5-HT₂ Receptor ( Ki = 4.8 nM ); D₂ Receptor ( Ki = 5.9 nM ); P-Glycoprotein

Risperidone is a strong antagonist of the dopamine D2 receptor and a blocker of the serotonin 5-HT2 receptor. It is also an inhibitor of P-glycoprotein with Kis values of 4.8 and 5.9 nM for 5-HT2A and dopamine D2 receptors, respectively. Risperidone increases the production of IL-10 in mature DCs while dose-dependently inhibiting the release of IL-12. Risperidone at high dosages has the ability to cause mature DCs to release TNF-α[3].

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Antipsychotic drugs (APDs) that bind mainly to the dopamine D2 receptor or the type II 5-HT receptor have been used to ease the symptoms of schizophrenia. Several studies have reported that APDs can also regulate the immune response. Dendritic cells (DCs) are the major antigen-presenting cells in the immune system. DCs can release 5-HT and dopamine to modulate T-cell activation and differentiation. In this study, we use the monocyte-derived DCs to investigate the drug effects of typical APD (haloperidol) and atypical APD (risperidone) on DCs in vitro. Our studies revealed that only risperidone but not haloperidol affected the cytokine and chemokine production of mature DCs. Risperidone increased the production of IL-10 and MDC as well as the proinflammatory cytokines, such as IL-6, IL-8, and TNF-α, but decreased the production of IP-10 and IL-12. Furthermore, the exposure of DCs to risperidone led to lower IFN-γ production by T-cells. The results suggested that risperidone can modulate the DCs' immune function by inhibiting the potent Th1 cytokines and increasing the potent Th2 cytokines. In addition, the production of TNF-α by risperidone-treated mature DCs will induce the death of neutrophils. [2]

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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 [3].

In the first trial, it was discovered that rats given risperidone had a slight but significant reduction in body weight as they aged. In the second exercise experiment, age-dependent weight differences were also noted among the three treatment groups. On postnatal days 35, 38, and 41, rats treated with 3.0 mg/kg of risperidone weighed less than rats given a vehicle. Compared to the smaller single-sex litter used in the first two locomotion experiments, a larger mixed-sex litter was used in the third experiment. In the third experiment, rats treated with risperidone gained less weight in an age-dependent manner, as was observed in the first two experiments [4].

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It has been suggested that a combined blockade of 5-HT2 and D2 dopamine receptors may be superior to D2 dopamine antagonists alone in the treatment of schizophrenia. Risperidone, which has a high affinity for 5-HT2 and D2 dopamine receptors in vitro, is a new antipsychotic drug that has been developed according to this hypothesis. The aim of this study was to examine if risperidone indeed induces 5-HT2 and D2 dopamine receptor occupancy in vivo in humans. Central receptor occupancy was examined by positron emission tomography (PET) in three healthy men after oral administration of 1 mg risperidone. [11C]N-methylspiperone ([11C]NMSP) was used as a radioligand for determination of 5-HT2 receptor occupancy in the neocortex. Both an equilibrium ratio analysis and a kinetic three-compartmental analysis indicated a 5-HT2 receptor occupancy about 60%. [11C]raclopride was used as a radioligand for determination of D2 dopamine receptor occupancy in the striatum and the calculated occupancy was about 50%. This is the first quantitative determination of 5-HT2 receptor occupancy induced by an antipsychotic drug in the living human brain. The results indicate that 5-HT2 receptor occupancy should be very high at the dose level of 4-10 mg risperidone daily, as suggested for clinical use. Risperidone is thus an appropriate compound for clinical evaluation of the benefit of combined 5-HT2 and D2 dopamine receptor blockade in the treatment of schizophrenia. [1]

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Risperidone is an antipsychotic drug approved for use in children, but little is known about the long-term effects of early-life risperidone treatment. In animals, prolonged risperidone administration during development increases forebrain dopamine receptor expression immediately upon the cessation of treatment. A series of experiments was performed to ascertain whether early-life risperidone administration altered locomotor activity, a behavior sensitive to dopamine receptor function, in adult rats. One additional behavior modulated by forebrain dopamine function, spatial reversal learning, was also measured during adulthood. In each study, Long-Evans rats received daily subcutaneous injections of vehicle or 1 of 2 doses of risperidone (1.0 and 3.0 mg/kg per day) from postnatal Days 14 to 42. Weight gain during development was slightly yet significantly reduced in risperidone-treated rats. In the first 2 experiments, early-life risperidone administration was associated with increased locomotor activity at 1 week postadministration through approximately 9 months of age, independent of changes in weight gain. In a separate experiment, it was found that the enhancing effect of early-life risperidone on locomotor activity occurred in males and female rats. A final experiment indicated that spatial reversal learning was unaffected in adult rats administered risperidone early in life. These results indicate that locomotor activity during adulthood is permanently modified by early-life risperidone treatment. The findings suggest that chronic antipsychotic drug use in pediatric populations (e.g., treatment for the symptoms of autism) could modify brain development and alter neural set points for specific behaviors during adulthood [4].

