Long-acting parenteral formulations of hydrophilic drugs, proteins, and peptide therapeutics: mechanisms, challenges, and therapeutic benefits with a focus on technologies

Despite being the most widely prescribed formulation, oral formulations possess several limitations such as low adherence, low bioavailability, high toxicity (in the case of anticancer drugs), and multiple-time administration requirements. All these limitations can be overcome by long-acting injectables. Improved adherence, patient compliance, and reduced relapse have been observed with long-acting formulation which has increased the demand for long-acting injectables. Drugs or peptide molecules with oral bioavailability issues can be easily delivered by long-acting systems. This review comprehensively addresses the various technologies used to develop long-acting injections with a particular focus on hydrophilic drugs and large molecules as well as the factors affecting the choice of formulation strategy. This is the first review that discusses the possible technologies that can be used for developing long-acting formulations for hydrophilic molecules along with factors which will affect the choice of the technology. Furthermore, the mechanism of drug release as well as summaries of marketed formulations will be presented. This review also discusses the challenges associated with the manufacturing and scale-up of the long-acting injectables.

Practical Guidance for the Use of Long-Acting Injectable Antipsychotics in the Treatment of Schizophrenia

Schizophrenia is a severe mental illness causing a high degree of disability. First- and second-generation antipsychotics (FGAs and SGAs) represent key resources for its acute and long-term management. Since a poor adherence to oral treatments may negatively impact the course of the disorder, long-acting injectable antipsychotics (LAIs) are often used to reduce clinical relapses. Notwithstanding their potential beneficial features, LAIs use in clinical practice remains somewhat hampered by the limited amount of relevant systematic information. This review thus aims at providing a clinical, practical guidance for the use of LAIs in the treatment of schizophrenia. We synthetized main information on indications, dosage, and administration of LAIs approved by the US Food and Drug Administration (FDA) and/or in EU countries, as well as evidence from the most recent systematic reviews and meta-analyses. Currently available information, though heterogeneous, shows that LAIs can prevent relapses and rehospitalizations, improving clinical outcomes and favouring sustained remission among people with schizophrenia. The use of SGA LAIs is supported by more robust evidence than FGA LAIs. Along with their positive impact on the prevention of treatment discontinuation, some LAIs might also enhance individual global functioning and quality of life, without additional adverse events or health-care costs, as compared with oral antipsychotics. Although which LAIs can be considered a first-choice option, as well as their superiority over oral antipsychotics, remain unclear issues, this review offers a comprehensive overview of information available on the use of LAIs for people with schizophrenia, providing clinicians with practical guidance in terms of efficacy and acceptability of single agents. Literature gaps and future research needs are also described.

Therapeutic Drug Monitoring of Paliperidone in Patients With Schizophrenia in Taiwan

BACKGROUND

The blood level of antipsychotics affects clinical responses to the drug; it can be influenced by race and several individual factors. This study analyzed the therapeutic plasma concentrations (Cps) of paliperidone for both oral and long-acting injectable (LAI) formulations in clinical samples from Taiwanese patients.

METHODS

Patients diagnosed with schizophrenia and treated with either oral paliperidone for at least 4 weeks or LAI paliperidone for at least 6 months were enrolled. Blood samples were taken before the morning dose of oral paliperidone or the injection of LAI paliperidone to obtain the trough Cps.

RESULTS

Among the patients in this study, 51 were taking oral paliperidone, and 26 were receiving LAI paliperidone. In the oral group, the mean Cps were 40.2 ± 19.8 ng/mL in patients taking 9 mg/d and 44.2 ± 15.9 ng/mL in those taking 12 mg/d. In the LAI group, the mean Cps were 32.9 ± 12.7 ng/mL in patients receiving 100 mg per 28 days and 49.9 ± 25.9 ng/mL in those receiving 150 mg per 28 days. The mean Cps per daily dose (Cps/DD) were 4.11 ± 1.99 ng/mL/mg in the oral group and 9.24 ± 3.78 ng/mL/mg in the LAI group.

