In vitro and in vivo considerations associated with parenteral sustained release products: A review based upon information presented and points expressed at the 2007 Controlled Release Society Annual Meeting

Patient-Centric Long-Acting Injectable and Implantable Platforms─An Industrial Perspective

The increasing focus on patient centricity in the pharmaceutical industry over the past decade and the changing healthcare landscape, driven by factors such as increased access to information, social media, and evolving patient demands, has necessitated a shift toward greater connectivity and understanding of patients' unique treatment needs. One pharmaceutical technology that has supported these efforts is long acting injectables (LAIs), which lower the administration frequency for the patient's provided convenience, better compliance, and hence better therapeutical treatment for the patients. Furthermore, patients with conditions like the human immunodeficiency virus and schizophrenia have positively expressed the desire for less frequent dosing, such as that obtained through LAI formulations. In this work, a comprehensive analysis of marketed LAIs across therapeutic classes and technologies is conducted. The analysis demonstrated an increasing number of new LAIs being brought to the market, recently most as aqueous suspensions and one as a solution, but many other technology platforms were applied as well, in particular, polymeric microspheres and in situ forming gels. The analysis across the technologies provided an insight into to the physicochemical properties the compounds had per technology class as well as knowledge of the excipients typically used within the individual formulation technology. The principle behind the formulation technologies was discussed with respect to the release mechanism, manufacturing approaches, and the possibility of defining predictive in vitro release methods to obtain in vitro in vivo correlations with an industrial angle. The gaps in the field are still numerous, including better systematic formulation and manufacturing investigations to get a better understanding of potential innovations, but also development of new polymers could facilitate the development of additional compounds. The biggest and most important gaps, however, seem to be the development of predictive in vitro dissolution methods utilizing pharmacopoeia described equipment to enable their use for product development and later in the product cycle for quality-based purposes.

Long-Acting Injectable Antipsychotics-A Review on Formulation and In Vitro Dissolution

Long-acting injectable (LAI) neuroleptics constitute an effective therapeutical alternative for individuals suffering from persistent mental illness. These injectable pharmaceuticals help patients manage their condition better and improve long-term outcomes by preventing relapses and improving compliance. This review aims to analyse the current formulation aspects of LAI neuroleptics, with particular emphasis on analysis of drug release profiles as a critical test to guarantee drug quality and relevant therapeutical activity. While there is no officially approved procedure for depot parenteral drug formulations, various dissolution tests which were developed by LAI manufacturers are described. In vitro dissolution tests also possess a critical function in the estimation of the in vivo performance of a drug formulation. For that reason, thorough inspection of the in vitro-in vivo correlation (IVIVC) is also discussed.

Long-acting PLGA microspheres: advances in excipient and product analysis toward improved product understanding

Poly(lactic-co-glycolic acid) (PLGA) microspheres are a sustained-release drug delivery system with several successful commercial products used for the treatment of a variety of diseases. By utilizing PLGA polymers with different compositions, therapeutic agents can be released over durations varying from several weeks to several months. However, precise quality control of PLGA polymers and a fundamental understanding of all the factors associated with the performance of PLGA microsphere formulations remains challenging. This knowledge gap can hinder product development of both innovator and generic products. In this review, variability of the key release controlling excipient (PLGA), as well as advanced physicochemical characterization techniques for the PLGA polymer and PLGA microspheres are discussed. The relative merits and challenges of different in vitro release testing methods, in vivo pharmacokinetic studies, and in vitro-in vivo correlation development are also summarized. This review is intended to provide an in-depth understanding of long-acting microsphere products and consequently facilitate the development of these complex products.

Polymer source affects in vitro-in vivo correlation of leuprolide acetate PLGA microspheres

Poly(lactic-co-glycolic acid) PLGA (release controlling excipient) plays a dominant role on the performance of PLGA based long-acting parenterals. These types of drug products typically exhibit complex multi-phasic in vitro/in vivo release/absorption characteristics. In particular, owing to their large size, charged state, and hydrophilicity, peptide loaded microspheres can exhibit more complex release mechanisms. Accordingly, it is challenging to develop Level A in vitro-in vivo correlations (IVIVCs) for such complex long-acting parenterals. With the objective of gaining a better understanding of how to achieve IVIVCs for peptide loaded PLGA microspheres, formulations with similar as well as different release characteristics were prepared with PLGAs from different sources. Leuprolide acetate was selected as the model drug. Owning to the different physicochemical properties of the PLGAs (such as inherent viscosity, molecular weight and blockiness), the formulations exhibited significant differences in their critical quality attributes (such as particle size, porosity and pore size) and consequently had different in vitro and in vivo performance. Affirmative conventional IVIVCs were developed that were able to predict the in vivo performance using the corresponding in vitro release profiles. In addition, the developed conventional IVIVCs were able to discriminate between formulations with comparable in vitro/in vivo performance and those that had dissimilar in vitro/in vivo performance. The present work provides a comprehensive understanding of the influence of PLGA source variations on IVIVC development and predictability for peptide loaded PLGA microspheres.

