Design of a long-term antipsychotic in situ forming implant and its release control method and mechanism

PLGA and PDMS-based in situ forming implants loaded with rosuvastatin and copper-selenium nanoparticles: a promising dual-effect formulation with augmented antimicrobial and cytotoxic activity in breast cancer cells

Breast cancer is among the most prevalent tumors worldwide. In this study, in-situ forming implants (ISFIs) containing rosuvastatin calcium were prepared using three types of poly (D, L-lactic-co-glycolic acid) (PLGA), namely, PLGA 50/50 with ester terminal and PLGA 75/25 with ester or acid terminal. Additionally, polydimethylsiloxane (PDMS) was added in concentrations of 0, 10, 20, and 30% w/v to accelerate matrix formation. The prepared ISFIs were characterized for their rheological behaviors, rate of matrix formation, and in-vitro drug release. All the prepared formulations revealed a Newtonian flow with a matrix formation rate between 0.017 and 0.059 mm/min. Generally, increasing the concentration of PDMS increased the matrix formation rate. The prepared implants' release efficiency values ranged between 46.39 and 89.75%. The ISFI containing PLGA 50/50 with 30% PDMS was selected for further testing, as it has the highest matrix formation rate and a promising release efficiency value. Copper-selenium nanoparticles were prepared with two different particle sizes (560 and 383 nm for CS1 and CS2, respectively) and loaded into the selected formulation to enhance its anticancer activity. The unloaded and loaded implants with rosuvastatin and copper-selenium nanoparticles were evaluated for their antibacterial activity, against Gram-positive and negative microorganisms, and anticancer efficacy, against MCF-7 and MDA-MB-231 cell lines. The results confirmed the potency of rosuvastatin calcium against cancer cells and the synergistic effect when loaded with smaller particle sizes of copper-selenium nanoparticles. This formulation holds a considerable potential for efficient breast cancer therapy.

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.

Optimizing formulation parameters for the development of carvedilol injectable in situ forming depots

In situ forming depots (ISFDs) represent attractive alternatives to the conventional sustained drug delivery systems. Carvedilol, a short half-life drug used on a daily basis to manage chronic conditions, could benefit from this technology. The aim of this work was to develop, for the first time, a new injectable long-acting carvedilol-ISFD. Accordingly, 4 different grades of polyesters with varying properties as i) lactide-to glycolide ratio (polylactide-co-glycolide (PLGA) vs. polylactide (PLA)), and ii) end functionality (acid- vs. ester-capped) were utilized for the preparation of ISFD formulations. In addition, 4 different organic solvents with varying properties (i.e. N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), ethyl acetate, and benzyl benzoate) were also investigated. It was found that NMP and DMSO were more suitable for the formation of depots. Furthermore, all ISFD formulations demonstrated excellent encapsulation efficiency (i.e. 96-98%). Interestingly, both PLGA-based ISFDs (acid-capped and ester-capped) exhibited similar release behaviors and were able to extend carvedilol release over 30 days. On the other hand, acid-capped and ester-capped PLA-based ISFDs exhibited slower release over the 30 days with an average release of only 36% and 60%, respectively. In conclusion, the developed carvedilol-ISFDs resulted in a tunable extended-release behavior, simply by choosing the appropriate grade of polymer. These results open the door toward a novel injectable carvedilol-ISFD formulation.

Levofloxacin HCl-Loaded Eudragit L-Based Solvent Exchange-Induced In Situ Forming Gel Using Monopropylene Glycol as a Solvent for Periodontitis Treatment