CONCLUSIONS

Under the suggested DD for oral and LAI paliperidone treatment, most Taiwanese patients with schizophrenia can reach the suggested therapeutic Cps range. Wide interindividual differences were observed in the Cps/DD for both the oral (7-fold) and LAI paliperidone (4-fold) groups. Compared with Western reports, no difference was observed in the body weight-adjusted Cps/DD.

Antibiotic depot system with radiofrequency controlled drug release

Drug depot systems have traditionally relied on the spontaneous dissolution and diffusion of drugs or prodrugs from a reservoir with constant exposure to the surrounding physiological fluids. While this is appropriate for clinical scenarios that require constant plasma concentration of the drug over time, there are also situations where multiple bursts of the drug at well-defined time intervals are preferred. This work presents a drug depot system that enables repeated on-demand release of antibiotics in precise doses, controlled by an external radiofrequency magnetic field. The remotely controlled depot system consists of composite microcapsules with a core-shell structure. The core contains micronized drug particles embedded in a low-melting hydrophobic matrix. The shell is formed by a hydrogel with immobilised magnetic nanoparticles that facilitate local heat dissipation after exposure to a radiofrequency magnetic field. When the melting point of the core material is locally exceeded, the embedded drug particles are mobilised and their surface is exposed to the external aqueous phase. It is shown that drug release can be controlled in an on/off manner by a chosen sequence and duration of radiofrequency pulses. The capacity of the depot system is shown to be significantly higher than that of purely diffusion-controlled systems containing a pre-dissolved drug. The functionality of the depot system is demonstrated in vitro for the specific case of norfloxacin acting on E. coli.

Drug Nanocrystals: Focus on Brain Delivery from Therapeutic to Diagnostic Applications

The development of new drugs is often hindered by low solubility in water, a problem common to nearly 90% of natural and/or synthetic molecules in the discovery pipeline. Nanocrystalline drug technology involves the reduction in the bulk particle size down to the nanosize range, thus modifying its physico-chemical properties with beneficial effects on drug bioavailability. Nanocrystals (NCs) are carrier-free drug particles surrounded by a stabilizer and suspended in an aqueous medium. Due to high drug loading, NCs maintain a potent therapeutic concentration to produce desirable pharmacological action, particularly useful in the treatment of central nervous system (CNS) diseases. In addition to the therapeutic purpose, NC technology can be applied for diagnostic scope. This review aims to provide an overview of NC application by different administration routes, especially focusing on brain targeting, and with a particular attention to therapeutic and diagnostic fields. NC therapeutic applications are analyzed for the most common CNS pathologies (i.e., Parkinson's disease, psychosis, Alzheimer's disease, etc.). Recently, a growing interest has emerged from the use of colloidal fluorescent NCs for brain diagnostics. Therefore, the use of NCs in the imaging of brain vessels and tumor cells is also discussed. Finally, the clinical effectiveness of NCs is leading to an increasing number of FDA-approved products, among which the NCs approved for neurological disorders have increased.

Journey to the Market: The Evolution of Biodegradable Drug Delivery Systems

Biodegradable polymers have been used as carriers in drug delivery systems for more than four decades. Early work used crude natural materials for particle fabrication, whereas more recent work has utilized synthetic polymers. Applications include the macroscale, the microscale, and the nanoscale. Since pioneering work in the 1960’s, an array of products that use biodegradable polymers to encapsulate the desired drug payload have been approved for human use by international regulatory agencies. The commercial success of these products has led to further research in the field aimed at bringing forward new formulation types for improved delivery of various small molecule and biologic drugs. Here, we review recent advances in the development of these materials and we provide insight on their drug delivery application. We also address payload encapsulation and drug release mechanisms from biodegradable formulations and their application in approved therapeutic products.