In vitro-in vivo correlation of PLGA microspheres: Effect of polymer source variation and temperature

Development of Level A in vitro-in vivo correlations (IVIVCs) remains challenging for complex long-acting parenterals, such as poly(lactic-co-glycolic acid) PLGA microspheres. The nature of the PLGA polymer excipient has a dominant influence on the performance of PLGA microspheres. These microsphere systems typically exhibit multiphasic in vitro/in vivo release/absorption characteristics and may also show interspecies differences (animal model versus human data). These issues contribute to the difficulties in the development of IVIVCs for PLGA microsphere systems. To gain a better understanding of how to achieve IVIVCs for PLGA microspheres, microsphere formulations with similar as well as different release characteristics were prepared using PLGAs from different sources. Efforts were then made to establish IVIVCs for these formulations using in vitro release profiles obtained at both 37°C (human body temperature) and 39°C (rabbit body temperature) with in vivo data obtained from an animal model (rabbit). Risperidone was selected as the model drug; microsphere formulations were prepared under the same processing methods using apparently similar PLGAs from different sources. Owning to the different physicochemical properties of the PLGAs (such as inherent viscosity, monomer ratio (L/G ratio) and blockiness), the formulations exhibited significant differences in critical quality attributes (such as particle size, particle size distribution, porosity and pore size) and consequently had different in vitro and in vivo performance. IVIVCs were developed and it was shown that model predictability improved when IVIVCs were established using those formulations with comparable release characteristics. In addition, IVIVCs were established with T_scaling factors close to 1 using in vitro release profiles acquired at 39°C, emphasizing the importance of considering the body temperature in understanding interspecies differences. The present work provides a comprehensive understanding of the impact of the PLGA source variation on IVIVC development and predictability for complex long-acting parenterals such as PLGA microspheres.

An in vitro gel-based system for characterizing and predicting the long-term performance of PLGA in situ forming implants

In situ forming implants are exposed to an extracellular matrix resembling a gel rather than aqueous solution upon subcutaneous administration. The aim of study was to develop a gel-based release testing system for characterizing the long-term in vitro behavior of in situ forming implants. The gel-based system consisted of an agarose gel mimicking the subcutaneous injection site and a receiver layer comprising phosphate buffer. Poly(D,L-lactide-co-glycolide) in situ forming implants containing leuprolide acetate as the model peptide and N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO) or triacetin as co-solvent were investigated. The gel-based release testing system discriminated between the formulations. Accelerated release data obtained at elevated temperatures were able to predict real-time release applying the Arrhenius equation. Monitoring of the microenvironmental pH of the implants was performed by UV-Vis imaging in the gel-based system at 50 °C. A pH drop (from pH 7.4 to 6.7 for the NMP and DMSO implants, to pH 5.5 for the triacetin implants) within the first day was observed, followed by an increase to pH ∼7.4. The gel-based system coupled with UV imaging offered opportunity for detailed evaluation and prediction of the in vitro performance of long-acting injectables, facilitating future development of in situ depot forming delivery systems.

The Effect of Phase Transition Temperature on Therapeutic Efficacy of Liposomal Bortezomib

AIMS

Here, three liposomal formulations of DPPC/DPPG/Chol/DSPE-mPEG2000 (F1), DPPC/DPPG/Chol (F2) and HSPC/DPPG/Chol/DSPE-mPEG2000 (F3) encapsulating BTZ were prepared and characterized in terms of their size, surface charge, drug loading, and release profile. Mannitol was used as a trapping agent to entrap the BTZ inside the liposomal core. The cytotoxicity and anti-tumor activity of formulations were investigated in vitro and in vivo in mice bearing tumor.

BACKGROUND

Bortezomib (BTZ) is an FDA approved proteasome inhibitor for the treatment of mantle cell lymphoma and multiple myeloma. The low solubility of BTZ has been responsible for the several side effects and low therapeutic efficacy of the drug. Encapsulating BTZ in a nano drug delivery system; helps overcome such issues. Among NDDSs, liposomes are promising diagnostic and therapeutic delivery vehicles in cancer treatment.

OBJECTIVE

Evaluating anti-tumor activity of bortezomib liposomal formulations.

