α2 adrenergic receptor; α1 adrenergic receptor; α adrenergic receptor; 5-HT_2A Receptor; D₂ Receptor

In vitro activity: Paliperidone raises Rh123 and DOX intracellular accumulation considerably in a concentration-dependent way.[1] Paliperidone exclusively shields SH-SY5Y from hydrogen peroxide and functions well at low concentrations (10 and 50 μM) against Aβ(25-35) and MPP(+). Regardless of the dosage, paliperidone (100 μM) completely mitigates cell reduction caused by various stressors. In comparison to other APDs, paliperidone is shown to have better oxidative stress-scavenging abilities in a number of areas, including produced bulk glutathione, low HNE, and protein carbonyl productions.[2] The only AP that considerably raises cell viability (8.1%) when compared to cells treated with dopamine alone is paliperidone, which also increases dopamine toxicity at the highest dosage.[3]

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Risperidone (RSP) and its major active metabolite, 9-hydroxy-risperidone (Paliperidone, PALI), are substrates of the drug transporter P-glycoprotein (P-gp). The goal of this study was to examine the in vitro effects of RSP and PALI on P-gp-mediated transport. The intracellular accumulation of rhodamine123 (Rh123) and doxorubicin (DOX) were examined in LLC-PK1/MDR1 cells to evaluate P-gp inhibition by RSP and PALI. Both compounds significantly increased the intracellular accumulation of Rh123 and DOX in a concentration-dependent manner. The IC(50) values of RSP for inhibiting P-gp-mediated transport of Rh123 and DOX were 63.26 and 15.78 microM, respectively, whereas the IC(50) values of PALI were >100 microM, indicating that PALI is a less potent P-gp inhibitor. Caco-2 and primary cultured rat brain microvessel endothelial cells (RBMECs) were utilized to investigate the possible influence of RSP on intestinal absorption and blood-brain barrier (BBB) transport of coadministered drugs that are P-gp substrates. RSP, 1-50 microM, significantly enhanced the intracellular accumulation of Rh123 in Caco-2 cells by inhibiting P-gp activity with an IC(50) value of 5.87 microM. Following exposure to 10 microM RSP, the apparent permeability coefficient of Rh123 across Caco-2 and RBMECs monolayers was increased to 2.02 and 2.63-fold in the apical to basolateral direction, but decreased to 0.37 and 0.21-fold in the basolateral to apical direction, respectively. These data suggest that RSP and PALI, to a lesser extent, have a potential to influence the pharmacokinetics and hence the pharmacodynamics of coadministered drugs via inhibition of P-gp-mediated transport. However, no human data exist that address this issue. In particular, RSP may interact with its own active metabolite PALI by promoting its brain concentration through inhibiting P-gp-mediated efflux of PALI across endothelial cells of the BBB. [1]

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Paliperidone has the lowest baseline cytotoxicity compared with other APDs at 24 h; in addition, the Paliperidone group showed a better survival than the other APD groups (P < 0.05). In stressor challenging, with a fixed concentration of stressors, olanzapine provided the best neuroprotection at 100 μM against Aβ(25-35) and MPP(+) (P < 0.05). In contrast, paliperidone works finely at low concentrations (10 and 50 μM) against Aβ(25-35) and MPP(+) and solely protected SH-SY5Y from hydrogen peroxide. At 100 μM, paliperidone completely diminished cell reduction induced by different stressors, regardless of their dosages. Paliperidone was demonstrated with a higher oxidative stress-scavenging properties than other APDs in several aspects, such as generated bulk glutathione, low HNE, and protein carbonyl productions. Contradictorily, olanzapine, at 24 h, also enhanced HNE and protein carbonyl productions, which may underlie its induced cytotoxicity. Conclusions: Different APDs exhibit variations against different stressors. Paliperidone might be useful not only in alleviating oxidative stress induced by Aβ(25-35) and MPP(+) but also in providing neuroprotection against hydrogen peroxide.[2]

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The neurotoxicity of antipsychotic (AP) drugs seems to be linked with neurological side effects like extrapyramidal symptoms (EPS). On the other hand, neuroprotective effects can mitigate or slow the progressive degenerative structural changes in the brain leading to improved outcome of schizophrenia. First and second-generation antipsychotics may differ in their neurotoxic and neuroprotective properties. The aim of this study was to compare the neurotoxic/neuroprotective activity of haloperidol, a first-generation antipsychotic, and risperidone, a second-generation one, with Paliperidone, a relatively new second-generation antipsychotic, in SK-N-SH cells. Haloperidol, risperidone and paliperidone (10, 50, 100 μM) were administered, either alone or in combination with dopamine (100 μM), to human neuroblastoma SK-N-SH. We examined the effects of the drugs on cell viability (measured by alamarBlue®), caspase-3 activity (measured by fluorimetric assay) and cell death (by measuring the externalization of phosphatidylserine). Haloperidol significantly decreased cell viability and increased caspase-3 activity and cell death. Risperidone and paliperidone did not affect cell viability or cell death. Both second-generation APs decreased caspase-3 activity, especially paliperidone. In cells treated with dopamine in combination with antipsychotics, only paliperidone (10 μM) induced a slight improvement in cell viability. While haloperidol potentiated the dopamine-induced increase in caspase-3 activity, risperidone and paliperidone reduced this effect. The results indicate that haloperidol induces apoptosis, whereas risperidone and paliperidone may afford protection against it. Of the APs tested, paliperidone always showed the strongest neuroprotective effect. The different antipsychotic effects on survival and cell death might be related to differences in their capacity to induce EPS [3].

