Rats and rabbits as pharmacokinetic screening tools for long acting intramuscular depots: case study with paliperidone palmitate suspension.

Development of prodrug of 9-hydroxyrisperidone (paliperidone) long-acting intramuscular injection has enabled delivery over four-week time period with improved compliance. The key aim of this work was to establish a reliable preclinical model which may potentially serve as a screening tool for judging the pharmacokinetics of paliperidone formulation(s) prior to human clinical work. Sparse sampling composite study was used in rats, (Wistar/Sprague-Dawley (SD; n = 10)) and a serial blood sampling study design was used in rabbits (n = 4). Animals received intramuscular injection of paliperidone palmitate in the thigh muscle at dose of 16 (rats) and 4.5 mg/kg (rabbits). Samples were drawn in rats (retro-orbital sinus) and rabbits (central ear artery) and were analysed for paliperidone using liquid chromatography-mass spectrometry/ mass spectrometry (LC-MS/MS) assay. The plasma data was subjected to pharmacokinetic analysis. Following intramuscular injection of depot formulation in Wistar/SD rats and rabbits, absorption of paliperidone was slow and gradual with median value of time to reach maximum concentration (Tmax) occurring on day 7. The exposures (i.e. area under the curve (AUC; 0-28) days) were 18,597, 21,865 and 18,120 ng.h/mL, in Wistar, SD and rabbits, respectively. The clearance was slow and supported long half-life (8-10 days). Either one of the two models can serve as a research tool for establishing pharmacokinetics of paliperidone formulation(s).

CDI cross-linked ß-cyclodextrin nanosponges of paliperidone: synthesis and physicochemical characterization.

Paliperidone (PLP) is an antipsychotic drug indicated for treatment and management of schizophrenia. The current study demonstrates potential of PLP-loaded ß-cyclodextrin-based nanosponges (CDNS) for solubility enhancement and prolonged release of PLP. The inclusion complexes of PLP with carbonyldiimidazole (CDI) cross-linked nanosponges were synthesized. The drug-loaded CDNS were characterized for particle size, zeta potential, encapsulation efficiency, stability study, in vitro drug release studies. The interaction of PLP with CDNS was ascertained by FTIR, DSC and PXRD studies. The particle size and zeta potential values were sufficient to obtain stable formulations. Solubility was significantly increased and in vitro drug release studies revealed prolonged release of PLP from the CDNS for 6 h. PXRD study revealed that the crystallinity of PLP was decreased due to complexation with the CDNS. Thus, cyclodextrin-based nanosponges represent a novel approach for solubility enhancement and improved dissolution of selected model drug PLP.

Stability, degradation impurities and decomposition kinetics for paliperidone from osmotic tablets.

The antipsychotic paliperidone was investigated with a focus on stability, degradation impurities and kinetics reaction profile. Osmotic tablets 3 mg (OROS® ) were subjected to extraction in an ultrasonic bath and the resulting acidic solution was stressed by forced conditions. Degraded samples were monitored by HPLC-DAD in different storage times for acidic and alkaline hydrolysis, oxidation, heat and photolysis. Photolysis was shown to be a strong degradation factor, with a drug content of 24.64% remaining after 24 h. Oxidation (H2 O2 18%) caused a slow decomposition, with a drug content of 83.49% remaining after 72 h. Through kinetics graphics, first-order reactions were found for oxidation, heat and photolysis. By UPLC-MS analysis, the degraded matrix could be investigated for identification of impurities with m/z 445.3128, m/z 380.8906, m/z 364.9391, m/z 232.9832 and m/z 217.0076, allowing the identification of derivatives N-oxide and with modifications in the lactam, benzisoxazole and pyrimidine rings. Paliperidone in liquid state, like analytical solutions or formulation, must be carefully handled to avoid drug exposure, specially in storage conditions.

Quantitative determination of risperidone, paliperidone and olanzapine in human serum by liquid chromatography-tandem mass spectrometry coupled with on-line solid-phase extraction.

