilizing an optimized NMDA/PCP site tracer, will be carried out to further explore these hypotheses. We conclude that, even though [11C]GMOM is not an optimized PCP site radiotracer, its binding is altered in vivo in awake rats as expected by modulation of NMDA ion channel activity by MK801, D-serine or RO 25-6981. The development of higher affinity NMDA/PCP site radioligands is in progress.

Effect of amphetamine on [(18)F]fallypride in vivo binding to D(2) receptors in striatal and extrastriatal regions of the primate brain: Single bolus and bolus plus constant infusion studies.

[(18)F]fallypride is a new positron emission tomography (PET) dopamine D(2) receptor radiotracer that provides visualization of D(2) receptors in both striatal and extrastriatal areas. Here, the vulnerability of [(18)F]fallypride binding to endogenous dopamine (DA) levels was evaluated by examining the effect of amphetamine on [(18)F]fallypride binding in striatal and extrastriatal regions. Data were acquired in three male baboons at three different doses of i.v. amphetamine, using two different [(18)F]fallypride administration protocols (single bolus and bolus plus constant infusion). Scans were performed following a single bolus of [(18)F]fallypride under control conditions and following 1 mg/kg i.v. amphetamine and with an [(18)F]fallypride bolus plus constant infusion design under control, 0.5 mg/kg, and 0.3 mg/kg amphetamine i.v. conditions. Significant decreases in [(18)F]fallypride binding potential were seen in striatum (-49%, -18%, and -14%), thalamus (-25%, -23%, and -14%), and hippocampus (-36%, -24%, and -12%) following 1 mg/kg, 0.5 mg/kg, and 0.3 mg/kg doses of amphetamine, respectively. Additional analyses were performed suggesting that these results were not artifacts of nonreceptor-related effects such as regional flow changes or partial volume effects. In conclusion, [(18)F]fallypride binding is vulnerable to endogenous competition by DA in striatum as well as extrastriatal regions, suggesting that this ligand may be suitable for the study presynaptic DA function in striatal and extrastriatal areas.

A new positron emission tomography imaging agent for the serotonin transporter: synthesis, pharmacological characterization, and kinetic analysis of [11C]2-[2-(dimethylaminomethyl)phenylthio]-5-fluoromethylphenylamine ([11C]AFM).

The synthesis, radiolabeling, and in vitro and in vivo evaluation of a new positron emission tomography (PET) radioligand for the serotonin transporter (SERT), [(11)C]2-[2-(dimethylaminomethyl)phenylthio]-5-fluoromethylphenylamine ([(11)C]AFM) is reported. AFM was prepared from 4-chloro-3-nitrobenzyl acetate and thiosalicylic acid in a five-step synthetic sequence. In binding studies in vitro with cloned human transporters, AFM displayed high binding affinity (Ki 1.04 nmol/L for hSERT) and good selectivity (Ki 664 nmol/L for hNET and >10,000 nmol/L for hDAT) for SERT. The radiolabled compound [(11)C]AFM was prepared in 30-37 minutes from its monomethylamine precursor by reaction with high specific activity [(11)C]iodomethane. Radiochemical yield was 12.3 +/- 8.1% based on [(11)C]iodomethane and specific activity was 1733 +/- 428 Ci/mmol at end of synthesis (EOS, n = 14). Radiochemical and chemical purity of the final product was >97%. Biodistribution studies in rats indicated that [(11)C]AFM entered the brain readily and localized in regions known to contain high concentrations of SERT, with high specific to nonspecific binding ratios. Furthermore, binding of [(11)C]AFM in SERT-rich regions was blocked by the cold compound AFM and the selective serotonin reuptake inhibitor citalopram but not by the selective norepinephrine reuptake inhibitor nisoxetine or the selective dopamine reuptake inhibitor GBR 12935. At 30 minutes after injection, >95% of the brain activity corresponded to the parent compound, indicating the absence of radiolabeled metabolites in the rat brain. PET imaging experiments in baboons showed a brain distribution pattern of [(11)C]AFM consistent with the regional concentrations of SERT, with the highest levels of radioactivity detected in the midbrain and thalamus, moderate levels in the hippocampus and striatum, and the low levels in the cortical regions. Pretreatment of the baboons with citalopram (4 and 6 mg/kg, intravenously) reduced regional brain distribution volumes to low and homogeneous levels, thus underlining the binding specificity of [(11)C]AFM for SERT in vivo. Analysis of blood samples indicated a fast metabolism of the radioligand into more hydrophilic components, as well as the absence of radiolabeled lipophilic metabolites. Regional time-activity curves were analyzed with kinetic and graphical analysis methods using the arterial concentrations as input function. Both methods returned similar kinetic parameters and documented high specific to nonspecific equilibrium coefficients (V(3)") for [(11)C]AFM. Identical V(3)" values were also derived with the simple reference tissue method, indicating that quantification of SERT with [(11)C]AFM can be achieved without arterial blood sampling. In summary, [(11)C]AFM appears to be an excellent PET radioligand for the visualization and reliable quantification of SERT in vivo.