Paliperidone brings basal extracellular glutamate in the prefrontal cortex back to normal in rats. Additionally, paliperidone keeps rats' extracellular glutamate levels from rising sharply in response to MK-801.[4] The percentage of neurons exhibiting burst firing and the suppression of the NE neuronal firing rate (n = 5 rats) are restored when paliperidone and escitalopram are administered together.[5] When paliperidone is used at an effective dose, bite and attack behaviors decrease in a dose-dependent manner. The most significant decrease in aggressive behavior is observed with paliperidone.[6]

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Here we report indices of NMDA glutamate receptor hypofunction following prenatal immune activation, as well as the effects of treatment during periadolescence with the atypical antipsychotic medications risperidone and Paliperidone. Pregnant Sprague-Dawley rats were injected with polyinosinic:polycytidylic acid (poly I:C) or saline on gestational day 14. Male offspring were treated orally via drinking water with vehicle, risperidone (0.01mg/kg/day), or paliperidone (0.01mg/kg/day) between postnatal days 35 and 56 (periadolescence) and extracellular glutamate levels in the prefrontal cortex were determined by microdialysis at PD 56. Consistent with decreased NMDA receptor function, MK-801-induced increases in extracellular glutamate concentration were markedly blunted following prenatal immune activation. Further suggesting NMDA receptor hypofunction, prefrontal cortex basal extracellular glutamate was significantly elevated (p<0.05) in offspring of poly I:C treated dams. Pretreatment with low dose paliperidone or risperidone (0.01mg/kg/day postnatal days 35-56) normalized prefrontal cortical basal extracellular glutamate (p<0.05 vs. poly I:C vehicle-treatment). Pretreatment with paliperidone and risperidone also prevented the acute MK-801-induced increase in extracellular glutamate. These observations demonstrate decreased NMDA receptor function and elevated extracellular glutamate, two key features of the NMDA glutamate receptor hypofunction model of schizophrenia, during periadolescence following prenatal immune activation. Treatment with the atypical antipsychotic medications paliperidone and risperidone normalized basal extracellular glutamate. Demonstration of glutamatergic abnormalities consistent with the NMDA glutamate receptor hypofunction model of schizophrenia as an early developmental consequence of prenatal immune action provides a model to identify novel early interventions targeting glutamatergic systems which play an important role in both positive and negative symptoms of schizophrenia.[4]

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Acute administration of risperidone but not Paliperidone inhibited the firing of 5-HT neurons, as previously reported. This inhibition was partially antagonized by the NE reuptake inhibitor desipramine, by the 5-HT(1A) receptor antagonist WAY 100635, and completely reversed when both drugs were given consecutively. Risperidone inhibited the firing of 5-HT neurons after 2 and 14 days of administration, with or without escitalopram. Paliperidone did not alter the firing rate of NE neurons by itself, but it reversed the suppression of NE neurons induced by escitalopram, as it was previously reported for risperidone. Conclusion: These results indicate that although risperidone and Paliperidone share a qualitatively similar receptor binding profile in vitro, they differentially alter the firing of 5-HT and NE neurons in vivo. The capacity of paliperidone to reverse the selective serotonin reuptake inhibitor (SSRI)-induced inhibition of NE neuronal firing, without interfering with the effect of SSRIs of 5-HT neuronal activity, suggests that paliperidone may be a very effective adjunct in SSRI-resistant depression.[5]

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Objectives: Investigate whether paliperidone administration would reduce heightened aggressive behavior induced by low-dose cocaine exposure in a developmentally sensitive model of offensive aggression. Materials and methods: Male Syrian hamsters (n = 12/group) were administered an acute dose of Paliperidone (0.05, 0.1, 0.2, and 0.3 mg/kg) and then tested for aggressive behavior using the resident-intruder paradigm. To investigate the effects of chronic paliperidone administration, a separate set of animals (n = 12/group) was exposed to repeated paliperidone administration (0.1 mg kg(-1) day(-1)) during different developmental periods and varying lengths of time (1-4 weeks). Results: Experiment 1 results revealed a dose-dependent decrease in bite and attack behaviors with an effective dose observed at 0.1 mg/kg. In Experiment 2, the maximal reduction in aggressive behavior in response to chronic paliperidone treatment was observed in animals treated during the third week of adolescence, and this reduction occurred without concomitant alterations in non-aggressive behaviors. Conclusions: These results support the specific aggression-suppressing properties of Paliperidone and the potential use of this compound in the treatment of maladaptive aggression in clinical settings [6].