A recent guideline recommends therapeutic drug monitoring for risperidone, paliperidone and olanzapine, which are frequently used second-generation antipsychotics. We developed a simple high-performance liquid chromatography-tandem mass spectrometry coupled with an online solid-phase extraction method that can be used to measure risperidone, paliperidone and olanzapine using small (40 µL) samples. The analytes were extracted from serum samples automatically pre-concentrated and purified by C8 (5 µm, 2.1 × 30 mm) solid-phase extraction cartridges, then chromatographed on an Xbidge™ C18 column (3.5 µm, 100 × 2.1 mm) thermostatted at 30°C with a mobile phase consisting of 70% acetonitrile and 30% ammonium hydroxide 1% solution at an isocratic flow rate of 0.3 mL/min, and detected with tandem mass spectrometry. The assay was validated in the concentration range from 2.5 to 160 ng/mL. Intra- and inter-day precision for all analytes was between 1.1 and 8.2%; method accuracy was between 6.6 and 7.6%. The risperidone and paliperidone assay was compared with a high-performance liquid chromatography-ultraviolet assay currently used in our hospital for risperidone and paliperidone therapeutic drug monitoring, and the results of weighted Deming regression analysis showed good agreement. For the olanzapine assay, we compared 20 samples in separate re-assays on different days; all the relative errors were within the 20% recommended limit.

Development and Evaluation of pH-Responsive Cyclodextrin-Based in situ Gel of Paliperidone for Intranasal Delivery.

Paliperidone (PLPD) is approved for treatment and management of schizophrenia. The current study demonstrates the potential of in situ gel of PLPD for nasal delivery. The permeation of drug through sheep nasal mucosa was analyzed since the nose-to-brain pathway has been indicated for delivering drugs to the brain. The carbopol 934 (CP)- and hydroxypropyl methyl cellulose K4M (HPMC)-based in situ gels containing 0.2% CP and 0.4% w/v HPMC were optimized using experimental design software. The use of hydroxypropyl-ß-cyclodextrin (HP-ß-CD) in nasal permeation of drug was investigated. Transmucosal permeation of PLPD was examined using sheep nasal mucosa. The in situ gels of PLPD exhibited satisfactory mucoadhesion and showed sustained drug release. The mucocilliary toxicity and histopathological examination confirmed that the nasal mucosa architecture remains unaffected after treatment with PLPD in situ gel. The formulation containing HP-ß-CD complex of PLPD exhibited higher rate of drug permeation through sheep nasal mucosa revealing the role of HP-ß-CD as nasal absorption enhancer. Thus, CP- and HPMC-based pH-triggered in situ gel containing HP-ß-CD-drug inclusion complex demonstrates a novel nasal delivery of PLPD.

Paliperidone-Loaded Nanolipomer System for Sustained Delivery and Enhanced Intestinal Permeation: Superiority to Polymeric and Solid Lipid Nanoparticles.

Paliperidone (PPD) is the most recent second-generation atypical antipsychotic approved for the treatment of schizophrenia. An immediate release dose causes extrapyramidal side effects. In this work, a novel nanolipomer carrier system for PPD with enhanced intestinal permeability and sustained release properties has been developed and optimized. PPD was successfully encapsulated into a lipomer consisting of a specific combination of biocompatible materials including poly-ε-caprolactone as a polymeric core, Lipoid S75, and Gelucire® 50/13 as a lipid shell and polyvinyl alcohol as a stabilizing agent. The lipomer system was characterized by dynamic light scattering, TEM, DSC, and FTIR. An optimized lipomer formulation possessed a particle size of 168 nm, PDI of 0.2, zeta potential of -23 mV and an encapsulation efficiency of 87.27% ± 0.098. Stability in simulated gastrointestinal fluids investigated in terms of particle size, zeta potential, and encapsulation efficiency measurements ensured the integrity of the nanoparticles upon oral administration. PPD-loaded nanolipomers demonstrated a superior sustained release behavior up to 24 h and better ex vivo intestinal permeation for PPD compared to the corresponding polymeric and solid lipid nanoparticles and drug suspension. The in vitro hemocompatibility test on red blood cells revealed no hemolytic effect of PPD-loaded lipomers which reflects its safety. The elaborated nanohybrid carrier system represents a promising candidate for enhancing the absorption of PPD providing a 2.6-fold increase in the intestinal permeation flux compared to the drug suspension while maintaining a sustained release behavior. It is a convenient alternative to the commercially available dosage form of PPD.