METHODS

Data prompted us to design and develop three different liposomal formulations of BTZ based on Tm parameter, which determines liposomal stiffness. DPPC (Tm 41°C) and HSPC (Tm 55°C) lipids were chosen as variables associated with liposome rigidity. In vitro cytotoxicity assay was then carried out for the three designed liposomal formulations on C26 and B16F0, which are the colon and melanoma cancer mouse-cell lines, respectively. NIH 3T3 mouse embryonic fibroblast cell line was also used as a normal cell line. The therapeutic efficacy of these formulations was further assessed in mice tumor models.

RESULT

MBTZ were successfully encapsulated into all the three liposomal formulations with a high entrapment efficacy of 60, 64, and 84% for F1, F2, and F3, respectively. The findings showed that liposomes mean particle diameter ranged from 103.4 to 146.8nm. In vitro cytotoxicity studies showed that liposomal-BTZ formulations had higher IC50 value in comparison to free BTZ. F2-liposomes with DPPC, having lower Tm of 41°C, showed much higher anti-tumor efficacy in mice models of C26 and B16F0 tumors compared to F3-HSPC liposomes with a Tm of 55°C. F2 formulation also enhanced mice survival compared with untreated groups, either in BALB/c or in C57BL/6 mice.

CONCLUSION

Our findings indicated that F2-DPPC-liposomal formulations prepared with Tm close to body temperature seem to be effective in reducing the side effects and increasing the therapeutic efficacy of BTZ and merits further investigation.

ELISA- and Activity Assay-Based Quantification of BMP-2 Released In Vitro Can Be Biased by Solubility in "Physiological" Buffers and an Interfering Effect of Chitosan

Chitosan nanogel-coated polycaprolactone (PCL) fiber mat-based implant prototypes with tailored release of bone morphogenic protein 2 (BMP-2) are a promising approach to achieve implant-mediated bone regeneration. In order to ensure reliable in vitro release results, the robustness of a commercially available ELISA for E. coli-derived BMP-2 and the parallel determination of BMP-2 recovery using a quantitative biological activity assay were investigated within a common release setup, with special reference to solubility and matrix effects. Without bovine serum albumin and Tween 20 as solubilizing additives to release media buffed at physiological pH, BMP-2 recoveries after release were notably reduced. In contrast, the addition of chitosan to release samples caused an excessive recovery. A possible explanation for these effects is the reversible aggregation tendency of BMP-2, which might be influenced by an interaction with chitosan. The interfering effects highlighted in this study are of great importance for bio-assay-based BMP-2 quantification, especially in the context of pharmaceutical release experiments.

Muscle Tissue as a Surrogate for In Vitro Drug Release Testing of Parenteral Depot Microspheres

Despite the importance of drug release testing of parenteral depot formulations, the current in vitro methods still require ameliorations in biorelevance. We have investigated here the use of muscle tissue components to better mimic the intramuscular administration. For convenient handling, muscle tissue was used in form of a freeze-dried powder, and a reproducible process of incorporation of tested microspheres to an assembly of muscle tissue of standardized dimensions was successfully developed. Microspheres were prepared from various grades of poly(lactic-co-glycolic acid) (PLGA) or ethyl cellulose, entrapping flurbiprofen, lidocaine, or risperidone. The deposition of microspheres in the muscle tissue or addition of only isolated lipids into the medium accelerated the release rate of all model drugs from microspheres prepared from ester-terminated PLGA grades and ethyl cellulose, however, not from the acid-terminated PLGA grades. The addition of lipids into the release medium increased the solubility of all model drugs; nonetheless, also interactions of the lipids with the polymer matrix (ad- and absorption) might be responsible for the faster drug release. As the in vivo drug release from implants is also often faster than in simple buffers in vitro, these findings suggest that interactions with the tissue lipids may play an important role in these still unexplained observations.

Fabrication of PLGA in situ forming implants and study on their correlation of in vitro release profiles with in vivo performances

In this study, a novel PLGA in situ forming implants (ISFIs) were fabricated and methods for testing the in vitro release profiles were also developed. The correlations between in vitro release profiles and in vivo performances (in vitro-in vivo correlation, IVIVC) were also studied. PLGA with different molecular weights were selected as the polymeric matrix. Biocompatible N-methy1-2-pyrrolidone (NMP) or glyceryl triacetate (GTA) were used as the solvents with the ratios of NMP/GTA from 60/40 (vol/vol) to 20/80 (vol/vol). Eprinomectin (EPR) was chosen as the model therapeutic. In vitro release profiles of the EPR-loaded PLGA ISFIs were investigated using various methods (i.e. 'tubule' sample-and-separate and dialysis method). Sprague-Dawley rats were used to study the in vivo pharmacokinetics of EPR-loaded PLGA ISFIs. The release data obtained via 'tubule' sample-separate method had a good IVIVC (Level A, R² > 0.99). These results showed that the 'tubule' sample-separate method was capable of discriminating the EPR-loaded ISFIs which were equivalent in formulation composition with manufacturing differences. Meanwhile, this method could be used to predict the in vivo performances of ISFIs in the investigated animal model.