Intracellular Rh123 and DOX Accumulation Studies [1]
Intracellular accumulation of P-gp substrates Rh123 and DOX were measured to evaluate the P-gp activity in LLC-PK1/MDR1 and Caco-2 cells whereas LLC-PK1 was included as a negative control (van der Sandt et al, 2000). After reaching confluence, cells were preincubated at 37°C for 30 min with transport buffer (serum-free DMEM containing 25 mM N-2-hydroxyl piperazine-N′-2-ehane sulfonic acid, pH 7.4). Vehicle control (0.5% dimethylsulfoxide (DMSO)), specific concentrations of RSP, Paliperidone/PALI, or PSC833 were added, then 5 μM of Rh123 or 10 μM of DOX were added for an additional 60 min incubation. After incubation, the solutions were discarded, and the cells were washed three times with ice-cold DPBS and solubilized with 1% Triton X-100. The fluorescence of Rh123 and DOX were measured by high-performance liquid chromatography (HPLC) assay. The concentrations were determined from the fluorescence value through the construction of Rh123 and DOX standard curves. The amount of Rh123 or DOX in each sample was standardized with the protein content as determined by the Lowry assay.

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To determine the protective effect of APDs, cells were initiated for culturing in the presence or absence of olanzapine (10, 50, 100, or 200 μM); Paliperidone (10, 50, or 100 μM); risperidone (10, 50, or 100 μM); or haloperidol (10, 50, or 100 μM) for 24 h. Afterward, to test the effects of different stressors, DMEM was replaced with a serum-free DMEM/high-glucose medium containing various concentrations (0, 0.01, 0.1, 1, 10, 20, 40 μM) of Aβ25-35, MPP+ (5, 12.5, 25, 50, or 100 μM) and hydrogen peroxide (0, 100, 200, or 400 μM), and the cells were cultured for another 24 h. Control cells were cultured for 48 h with neither different stressors nor APDs. The different stressors were prepared in distilled water and the stock solution (1 mM) stored in a −80°C freezer for further use. Cell survival was determined by the WST-1 assay. To determine gene expression consequent to stressor challenging, SH-SY5Y cells were seeded in 10-mm2 Petri dishes and treated and/or untreated with various concentrations of atypical APDs prior to stressor exposure. The cultures were harvested at 48 h and also assayed for cell survival.

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Cell viability assay [2]
SH-SY5Y cells were pre-incubated with various concentrations (0–100 μM) of APDs (haloperidol, risperidone, Paliperidone, and olanzapine) for 24 h and then were exposed to various concentrations of Aβ25-35, superoxide, and MPP+ in the presence of APDs for 24 h. All APDs were dissolved in 20% acetic acid and diluted with 9 volumes of DMEM to a concentration of 5 mM, respectively. Immediately before use, the solutions were diluted into various concentrations with DMEM. The cell viability assay was carried out using a WST-1 reagent to identify the activation of mitochondrial dehydrogenase in SH-SY5Y cells. For the experiments of establishing 96-h survival curve, the cells were seeded at the density of 2.5 × 104 cells/well in six-well clustered plates and harvested at the 48-, 72-, and 96-h time points, which had been pre-incubated with various concentrations (0, 50, and 100 mM) of APDs (haloperidol, risperidone, <Paliperidone, and olanzapine). For stressor challenging experiments, the cells were seeded at the density of 2.5 × 104 cells/well in six-well clustered plates and harvested for WST-1 assay at the 0-, 8-, 12-, and 24-h time points, into which 10 μl/well of the WST-1 cell proliferation reagent was added and further incubated for an additional 1–2 h. The formazan colorimetric signal was measured using an Infinite M200 microplate reader at a wavelength of 440 nm with a reference wavelength of 600 nm. Moreover, the samples’ OD values were normalized by that of the controls and indicated as percentages. The control was defined as cells not exposed to any stressor and preconditioned with APDs.