Concurrent determination of olanzapine, risperidone and 9-hydroxyrisperidone in human plasma by ultra performance liquid chromatography with diode array detection method: application to pharmacokinetic study.

A simple and sensitive ultra-performance liquid chromatography (UPLC) method has been developed and validated for simultaneous estimation of olanzapine (OLZ), risperidone (RIS) and 9-hydroxyrisperidone (9-OHRIS) in human plasma in vitro. The sample preparation was performed by simple liquid-liquid extraction technique. The analytes were chromatographed on a Waters Acquity H class UPLC system using isocratic mobile phase conditions at a flow rate of 0.3 mL/min and Acquity UPLC BEH shield RP18 column maintained at 40°C. Quantification was performed on a photodiode array detector set at 277 nm and clozapine was used as internal standard (IS). OLZ, RIS, 9-OHRIS and IS retention times were found to be 0.9, 1.4, .1.8 and 3.1 min, respectively, and the total run time was 4 min. The method was validated for selectivity, specificity, recovery, linearity, accuracy, precision and sample stability. The calibration curve was linear over the concentration range 1-100 ng/mL for OLZ, RIS and 9-OHRIS. Intra- and inter-day precisions for OLZ, RIS and 9-OHRIS were found to be good with the coefficient of variation <6.96%, and the accuracy ranging from 97.55 to 105.41%, in human plasma. The validated UPLC method was successfully applied to the pharmacokinetic study of RIS and 9-OHRIS in human plasma.

Characterization of paliperidone photodegradation products by LC-Q-TOF multistage mass spectrometry.

The photodegradation of paliperidone in aqueous and methanol media under UVA and UVC irradiation was investigated. The identification and structural elucidation of its photodegradation products were performed by the use of the reversed-phase liquid chromatography coupled with accurate mass hybrid Q-TOF mass spectrometry and an atmospheric pressure chemical ionization source. Five degradation products were found and their masses were obtained with high accuracy (1.10-5.26 ppm) based on the TOF (MS) spectra. For the structural elucidation of unknown degradation products MS/MS spectra were also registered. However, for the identification of the main photodegradation product (3-{2-[4-(6-fluoro-1,3-benzoxazol-2-yl)piperidin-1-yl]ethyl}-9-hydroxy-2-methyl-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidin-4-one) in-source fragmentation connected with collision-induced dissociation was used and MS(3) spectra were finally performed. The photodegradation of paliperidone yields the first-order kinetics in all tested conditions. The aqueous medium was in this case much less stable than the methanol solvent regardless of the irradiation source. Additionally, the toxicity of the analyzed photodegradation products was predicted by the use of ECOSAR software and comparable values of LC50 for the main degradants and the parent compound were obtained. Copyright © 2015 John Wiley & Sons, Ltd.

Tailoring lipid nanoconstructs for the oral delivery of paliperidone: Formulation, optimization and in vitro evaluation.