In-vitro drug release testing of parenteral formulations via an agarose gel envelope to closer mimic tissue firmness

Current in vitro drug-release testing of the sustained-release parenterals represents the in vivo situation insufficiently. In this work, a thin agarose hydrogel layer surrounding the tested dosage form was proposed to mimic the tissue. The method was applied on implantable formulations of different geometries (films, microspheres, and cylindrical implants); prepared from various polymers (several Resomer® grades or ethyl cellulose) and loaded with different model drugs: flurbiprofen, lidocaine or risperidone. The hydrogel layer did not possess any retarding effect on the released drug and acted as a physical restriction to swelling and/or plastic deformation of the tested dosage forms. This led to a different surface area available for drug-release compared with testing in release medium alone and correspondingly to significantly different release profiles of the majority of the formulations obtained between the two methods (e.g. t50% = 18 days in pure release medium vs. t50% = 26 days in gel-setup for risperidone loaded Resomer® 503 H films or t50% = 7 days vs. t50% = 19 days for risperidone loaded Resomer® 503 H microspheres). The limited space for swelling and the rigidity of the agarose gel might mimic the tight encapsulation of the dosage form in the tissue better than the conventional liquid medium.

Regulatory aspects and quality controls of polymer-based parenteral long-acting drug products: the challenge of approving copies

To assure the safety and the efficacy of a medicinal product, quality and batch-to-batch reproducibility need to be guaranteed. In the case of parenteral long-acting products, the European Union (EU) and US Regulatory Authorities provide different indications, from the classification to the in vitro release assays related to such products. Despite their relevance, there are few in vitro experimental set-ups enabling researchers to discriminate among products with different in vivo behaviors. Consequently, most copies are authorized through hybrid instead of generic applications. Here, we review the actual regulatory frameworks to evaluate the in vitro release of drugs from polymer-based long-acting parenterals to highlight the directions followed by the Regulatory Agencies in the USA and EU.

In vitro-in vivo correlation of parenteral PLGA microspheres: Effect of variable burst release

Development of IVIVCs is a very complicated process, especially for complex drug products such as parenteral PLGA microspheres with multiphasic drug release characteristics. Specifically, microspheres that exhibit an initial burst release phase are even more challenging since the in vitro and in vivo burst release phases may not be comparable if drug absorption is rate-limiting at this stage. Therefore, the objectives of the present work were: 1) to investigate the predictability of developed IVIVCs for the in vivo burst release phase based on the in vitro burst release phase of the formulations; and 2) to evaluate the impact of variable burst release on the predictability of the developed IVIVCs for two different types of microsphere-based drug products. Accordingly, Risperdal Consta® (Risperidone) and Lupron Depot® (Leuprolide acetate, LA) were selected as model products. Compositionally equivalent risperidone and LA formulations with variable burst release phases were prepared with manufacturing process changes (such as solvent systems and mixing methods). The prepared microspheres exhibited differences in critical physicochemical properties (such as particle size, porosity, average pore diameter, and drug distribution) and hence differences in their in vitro release characteristics (such as variable burst release and release rate). The in vitro and in vivo (rabbit model (intramuscular injection) burst release were similar for the risperidone microspheres but were significantly different for the LA microspheres. This had an impact on the complexity of the developed IVIVC models. Level A IVIVCs with the ability to predict various types of burst release were developed using time scaling and shifting factors. Moreover, it was observed that IVIVCs developed using formulations with less variation in burst release had better predictability and vice-versa. Thus, the present research has provided a comprehensive understanding of the impact of the burst release phase on the development, complexity, and predictability of IVIVCs for complex parenteral microspheres containing a variety of therapeutic molecules.

Formulation and Evaluation of a Novel Oral Oil-Based Suspension Using Micro-environmental pH-Modifying Solid Dispersion

Drugs with pH-dependent solubility that have poor water solubility can be identified in the drug discovery pipeline. Some of them have poor oral absorption, which can result in insufficient efficacy. Micro-environmental pH-modifying solid dispersion (micro pHm SD) is a promising approach to overcome the poor oral absorption of these drugs. In the present study, toltrazuril (TOL), a weakly acidic drug with poor aqueous and pH-dependent solubility, was used as a model drug. Using micro pHm SD, a novel oral oil-based suspension of TOL SD (TSDS) was developed, and the stability of this formulation was evaluated based on particle size, settling volume ratio, redispersibility, thermal stability, and drug content. The optimized soybean oil-based TSDS (S-TSDS) had high physicochemical stability and good histocompatibility with common inflammatory reactions. The results of the in vitro dissolution analysis showed that S-TSDS rapidly and markedly released the drug and provided higher efficacy and longer persistence against coccidiosis (above 90.9%) in rabbits. This technique could increase the oral absorption and bioavailability of new drug candidates.