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Glutathione, HNE, and protein carbonyl assay [2]
For detecting the baseline level of oxidative stress indicators triggered by each APD, SH-SY5Y cells were pre-incubated with 100 μM of APDs (haloperidol, risperidone, Paliperidone, and olanzapine) for 24 h and then assayed for glutathione, HNE, and protein carbonyls directly. For clarification of the abilities of each APD in modulating the level of oxidative stress indicators after treatments with different stressors, the cells were preconditioned with APDs for 24 h and then were exposed to various concentrations of Aβ25-35, superoxide, and MPP+ in the presence of APDs for another 24 h. Finally, the cells were harvested for detecting the cellular level of each oxidative stress indicator, respectively. The total glutathione assay was carried out using a glutathione assay reagent which measured the reduced GSH level using a kinetic assay. For detecting the glutathione content of the sample, the sample is first deproteinized with the 5% 5-sulfosalicylic acid solution and then the kinetic assay in which catalytic amounts of glutathione cause a continuous reduction of 5,5′-dithiobis-(2-nitrobenzoic) acid to 5-thio-2-nitrobenzoic acid (TNB). The oxidized glutathione formed is recycled by glutathione reductase and NADPH. The product, TNB, is assayed colorimetrically at 412 nm. The HNE assay was performed using Oxiselect HNE-His Adduct ELISA kit, an enzyme immunoassay, in which the quantity of the HNE-His adduct in protein samples is determined by comparing its absorbance at 450 nm with that of a known HNE–bovine serum albumin (BSA) standard curve. The protein carbonyl assay was done using an Oxiselect protein carbonyl ELISA kit in which the quantity of protein carbonyls in protein samples is determined by comparing its absorbance at 450 nm with that of a known reduced/oxidized BSA standard curve. All procedures of detecting the oxidative stress-related molecule within cells were according to the manufacturer’s protocol.

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Measurement of cell viability [3]
SK-N-SH cells were seeded on 24-well plates at a density of 2 × 105 cells/well and treated with haloperidol, risperidone and Paliperidone at concentrations of 10, 50 and 100 μM, either alone or in combination with dopamine 100 μM. Controls were treated with vehicle (0.4% DMSO, v/v) either alone or in combination with DA. Each condition was assessed at least in triplicate. Cell viability was determined by alamarBlue®. Resazurin, a non-fluorescent indicator dye, is converted to bright red-fluorescent resorufin via the reduction reactions of metabolically active cells. The amount of fluorescence produced is proportional to the number of living cells. After 24 h of incubation, 50 μl of alamarBlue® was added to each well and incubated for 2 h. Fluorescence was measured at the excitation wavelength of 540 nm and the emission wavelength of 610 nm using a microplate reader. Each measurement was done at least in duplicate. Cell viability is expressed as a percentage of control (vehicle-treated) or DA-treated cells.

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Measurement of caspase-3 activity as apoptotic marker [3]
Cells were cultured at a density of 1 × 105 cells/well on 24-well plates until 70–80% confluence. Then, normal culture medium was replaced by culture medium containing haloperidol, risperidone and Paliperidone at concentrations of 10, 50 and 100 μM, either alone or in combination with dopamine 100 μM. Culture medium for controls contained vehicle (0.4% DMSO, v/v) either alone or in combination with DA. Each condition was assessed at least in triplicate. After 12 h or 24 h, caspase-3 activity was measured by the cleavage of Acetyl-Asp-Glu-Val-Asp (Ac-DEVD) peptide-conjugated 7-amino-4-methyl-coumarin (AMC) using the Caspase-3 Fluorimetric Assay Kit. The cells were incubated with 100 μl of ice-cold cell lysis buffer on ice for 20 min. The lysate was centrifuged at 4 °C for 5 min at 10,000 × g. 20 μl of the supernatant was transferred to a 96-well plate, then 200 μl of reaction buffer containing the caspase-3 substrate (DEVD-AMC) was added to each well. To verify that the signal detected by the reaction was due to protease activity, an induced sample was incubated with caspase-3 inhibitor Acetyl-Asp-Glu-Val-Asp-al (Ac-DEVD-CHO) before adding the substrate. After incubation at 37 °C for 1 h, the fluorescence counts of AMC in the wells with a 355 nm excitation filter and 460 nm emission filter were measured, at least, in duplicate using a microplate reader. Fluorescence of blanks was subtracted from each value. Fluorescence values were converted to caspase-3 activity using a standard curve for AMC. Caspase-3 activity was normalized to the total protein content of the cell extracts, as measured by a DC protein assay kit. Results are expressed as percentage of control (vehicle-treated) or DA-treated cells.

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Flow cytometry measurement of cell death using annexin-V/PI [3]
We used the Annexin V-FITC (fluorescein isothiocyanate) cell membrane labeling assay to detect the translocation of phosphatidylserine (PS) from the inner face of the cell membrane to the outer surface, as a marker of cell death. Propidium iodide (PI) was used to label the DNA in cells where the cell membrane had been compromised. The assay was performed using the Annexin-V-Fluos Staining Kit. Cells were cultured at a density of 4 × 105 cells/well on 6-well plates until 70–80% confluence. Then, normal culture medium was replaced by culture medium containing haloperidol, risperidone or Paliperidone at a concentration of 50 μM either alone or in combination with dopamine 100 μM. Culture medium for controls contained vehicle (0.4% DMSO, v/v) either alone or in combination with DA. Each condition was assessed at least in triplicate. SK-N-SH cells were harvested by trypsinization and any floating cells were then added back to the trypsinized cells, and pelleted by centrifugation at 300 × g for 5 min. 5 × 105 cells were resuspended twice in cold PBS and spun at 300 ×g for 5 min. The pellet was resuspended in 100 μl of Annexin-V-Fluos labeling solution and incubated with 1.2 μl FITC-conjugated annexin-V and 1.5 μl of PI for 15 min at room temperature in the dark. Samples were kept on ice and analyzed on a BD LSRFortessa SORP flow cytometer equipped with five lasers. Emission fluorescence was measured with a 525/50 filter for FITC and with a 610/20 filter for red PI. FITC and PI were excited with two different lasers of 488 nm for the first and 561 nm for the second, thus avoiding signal compensation. Data were acquired and analyzed using BD FACSDIVA™ software. A minimum of 10,000 events were collected for each sample. For each experimental situation, quadrants were adjusted depending on their respective controls.