The Switch From Paliperidone Long-Acting Injectable 1- to 3-Monthly: Clinical Pharmacokinetic Evaluation in Patients With Schizophrenia (Preliminary Data)

PURPOSE/BACKGROUND

The aim of the study was a preliminary evaluation of the maintenance of clinical efficacy and tolerability of paliperidone palmitate in patients with schizophrenia during the transition phase from 1-monthly paliperidone palmitate formulation (PP1M) to PP3M, with the evaluation of plasma levels of the drug.

METHODS/PROCEDURES

A prospective observational study was conducted for 13 months involving 22 outpatients, aged 18 to 66 years and clinically stabilized. Patients were affected by schizophrenia according to Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, criteria. For each patient, clinical assessment, safety and tolerability, and drug plasma level determination were performed. Clinical efficacy was assessed by Brief Psychiatric Rating Scale, Positive and Negative Symptom Scale, and Hamilton Rating Scale for Depression. During the first 4 months of the study, once-monthly paliperidone palmitate was administered, and then during the following 9 months, the 3-monthly formulation was administered.

FINDINGS/RESULTS

The time course of the Brief Psychiatric Rating Scale total scores showed a statistically significant (P = 0.006) improvement from T0 to T8; Positive and Negative Symptom Scale scores showed a similar time course, with a statistically significant (P = 0.0016) reduction of the mean total score; Hamilton Rating Scale for Depression mean scores showed a statistically significant (P = 0.003) reduction with substantial maintenance of clinical stabilization of the patients. Only 1 patient dropped out after the first PP3M injection.

IMPLICATIONS/CONCLUSIONS

Our preliminary data currently confirm the maintenance of clinical stability shifting from PP1M to PP3M.

Enhancement of bioavailability through transdermal drug delivery of paliperidone palmitate-loaded nanostructured lipid carriers

Aim: The work describes enhanced bioavailability of paliperidone palmitate through transdermal delivery using nanostructured lipid carriers (NLC). Materials & methods: NLCs were formulated by nanoprecipitation method followed by incorporation in transdermal patch and physicochemical characterization. Results: NLCs showed high percentage entrapment efficiency of 83.44 ± 0.8%, drug loading of 24.75 ± 1.10% (w/w), particle size of 173.8 ± 3.25 nm, polydispersity index of 0.143 ± 0.05 and zeta potential of -15.9 ± 0.75 mV. In vitro and ex vivo studies indicated zero-order controlled drug release from NLCs and transdermal patch up to 48 h. Pharmacokinetic studies indicated 1.76-fold enhanced bioavailability by transdermal route as compared with oral drug delivery. Conclusion: From the results, it was concluded that drug-loaded NLCs-transdermal patch is promising drug delivery system for poorly bioavailable drugs.

Nanopharmaceutical-based regenerative medicine: a promising therapeutic strategy for spinal cord injury

Spinal cord injury (SCI) is a neurological disorder that can lead to loss of perceptive and athletic function due to the severe nerve damage. To date, pieces of evidence detailing the precise pathological mechanisms in SCI are still unclear. Therefore, drug therapy cannot effectively alleviate the SCI symptoms and faces the limitations of systemic administration with large side effects. Thus, the development of SCI treatment strategies is urgent and valuable. Due to the application of nanotechnology in pharmaceutical research, nanopharmaceutical-based regenerative medicine will bring colossal development space for clinical medicine. These nanopharmaceuticals (i.e. nanocrystalline drugs and nanocarrier drugs) are designed using different types of materials or bioactive molecules, so as to improve the therapeutic effects, reduce side effects, and subtly deliver drugs, etc. Currently, an increasing number of nanopharmaceutical products have been approved by drug regulatory agencies, which has also prompted more researchers to focus on the potential treatment strategies of SCI. Therefore, the purpose of this review is to summarize and elaborate the research progress as well as the challenges and future of nanopharmaceuticals in the treatment of SCI, aiming to promote further research of nanopharmaceuticals in SCI.