PURPOSE: The present research work involves Quality by Design (QbD)-based fabrication of lipid nanoconstructs (LNC) of paliperidone (PPD) bearing superior biopharmaceutical attributes. METHODS: LNC of paliperidone was prepared by melt emulsification-probe sonication and high-pressure homogenization method followed by optimization using QbD approach. Preparing LNC by both these methods will give the benefit of identifying the best optimized formulation which will be further evaluated for in vitro studies. RESULTS: The best optimized formulation was obtained using melt emulsification-probe sonication technique with small particle size (86.35 nm), high entrapment efficiency (90.07 %), and high loading capacity (8.49 %). The drug release from LNC was found to be 5, 8, and 9-folds greater than drug suspension in pH 1.2, 6.8, and 7.4 respectively (p < 0.001). Stability studies of LNC in simulated gastric fluid pH 1.2 and fasted state simulated intestinal fluid depicted no alteration in particle size and polydispersity index of LNC but were found to increase in fed state simulated intestinal fluid. The drug permeability through rat intestine for LNC was found to be approximately 6-folds (p < 0.05) greater as compared to the drug suspension which was further confirmed by confocal microscopy. The in vitro lipolysis study presented significantly highest solubilization (p < 0.001) in the aqueous phase thereby anticipating higher in vivo absorption. CONCLUSION: Thus, it was concluded that LNC bears the knack of improving the solubilization and permeation potential of an otherwise hydrophobic drug, paliperidone."

Modulation of the clinically accessible gelation time using glucono-d-lactone and pyridoxal 5'-phosphate for long-acting alginate in situ forming gel injectable.

The purpose of this study was to design alginate in situ forming gel (ISFG) injectable with clinically acceptable gelation time and controlled release of hydrophobic drug. Milled or unmilled paliperidone palmitate (PPP) was used. The gelation time was controlled by varying the ratios of glucono-d-lactone (GDL) and pyridoxal 5'-phosphate (PLP) in prefilled alginate solution mixtures (ASMs) containing PPP, CaCO3, GDL and PLP for clinically acceptable injectability. However, the gelation time was varied by the alginate type (M/G ratio), storage condition, and drug solubilizers. This ISFG exhibited 32.15 kPa of the maximal compressive stress without causing pain and stiffness. The ISFG containing conically milled PPP released PPP in a controlled manner without exhibiting any initial burst release for 4 weeks. The current alginate ISFG injectable using new combination of PLP and GDL could be used to deliver long-acting injectable drugs.

Butyl stearate prolongs the drug release period of isoperidone­loaded poly (lactic­co­glycolic acid) microspheres: In vitro and in vivo investigation.

The present study aimed to investigate the effects of butyl stearate on t­butoxyl paliperidone derivative (isoperidone)­loaded poly(lactide­co­glycolide) (PLGA) microspheres. The mechanism of drug release rate delay by butyl stearate was examined by accelerated testing, morphological observation, thermal and fluorescence analyses. In vivo pharmacokinetic study was conducted on female beagle dogs. Spherical microspheres with smooth surfaces, small internal pores and shell structures were initially prepared. It was found that 3% (w/w) butyl stearate prolonged the in vitro drug release period from 46 to 82 days, and in vivo release period from 20 to 27 days. Furthermore, the results demonstrated that the green fluorescence imaging of isoperidone approaching the cores of microspheres with 3% butyl stearate was brighter than in microspheres without additives. In conclusion, it was shown that butyl stearate affected the microsphere structure, isoperidone microsphere distribution and isoperidone crystallinity. The results of the present study thus provide a potential method to develop sustained­release preparations.

A water-compatible magnetic molecularly imprinted polymer for the selective extraction of risperidone and 9-hydroxyrisperidone from human urine.

An accurate, rapid, and sensitive method for the determination of risperidone and 9-hydroxyrisperidone in urine samples was developed by combining water-compatible magnetic molecularly imprinted solid-phase extraction with high performance liquid chromatography. Several variables relating to the efficiency of magnetic solid phase extraction were optimized, including the amount of adsorbent, adsorption time, type of elution solvent, and desorption time. The analytical performance of this method was validated under the optimized conditions. The linearity for risperidone and 9-hydroxyrisperidone was obtained in the range 1-2000ngmL-1 with correlation coefficient ≥ 0.991. Limits of detection of risperidone and 9-hydroxyrisperidone are 0.21ngmL-1 and 0.24ngmL-1, respectively. Recoveries at three spike levels (10, 100, and 1000ngmL-1) ranged from 94.6% to 102.4% with relative standard deviations (%) ≤ 5.3. These results confirmed that this method can be successfully and facilely used to analyze the multi-residues of risperidone and 9-hydroxyrisperidone in urine samples with high efficiency and good sensitivity.