Litters were culled to 8 on P1, weaned on postnatal day (PD) 21 and housed 2–3 per cage with same sex siblings in a temperature- and humidity-controlled room with 12-h light/dark cycle (0600 on:1800 off) and allowed food and water ad libitum. Male pups were randomly assigned among six treatment groups (minimum 8 rats/group) with variables of pretreatment (poly I:C vs. saline); and drug [risperidone (0.01 mg/kg/day), Paliperidone (0.01 mg/kg/day) or vehicle]. Treatment groups were balanced across breeding cohorts, with no more than 2 rats/litter in any experimental group to avoid litter effect confounds. Animals undergoing surgery were single-housed postoperatively. Microdialysis was performed between PD 55–58.

Drugs and Drug Treatment: (+)-MK-801 hydrogen maleate and polyinosinic:polycytidylic acid (PolyI:C) were used. Drugs were dissolved in 0.15 M NaCl. The NMDA receptor antagonist MK-801 dose was 0.3 mg/kg s.c. The atypical antipsychotic medications risperidone (oral solution) and Paliperidone (powder) were used. Rats were treated with risperidone (0.01 mg/kg/day), paliperidone (0.01 mg/kg/day) or vehicle via drinking water from PD 34–35 until day of microdialysis (PD 55–58). Risperidone and paliperidone dosages were selected to be similar to commonly prescribed human oral dosages of 0.5 mg/day to a 50 kg adolescent [4].

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Risperidone and Paliperidone were dissolved in 10% tartaric acid and then in distilled water (1:100). Desipramine and WAY 100635 were dissolved in distilled water.
Treatments: Escitalopram was administered via osmotic minipumps for 2 and 14 days at a daily dosage of 10 mg kg−1 day−1. Control animals were implanted with minipumps containing distilled water. Acute administration of risperidone and paliperidone were performed using two and five cumulative intravenous (i.v.) injections of 0.2 mg/kg, respectively. Repeated administration of risperidone and paliperidone were performed using subcutaneous injections of 1 mg kg−1 day−1 for 2 and 14 days, alone or in combination with escitalopram. The doses of escitalopram and risperidone were chosen on the basis of previous experiments [5].

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Cocaine hydrochloride was dissolved in 0.9% (w/v) saline. Paliperidone was dissolved in 500 μl of 1 M hydrochloric acid, diluted in 0.9% saline, and the pH raised to 7.2 using 1 N sodium hydroxide.

Experiment 1: Acute Paliperidone effects on adolescent cocaine-induced offensive aggression [6]
Adolescent (P27) Syrian hamsters (N = 60) received daily intraperitoneal (i.p.) injections of low-dose (0.5 mg/kg) cocaine hydrochloride throughout adolescent development (P27–P56), as described elsewhere (Harrison et al. 2000b; DeLeon et al. 2002; Ricci et al. 2005). The day after the last injection (P57), experimental animals were randomly assigned to one of five treatment groups (n = 12 animals per group) and were tested for offensive aggression after an i.p. injection of saline or one of four doses (0.05, 0.1, 0.2, and 0.3 mg/kg) of paliperidone. All injections were performed on unanesthetized animals and took no longer than 10 seconds. After injection, animals were returned to their home cages. Thirty minutes post-injection, animals were tested for offensive aggression as described below. As a behavioral control (non-aggressive baseline), a separate set of hamsters (n = 12) was treated with saline throughout adolescence and tested for aggression in parallel with the paliperidone-treated subjects.

Experiment 2: Chronic Paliperidone effects on adolescent cocaine-induced offensive aggression [6]
In a second experiment, adolescent low-dose cocaine-treated animals (N = 132) were assigned to one of four main groups based on the length of paliperidone exposure during development (i.e., 1, 2, 3, or 4 weeks). Within each group, animals were subdivided to vary the onset of drug treatment as outlined in Fig. 1. For example, animals receiving paliperidone for 1 week began treatment either at the start or 1 to 3 weeks after the start of cocaine treatment [i.e., 1 week (G1–G5), 2 weeks (G6–G8), 3 weeks (G9–G10), and 4 weeks (G11); Fig. 1]. Each subgroup contained equal number of animals (n = 12) resulting in a total of 11 treatment groups (G1–G11; Fig. 1). All groups received two daily i.p. injections: (1) low-dose cocaine (0.5 mg/kg) throughout adolescence (P27–P56) and (2) 0.1 mg/kg paliperidone or saline on days when paliperidone was not administered. The dose of paliperidone (0.1 mg/kg) was selected based on its anti-aggressive effects from Experiment 1. The day after the last injection (P57), experimental animals were tested for offensive aggression using the resident–intruder paradigm. As an aggressive control, a separate set of animals (n = 12) was treated with cocaine alone throughout puberty and tested for aggression in parallel with the above animals. Similarly, as a non-aggressive baseline behavioral control, a last set of hamsters was treated with saline alone throughout adolescence and tested for aggression.