Guidance on the clinical understanding and use of long-acting injectable antipsychotics in Schizophrenia: Hong Kong Consensus Statements

AIMS

There is increasing evidence showing the importance of long-acting injectable antipsychotics in the management of schizophrenia, especially in terms of improving patient medication compliance. A panel of experienced clinicians in Hong Kong mapped out a set of consensus statements with an aim to facilitate the understanding and use of long-acting injectable antipsychotics among local physicians.

METHODS

Eight discussion areas regarding long-acting injectable antipsychotics were selected by the chairman of the consensus group. A series of meetings were held for the panelists to discuss the published literature and their clinical experience, followed by the drafting of consensus statements. At the final meeting, each consensus statement was voted on anonymously by all members based on its practicability of recommendation in Hong Kong.

RESULTS

A total of 12 consensus statements on the rational use of long-acting injectable antipsychotics were established and accepted by the consensus group.

CONCLUSION

The consensus statements aim to provide practical guidance for Hong Kong physicians on the use of long-acting injectable antipsychotics in schizophrenia patients. These statements may also serve as a reference for doctors in other parts of the Asia-Pacific region.

Nanomedicines - Tiny particles and big challenges

After decades of research, nanotechnology has been used in a broad array of biomedical products including medical devices, drug products, drug substances, and pharmaceutical-grade excipients. But like many great achievements in science, there is a fine balance between the risks and opportunities of this new technology. Some materials and surface structures in the nanosize range can exert unexpected toxicities and merit a more detailed safety assessment. Regulatory agencies such as the United States Food and Drug Administration or the European Medicines Agency have started dealing with the potential risks posed by nanomaterials. Considering that a thorough characterization is one of the key aspects of controlling such risks this review presents the regulatory background of nanosafety assessment and provides some practical advice on how to characterize nanomaterials and drug formulations. Further, the challenges of how to maintain and monitor pharmaceutical quality through a highly complex production processes will be discussed.

Cost-Minimisation Analysis of Paliperidone Palmitate Long-Acting Treatment versus Risperidone Long-Acting Treatment for Schizophrenia in Spain

BACKGROUND AND OBJECTIVE

Long-acting formulations for paliperidone (PPLAT) and risperidone (RLAT) are effective second-generation antipsychotics. This study aimed to compare treatment costs between PPLAT and RLAT in schizophrenia patients.

METHODS

A cost-minimization analysis was performed from the perspective of the Spanish National Healthcare System (NHS), in line with the approach accepted by the Scottish Medicine Consortium evaluation. Only direct health costs (€, 2015) were included, i.e. medication (including oral antipsychotic drug supplementation), hospitalization and cost of administration in the community. Two time horizons were used: 1 year (to compare initiation treatment) and 2 years (to compare maintenance treatment). Base-case considered the following assumptions: setting for treatment initiation (50 % hospital and 50 % community); 50 % of patients initiating from a long-acting treatment and 50 % from an oral antipsychotic; no reduction in the length of stay. One-way sensitivity analyses (SA) were performed.

RESULTS

The estimated costs/patient were €7698 (PPLAT) and €8168 (RLAT) for the first year, and €4314 (PPLAT) and €5003 (RLAT) for the second year. Cost savings related to PPLAT therapy were €470 and €689 for first and second year, respectively. SA results confirmed the robustness of the model results, even in the most conservative scenarios: (1) if 100 % of patients initiate treatment in hospital, the savings could be €454 per patient; (2) if 100 % of patients initiate treatment from an oral antipsychotic, the savings could be €277 per patient/year; and (3) if PPLAT could not reduce the length of stay by approximately one-third, as some studies indicate, the savings could be €470 per patient/year.

CONCLUSIONS

The use of PPLAT instead of RLAT could be a cost-saving strategy for the Spanish NHS.

