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

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]

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.

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.)