Paliperidone Palmitate Intramuscular 3-Monthly Formulation: A Review in Schizophrenia.

A 3-monthly formulation of intramuscular paliperidone palmitate (3-monthly paliperidone palmitate) has recently been approved for the maintenance treatment of schizophrenia in adult patients in the EU (Trevicta®), following earlier approval in the USA (Invega Trinza®). This narrative review discusses the clinical use of 3-monthly paliperidone palmitate in the maintenance treatment of schizophrenia in adult patients and summarizes its pharmacological properties. The efficacy of the 3-monthly paliperidone palmitate formulation as a maintenance treatment for schizophrenia has been demonstrated in well designed, phase III trials. Three-monthly paliperidone palmitate was more effective than placebo in delaying time to relapse and reducing relapse rates, and was noninferior to 1-monthly paliperidone palmitate in the proportion of patients that remained relapse-free. The 3-monthly formulation was also more effective than placebo in controlling the symptoms of schizophrenia, whilst not differing significantly from the 1-monthly formulation in terms of symptomatic control. Three-monthly paliperidone palmitate was generally well tolerated in clinical trials, with a tolerability profile consistent with that of the 1-monthly formulation. In conclusion, 3-monthly paliperidone palmitate is a useful treatment option for adult patients with schizophrenia who are adequately treated with the 1-monthly formulation, particularly for those who would prefer, or may benefit from, longer dosing intervals.

Design and evaluation of a specific, bi-phase extended release system based on differently coated mini-tablets.

Mini-tablets are gaining great attention as systems capable of being formulated into multiple unit systems providing a specific drug release pattern. Within the presented research a combined, multiple-unit system, based on different coated matrix mini-tablets, has been developed in order to achieve 24-h specific sigmoid extended release of the model drug paliperidone. The mini-tablets were based on different amounts of polyvinyl acetate/polyvinyl pyrolidone mixture as the matrix former, providing extended release, and two different types of pH-dependent, acrylic polymer coatings, providing delay in release onset, and thus achieving the required specific sigmoid release pattern imposed by the original drug on the market. The selected formulation proved to be consistent with pharmacopoeial requirements. It was also in vitro similar (f2) to the original drug and the theoretical linear release profile, as well as robust and reproducible regarding in vitro release in different fasted gastro-intestinal conditions. This is proof of concept that 24-h, specific, and almost linear release profile of drugs with high solubility can be achieved by employing technology of coated matrix mini-tablets.

Genetics-Based Population Pharmacokinetics and Pharmacodynamics of Risperidone in a Psychiatric Cohort.

BACKGROUND: High interindividual variability in plasma concentrations of risperidone and its active metabolite, 9-hydroxyrisperidone, may lead to suboptimal drug concentration. OBJECTIVE: Using a population pharmacokinetic approach, we aimed to characterize the genetic and non-genetic sources of variability affecting risperidone and 9-hydroxyrisperidone pharmacokinetics, and relate them to common side effects. METHODS: Overall, 150 psychiatric patients (178 observations) treated with risperidone were genotyped for common polymorphisms in NR1/2, POR, PPARα, ABCB1, CYP2D6 and CYP3A genes. Plasma risperidone and 9-hydroxyrisperidone were measured, and clinical data and common clinical chemistry parameters were collected. Drug and metabolite concentrations were analyzed using non-linear mixed effect modeling (NONMEM(®)). Correlations between trough concentrations of the active moiety (risperidone plus 9-hydroxyrisperidone) and common side effects were assessed using logistic regression and linear mixed modeling. RESULTS: The cytochrome P450 (CYP) 2D6 phenotype explained 52% of interindividual variability in risperidone pharmacokinetics. The area under the concentration-time curve (AUC) of the active moiety was found to be 28% higher in CYP2D6 poor metabolizers compared with intermediate, extensive and ultrarapid metabolizers. No other genetic markers were found to significantly affect risperidone concentrations. 9-hydroxyrisperidone elimination was decreased by 26% with doubling of age. A correlation between trough predicted concentration of the active moiety and neurologic symptoms was found (p = 0.03), suggesting that a concentration >40 ng/mL should be targeted only in cases of insufficient, or absence of, response. CONCLUSIONS: Genetic polymorphisms of CYP2D6 play an important role in risperidone, 9-hydroxyrisperidone and active moiety plasma concentration variability, which were associated with common side effects. These results highlight the importance of a personalized dosage adjustment during risperidone treatment.