Solvent exchange-induced in situ forming gel (ISG) is currently an appealing dosage form for periodontitis treatment via localized injection into the periodontal pocket. This study aims to apply Eudragit L and Eudragit S as matrix components of ISG by using monopropylene glycol as a solvent for loading levofloxacin HCl for periodontitis treatment. The influence of Eudragit concentration was investigated in terms of apparent viscosity, rheological behavior, injectability, gel-forming behavior, and mechanical properties. Eudragit L-based formulation presented less viscosity, was easier to inject, and could form more gel than Eudragit S-based ISG. Levofloxacin HCl-loading diminished the viscosity of Eudragit L-based formulation but did not significantly change the gel formation ability. Higher polymer loading increased viscosity, force-work of injectability, and hardness. SEM photographs and µCT images revealed their scaffold formation, which had a denser topographic structure and less porosity attained owing to higher polymer loading and less in vitro degradation. By tracking with fluorescence dyes, the interface interaction study revealed crucial information such as solvent movement ability and matrix formation of ISG. They prolonged the drug release for 14 days with fickian drug diffusion kinetics and increased the release amount above the MIC against test microbes. The 1% levofloxacin HCl and 15% Eudragit L dissolved in monopropylene glycol (LLM15) was a promising ISG because of its appropriate viscosity (3674.54 ± 188.03 cP) with Newtonian flow, acceptable gel formation and injectability (21.08 ± 1.38 N), hardness (33.81 ± 2.3 N) and prolonged drug release with efficient antimicrobial activities against S. aureus (ATCC 6538, 6532, and 25923), methicillin-resistant S. aureus (MRSA) (S. aureus ATCC 4430), E. coli ATCC 8739, C. albicans ATCC 10231, P. gingivalis ATCC 33277, and A. actinomycetemcomitans ATCC 29522; thus, it is the potential ISG formulation for periodontitis treatment by localized periodontal pocket injection.

Injectable In-Situ Forming Depot Based on PLGA and PLGA-PEG-PLGA for Sustained-Release of Risperidone: In Vitro Evaluation and Pharmacokinetics in Rabbits

In the current research, novel drug delivery systems based on in situ forming gel (ISFG) (PLGA-PEG-PLGA) and in situ forming implant (ISFI) (PLGA) were developed for one-month risperidone delivery. In vitro release evaluation, pharmacokinetics, and histopathology studies of ISFI, ISFG, and Risperdal CONSTA^® were compared in rabbits. Formulation containing 50% (w/w %) of PLGA-PEG-PLGA triblock revealed sustained release for about one month. Scanning electron microscopy (SEM) showed a porous structure for ISFI, while a structure with fewer pores was observed in the triblock. Cell viability in ISFG formulation in the first days was more than ISFI due to the gradual release of NMP to the release medium. Pharmacokinetic data displayed that optimal PLGA-PEG-PLGA creates a consistent serum level in vitro and in vivo through 30 days, and histopathology results revealed nearly slight to moderate pathological signs in the rabbit's organs. The shelf life of the accelerated stability test didn't affect the results of the release rate test and demonstrated stability in 24 months. This research confirms the better potential of the ISFG system compared with ISFI and Risperdal CONSTA^®, which would increase patients' compliance and avoid problems of further oral therapy.

Investigation on Characterization of Novel Anti-bacterial Chitosan/Gelatin Composite Membranes Loaded with Quercetin via Electrophoretic Deposition

Peri-implantitis is characterized by inflammation resulting from bacterial infections in peri-implant connective tissue. The purpose of this study was to prepare and characterize chitosan/gelatin (CSG)-based membranes with antibacterial agents to functionalize the surface of titanium (Ti) implants. CSG membranes were prepared on Ti substrates via electrophoretic deposition (EPD). Quercetin, an active flavonoid responsible for fulfilling various plant functions, was introduced as an antibacterial agent to be loaded into the membrane during preparation. The fabrication of quercetin-loaded CSG membranes via EPD was also investigated. Fluorescent microscope, Attenuated Total Reflection Fourier transform infrared spectroscopy, and X-ray diffraction results verified the entrapment of quercetin. The membranes swelled by 150% of mass after rehydration. The antibacterial effects of quercetin on Gram-positive bacteria, such as Staphylococcus aureus and methicillin-resistant Staphylococcus aureus, were verified by spread-plate, scanning electron microscopy, and live/dead staining. Cytological experiments showed that the biocompatibility of rat bone marrow mesenchymal stromal cells was promoted by quercetin-loaded membranes, exclusively in the group with the highest content of quercetin. The quercetin-loaded groups also enhanced the antineoplastic activity of MG-63 cells. These results suggested that quercetin-loaded CSG membranes were successfully fabricated via EPD. Thus, biocompatible and antibacterial membranes could be a potential strategy to functionalize Ti implants.