Long-Acting Release Microspheres Containing Novel GLP-1 Analog as an Antidiabetic System

Glucagon-like peptide 1 (GLP-1) has recently received significant attention as an efficacious way to treat diabetes mellitus. However, the short half-life of the peptide limits its clinical application in diabetes. In our previous study, a novel GLP-1 analog (PGLP-1) with a longer half-life was synthesized and evaluated. Herein, we prepared the PGLP-1-loaded poly(d,l-lactide- co-glycolide) microspheres to achieve long-term effects on blood glucose control. The incorporation of zinc ion into the formulation can effectively decrease the initial burst release, and a uniform drug distribution was obtained, in contrast to native PGLP-1 encapsulated microspheres. We demonstrated that the solubility of the drug encapsulated in microspheres played an important role in in vitro release behavior and drug distribution inside the microspheres. The Zn-PGLP-1 microspheres had a prominent acute glucose reduction effect in the healthy mice. A hypoglycemic effect was observed in the streptozotocin (STZ) induced diabetic mice through a 6-week treatment of Zn-PGLP-1-loaded microspheres. Meanwhile, the administration of Zn-PGLP-1 microspheres led to the β-cell protection and stimulation of insulin secretion. The novel GLP-1 analog-loaded sustained microspheres may greatly improve patient compliance along with a desirable safety feature.

Improving long-term subcutaneous drug delivery by regulating material-bioenvironment interaction

Subcutaneous long-acting release (LAR) formulations have been extensively developed in the clinic to increase patient compliance and reduce treatment cost. Despite preliminary success for some LAR systems, a major obstacle limiting the therapeutic effect remains on their interaction with surrounding tissues. In this review, we summarize how living bodies respond to injected or implanted materials, and highlight some typical strategies based on smart material design, which may significantly improve long-term subcutaneous drug delivery. Moreover, possible strategies to achieve ultra-long (months, years) subcutaneous drug delivery systems are proposed. Based on these discussions, we believe the well-designed subcutaneous long-acting formulations will hold great promise to improve patient quality of life in the clinic.

PLGA-based monolithic filaments prepared by hot-melt extrusion: In-vitro comparative study

To avoid frequent drug administration, PLGA-based monolithic filament-shaped implants were prepared. In this study, the effect of different formulation variables was studied, namely: type of PLGA (PLGA 502 and PLGA 503), type of drug (the lipophilic Prednisolone acetate, PA and the hydrophilic Propranolol Hydrochloride, PH) and drug loading (10 and 30% w/w). PLGA 503-based implants showed a lower water uptake, lower mass loss and erosion, slower drug release, and better mechanical properties and elasticity (P<0.05) compared to the corresponding PLGA 502-based implants. PH-loaded implants showed a faster swelling and degradation as well as drug release (P<0.05) compared to PA-loaded implants; the former attained almost complete drug release after about 18 days, while the latter attained it after about 30 days. All the implants followed a zero-order kinetic pattern suitable for a controlled drug release. Characterization was done using SEM and DSC. This study proved the potential tailoring of the properties of PLGA-implants, prepared by hot-melt extrusion (HME), based on some formulation variables.

A New Level A Type IVIVC for the Rational Design of Clinical Trials Toward Regulatory Approval of Generic Polymeric Long-Acting Injectables