Low dopamine d(2) receptor binding in subregions of the thalamus in schizophrenia.

OBJECTIVE: Several structural and functional brain imaging studies have pointed to a disturbance of thalamic subnuclei in patients with schizophrenia. The dopamine hypothesis of schizophrenia has, however, not been thoroughly examined in terms of this complex structure, which has connections with most brain regions of central interest in schizophrenia research. The aim of the present study was to examine dopamine D(2) receptor binding in subregions of the thalamus in patients with schizophrenia. METHOD: The authors used positron emission tomography and the radioligand [(11)C]FLB457 to examine dopamine D(2) receptor binding in thalamic subregions of 10 drug-naive patients with schizophrenia. Binding potential was calculated by the reference tissue method and used as an index for dopamine D(2) receptor binding. Comparisons were made with 19 healthy subjects. Subregions of interest were defined on individual magnetic resonance images using a percentage-based operational approach. Clinical symptoms were rated by using the Brief Psychiatric Rating Scale (BPRS). RESULTS: The [(11)C]FLB457 binding potential was lower in the central medial and posterior subregions of the thalamus in patients with schizophrenia. At a functional level, there was a significant negative correlation between binding potential and BPRS positive symptom scores. CONCLUSIONS: The subregions with low D(2) receptor binding comprise primarily the dorsomedial nucleus and pulvinar, two important components in circuitries previously suggested in the pathophysiology of schizophrenia. Aberrant dopaminergic neurotransmission in thalamic subregions might be a mechanism underlying positive symptoms in schizophrenia.

In vivo affinity of [18F]fallypride for striatal and extrastriatal dopamine D2 receptors in nonhuman primates.

RATIONALE: [18F]Fallypride is a new and promising radiotracer, suitable for imaging D2 receptors with Positron Emission Tomography (PET) in both striatal and extrastriatal regions. The high signal to noise ratio of [18F]fallypride has been attributed to its high affinity for D2 receptors (K(D) of 0.03 nM, measured in vitro at room temperature). OBJECTIVES: We sought to further characterize this tracer in terms of its in vivo affinity, possible affinity differences between brain regions and dependence of in vitro affinity on temperature. METHODS: PET scans were performed in baboons over a wide range of concentrations to measure the in vivo K(D) of [18F]fallypride in striatal and extrastriatal regions. Several analytical approaches were used, including nonlinear kinetic modeling and equilibrium methods. Also, in vitro assays were performed at 22 and 37 degrees C. RESULTS: No significant differences in the in vivo K(D) were detected between regions. In vivo K(D) of [18F]fallypride was 0.22+/-0.05 nM in striatum, 0.17+/-0.05 nM in thalamus, and 0.21+/-0.07 nM in hippocampus. These values were intermediate between in vitro K(D) measured at 22 (0.04+/-0.03 nM) and 37 degrees (2.03+/-1.07 nM). CONCLUSION: The in vivo affinity of [18F]fallypride was not as high as previously estimated from in vitro values. This property might contribute to the favorable kinetic properties of the tracer. The in vivo affinity was similar between striatal and extrastriatal regions. This result indicates that the measured regional in vivo affinities of this tracer are not affected by putative regional differences in endogenous dopamine, and that [18F]fallypride is an appropriate tool to provide unbiased estimates of the occupancy of D2 receptors by antipsychotic drugs in striatal and extrastriatal regions.