Self-assembled zein organogels as in situ forming implant drug delivery system and 3D printing ink

Recently, biomedical applications of organogels have been increasing; however, there is a demand for bio-based polymers. Here, we report self-assembled zein organogels in N-methyl pyrrolidone (NMP), Dimethyl sulfoxide (DMSO), and glycerol formal (GF). The gel formation was driven by the solvent's polarity and the hydrogen bonding component of Hansen Solubility Parameters was important in promoting gelation. Gels exhibited shear-thinning and thixotropic properties. Furthermore, water-induced self-assembly of zein allows mechanically robust in situ implant formation by solvent exchange. Ciprofloxacin was incorporated as a model drug and sustained release depending upon the solvent exchange rate was observed. In situ implants in agarose gel retained antibacterial efficacy against S. aureus for more than 14 days. Zein-based organogels were further applied as 3D printing ink and it was found that zein gel in DMSO had superior printability than gels prepared in NMP and GF. Using three solvents to prepare organogels can enable the encapsulation of various drugs and facilitate the preparation of composite gels with other biocompatible polymers. These organogel systems can further be used for developing 3D printed drug delivery systems or scaffolds for tissue engineering.

Imatinib Mesylate-Loaded Rosin/Cinnamon Oil-Based In Situ Forming Gel against Colorectal Cancer Cells

Localized delivery systems have been typically designed to enhance drug concentration at a target site and minimize systemic drug toxicity. A rosin/cinnamon oil (CO) in situ forming gel (ISG) was developed for the sustainable delivery of imatinib mesylate (IM) against colorectal cancer cells. CO has been claimed to express a potent anticancer effect against various cancer cells, as well as a synergistic effect with IM on colorectal cancer cells; however, poor aqueous solubility limits its application. The effect of rosin with the adding CO was assessed on physicochemical properties and in vitro drug release from developed IM-loaded rosin/CO-based ISG. Moreover, in vitro cytotoxicity tests were conducted against two colorectal cancer cells. All formulations exhibited Newtonian flow behavior with viscosity less than 266.9 cP with easier injectability. The adding of CO decreased the hardness and increased the adhesive force of the obtained rosin gel. The gel formation increased over time under microscopic observation. CO-added ISG had a particle-like gel appearance, and it promoted a higher release of IM over a period of 28 days. All tested ISG formulations revealed cytotoxicity against HCT-116 and HT-29 cell lines at different incubation times. Thus, CO-loaded rosin-based ISG can act as a potentially sustainable IM delivery system for chemotherapy against colorectal cancer cells.

A long-acting formulation of rifabutin is effective for prevention and treatment of Mycobacterium tuberculosis

Tuberculosis (TB) is a communicable disease caused by Mycobacterium tuberculosis (Mtb) and is a major cause of morbidity and mortality. Successful treatment requires strict adherence to drug regimens for prolonged periods of time. Long-acting (LA) delivery systems have the potential to improve adherence. Here, we show the development of LA injectable drug formulations of the anti-TB drug rifabutin made of biodegradable polymers and biocompatible solvents that solidifies after subcutaneous injection. Addition of amphiphilic compounds increases drug solubility, allowing to significantly increase formulation drug load. Solidified implants have organized microstructures that change with formulation composition. Higher drug load results in smaller pore size that alters implant erosion and allows sustained drug release. The translational relevance of these observations in BALB/c mice is demonstrated by (1) delivering high plasma drug concentrations for 16 weeks, (2) preventing acquisition of Mtb infection, and (3) clearing acute Mtb infection from the lung and other tissues.