Chronic neuropsychiatric disorders and diabetes mellitus affect millions of patients and require long-term supervision and expensive medical care. Although repeated drug administration can help manage these diseases, relapses and re-hospitalization owing to patient non-adherence and reduced therapeutic efficacy remain challenging. In response, long-acting injectables, which provide sustained drug release over longer periods at concentrations close to therapeutic ranges, have been proposed. Recent advancements include polymeric long-acting injectables (pLAIs), in which the active pharmaceutical ingredient (API) is encapsulated within U.S. Food and Drug Administration (FDA)-approved biocompatible polymers, such as poly(lactic-co-glycolic acid), or PLGA. Despite significant progress and development in the global pLAI market, FDA guidance for the approval of complex drug products, such as generic pLAIs, is not clearly defined. Although in vitro to in vivo correlation (IVIVC) can facilitate the identification of critical quality attributes (CQAs), drug formulations, and in vitro test platforms for evaluating drug performance in vivo, the application of IVIVC in order to shortlist time- and resource-intensive clinical trials for generic pLAIs has not been reported. Here, we propose a new Level A Type IVIVC that directly correlates the in vitro outcomes, such as drug dissolution, of candidate generic formulations with the clinical characteristics, such as drug absorption, of a reference listed drug (RLD), to help identify the specific generic pLAI formulations with clinical absorptions that are likely to be similar to that of the RLD, thereby reducing the number of clinical trials required for evaluation of clinical bioequivalence (BE). Therefore, the scope of the proposed method is intended only for the rational design of clinical trials, i.e., to shortlist the specific pLAI generic formulations for clinical BE evaluation, and not necessarily to analyze drug performances (i.e., drug safety and effectiveness) in the shortlisted clinical trials or post-approval. Once validated, this method will be of great value to developers of generic pLAIs and regulatory bodies to accelerate their approval of these generic pLAIs.

Development and evaluation of accelerated drug release testing methods for a matrix-type intravaginal ring

Accelerated drug release testing is a valuable quality control tool for long-acting non-oral extended release formulations. Currently, several intravaginal ring candidates designed for the long-term delivery of steroids or anti-infective drugs are being in the developing pipeline. The present article addresses the demand for accelerated drug release methods for these formulations. We describe the development and evaluation of accelerated release methods for a steroid releasing matrix-type intravaginal ring. The drug release properties of the formulation were evaluated under real-time and accelerated test conditions. Under real-time test conditions drug release from the intravaginal ring was strongly affected by the steroid solubility in the release medium. Under sufficient sink conditions that were provided in release media containing surfactants drug release was Fickian diffusion driven. Both temperature and hydro-organic dissolution media were successfully employed to accelerate drug release from the formulation. Drug release could be further increased by combining the temperature effect with the application of a hydro-organic release medium. The formulation continued to exhibit a diffusion controlled release kinetic under the investigated accelerated conditions. Moreover, the accelerated methods were able to differentiate between different prototypes of the intravaginal ring that exhibited different release profiles under real-time test conditions. Overall, the results of the present study indicate that both temperature and hydro-organic release media are valid parameters for accelerating drug release from the intravaginal ring. Variation of either a single or both parameters yielded release profiles that correlated well with real-time release.

Controlled Drug Delivery: Historical perspective for the next generation

The modern day drug delivery technology is only 60years old. During this period numerous drug delivery systems have been developed. The first generation (1950-1980) has been very productive in developing many oral and transdermal controlled release formulations for clinical applications. On the other hand, the second generation (1980-2010) has not been as successful in generating clinical products. This is in large part due to the nature of the problems to overcome. The first generation of drug delivery technologies dealt with physicochemical problems, while the second struggled with biological barriers. Controlled drug delivery systems can be made with controllable physicochemical properties, but they cannot overcome the biological barriers. The third generation (from 2010) drug delivery systems need to overcome both physicochemical and biological barriers. The physicochemical problems stem from poor water solubility of drugs, large molecular weight of peptide and protein drugs, and difficulty of controlling drug release kinetics. The biological barriers to overcome include distribution of drug delivery systems by the body rather than by formulation properties, limiting delivery to a specific target in the body. In addition, the body's reaction to formulations limits their functions in vivo. The prosperous future of drug delivery systems depends on whether new delivery systems can overcome limits set by human physiology, and the development process can be accelerated with new ways of thinking.

In vitro-in vivo correlation of parenteral risperidone polymeric microspheres

The objective of the present study was to determine whether an in vitro-in vivo correlation (IVIVC) can be established for polymeric microspheres that are equivalent in formulation composition but prepared with different manufacturing processes. Risperidone was chosen as a model therapeutic and poly(lactic-co-glycolic acid) (PLGA) with similar molecular weight as that used in the commercial product Risperdal® Consta® was used to prepare risperidone microspheres. Various manufacturing processes were investigated to produce the risperidone microspheres with similar drug loading (approx. 37%) but distinctly different physicochemical properties (e.g. porosity, particle size and particle size distribution). In vitro release of the risperidone microspheres was investigated using different release testing methods (such as sample-and-separate and USP apparatus 4). In vivo pharmacokinetic profiles of the risperidone microsphere formulations following intramuscular administration were determined using a rabbit model. Furthermore, the obtained pharmacokinetic profiles were deconvoluted using the Loo-Riegelman method and the calculated in vivo release was compared with the in vitro release of these microspheres. Level A IVIVCs were established and validated for the compositionally equivalent risperidone microspheres based on the in vitro release data obtained using USP apparatus 4. The developed IVIVCs demonstrated good predictability and were robust. These results showed that the developed USP apparatus 4 method was capable of discriminating PLGA microspheres that are equivalent in formulation composition but with manufacturing differences and predicting their in vivo performance in the investigated animal model.