Absorption, Distribution and Excretion
The absolute oral bioavailability of paliperidone following paliperidone administration is 28%.
One week following administration of a single oral dose of 1 mg immediate-release 14C-paliperidone to 5 healthy volunteers, 59% (range 51% – 67%) of the dose was excreted unchanged into urine, 32% (26% – 41%) of the dose was recovered as metabolites, and 6% – 12% of the dose was not recovered.
487 L
The absolute oral bioavailability of paliperidone following Invega administration is 28%. Administration of a 12 mg paliperidone extended-release tablet to healthy ambulatory subjects with a standard high-fat/high-caloric meal gave mean Cmax and AUC values of paliperidone that were increased by 60% and 54%, respectively, compared with administration under fasting conditions. Clinical trials establishing the safety and efficacy of Invega were carried out in subjects without regard to the timing of meals. While Invega can be taken without regard to food, the presence of food at the time of Invega administration may increase exposure to paliperidone. Based on a population analysis, the apparent volume of distribution of paliperidone is 487 L. The plasma protein binding of racemic paliperidone is 74%.
Following a single dose, the plasma concentrations of paliperidone gradually rise to reach peak plasma concentration (Cmax) approximately 24 hours after dosing. The pharmacokinetics of paliperidone following Invega administration are dose-proportional within the available dose range. The terminal elimination half-life of paliperidone is approximately 23 hours. Steady-state concentrations of paliperidone are attained within 4-5 days of dosing with Invega in most subjects. The mean steady-state peak:trough ratio for an Invega dose of 9 mg was 1.7 with a range of 1.2-3.1.
One week following administration of a single oral dose of 1 mg immediate-release (14)C-paliperidone to 5 healthy volunteers, 59% (range 51% - 67%) of the dose was excreted unchanged into urine, 32% (26% - 41%) of the dose was recovered as metabolites, and 6% - 12% of the dose was not recovered. Approximately 80% of the administered radioactivity was recovered in urine and 11% in the feces.
Paliperidone is excreted in human breast milk.
For more Absorption, Distribution and Excretion (Complete) data for Paliperidone (7 total), please visit the HSDB record page.

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Metabolism / Metabolites
Although in vitro studies suggested a role for CYP2D6 and CYP3A4 in the metabolism of paliperidone, in vivo results indicate that these isozymes play a limited role in the overall elimination of paliperidone. Four primary metabolic pathways have been identified in vivo, none of which could be shown to account for more than 10% of the dose: dealkylation, hydroxylation, dehydrogenation, and benzisoxazole scission. Paliperidone does not undergo extensive metabolism and a significant portion of its metabolism occurs in the kidneys.
Four primary metabolic pathways have been identified in vivo, none of which could be shown to account for more than 10% of the dose: dealkylation, hydroxylation, dehydrogenation, and benzisoxazole scission.
Although in vitro studies suggested a role for CYP2D6 and CYP3A4 in the metabolism of paliperidone, in vivo results indicate that these isozymes play a limited role in the overall elimination of paliperidone.
Paliperidone is a known human metabolite of risperidone.

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Biological Half-Life
The terminal elimination half-life of paliperidone is approximately 23 hours.
The median apparent half-life of paliperidone following Invega Sustenna single-dose administration over the dose range of 39 mg - 234 mg ranged from 25 days - 49 days. /Paliperidone palmitate/
The terminal elimination half-life of paliperidone is approximately 23 hours.

Hepatotoxicity
Liver test abnormalities occur in up to 1% of patients receiving paliperidone, but similar rates have been reported with placebo therapy and with comparator agents. The ALT elevations are usually mild, transient and often resolve even without dose modification or drug discontinuation. There have been no published reports of clinically apparent liver injury with symptoms or jaundice attributed solely to paliperidone therapy, even with the long acting parenteral formulations.
Likelihood score: E (unlikely cause of clinically apparent liver injury).