Design and Comparative Evaluation of Vancomycin HCl-Loaded Rosin-Based In Situ Forming Gel and Microparticles

Vancomycin hydrochloride (HCl) is a glycopeptide antibiotic used to treat serious or life-threatening infections, and it reduces plaque scores and gingivitis in periodontal patients. In this study, vancomycin HCl was incorporated into rosin in situ forming gel (ISG) and rosin in situ forming microparticles (ISM) to generate a local drug delivery system to treat periodontal disease. The physical properties of the ISG and ISM were measured, including pH, viscosity, injectability, adhesion properties, in-vitro transformation, and drug release. Moreover, the effectiveness of antimicrobial activity was tested using the agar-cup diffusion method against Staphylococcus aureus, Streptococcus mutans, Porphyromonas gingivalis, and Escherichia coli. Vancomycin HCl-loaded rosin-based ISG and ISM had a pH value in the range of 5.02−6.48 and exhibited the ease of injection with an injection force of less than 20 N. Additionally, the lubricity effect of the external oil phase of ISM promoted less work of injection than ISG and 40−60% rosin-based ISM showed good emulsion stability. The droplet size of emulsions containing 40%, 50%, and 60% rosin was 98.48 ± 16.11, 125.55 ± 4.75, and 137.80 ± 16.8 µm, respectively. Their obtained microparticles were significantly smaller in diameter, 78.63 ± 12.97, 93.81 ± 10.53, and 118.32 ± 15.61 µm, respectively, because the particles shrank due to the solvent loss from solvent exchange. Moreover, increasing the concentration of rosin increased the size of microparticles. After phase transformation, all formulations had better plasticity properties than elasticity; therefore, they could easily adapt to the specific shape of a patient’s gum cavity. Both developed ISG and ISM presented inhibition zones against S. mutans and P. gingivalis, with ISG presenting significantly more effectively against these two microbes (p < 0.05). The vancomycin HCl-loaded rosin ISG and ISM delayed drug release for 7 days with efficient antimicrobial activities; thus, they exhibit potential as the drug delivery systems for periodontitis treatment.

Challenges and opportunities in the development of complex generic long-acting injectable drug products

Long-acting injectable (LAI) drug products enable the controlled release of a drug over an extended duration of time to improve the therapeutic effect, safety profile, or administration of an injectable product. The development of generic [505(j)] and differentiated [505(b)(2)] LAI products helps to provide patients and healthcare providers with more treatment options and to reduce overall healthcare costs, including those associated with drug product administration and patient compliance. In this review, we analyze the landscape of LAI products and identify the most common technical challenges that potential generic product entrants face. We focus on five formulation technologies that account for ~90% of approved LAI products, including those eligible for generic product registration over the next five years, to illustrate technology-specific challenges. We then review efforts from the U.S. Food and Drug Administration (FDA) to promote more generic product competition and emphasize the importance of collaboration among government, industry, and academia to advance the knowledge and capabilities of the scientific community. Regulatory bodies, industry, and academia are encouraged to anticipate challenges with emerging innovative LAI technologies and to leverage the experiences built on established technologies to foster generic product development.

In Vitro Evaluation of Poly(lactide-co-glycolide) In Situ Forming Gels for Bedaquiline Fumarate Salt and Pharmacokinetics Following Subcutaneous Injection in Rats

This study evaluated in vitro and in vivo drug release of bedaquiline from in situ forming gels (ISGs) containing 200 mg eq./g bedaquiline fumarate salt prepared with four different grades of poly(d,l-lactide) (PDLLA) or poly(d,l-lactide-co-glycolide) (PLGA) with a lactide/glycolide ratio of 50/50 or 75/25 and acid (A) or ester (E) end-capping in N-methyl-2-pyrrolidone at a polymer/solvent ratio of 20/80% (w/w). Mean in vitro drug release in 0.05 M phosphate buffer pH 7.4 with 1% (w/v) sodium lauryl sulphate was 37.3, 47.1, 53.3, and 62.3% within 28 days for ISGs containing PLGA5050A, PDLLA, PLGA7525A, and PLGA7525E, respectively. The data suggested that drug release was primarily controlled by precipitated drug redissolving, rather than polymer erosion. In vivo pharmacokinetic profiles after subcutaneous injections in rats were comparable for all ISGs (mean half-lives (t_1/2) ranged from 1411 to 1695 h) and indicated a sustained drug release when compared to a solution of bedaquiline fumarate salt in polyethylene glycol 400/water 50/50% (v/v) (mean t_1/2 of 895 h). In conclusion, PLGA or PDLLA-based ISGs have shown potential for parenteral sustained delivery of bedaquiline, suggesting further preclinical and clinical studies. From a formulation point of view, this case example highlights the importance of the interplay between drug solubility in biological media and dissolution of drug precipitates, which, in addition to the incorporation of diffusion controlling polymers, governs the release of the active drug.