Drug delivery system innovation and Health Technology Assessment: Upgrading from Clinical to Technological Assessment

Health Technology Assessment (HTA) is a multidisciplinary health political instrument that evaluates the consequences, mainly clinical and economical, of a health care technology; the HTA aim is to produce and spread information on scientific and technological innovation for health political decision making process. Drug delivery systems (DDS), such as nanocarriers, are technologically complex but they have pivotal relevance in therapeutic innovation. The HTA process, as commonly applied to conventional drug evaluation, should upgrade to a full pharmaceutical assessment, considering the DDS complexity. This is useful to study more in depth the clinical outcome and to broaden its critical assessment toward pharmaceutical issues affecting the patient and not measured by the current clinical evidence approach. We draw out the expertise necessary to perform the pharmaceutical assessment and we propose a format to evaluate the DDS technological topics such as formulation and mechanism of action, physicochemical characteristics, manufacturing process. We integrated the above-mentioned three points in the Evidence Based Medicine approach, which is data source for any HTA process. In this regard, the introduction of a Pharmaceutics Expert figure in the HTA could be fundamental to grant a more detailed evaluation of medicine product characteristics and performances and to help optimizing DDS features to overcome R&D drawbacks. Some aspects of product development, such as manufacturing processes, should be part of the HTA as innovative manufacturing processes allow new products to reach more effectively patient bedside. HTA so upgraded may encourage resource allocating payers to invest in innovative technologies and providers to focus on innovative material properties and manufacturing processes, thus contributing to bring more medicines in therapy in a sustainable manner.

In vitro-in vivo correlation from lactide-co-glycolide polymeric dosage forms

The objective of this study was to compare the in vitro behavior of four long-acting subcutaneous risperidone formulations with in vivo performance, with the intent of establishing an IVIVC. Two copolymers of PLGA (50:50 and 75:25) were used to prepare four microsphere formulations of risperidone, an atypical antipsychotic. In vitro behavior was assessed at the physiological temperature (37 °C) using the ‘modified dialysis’ technique. The in vitro release profile demonstrated rank order behavior with Formulations A and B, prepared using the 50:50 copolymer, exhibiting rapid drug release, while Formulations C and D, prepared using 75:25 PLGA, released drug in a slower manner. In vivo profiles were obtained by two approaches, i.e., deconvolution using the Nelson–Wagner equation (the FDA recommended approach) and using fractional AUC. With both in vivo approaches, the 50:50 PLGA preparations released drug faster than the 75:25 PLGA microspheres, exhibiting the same rank order observed in vitro. Additionally, profiles for the four formulations obtained using the deconvolution approach were nearly superimposable with fractional AUC, implying that the latter procedure could be used as a substitute for the Nelson–Wagner method. A comparison of drug release profiles for the four formulations revealed that in three of the four formulations, in vivo release was slightly faster than that in vitro, but the results were not statistically significant (P > 0.0001). An excellent linear correlation (R² values between 0.97 and 0.99) was obtained when % in vitro release for each formulation was compared with its corresponding in vivo release profile, obtained by using fraction absorbed (Nelson–Wagner method) or fractional AUC. In summary, using the four formulations that exhibited different release rates, a Level A IVIVC was established using the FDA-recommended deconvolution method and fractional AUC approach. The excellent relationship between in vitro drug release and the amount of drug absorbed in vivo in this study was corroborated by the nearly 1:1 correlation (R² greater than 0.97) between in vitro release and in vivo performance. Thus, the results of the current study suggest that proper selection of an in vitro method to assess drug release from long-acting injectables will aid in obtaining a Level A IVIVC.

A Review of In Vitro Drug Release Test Methods for Nano-Sized Dosage Forms

This review summarizes the methods used to study real-time (37°C) drug release from nanoparticulate drug delivery systems and establish an IVIVC. Since no compendial standards exist, drug release is currently assessed using a variety of methods including sample and separate (SS), continuous flow (CF), dialysis membrane (DM) methods, and a combination thereof, as well as novel techniques like voltametry and turbidimetry. This review describes the principle of each method along with their advantages and disadvantages, including challenges with set-up and sampling. The SS method allows direct measurement of drug release with simple set-up requirements, but sampling is cumbersome. With the CF method, sampling is straightforward but the set-up is time consuming. Set-up as well as sampling is easier with the DM, but it may not be suitable for drugs that bind to the membrane. Novel methods offer the possibility of real-time drug release measurement but may be restricted to certain types of drugs. Of these methods, Level A IVIVCs have been obtained with dialysis, alone or in combination with the sample and separate technique. Future efforts should focus on developing mathematical models that describe drug release mechanisms as well as facilitate formulation development of nano-sized dosage forms.