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Effects During Pregnancy and Lactation
◉ Summary of Use during Lactation
Although no data are available for the use of paliperidone during breastfeeding, it is the active metabolite of risperidone. Risperidone data indicate that the concentrations of paliperidone (9-hydroxyrisperidone) in breastmilk are low, and amounts ingested by the infant are small. A safety scoring system finds paliperidone possible to use cautiously during breastfeeding, although others do not recommend it. Because there is no published experience with paliperidone during breastfeeding and little long-term follow-up data, other agents may be preferred, especially while nursing a newborn or preterm infant. Because paliperidone is available only as long-acting products, timing of nursing with respect to doses would not be useful. Long-acting injectable formulations may continue to deliver small amounts to breastmilk for many months. Monitor breastfed infants for drowsiness, adequate growth and weight gain, jitteriness, tremors, and abnormal movements.
◉ Effects in Breastfed Infants
No published information on paliperidone was found as of the revision date. However, limited data from the use of its parent drug, risperidone, during nursing indicate no short- or long-term adverse effects on the infant.
Patients enlisted in the National Pregnancy Registry for Atypical Antipsychotics who were taking a second-generation antipsychotic drug while breastfeeding (n = 576) were compared to control breastfeeding patients who were not treated with a second-generation antipsychotic (n = 818). Of the patients who were taking a second-generation antipsychotic drug, 60.4% were on more than one psychotropic. A review of the pediatric medical records, no adverse effects were noted among infants exposed or not exposed to second-generation antipsychotic monotherapy or to polytherapy. The number of women taking paliperidone was not reported.
◉ Effects on Lactation and Breastmilk
Paliperidone has caused elevated prolactin serum levels, gynecomastia, and galactorrhea in patients taking the drug. The prolactin level in a mother with established lactation may not affect her ability to breastfeed.
Patients enlisted in the National Pregnancy Registry for Atypical Antipsychotics who were taking a second-generation antipsychotic drug while breastfeeding (n = 576) were compared to control breastfeeding patients who had primarily diagnoses of major depressive disorder and anxiety disorders, most often treated with SSRI or SNRI antidepressants, but not with a second-generation antipsychotic (n = 818). Among women on a second-generation antipsychotic, 60.4% were on more than one psychotropic compared with 24.4% among women in the control group. Of the women on a second-generation antipsychotic, 59.3% reported “ever breastfeeding” compared to 88.2% of women in the control group. At 3 months postpartum, 23% of women on a second-generation antipsychotic were exclusively breastfeeding compared to 47% of women in the control group. The number of women taking paliperidone was not reported.

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Protein Binding
The plasma protein binding of racemic paliperidone is 74%.

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Interactions
Concurrent administration of carbamazepine and paliperidone decreased mean steady-state peak plasma concentrations and area under the concentration-time curves (AUCs) of paliperidone by approximately 37%. The manufacturer recommends reevaluating the dosage of paliperidone upon initiation of carbamazepine and increasing it, if necessary, based on clinical assessment. Upon discontinuance of carbamazepine, the dosage of paliperidone should also be reevaluated and decreased, if necessary.
Potential pharmacologic interaction (possible disruption of body temperature regulation); use paliperidone with caution in patients concurrently receiving drugs with anticholinergic activity.
Potential pharmacologic interaction /when used with othe CNS agents/ (additive CNS effects).Use with caution.
Potential pharmacologic interaction (additive CNS effects). Avoid alcoholic beverages during paliperidone therapy.
For more Interactions (Complete) data for Paliperidone (10 total), please visit the HSDB record page.

[1]. Neuropsychopharmacology. 2007 Apr;32(4):757-64.

[2]. Psychopharmacology (Berl). 2011 Oct;217(3):397-410.

[3]. Prog Neuropsychopharmacol Biol Psychiatry. 2012 Jan 10;36(1):71-7.

[4]. Neurosci Lett. 2011 Aug 18;500(3):167-71.

[5]. Psychopharmacology (Berl). 2007 Sep;194(1):63-72.

[6]. Psychopharmacology (Berl). 2009 May;203(4):653-63.

Therapeutic Uses
Antipsychotic Agent
Invega (paliperidone) Extended-Release Tablets are indicated for the treatment of schizophrenia. The efficacy of Invega in schizophrenia was established in three 6-week trials in adults and one 6-week trial in adolescents, as well as one maintenance trial in adults. /Included in US product label/
Invega (paliperidone) Extended-Release Tablets are indicated for the treatment of schizoaffective disorder as monotherapy and an adjunct to mood stabilizers and/or antidepressant therap. The efficacy of Invega in schizoaffective disorder was established in two 6-week trials in adults. /Included in US product label/
Invega Sustenna (paliperidone palmitate) is indicated for the treatment of schizophrenia. Efficacy was established in four short-term studies and one longer-term study in adults. /Paliperidone palmitate; Included in US product label/