An overview of PLGA in-situ forming implants based on solvent exchange technique: effect of formulation components and characterization

As a result of the low oral bioavailability of several drugs, there is a renewed interest for parenteral administration to target their absorption directly into the blood bypassing the long gastrointestinal route and hepatic metabolism. In order to address the potential side effects of frequent injections, sustained release systems are the most popular approaches for achieving controlled long-acting drug delivery. Injectable in-situ forming implants (ISFIs) have gained greater popularity in comparison to other sustained systems. Their significant positive aspects are attributed to easier production, acceptable administration route, reduced dosing frequency and patient compliance achievement. ISFI systems, comprising biodegradable polymers such as poly (lactide-co-glycolide) (PLGA) based on solvent exchange mechanisms, are emerged as liquid formulations that develop solid or semisolid depots after injection and deliver drugs over extended periods. The drug release from ISFI systems is generally characterized by an initial burst during the matrix solidification, followed by diffusion processes and finally polymeric degradation and erosion. The choice of suitable solvent with satisfactory viscosity, miscibility and biocompatibility along with considerable PLGA hydrophobicity and molecular weights is fundamental for optimizing the drug release. This overview gives a particular emphasis on evaluations and the wide ranges of requirements needed to achieve reasonable physicochemical characteristics of ISFIs.

Saturated Fatty Acid-Based In Situ Forming Matrices for Localized Antimicrobial Delivery

In recent years, the world has faced the issue of antibiotic resistance. Methicillin-resistant Staphylococcus aureus (MRSA) is a significant problem in various treatments and control of infections. Biocompatible materials with saturated fatty acids of different chain lengths (C₈-C₁₈) were studied as matrix formers of localized injectable vancomycin HCl (VCM)-loaded antisolvent-induced in situ forming matrices. The series of fatty acid-based in situ forming matrices showed a low viscosity (5.47-13.97 cPs) and pH value in the range of 5.16-6.78, with high injectability through a 27-G needle (1.55-3.12 N). The preparations exhibited low tolerance to high concentrations of KH₂PO₄ solution (1.88-5.42% v/v) and depicted an electrical potential change during phase transformation. Their phase transition and matrix formation at the microscopic and macroscopic levels depended on the chain length of fatty acids and solvent characteristics. The VCM release pattern depended on the nucleation/crystallization and solvent exchange behaviors of the delivery system. The 35% w/v of C₁₂-C₁₆ fatty acid-based in situ forming matrix prolonged the VCM release over seven days in which C₁₂, C₁₄, C₁₆ -based formulation reached 56, 84, and 85% cumulative drug release at 7^th day. The release data fitted well with Higuchi's model. The developed formulations presented efficient antimicrobial activities against standard S. aureus, MRSA, Escherichia coli, and Candida albicans. Hence, VCM-loaded antisolvent-induced fatty acid-based in situ forming matrix is a potential local delivery system for the treatment of local Gram-positive infection sites, such as joints, eyes, dermis of surgery sites, etc., in the future.