Intracellular Rh123 and DOX Accumulation Studies [3]
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/Risperidone, 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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Rh123 Transport Studies [3]
When RBMECs or Caco-2 cells reached confluence, the integrity of monolayers was checked by both TEER value and the transport rate of fluorescein, a recognized paracellular transport marker (van Bree et al, 1988). The qualified monolayers were rinsed two times with DPBS and preincubated with transport buffer at 37°C for 30 min. In all, 0.5% DMSO, RSP/Risperidone, or PSC833 was loaded at both sides of the monolayers, then Rh123 (5 μM) was added into the basolateral side for the basolateral to apical (B–A) transport study or apical side for the apical to basolateral (A–B) transport study. At designated times, 150 μl samples were taken from the receiver compartment, and the same volume of receiver compartment solution was replaced immediately after each sampling. Concentrations of Rh123 were determined by HPLC. Apparent permeability coefficients, Papp (cm/s) were calculated according to the following equation:

Rats: A total of 211 Long-Evans rats are utilized, comprising 56 females and 155 males. Three groups of approximately equal numbers of rats are injected with either 1.0 mg/kg of risperidone, 3.0 mg/kg of risperidone, or the vehicle used to administer the risperidone solution as a control within each study. Twenty-six male rats (n = 9 in the vehicle and 3.0 mg/kg Risperidone groups; n = 8 in the 1.0 mg/kg Risperidone group) are used in the first experiment. They are tested for locomotor activity for 20 minutes every day starting on postnatal day 49 and continuing every day until postnatal day 53. The long-term effects of early-life Risperidone treatment on locomotion were examined in a follow-up study. In a third experiment, the effects of sex on early-life Risperidone's locomotor effects in young adult rats are investigated. Sixty male (n = 20 per treatment group) and fifty-six female (n = 19 rats in the vehicle and 3.0 mg/kg dose group, n = 18 in the 1.0 mg/kg dose group) rats are treated in this experiment. In a fourth experiment, rats given risperidone early in life were evaluated for reversal learning during adulthood. Treatment is given to 42 male rats (n=14 per treatment group)[4].

Absorption, Distribution and Excretion
Well absorbed. The absolute oral bioavailability of risperidone is 70% (CV=25%). The relative oral bioavailability of risperidone from a tablet is 94% (CV=10%) when compared to a solution.
Risperidone is extensively metabolized in the liver. In healthy elderly subjects, renal clearance of both risperidone and 9-hydroxyrisperidone was decreased, and elimination half-lives are prolonged compared to young healthy subjects.
The volume of distribution of risperidone is approximately 1 to 2 L/kg.
Risperidone is cleared by the kidneys. Clearance is decreased in the elderly and those with a creatinine clearance (ClCr) between 15-59 mL/min, in whom clearance is decreased by approximately 60%.
Risperidone is well absorbed. The absolute oral bioavailability of risperidone is 70% (CV=25%). The relative oral bioavailability of risperidone from a tablet is 94% (CV=10%) when compared to a solution.
Risperidone is rapidly distributed. The volume of distribution is 1-2 L/kg. In plasma, risperidone is bound to albumin and a1-acid glycoprotein. The plasma protein binding of risperidone is 90%, and that of its major metabolite, 9-hydroxyrisperidone, is 77%. Neither risperidone nor 9-hydroxyrisperidone displaces each other from plasma binding sites. High therapeutic concentrations of sulfamethazine (100 ug/mL), warfarin (10 ug/mL), and carbamazepine (10 ug/mL) caused only a slight increase in the free fraction of risperidone at 10 ng/mL and 9-hydroxyrisperidone at 50 ng/mL, changes of unknown clinical significance.
Plasma concentrations of risperidone, its major metabolite, 9-hydroxyrisperidone, and risperidone plus 9-hydroxyrisperidone are dose proportional over the dosing range of 1 to 16 mg daily (0.5 to 8 mg twice daily). Following oral administration of solution or tablet, mean peak plasma concentrations of risperidone occurred at about 1 hour. Peak concentrations of 9-hydroxyrisperidone occurred at about 3 hours in extensive metabolizers, and 17 hours in poor metabolizers. Steady-state concentrations of risperidone are reached in 1 day in extensive metabolizers and would be expected to reach steady-state in about 5 days in poor metabolizers. Steady-state concentrations of 9-hydroxyrisperidone are reached in 5-6 days (measured in extensive metabolizers).
Risperidone and 9-hydroxyrisperidone are present in human breast milk.
For more Absorption, Distribution and Excretion (Complete) data for RISPERIDONE (6 total), please visit the HSDB record page.

