- Schizophrenia is a chronic, severe, debilitating mental illness that affects about 1% of the population, more than 2 million people in the United States alone.
- With the sudden onset of severe p"...
Mechanism of Action
Paliperidone palmitate is hydrolyzed to paliperidone. Paliperidone is the major active metabolite of risperidone. The mechanism of action of paliperidone, as with other drugs having efficacy in schizophrenia, is unknown, but it has been proposed that the drug's therapeutic activity in schizophrenia is mediated through a combination of central dopamine Type 2 (D2) and serotonin Type 2 (5HT2A) receptor antagonism.
Paliperidone is a centrally active dopamine Type 2 (D2) receptor antagonist and a serotonin Type 2 (5HT2A) receptor antagonist. Paliperidone is also active as an antagonist at α1 and α2 adrenergic receptors and H1 histaminergic receptors, which may explain some of the other effects of the drug. Paliperidone has no affinity for cholinergic muscarinic or β1- and β2-adrenergic receptors. The pharmacological activity of the (+)- and (-)- paliperidone enantiomers is qualitatively and quantitatively similar in vitro .
Absorption and Distribution
Due to its extremely low water solubility, paliperidone palmitate dissolves slowly after intramuscular injection before being hydrolyzed to paliperidone and absorbed into the systemic circulation. Following a single intramuscular dose, the plasma concentrations of paliperidone gradually rise to reach maximum plasma concentrations at a median Tmax of 13 days. The release of the drug starts as early as day 1 and lasts for as long as 126 days.
Following intramuscular injection of single doses (39 mg - 234 mg) in the deltoid muscle, on average, a 28% higher Cmax was observed compared with injection in the gluteal muscle. The two initial deltoid intramuscular injections of 234 mg on day 1 and 156 mg on day 8 help attain therapeutic concentrations rapidly. The release profile and dosing regimen of INVEGA® SUSTENNA® results in sustained therapeutic concentrations. The AUC of paliperidone following INVEGA® SUSTENNA® administration was dose-proportional over a 39 mg-234 mg dose range, and less than dose-proportional for Cmax for doses exceeding 78 mg. The mean steady-state peak:trough ratio for an INVEGA® SUSTENNA® dose of 156 mg was 1.8 following gluteal administration and 2.2 following deltoid administration.
Following administration of paliperidone palmitate the (+) and (-) enantiomers of paliperidone interconvert, reaching an AUC (+) to (-) ratio of approximately 1.6–1.8.
Based on a population analysis, the apparent volume of distribution of paliperidone is 391 L. The plasma protein binding of racemic paliperidone is 74%.
Metabolism and Elimination
In a study with oral immediate-release 14C-paliperidone, one week following administration of a single oral dose of 1 mg immediate-release 14C-paliperidone, 59% of the dose was excreted unchanged into urine, indicating that paliperidone is not extensively metabolized in the liver. Approximately 80% of the administered radioactivity was recovered in urine and 11% in the feces. Four metabolic pathways have been identified in vivo, none of which accounted 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, there is no evidence in vivo that these isozymes play a significant role in the metabolism of paliperidone. Population pharmacokinetics analyses indicated no discernable difference on the apparent clearance of paliperidone after administration of oral paliperidone between extensive metabolizers and poor metabolizers of CYP2D6 substrates. In vitro studies in human liver microsomes showed that paliperidone does not substantially inhibit the metabolism of medicines metabolized by cytochrome P450 isozymes, including CYP1A2, CYP2A6, CYP2C8/9/10, CYP2D6, CYP2E1, CYP3A4, and CYP3A5.
In vitro studies have shown that paliperidone is a P-gp substrate and a weak inhibitor of P-gp at high concentrations. No in vivo data are available and the clinical relevance is unknown.
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.
Long-Acting Paliperidone Palmitate Injection versus Oral Extended-Release Paliperidone
INVEGA® SUSTENNA® is designed to deliver paliperidone over a monthly period while extended-release oral paliperidone is administered on a daily basis. The initiation regimen for INVEGA® SUSTENNA® (234 mg/156 mg in the deltoid muscle on Day 1/Day 8) was designed to rapidly attain steady-state paliperidone concentrations when initiating therapy without the use of oral supplementation.
In general, overall initiation plasma levels with INVEGA® SUSTENNA® were within the exposure range observed with 6-12 mg extended-release oral paliperidone. The use of the INVEGA® SUSTENNA® initiation regimen allowed patients to stay in this exposure window of 6-12 mg extended-release oral paliperidone even on trough pre-dose days (Day 8 and Day 36). The intersubject variability for paliperidone pharmacokinetics following delivery from INVEGA® SUSTENNA® was lower relative to the variability determined from extended-release oral paliperidone tablets. Because of the difference in median pharmacokinetic profiles between the two products, caution should be exercised when making a direct comparison of their pharmacokinetic properties.
INVEGA® SUSTENNA® has not been systematically studied in patients with renal impairment. Based on a limited number of observations with INVEGA® SUSTENNA® in subjects with mild renal impairment and pharmacokinetic simulations, the dose of INVEGA® SUSTENNA® should be reduced in patients with mild renal impairment; INVEGA® SUSTENNA® is not recommended in patients with moderate or severe renal impairment [see DOSAGE AND ADMINISTRATION]. Although INVEGA® SUSTENNA® was not studied in patients with moderate or severe renal impairment, the disposition of a single oral dose paliperidone 3 mg extended-release tablet was studied in subjects with varying degrees of renal function. Elimination of paliperidone decreased with decreasing estimated creatinine clearance. Total clearance of paliperidone was reduced in subjects with impaired renal function by 32% on average in mild (CrCl = 50 mL/min to < 80 mL/min), 64% in moderate (CrCl = 30 mL/min to < 50 mL/min), and 71% in severe (CrCl = 10 mL/min to < 30 mL/min) renal impairment, corresponding to an average increase in exposure (AUCinf) of 1.5 fold, 2.6 fold, and 4.8 fold, respectively, compared to healthy subjects. Based on a limited number of observations with INVEGA® SUSTENNA® in subjects with mild renal impairment and pharmacokinetic simulations, the recommended initiation of INVEGA® SUSTENNA® for patients with mild renal impairment is with a dose of 156 mg on treatment day 1 and 117 mg on treatment day 8; thereafter, follow with monthly injections of 78 mg [see DOSAGE AND ADMINISTRATION].