Paliperidone palmitate: factors predicting continuation with treatment at 2 years

Our aim was to determine factors relating to continuation with treatment with paliperidone palmitate long-acting injection (PP) in a 2 year, non-interventional, observational study of the use of PP in consecutive patients treated in a secondary care environment. We followed-up 300 consecutive patients; 24 (8%) were lost to follow-up (7 deceased and 17 left the care of the trust). Overall, 107 patients of the remaining 276 who were not lost to follow-up (38.7%) completed 2 years' continuous treatment. A further 21 (7.6%) patients discontinued PP but restarted it after >2 months, 11 (4.0%) of whom were still receiving PP at 2 years. Median treatment time for PP was 465 days (95% CI 333, 583 days). Prior treatment with risperidone reduced the risk of discontinuation by 39% (RR 0.61 (95% CI -0.44, 0.86, p=0.004)); being initiated as an out-patient by 49% (RR 0.51 (95% CI 0.36, 0.73 p=0.001)). Risk of discontinuation was increased by 63% when the reason for prescribing PP was poor tolerability of prior treatment (RR 1.63 (95% CI 1.05, 2.51 p=0.028)). The rate of continuation with PP at 2 years was higher than that seen with other long acting depot formulations. Likelihood of continuation can be vastly improved by targeting PP for those most likely to benefit.

A review of aripiprazole long-acting injection

OBJECTIVES

To review the published literature on aripiprazole once monthly, a second generation antipsychotic (SGA) recently developed as a long-acting injection (LAI), in the form of a suspension of lyophilized aripiprazole reconstituted with an aqueous diluent, for intramuscular administration.

METHODS

An electronic database search was conducted using the key words; relevant articles were then hand searched and websites (FDA, EMA, Otsuka, Lundbeck, NIH) reviewed.

RESULTS

Efficacy has been demonstrated in preventing relapse in a 52 week study versus placebo, and non-inferiority to oral aripiprazole in a 38 week study, as well as in the treatment of hospitalized adult patients with acutely relapsed schizophrenia. Aripiprazole LAI appears cost-effective versus other SGA-LAIs, with improved health-related quality of life and functioning in a head-to-head study with paliperidone LAI. A 6 month (pre and post), mirror-image switch study demonstrated a reduction in hospitalization and associated costs compared with previous antipsychotic treatment. Safety and tolerability are comparable to oral aripiprazole with no new safety signals.

CONCLUSIONS

Experience with oral aripiprazole and the current availability of the long-acting formulation suggest a potential benefit in a variety of clinical scenarios and therefore consideration as a treatment option in the treatment of schizophrenia.

Paliperidone palmitate in non-acute patients with schizophrenia previously unsuccessfully treated with risperidone long-acting therapy or frequently used conventional depot antipsychotics

PALMFlexS, a prospective multicentre, open-label, 6-month, phase IIIb interventional study, explored tolerability, safety and treatment response in adults (n = 231) with non-acute but symptomatic schizophrenia switching to flexibly dosed paliperidone palmitate (PP) after unsuccessful treatment with risperidone long-acting injectable therapy (RLAT) or conventional depot antipsychotics (APs). Treatment response was measured by change in Positive and Negative Syndrome Scale (PANSS) total score from baseline (BL) to last-observation-carried-forward (LOCF) endpoint (EP). Safety and tolerability assessments included Extrapyramidal Symptom Rating Scale (ESRS) total score and treatment-emergent adverse events. Significant reductions in mean PANSS total score were observed for all groups (-7.5 to -10.6; p ⩽ 0.01 [BL to LOCF EP]). After switching to PP, more than 50% of all patients achieved ⩾20% and one-third of RLAT-treated patients even achieved ⩾50% improvement in PANSS total score. Across groups, there were significant improvements (p < 0.05) in symptom severity as measured by Clinical Global Impression-Severity (CGI-S; trend for improvement with RLAT; p = 0.0568), subjective well-being, medication satisfaction, and patient functioning with PP. PP was generally well tolerated. Clinically relevant benefits were observed in non-acute patients with schizophrenia switched from RLAT or conventional depot APs to PP.