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Metabolism / Metabolites
Extensively metabolized by hepatic cytochrome P450 2D6 isozyme to 9-hydroxyrisperidone (i.e. [paliperidone]), which has approximately the same receptor binding affinity as risperidone. Hydroxylation is dependent on debrisoquine 4-hydroxylase and metabolism is sensitive to genetic polymorphisms in debrisoquine 4-hydroxylase. Risperidone also undergoes N-dealkylation to a lesser extent.
Risperidone is extensively metabolized in the liver. The main metabolic pathway is through hydroxylation of risperidone to 9-hydroxyrisperidone by the enzyme, CYP 2D6. A minor metabolic pathway is through N-dealkylation. The main metabolite, 9-hydroxyrisperidone, has similar pharmacological activity as risperidone. Consequently, the clinical effect of the drug results from the combined concentrations of risperidone plus 9-hydroxyrisperidone. CYP 2D6, also called debrisoquin hydroxylase, is the enzyme responsible for metabolism of many neuroleptics, antidepressants, antiarrhythmics, and other drugs. CYP 2D6 is subject to genetic polymorphism (about 6%-8% of Caucasians, and a very low percentage of Asians, have little or no activity and are "poor metabolizers") and to inhibition by a variety of substrates and some non-substrates, notably quinidine. Extensive CYP 2D6 metabolizers convert risperidone rapidly into 9-hydroxyrisperidone, whereas poor CYP 2D6 metabolizers convert it much more slowly. Although extensive metabolizers have lower risperidone and higher 9-hydroxyrisperidone concentrations than poor metabolizers, the pharmacokinetics of risperidone and 9-hydroxyrisperidone combined, after single and multiple doses, are similar in extensive and poor metabolizers.
Risperidone has known human metabolites that include 9-Hydroxy-risperidone, Paliperidone, 3-[2-[4-(6-fluoro-2-hydroxy-1,2-benzoxazol-2-ium-3-yl)piperidin-1-yl]ethyl]-2,9-dimethyl-6,7,8,9-tetrahydropyrido[1,2-a]pyrimidin-4-one, 3-ethyl-2,9-dimethyl-6,7,8,9-tetrahydropyrido[1,2-a]pyrimidin-4-one, and 6-Fluoro-3-(4-piperidinyl)-1,2-benzisoxazole.
Extensively metabolized by hepatic cytochrome P450 2D6 isozyme to 9-hydroxyrisperidone, which has approximately the same receptor binding affinity as risperidone. Hydroxylation is dependent on debrisoquine 4-hydroxylase and metabolism is sensitive to genetic polymorphisms in debrisoquine 4-hydroxylase. Risperidone also undergoes N-dealkylation to a lesser extent.
Route of Elimination: Risperidone is extensively metabolized in the liver.In healthy elderly subjects, renal clearance of both risperidone and 9-hydroxyrisperidone was decreased, and elimination half-lives were prolonged compared to young healthy subjects.
Half Life: 20-24 hours

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Biological Half-Life
3 hours in extensive metabolizers Up to 20 hours in poor metabolizers
The apparent half-life of risperidone plus 9-hydroxyrisperidone following Risperdal Consta administration is 3 to 6 days, and is associated with a monoexponential decline in plasma concentrations. This half-life of 3-6 days is related to the erosion of the microspheres and subsequent absorption of risperidone.
The apparent half-life of risperidone was 3 hours (CV=30%) in extensive metabolizers and 20 hours (CV=40%) in poor metabolizers. The apparent half-life of 9-hydroxyrisperidone was about 21 hours (CV=20%) in extensive metabolizers and 30 hours (CV=25%) in poor metabolizers. The pharmacokinetics of risperidone and 9-hydroxyrisperidone combined, after single and multiple doses, were similar in extensive and poor metabolizers, with an overall mean elimination half-life of about 20 hours.