Multimodal non-linear optical imaging for the investigation of drug nano-/microcrystal-cell interactions.

Drug nano-/microcrystals are being used for sustained parenteral drug release, but safety and efficacy concerns persist as the knowledge of the in vivo fate of long-living particulates is limited. There is a need for techniques enabling the visualization of drug nano-/microcrystals in biological matrices. The aim of this work was to explore the potential of coherent anti-Stokes Raman scattering (CARS) microscopy, supported by other non-linear optical methods, as an emerging tool for the investigation of cellular and tissue interactions of unlabeled and non-fluorescent nano-/microcrystals. Raman and CARS spectra of the prodrug paliperidone palmitate (PP), paliperidone (PAL) and several suspension stabilizers were recorded. PP nano-/microcrystals were incubated with RAW 264.7 macrophages in vitro and their cellular disposition was investigated using a fully-integrated multimodal non-linear optical imaging platform. Suitable anti-Stokes shifts (CH stretching) were identified for selective CARS imaging. CARS microscopy was successfully applied for the selective three-dimensional, non-perturbative and real-time imaging of unlabeled PP nano-/microcrystals having dimensions larger than the optical lateral resolution of approximately 400nm, in relation to the cellular framework in cell cultures and ex vivo in histological sections. In conclusion, CARS microscopy enables the non-invasive and label-free imaging of (sub)micron-sized (pro-)drug crystals in complex biological matrices and could provide vital information on poorly understood nano-/microcrystal-cell interactions in future.

Inclusion Complexes of Hydroxy Propyl-ß-Cyclodextrin and Paliperidone: Preparation and Characterization.

In the present investigation, an attempt has been made to improve aqueous solubility of a BCS class II drug by making an inclusion complex with Hydroxypropyl-ß-cyclodextrin (HP-ß-CD). Paliperidone (PALI) was selected as a model drug for the study. It is practically insoluble in water with low oral bioavailability. It is a major active metabolite of risperidone approved for the treatment of schizophrenia in adults. The inclusion complexes were prepared in 1:1 (PALI: HP-ß-CD) molar ratio. Phase solubility studies were performed according to Higuchi Connors method to determine the optimum conditions for the complexation. The prepared solid inclusion complexes were characterized by Differential Scanning Calorimetry (DSC), Fourier- Transform Infrared Spectroscopy (FT-IR), Powder X-ray Diffractometry (PXRD), Scanning Electron Microscopy (SEM) and Proton Nuclear Magnetic Resonance Spectroscopy ((1)H-NMR). Dissolution study was performed using USP apparatus II in phosphate buffer, pH 6.8 (37 ± 0.5°C). The solid state characterization studies confirmed the formation of inclusion complex between PALI and HP-ß-CD. The aqueous solubility and in-vitro dissolution study showed that the solubility and dissolution rate of drug were considerably improved by complexation with HP-ß-CD with respect to the drug alone. The enhanced solubility and dissolution may help to improve in-vivo performance of PALI. Thus, the binary complexation of PALI with HP-ß-CD can be used as an approach for its solubility enhancement.