Elucidating the in vivo fate of nanocrystals using a physiologically based pharmacokinetic model: a case study with the anticancer agent SNX-2112

Introduction

SNX-2112 is a promising anticancer agent but has poor solubility in both water and oil. In the study reported here, we aimed to develop a nanocrystal formulation for SNX-2112 and to determine the pharmacokinetic behaviors of the prepared nanocrystals.

Methods

Nanocrystals of SNX-2112 were prepared using the wet-media milling technique and characterized by particle size, differential scanning calorimetry, drug release, etc. Physiologically based pharmacokinetic (PBPK) modeling was undertaken to evaluate the drug’s disposition in rats following administration of drug cosolvent or nanocrystals.

Results

The optimized SNX-2112 nanocrystals (with poloxamer 188 as the stabilizer) were 203 nm in size with a zeta potential of −11.6 mV. In addition, the nanocrystals showed a comparable release profile to the control (drug cosolvent). Further, the rat PBPK model incorporating the parameters of particulate uptake (into the liver and spleen) and of in vivo drug release was well fitted to the experimental data following administration of the drug nanocrystals. The results reveal that the nanocrystals rapidly released drug molecules in vivo, accounting for their cosolvent-like pharmacokinetic behaviors. Due to particulate uptake, drug accumulation in the liver and spleen was significant at the initial time points (within 1 hour).

Conclusion

The nanocrystals should be a good choice for the systemic delivery of the poorly soluble drug SNX-2112. Also, our study contributes to an improved understanding of the in vivo fate of nanocrystals.

1,2-Benzisoxazole compounds: a patent review (2009 - 2014)

INTRODUCTION

Benzisoxazoles represent a class of heterocyclic compounds of great importance for the preparation of biologically active compounds. Benzisoxazoles are an important structure and some benzisoxazole-based medicines have been approved for human clinical use, including atypical antipsychotics (risperidone, paliperidone and iloperidone) and an anticonvulsant (zonisamide).

AREAS COVERED

This review puts emphasis on the recent progress in therapeutically attractive benzisoxazole derivatives especially 1,2-benzisoxazoles, which were published in the patent literature between 2009 and 2014. As for the class of medicines, the main focus is on atypical antipsychotics and potential therapeutic treatments for other CNS disorders. This review also covers the examples of benzisoxazole-based kinase inhibitors. Moreover, novel benzisoxazoles with significant therapeutic interest are also mentioned.

EXPERT OPINION

More recent examples of structural modification of existing drugs led to the discovery of some promising benzisoxazoles for antipsychotic use. The design of multi-target ligands is important for the manipulation of pharmacological properties and safety profiles for the use of antipsychotics. Benzisoxazoles have been widely used as pharmacophores in the search for novel drug candidates in a variety of therapeutic area. It is fair to assume that the wide and frequent use of benzisoxazoles in drug discovery and development will continue into the future.

The cost reduction in hospitalization associated with paliperidone palmitate in the People's Republic of China, Korea, and Malaysia

BACKGROUND

Schizophrenia results in substantial health care utilization costs. Much of these costs can be attributed to health care use resulting from nonadherence to treatment, relapse, and hospitalization.

AIMS OF THE STUDY

The objective of this research is to further estimate the health care resource utilization costs of patients with schizophrenia in the People's Republic of China, Korea, and Malaysia with a specific focus on the reduction in hospitalization costs associated with the use of long-acting, injectable paliperidone palmitate (PP) relative to alternative treatment medications.

METHODS

The study focuses exclusively on the estimated reduction in hospitalization days following treatment with PP and the potential associated cost savings. Cost analysis was done using a payer's perspective and only includes direct health care costs associated with hospitalization. Localized cost data were taken from published sources, and health care utilization was estimated based on a clinical study conducted in countries in the Asia-Pacific region. People's Republic of China, Korea, and Malaysia had the highest number of patients enrolled in the clinical study, and thus were chosen for this research. Analysis looked at 12-month and 18-month periods following initial treatment with PP relative to a retrospective 12-month period utilizing alternative treatment medications.