Toxicity Summary
Blockade of dopaminergic D2 receptors in the limbic system alleviates positive symptoms of schizophrenia such as hallucinations, delusions, and erratic behavior and speech. Blockade of serotonergic 5-HT₂ receptors in the mesocortical tract, causes an excess of dopamine and an increase in dopamine transmission, resulting in an increase in dopamine transmission and an elimination of core negative symptoms. Dopamine receptors in the nigrostriatal pathway are not affected by risperidone and extrapyramidal effects are avoided. Like other 5-HT₂ antagonists, risperidone also binds at alpha(1)-adrenergic receptors and, to a lesser extent, at histamine H1 and alpha(2)-adrenergic receptors.

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Toxicity Data
LD₅₀=82.1mg/kg (orally in mice).

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Interactions
Given the primary CNS effects of risperidone, caution should be used when Risperdal is taken in combination with other centrally-acting drugs and alcohol.
Risperdal may antagonize the effects of levodopa and dopamine agonists.
When Risperdal is co-administered with enzyme inducers (e.g., carbamazepine), the dose of Risperdal should be increased up to double the patient's usual dose. It may be necessary to decrease the Risperdal dose when enzyme inducers such as carbamazepine are discontinued [see Drug Interactions (7.1)]. Similar effect may be expected with co-administration of Risperdal with other enzyme inducers (e.g., phenytoin, rifampin, and phenobarbital).
Chronic administration of clozapine with Risperdal may decrease the clearance of risperidone.
For more Interactions (Complete) data for RISPERIDONE (10 total), please visit the HSDB record page.

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Hepatotoxicity
Liver test abnormalities may occur in up to 30% of patients on long term therapy with risperidone, usually arising within the first 8 weeks of treatment. The ALT elevations are usually mild, transient and may resolve even with continuation of medication. Instances of more marked ALT and alkaline phosphatase elevations, with or without symptoms and with or without jaundice, have also been reported. The onset of injury typically occurs within a few days of starting risperidone and resolves rapidly with stopping. Instances of acute liver injury with jaundice arising several months and even years after starting risperidone have also been reported. The pattern of serum enzyme elevations is typically cholestatic, but cases with hepatocellular and mixed patterns have also been described. Immunoallergic manifestations (rash, fever, eosinophilia) are rare; a case of autoimmune hepatitis apparently triggered by risperidone therapy has been published, but most cases do not have autoimmune features.

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Effects During Pregnancy and Lactation
◉ Summary of Use during Lactation
Limited information indicates that maternal risperidone doses of up to 6 mg daily produce low levels in milk. Sedation, failure to thrive, jitteriness, tremors, abnormal muscle movements and respiratory depression have been reported in infants exposed to risperidone in milk. Because there is little published experience with risperidone during breastfeeding and little long-term follow-up data, other agents may be preferred, especially while nursing a newborn or preterm infant. Systematic reviews of second-generation antipsychotics concluded that risperidone seemed to be a second-line agent during breastfeeding because of the limited data available and higher excretion into milk relative to other agents. A safety scoring system finds risperidone to be possible to use cautiously during breastfeeding. Monitor the infant for drowsiness, weight gain, tremors, respiratory rate, abnormal muscle movements, and developmental milestones, especially if other antipsychotics are used concurrently.