Quantitative analysis of (-)-N-(11)C-propyl-norapomorphine in vivo binding in nonhuman primates.

UNLABELLED: (-)-N-(11)C-propyl-norapomorphine ((11)C-NPA) is a new dopamine agonist PET radiotracer that holds potential for imaging the high-affinity states of dopamine D(2)-like receptors in the living brain. The goal of this study was to develop and evaluate analytic strategies to derive in vivo (11)C-NPA binding parameters. METHODS: Two baboons were scanned 4 times after (11)C-NPA injections. The metabolite-corrected arterial input functions were measured. Regional brain time-activity curves were analyzed with kinetic and graphical analyses, using the arterial time-activity curve as the input function. Data were also analyzed with the simplified reference-tissue model (SRTM) and graphical analysis with reference-region input. RESULTS: (11)C-NPA exhibited moderately fast metabolism, with 31% +/- 5% of arterial plasma concentration corresponding to the parent compound at 40 min after injection. Plasma clearance was 29 +/- 1 L/h, and plasma free fraction (f(1)) was 5% +/- 1%. For kinetic analysis, a 1-tissue compartment model (1TCM) provided a good fit to the data and more robust derivations of the tissue distribution volumes (V(T), in mL/g) than a 2-tissue compartment model (2TCM). Using 1TCM, V(T)s in the cerebellum and striatum were 3.4 +/- 0.4 and 7.5 +/- 2 mL/g, respectively, which led to estimates of striatal binding potential (BP) of 4.0 +/- 1.1 mL/g and striatal equilibrium specific-to-nonspecific partition coefficient (V(3)") of 1.2 +/- 0.2. V(T) values derived with graphical analysis were well correlated with but slightly lower than V(T) values derived with kinetic analysis. V(3)" values derived with SRTM were well correlated with but slightly higher than V(3)" values derived with kinetic analysis. Using any method, a significant difference was detected in BP and V(3)" values between the 2 animals. It was determined that 30 min of scanning data were sufficient to derive V(3)" values using kinetic, graphical (arterial input and reference-region input), and SRTM analyses. CONCLUSION: This study indicates that (11)C-NPA is a suitable PET tracer to quantify the agonist high-affinity sites of D(2)-like receptors.

Estimation of the time-course of dopamine D2 receptor occupancy in living human brain from plasma pharmacokinetics of antipsychotics.

Although the kinetic profile of antipsychotics at dopamine D2 receptor sites has been suggested to be important for antipsychotic action and dosing schedule, the kinetic profiles of the respective antipsychotic drugs in the brain have not yet been clearly defined. We aimed to estimate the time-course of dopamine D2 receptor occupancy from plasma pharmacokinetics and the apparent in-vivo affinity parameter (ED50; concentration required to induce 50% occupancy). Dopamine D2 receptor occupancies and plasma concentrations of risperidone were measured in five patients with schizophrenia using positron emission tomography with [11C]FLB 457. Measured dopamine D2 occupancies were compared with those estimated from plasma kinetics and in-vivo ED50. The time-course of dopamine D2 receptor occupancy was simulated with altered plasma kinetics or apparent in-vivo affinity parameters of the drug. Mean half-life of dopamine D2 receptor occupancy of risperidone was 80.2 h while that of the plasma concentration was 17.8 h. Dopamine D2 receptor occupancy estimated from plasma pharmacokinetics and in-vivo ED50 was within 1 S.D. of the mean measured occupancy. When the ED50 value was changed to one-tenth and 10-fold, the simulated half-life of receptor occupancy changed to 117.6 h and 27.3 h respectively. Using plasma pharmacokinetics and in-vivo ED50, the time-course of receptor occupancy could be calculated. Simulation of drug kinetics at receptors would provide useful information for the evaluation of antipsychotics.