RESULTS

Results suggest that reductions in hospital utilization cost over 12 months may occur through the use of PP relative to alternatives-ranging from $1,991 for the People's Republic of China to $6,698 for Korea and $6,716 for Malaysia.

CONCLUSION

Given the substantial costs associated with the treatment of schizophrenia both worldwide and in Asia, it is important to fully understand the costs and outcomes associated with various treatment options. In this research, we have specifically analyzed the direct health care cost savings associated with hospital utilization for patients taking PP relative to alternative treatment methods. The results suggest that reductions in hospital utilization cost were associated with PP treatment, likely largely due to increased adherence to treatment.

Onset and persistence of efficacy by symptom domain with long-acting injectable paliperidone palmitate in patients with schizophrenia

INTRODUCTION

Several long-acting injectable (LAI) second-generation antipsychotics are now available for the management of schizophrenia. As patients with schizophrenia frequently present with diverse and challenging symptoms, it is important to understand the effects of antipsychotics in treating these different symptom subgroups and the timing of these responses.

AREAS COVERED

For this review, data from two randomized, double-blind trials were analyzed in respect to the onset and persistence of effects on several measures of psychopathology (as measured by the Positive and Negative Syndrome Scale [PANSS]) after treatment with LAI paliperidone palmitate (PP) (NCT00590577 and NCT00589914).

EXPERT OPINION

Symptom reductions from baseline with PP were significant by day 4 for all five PANSS factors in both studies. Some effects may have been driven by the presence or absence of a placebo response. A significant effect for PP versus placebo was observed for all major symptom domains for one or more doses of PP during the first month of treatment. Once established, most (but not all) significant responses persisted to the end point. Similar improvements were observed in PANSS scores with PP and oral risperidone. Dose-dependent trends were observed for the effect of PP on positive, negative and uncontrolled hostility/excitement symptoms.

[Long-acting injectable antipsychotics. Overview and advice for daily routine care]

Recent investigations have demonstrated a significant reduction of relapse and hospitalization rates associated with the use of long-acting injectable antipsychotics (LAIs) in the treatment of schizophrenia. There are only marginal differences in the effectiveness of different specific LAIs. Furthermore, LAIs are comparable to the oral equivalents with respect to effectiveness and side effects. The occurrence of extrapyramidal motor disorders (EPD) is less frequent in second generation (SG) LAIs than in first generation (FG) LAIs. Moreover, specific characteristics of some substances should be considered: In SG-LAIs immediate onset of action is only applicable for olanzapine and paliperidone and FG-LAIs should always be given as a test dose first to assure a general tolerance. All LAIs have a high variability of plasma levels which complicates the dose titration. Last but not least, current research concerning long-term consequences of continuous treatment with antipsychotics and the potentially poorer response to antipsychotics should be considered.

A review of paliperidone palmitate

Risperidone long-acting injection (RLAI) was the first second-generation antipsychotic available as a long-acting injection. Paliperidone (9-hydroxyrisperidone) is the active metabolite of risperidone, introduced initially as an extended release oral (ORal Osmotic System, OROS®, Alza Corporation) formulation (Invega®, Janssen). Paliperidone long-acting injection (PLAI) has now been developed as a suspension of paliperidone palmitate nanocrystals in an aqueous formulation (Invega Sustenna®, Xeplion®), administered monthly by intramuscular injection (deltoid or gluteal). Doses of PLAI can be expressed either in milligram equivalents (mg eq) of paliperidone palmitate or in milligrams of the active fraction of paliperidone. The recommended initiation regimen of 150 mg eq (234 mg) on day 1 and 100 mg eq (156 mg) on day 8 (both administered in the deltoid) achieves therapeutic blood levels rapidly and without the necessity of oral supplementation. No refrigeration or reconstitution prior to administration is required. PLAI has been shown in to be effective in controlling the acute symptoms of schizophrenia as well as delaying time to relapse. Safety and tolerability are comparable to RLAI with no new safety signals. Thus, PLAI may represent the rational development of RLAI with greater ease of use.