◉ Effects in Breastfed Infants
One woman took risperidone 4 mg daily during breastfeeding. Her infant showed no developmental abnormalities on examinations up to 9 months of age. Another mother took risperidone 6 mg daily during breastfeeding. Her infant showed no developmental abnormalities on examinations up to 12 months of age.
Two women taking risperidone 4 mg and 1.5 mg daily breastfed their infants of 3.3 months and 6 weeks of age, respectively, were achieving normal developmental milestones and had no adverse effects reported.
A 1 week postpartum woman was started on risperidone 2 mg daily and increased after 10 days to a dosage of 3 mg daily. She breastfed her infant 6 times daily. The infant was observed for 5 weeks of inpatient therapy and judged normal by a pediatric neurologist. No sedation or other adverse effects were observed in the infant. After 3 months of treatment with risperidone, the mother and infant were judged to be well.
An infant had been exclusively breastfed for 3 months during maternal therapy with risperidone 1 mg daily. A pediatric examination found the infant to have no neurological or physical abnormalities, and appeared to interact appropriately.
In a telephone follow-up study, 124 mothers who took a benzodiazepine while nursing reported whether their infants had any signs of sedation. One mother who was taking 0.75 mg of risperidone daily, flurazepam 15 mg daily, clonazepam 0.25 mg twice daily, and 1 mg of bupropion daily reported sedation in her breastfed infant.
A woman diagnosed with schizophrenia was taking risperidone 1.5 mg daily during late pregnancy and postpartum while nursing (extent not stated) her full-term infant. At 2 weeks postpartum, haloperidol 0.8 mg daily was added because of a recurrence of symptoms. At these dosages, no adverse effects were seen in the infant. However, because of recurring symptoms, the dosage of haloperidol was increased to 1.5 mg daily. Three days later, the infant had excessive sedation, poor feeding, and slowing in motor movements. Pediatric assessment found no medical reason for these effects. Breastfeeding was discontinued and the infant's symptoms resolved completely in 5 days. The infant's symptoms were probably caused by the drug combination.
A prospective cohort study of infants breastfed by mothers in an inpatient mother-baby psychiatric unit in India followed 7 infants who were exposed to risperidone in breastmilk; most received partial supplementation. One infant whose mother was taking risperidone 4 mg and lorazepam 2 mg developed sedation that resolved when lorazepam was discontinued. One infant whose mother received risperidone 4 mg daily, trihexyphenidyl 2 mg daily, and electroconvulsive therapy developed constipation. Infants were followed for 1 to 3 months after discharge. One infant had delayed weight development, one infant had delay in height, one infant mental delay, and a fourth infant had motor and mental delay.
A woman with bipolar disorder was maintained on oral risperidone 2 mg at bedtime, long-acting injectable risperidone 50 mg intramuscular every 2 weeks, oral citalopram 20 mg daily, and oral benztropine 0.5 mg daily. She became pregnant and maintained the same regimen. Her infant was born at 35 weeks gestational age and was breastfed (extent and duration not stated). At 16 months of age, the infant was doing well and met his developmental milestones.
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 risperidone was not reported.
A preterm infant weighing 2.75 kg was born at 35 weeks gestation. The infant received bag and mask ventilation for 2 min and was kept on oxygen for the first 18 hours of life due to respiratory distress. The baby began breastfeeding on day 2 of life. On day 12, the mother was started on risperidone 1 mg daily for psychotic episodes. On day 13, the infant developed a respiratory rate of 16/min and no retractions and was placed on CPAP for 12 hours, with gradual weaning thereafter and was placed on formula. On day 15, the mother began breastfeeding again and the respiratory depression recurred. Feeding was changed to breastmilk expressed prior to the daily dose of risperidone and formula for 6 hours after each dose followed by direct breastfeeding. Over the next 2 days no further episodes of respiratory depression occurred. The baby was discharged on day 24, with advice to continue the same feeding pattern. Respiratory depression was probably caused by risperidone in milk.
A woman diagnosed with undifferentiated schizophrenia took risperidone 4 to 5 mg and trihexyphenidyl 2 mg daily throughout 5 pregnancies. She breastfed each infant for 20 to 24 months. No adverse developmental consequences were noted in any of the children. At the time of publication, the oldest three children, aged 26, 23 and 22 years, had completed their education and were employed, while the youngest two were 15 and 19 years old and were doing well academically in their education.

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◉ Effects on Lactation and Breastmilk
Risperidone has caused elevated prolactin serum levels, gynecomastia, and galactorrhea in patients taking the drug. In one case, euprolactinemic gynecomastia and galactorrhea occurred in a 19-year-old man who was also taking fluvoxamine. A meta-analysis of 3 studies found that the risk of gynecomastia with risperidone is 4.3 times greater than that of quetiapine. 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 primarily had 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 risperidone was not reported.

◈ What is risperidone?
Risperidone is a medication that has been used to treat mental health conditions such as schizophrenia, bipolar disorder, and depression. It can be taken by mouth or given as an injection. Risperidone belongs to a group of medications called atypical or second-generation antipsychotics. Brand names for risperidone include Risperdal®, Risperdal Consta®, and Perseris®.Sometimes when people find out they are pregnant, they think about changing how they take their medication, or stopping their medication altogether. However, it is important to talk with your healthcare providers before making any changes to how you take this medication. Your healthcare providers can talk with you about the benefits of treating your condition and the risks of untreated illness during pregnancy.