Pharmacokinetics of an injectable modified-release 2-hydroxyflutamide formulation in the human prostate gland using a semiphysiologically based biopharmaceutical model

The local distribution of 2-hydroxyflutamide (2-HOF) in prostate tissue after a single intraprostatic injection of a novel parenteral modified-release (MR) formulation in patients with localized prostate cancer was estimated using a semiphysiologically based biopharmaceutical model. Plasma concentration-time profiles for 2-HOF were acquired from a phase II study in 24 patients and the dissolution of the MR formulation was investigated in vitro. Human physiological values and the specific physicochemical properties of 2-HOF were obtained from the literature or calculated via established algorithms. A compartmental modeling approach was adopted for tissue and blood in the prostate gland, where the compartments were modeled as a series of concentric spherical shells contouring the centrally positioned depot formulation. Discrete fluid connections between the blood compartments were described by the representative flow of blood, whereas the mass transport of drug from tissue to tissue and tissue to blood was described by a one-dimensional diffusion approximation. An empirical dissolution approach was adopted for the release of 2-HOF from the formulation. The model adequately described the plasma concentration-time profiles of 2-HOF. Predictive simulations indicated that the local tissue concentration of 2-HOF within a distance of 5 mm from the depot formulation was approximately 40 times higher than that of unbound 2-HOF in plasma. The simulations also indicated that spreading the formulation throughout the prostate gland would expose more of the gland and increase the overall release rate of 2-HOF from the given dose. The increased release rate would initially increase the tissue and plasma concentrations but would also reduce the terminal half-life of 2-HOF in plasma. Finally, an in vitro-in vivo correlation of the release of 2-HOF from the parenteral MR formulation was established. This study shows that intraprostatic 2-HOF concentrations are significantly higher than systemic plasma concentrations and that increased distribution of 2-HOF throughout the gland, using strategic imaging-guided administration, is possible. This novel parenteral MR formulation, thus, facilitates good pharmacological effect while minimizing the risk of side effects.

Herbal delivery system for treatment of obesity administration of encapsulated khat-extracts on body weight of rats

SUMMARY

Obesity is one of the most important problems worldwide. Khat (Catha edulis), an evergreen shrub, is thought to reduce body-weight. Its effect is more prominent when khat leaves are chewed. Thus, anti-obesity effects of khat and its associated side effects may depend on the release rate of its active constituents. The present study aimed to investigate the effect of a selected low dose of dried-khat, extracted, formulated as controlled release delivery systems on the body weight (BW), food intake (FI), cholesterol (CS) and triglyceride (TG) levels in rats. Khat extract (KE) was microencapsulated (KE235) and formulated into a parenteral implant (InjKE235). The effects of KE, KE235 and InjKE235 on BW, FI, CS and TG in rats were investigated. The results showed that microcapsules sustained the khat alkaloid release with T50% 1.58 h for KE235 and 14.41 days for InjKE235. KE and KE235 caused maximum reduction in BW, FI, CS and TG during the first to third weeks but rebound gradually thereafter. On the contrary, InjKE235 exhibited a sustained reduction in BW, FI, CS and TG levels for 2 months. The T50% of KE, KE235 and InjKE235 correlated with the reduction in BW, CS and TG but not with FI. In conclusion, the subcutaneous injection and sustained release rate of khat extract play an important role in enhancing the anti-obesity effect in SD rats.:

In Vitro Dissolution Testing Strategies for Nanoparticulate Drug Delivery Systems: Recent Developments and Challenges

Nanoparticulate systems have emerged as prevalent drug delivery systems over the past few decades. These delivery systems (such as liposomes, emulsions, nanocrystals, and polymeric nanocarriers) have been extensively used to improve bioavailability, prolong pharmacological effects, achieve targeted drug delivery, as well as reduce side effects. Considering that any unanticipated change in product performance of such systems may result in toxicity and/or change in vivo efficacy, it is essential to develop suitable in vitro dissolution/release testing methods to ensure product quality and performance, and to assist in product development. The present review provides an overview of the current in vitro dissolution/release testing methods such as dialysis, sample and separate, as well as continuous flow methods. Challenges and future directions in the development of standardized and biorelevant in vitro dissolution/release testing methods for novel nanoparticulate systems are discussed.