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Drug Warnings
/BOXED WARNING/ WARNING: INCREASED MORTALITY IN ELDERLY PATIENTS WITH DEMENTIA-RELATED PSYCHOSIS. Elderly patients with dementia-related psychosis treated with antipsychotic drugs are at an increased risk of death. Analyses of 17 placebo-controlled trials (modal duration of 10 weeks), largely in patients taking atypical antipsychotic drugs, revealed a risk of death in drug-treated patients of between 1.6 to 1.7 times the risk of death in placebo-treated patients. Over the course of a typical 10-week controlled trial, the rate of death in drug-treated patients was about 4.5%, compared to a rate of about 2.6% in the placebo group. Although the causes of death were varied, most of the deaths appeared to be either cardiovascular (e.g., heart failure, sudden death) or infectious (e.g., pneumonia) in nature. Observational studies suggest that, similar to atypical antipsychotic drugs, treatment with conventional antipsychotic drugs may increase mortality. The extent to which the findings of increased mortality in observational studies may be attributed to the antipsychotic drug as opposed to some characteristic(s) of the patients is not clear. Invega (paliperidone) Extended-Release Tablets is not approved for the treatment of patients with dementia-related psychosis.
/BOXED WARNING/ WARNING: INCREASED MORTALITY IN ELDERLY PATIENTS WITH DEMENTIA-RELATED PSYCHOSIS: Elderly patients with dementia-related psychosis treated with antipsychotic drugs are at an increased risk of death. Invega Sustenna is not approved for use in patients with dementia-related psychosis. /Paliperidone palmitate/
Hypersensitivity reactions, including anaphylactic reactions and angioedema, have been observed in patients receiving risperidone or paliperidone. Paliperidone is therefore contraindicated in patients with a known hypersensitivity to paliperidone, risperidone, or any ingredient in the paliperidone formulation.
An increased incidence of adverse cerebrovascular events (cerebrovascular accidents and transient ischemic attacks), including fatalities, has been observed in geriatric patients with dementia-related psychosis treated with certain atypical antipsychotic agents (aripiprazole, olanzapine, risperidone) in placebo-controlled studies. The manufacturer states that paliperidone is not approved for the treatment of patients with dementia-related psychosis.
For more Drug Warnings (Complete) data for Paliperidone (32 total), please visit the HSDB record page.

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Pharmacodynamics
Paliperidone is an atypical antipsychotic developed by Janssen Pharmaceutica. Chemically, paliperidone is primary active metabolite of the older antipsychotic risperidone (paliperidone is 9-hydroxyrisperidone). The mechanism of action is unknown but it is likely to act via a similar pathway to risperidone.

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Because paliperidone is a major metabolite of risperidone (Ereshefsky and Lacombe 1993; Riedel et al. 2005), animals receiving risperidone are also exposed to paliperidone. However, most of risperidone is metabolized to paliperidone. Nevertheless, a small plasma concentration of risperidone was enough to attenuate the firing of 5-HT neurons. In summary, paliperidone and risperidone differentially affect the neuronal firing activity of 5-HT and NE neurons in vivo. The capacity of paliperidone to reverse the SSRI-induced inhibition of the NE neuronal firing rate, without the decreasing of the 5-HT neuronal activity like risperidone, suggests that paliperidone may be a very effective adjunct in SSRI-resistant depression.[5]

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In summary, the studies presented in this report examined the effects of acute and chronic paliperidone administration in a developmentally immature animal model of heightened offensive aggression. Our results indicate that short- and long- term exposure to paliperidone during a specific developmental period significantly reduces heightened levels of offensive aggression. Moreover, reductions in aggressive behavior occurred without concomitant alterations in non-aggressive behaviors supporting paliperidone’s targeted anti-aggressive effects. Our behavior results are novel and important in that they reveal the potential use of paliperidone in the treatment of a specific subtype of maladaptative aggression in emotionally disturbed youngsters in clinical and emergent settings.[6]

C23H27FN4O3

426.48

426.206

C, 64.77; H, 6.38; F, 4.45; N, 13.14; O, 11.25

144598-75-4

Paliperidone-d4; 1020719-55-4

115237

White to off-white solid powder

1.5±0.1 g/cm3

612.3±65.0 °C at 760 mmHg

158-160°C

324.1±34.3 °C

0.0±1.9 mmHg at 25°C

1.692

1.52

1

7

4

31

764

0

FC1C([H])=C([H])C2=C(C=1[H])ON=C2C1([H])C([H])([H])C([H])([H])N(C([H])([H])C([H])([H])C2=C(C([H])([H])[H])N=C3[C@@]([H])(C([H])([H])C([H])([H])C([H])([H])N3C2=O)O[H])C([H])([H])C1([H])[H]

PMXMIIMHBWHSKN-UHFFFAOYSA-N

InChI=1S/C23H27FN4O3/c1-14-17(23(30)28-9-2-3-19(29)22(28)25-14)8-12-27-10-6-15(7-11-27)21-18-5-4-16(24)13-20(18)31-26-21/h4-5,13,15,19,29H,2-3,6-12H2,1H3

3-[2-[4-(6-fluoro-1,2-benzoxazol-3-yl)piperidin-1-yl]ethyl]-9-hydroxy-2-methyl-6,7,8,9-tetrahydropyrido[1,2-a]pyrimidin-4-one

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Solubility in Formulation 1: ≥ 0.5 mg/mL (1.17 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 5.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 0.5 mg/mL (1.17 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 5.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 0.5 mg/mL (1.17 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 5.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)