◈ I take risperidone. Can it make it harder for me to get pregnant?
In some people, risperidone may raise the levels of a hormone called prolactin. High levels of prolactin can stop ovulation (part of the menstrual cycle when an ovary releases an egg). This would make it harder to get pregnant. Your healthcare provider can test your levels of prolactin if there is concern.

◈ Does taking risperidone increase the chance of miscarriage?
Miscarriage is common and can occur in any pregnancy for many different reasons. Based on the studies reviewed, risperidone is not expected to increase the chance of miscarriage.

◈ Does taking risperidone increase the chance of birth defects?
Every pregnancy starts out with a 3-5% chance of having a birth defect. This is called the background risk. Based on the studies reviewed, risperidone is not expected to increase the chance of birth defects above the background risk.

◈ Does taking risperidone in pregnancy increase the chance of other pregnancy-related problems?
Based on the studies reviewed, risperidone may cause low birth weight (weighing less than 5 pounds, 8 ounces [2500 grams] at birth).Risperidone may cause weight gain and problems with blood sugar in a person who is pregnant. This may increase the chance of developing gestational diabetes. More information about gestational diabetes can be found in our fact sheet https://mothertobaby.org/fact-sheets/diabetes-pregnancy/.

◈ I need to take risperidone throughout my entire pregnancy. Will it cause withdrawal symptoms in my baby after birth?
The use of some medications during pregnancy may cause temporary symptoms in newborns soon after birth. These symptoms are sometimes referred to as withdrawal. It is unknown if taking risperidone alone could increase the chance of withdrawal symptoms in a newborn. Similar medications have been associated with a chance for withdrawal, so babies exposed to risperidone near the time of delivery should be watched for stiff or floppy muscles, drowsiness, agitation, tremors, trouble breathing, and problems with feeding. In most cases, symptoms would be expected to go away in a few days without any long-term health effects. It is important that your healthcare providers know you are taking risperidone so that if symptoms occur your baby can get the care that is best for them.

◈ Does taking risperidone in pregnancy affect future behavior or learning for the child?
Studies have not been done to see if risperidone can cause behavior or learning issues for the child.

◈ Breastfeeding while taking risperidone:
Information on the use of risperidone during breastfeeding is limited. When taken in doses of up to 6 mg a day risperidone was found in breastmilk in small amounts. Side effects were not reported in a small number of breastfed infants who were exposed to risperidone only (in doses of up to 6 mg a day). If you take risperidone and other medications, there may be a higher chance for side effects in the baby. If you suspect the baby has any symptoms (sleepiness, poor feeding, crankiness, or unusual movements) contact the child’s healthcare provider.The product label for risperidone recommends that people who are breastfeeding not use this medication. But the benefit of using risperidone may outweigh the possible risks. Your healthcare providers can talk with you about using risperidone and what treatment is best for you. Be sure to talk to your healthcare provider about all of your breastfeeding questions.

◈ If a male takes risperidone, could it affect fertility (ability to get partner pregnant) or increase the chance of birth defects?
Using risperidone may raise a person’s levels of the hormone prolactin, which may affect fertility. Studies have not been done to see if risperidone could increase the chance of birth defects above the background risks. In general, exposures that fathers or sperm donors have are unlikely to increase the risks to a pregnancy. For more information, please see the MotherToBaby fact sheet Paternal Exposures at https://mothertobaby.org/fact-sheets/paternal-exposures-pregnancy/.

[1]. 5-HT2 and D2 dopamine receptor occupancy in the living human brain. A PET study with risperidone. Psychopharmacology (Berl). 1993;110(3):265-72.

[2]. Risperidone modulates the cytokine and chemokine release of dendritic cells and induces TNF-α-directed cell apoptosis in neutrophils. Int Immunopharmacol. 2012 Jan;12(1):197-204.

[3]. Risperidone and paliperidone inhibit p-glycoprotein activity in vitro. Neuropsychopharmacology. 2007 Apr;32(4):757-64.

[4]. Adult rats treated with risperidone during development are hyperactive. Exp Clin Psychopharmacol. 2013 Jun;21(3):259-67.

[5]. J Neurosci Res. 2000 Jun 15;60(6):783-94.

[6]. J Pharmacol Exp Ther. 2001 May;297(2):711-7.