INVEGA® SUSTENNA® has not been studied in patients with hepatic impairment. Based on a study with oral paliperidone in subjects with moderate hepatic impairment (Child-Pugh class B), no dose adjustment is required in patients with mild or moderate hepatic impairment [see DOSAGE AND ADMINISTRATION]. In the study with oral paliperidone in subjects with moderate hepatic impairment (Child-Pugh class B), the plasma concentrations of free paliperidone were similar to those of healthy subjects, although total paliperidone exposure decreased because of a decrease in protein binding. Paliperidone has not been studied in patients with severe hepatic impairment.
No dosage adjustment is recommended based on age alone. However, dose adjustment may be required because of age-related decreases in creatinine clearance [see Renal Impairment above and DOSAGE AND ADMINISTRATION].
No dosage adjustment is recommended based on race. No differences in pharmacokinetics were observed between Japanese and Caucasians.
No dosage adjustment is recommended based on gender, although slower absorption was observed in females in a population pharmacokinetic analysis.
No dosage adjustment is recommended based on smoking status. Based on in vitro studies utilizing human liver enzymes, paliperidone is not a substrate for CYP1A2; smoking should, therefore, not have an effect on the pharmacokinetics of paliperidone.
The efficacy of INVEGA® SUSTENNA® in the acute treatment of schizophrenia was evaluated in four short-term (one 9-week and three 13-week) double-blind, randomized, placebo-controlled, fixed-dose studies of acutely relapsed adult inpatients who met DSM-IV criteria for schizophrenia. The fixed doses of INVEGA® SUSTENNA® in these studies were given on days 1, 8, and 36 in the 9-week study, and additionally on day 64 of the 13-week studies, i.e., at a weekly interval for the initial two doses and then every 4 weeks for maintenance.
Efficacy was evaluated using the Positive and Negative Syndrome Scale (PANSS), a validated multi-item inventory composed of five factors to evaluate positive symptoms, negative symptoms, disorganized thoughts, uncontrolled hostility/excitement, and anxiety/depression.
In a 13-week study (n=636) comparing three fixed doses of INVEGA® SUSTENNA® (initial deltoid injection of 234 mg followed by 3 gluteal or deltoid doses of either 39 mg/4 weeks, 156 mg/4 weeks or 234 mg/4 weeks) to placebo, all three doses of INVEGA® SUSTENNA® were superior to placebo in improving the PANSS total score.
In another 13-week study (n=349) comparing three fixed doses of INVEGA® SUSTENNA® (78 mg/4 weeks, 156 mg/4 weeks, and 234 mg/4 weeks) to placebo, only 156 mg/4 weeks of INVEGA® SUSTENNA® was superior to placebo in improving the PANSS total score.
In a third 13-week study (n=513) comparing three fixed doses of INVEGA® SUSTENNA® (39 mg/4 weeks, 78 mg/4 weeks, and 156 mg/4 weeks) to placebo, all three doses of INVEGA® SUSTENNA® were superior to placebo in improving the PANSS total score.
In the 9-week study (n=197) comparing two fixed doses of INVEGA® SUSTENNA® (78 mg/4 weeks and 156 mg/4 weeks) to placebo, both doses of INVEGA® SUSTENNA® were superior to placebo in improving PANSS total score.
The efficacy of INVEGA® SUSTENNA® in maintaining symptomatic control in schizophrenia was established in a longer-term double-blind, placebo-controlled, flexible-dose study involving adult subjects who met DSM-IV criteria for schizophrenia. This study included a minimum 12-week fixed-dose stabilization phase, and a randomized, placebo-controlled phase to observe for relapse. During the double-blind phase, patients were randomized to either the same dose of INVEGA® SUSTENNA® they received during the stabilization phase, i.e., 39 mg, 78 mg, or 156 mg administered every 4 weeks, or to placebo. A total of 410 stabilized patients were randomized to either INVEGA® SUSTENNA® or to placebo until they experienced a relapse of schizophrenia symptoms. Relapse was pre-defined as time to first emergence of one or more of the following: psychiatric hospitalization, ≥ 25% increase (if the baseline score was > 40) or a 10-point increase (if the baseline score was ≤ 40) in total PANSS score on two consecutive assessments, deliberate self-injury, violent behavior, suicidal/homicidal ideation, or a score of ≥ 5 (if the maximum baseline score was ≤ 3) or ≥ 6 (if the maximum baseline score was 4) on two consecutive assessments of the individual PANSS items P1 (Delusions), P2 (Conceptual disorganization), P3 (Hallucinatory behavior), P6 (Suspiciousness/persecution), P7 (Hostility), or G8 (Uncooperativeness). The primary efficacy variable was time to relapse. A pre-planned interim analysis showed a statistically significantly longer time to relapse in patients treated with INVEGA® SUSTENNA® compared to placebo, and the study was stopped early because maintenance of efficacy was demonstrated.
An examination of population subgroups did not reveal any clinically significant differences in responsiveness on the basis of gender, age, or race.
Last reviewed on RxList: 10/6/2011
This monograph has been modified to include the generic and brand name in many instances.
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