[7]. Schizophr Res,?007, 92(1-3), 108-115.

[8]. Brain Res. 2002 Dec 6;957(1):144-51.

[9]. Clin Exp Pharmacol Physiol. 2002 Nov;29(11):980-9.

Therapeutic Uses
Antipsychotic Agents; Dopamine Antagonists; Serotonin Antagonists
Risperdal (risperidone) is indicated for the treatment of schizophrenia. Efficacy was established in 4 short-term trials in adults, 2 short-term trials in adolescents (ages 13 to 17 years), and one long-term maintenance trial in adults /Included in US product label/
Risperdal adjunctive therapy with lithium or valproate is indicated for the treatment of acute manic or mixed episodes associated with Bipolar I Disorder. Efficacy was established in one short-term trial in adults. /Included in US product label/
Risperdal is indicated for the treatment of irritability associated with autistic disorder, including symptoms of aggression towards others, deliberate self-injuriousness, temper tantrums, and quickly changing moods. Efficacy was established in 3 short-term trials in children and adolescents (ages 5 to 17 years). /Included in US product label/
Risperdal is indicated for the treatment of acute manic or mixed episodes associated with Bipolar I Disorder. Efficacy was established in 2 short-term trials in adults and one short-term trial in children and adolescents (ages 10 to 17 years). /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. Risperdal (risperidone) is not approved for the treatment of patients with dementia-related psychosis.
Like other antipsychotic agents (e.g., phenothiazines), risperidone has been associated with tardive dyskinesias. Although it has been suggested that atypical antipsychotics appear to have a lower risk of tardive dyskinesia, whether antipsychotic drugs differ in their potential to cause tardive dyskinesia is as yet unknown. In one open-label study, an annual incidence of tardive dyskinesia of 0.3% was reported in patients with schizophrenia who received approximately 8-9 mg of oral risperidone daily for at least 1 year. The prevalence of this syndrome appears to be highest among geriatric patients (particularly females). The risk of developing tardive dyskinesia and the likelihood that it will become irreversible also appear to increase with the duration of therapy and cumulative dose of antipsychotic agents administered; however, the syndrome may occur, although much less frequently, after relatively short periods of treatment with low dosages.
Neuroleptic malignant syndrome (NMS), a potentially fatal symptom complex, has been reported in patients receiving antipsychotic agents. NMS requires immediate discontinuance of the drug and intensive symptomatic and supportive care.
Dose-related somnolence was a commonly reported adverse effect associated with risperidone treatment. Approximately 8% of adult patients with schizophrenia receiving 16 mg of oral risperidone daily and 1% of patients receiving placebo reported somnolence in studies utilizing direct questioning or a checklist to detect adverse events, respectively.
For more Drug Warnings (Complete) data for RISPERIDONE (41 total), please visit the HSDB record page.

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Pharmacodynamics
The primary action of risperidone is to decrease dopaminergic and serotonergic pathway activity in the brain, therefore decreasing symptoms of schizophrenia and mood disorders. Risperidone has a high binding affinity for serotonergic 5-HT2A receptors when compared to dopaminergic D2 receptors in the brain. Risperidone binds to D2 receptors with a lower affinity than first-generation antipsychotic drugs, which bind with very high affinity. A reduction in extrapyramidal symptoms with risperidone, when compared to its predecessors, is likely a result of its moderate affinity for dopaminergic D2 receptors.

C₂₃H₂₈CLFN₄O₂

446.95

446.188

666179-74-4

Risperidone; 106266-06-2; Risperidone mesylate; 666179-96-0

9889802

Typically exists as solid at room temperature

1

6

4

31

731

0

Cl[H].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=C3C([H])([H])C([H])([H])C([H])([H])C([H])([H])N3C2=O)C([H])([H])C1([H])[H]

OCBZQKQWVUTYDN-UHFFFAOYSA-N

InChI=1S/C23H27FN4O2.ClH/c1-15-18(23(29)28-10-3-2-4-21(28)25-15)9-13-27-11-7-16(8-12-27)22-19-6-5-17(24)14-20(19)30-26-22;/h5-6,14,16H,2-4,7-13H2,1H3;1H

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

R 64 766 hydrochloride; Risperidone hydrochloride; 666179-74-4; Risperidone (hydrochloride); R 64 766 hydrochloride; SCHEMBL5774262; OCBZQKQWVUTYDN-UHFFFAOYSA-N; R-64 766; R64766

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)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*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.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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