Meloxicam-loaded solvent exchange-induced in situ forming beta-cyclodextrin gel and microparticle for periodontal pocket delivery

The in situ forming system has attracted attention for periodontitis treatment owing to its sustainable drug release localisation at a periodontal pocket. Given its low aqueous solubility, beta-cyclodextrin (β-CD) may serve as a matrix former of solvent exchange-induced in situ forming gel (ISG) and microparticle (ISM). Meloxicam (Mex)-loaded-β-CD ISG and ISM were prepared using β-CD in dimethyl sulphoxide (ISG) as the internal phase and camellia oil comprising 5% glyceryl monostearate as the external phase (ISM). Mex-loaded β-CD systems comprising 40% β-CD were easily injected via a 24-gauge needle. During solvent exchange with phosphate buffer saline (pH 6.8), the highly concentrated β-CD ISG promoted the phase inversion of β-CD aggregates into matrix-like. Upon exposure to aqueous phase, the ISM system comprising 40% β-CD transformed into microparticles and extended the drug release to 7 days with minimised initial burst release following Fickian diffusion. Moreover, the potential degradability was evident from the high weight loss. High maximum deformation force with high viscous character initiated the slow diffusion rate of the solvent from the ISM system. Therefore, 40% β-CD ISM is a potential local Mex-controlled release system of anti-inflammatory drug for periodontitis treatment.

Vancomycin hydrochloride-loaded stearic acid/lauric acid in situ forming matrix for antimicrobial inhibition in patients with joint infection after total knee arthroplasty

Knee joint infection following total knee arthroplasty (TKA) is a serious condition and the treatments are complicated. The intra-articular solvent exchange-induced in situ forming matrix is of interest for modulating the release of antibiotics with a high drug concentration and a long period of exposed time at the target site. Stearic acid (S) and lauric acid (L) at various ratios were used as matrix formers by dissolving them in biocompatible solvents such as N-methyl pyrrolidone (NMP) and dimethyl sulfoxide (DMSO). Their matrix formation behaviors in phosphate buffer (pH7.4) and hyaluronic acid (HA) solution were evaluated. Also, the density, viscosity, injectability, solvent diffusion, in vitro degradability and drug release using the dialysis tube method were investigated. The L:S ratio of 1:1 in DMSO exhibited rapid matrix formation and a remarkably low viscosity (7.67±0.03 cp) with acceptable injectability (0.608±0.027N and 0.867±0.010N through 18-G and 27-G, respectively). Vancomycin HCl (V)-loaded L/S in situ forming matrix still provided ease of injection (1.079±0.215N and 1.230±0.145N through 18-G and 27-G needle, respectively) with fatty acid matrix formation after solvent exchange within 1min, whilst V sustainably released over 6days. It also presented effective antimicrobial activities against standard Staphylococcus aureus and methicillin-resistant Staphylococcus aureus strains. Therefore, V-loaded solvent exchange-induced in situ forming matrix using L and S as the matrix formers may be a potential local delivery system for treating knee joint infections occurring after TKA in the future.

Long-Acting Paliperidone Parenteral Formulations Based on Polycaprolactone Nanoparticles; the Influence of Stabilizer and Chitosan on In Vitro Release, Protein Adsorption, and Cytotoxicity

Long-acting preparations containing the antipsychotic paliperidone for intramuscular injection has drawn considerable attention to achieve harmless long-term treatment. This study aimed to develop paliperidone loaded polycaprolactone (PCL) nanoparticles and investigate the influence of PCL/drug ratio, stabilizer type, and chitosan coating on physicochemical properties, protein adsorption, and cellular toxicity. Results showed that chitosan coating produced enlarged particle sizes, shifted the surface charges from negative into positive and did not influence encapsulation efficiencies. Chitosan coating relatively sustained the drug release especially in pluronic stabilized formulations. Pluronic F127 based formulations exhibited the least protein adsorption (384.3 μg/mL). Chitosan coating of Tween 80 and polyvinyl alcohol stabilized formulations significantly (p < 0.05) increased protein adsorption. Cellular viability was concentration-dependent and negatively affected by stabilizers. All formulations did not show cellular death at 1.56 μg/mL. Inflammatory responses and oxidative stress were less affected by Tween 80 compared with other stabilizers. Chitosan minimized all aspects of cellular toxicity. Collectively, stabilizer type and chitosan coating play critical roles in developing safe and effective long-acting PCL nanoparticles intended for parenteral drug delivery. The coated formulations containing Tween 80 and Pluronic F127 as stabilizers are warranted a future in vivo study to delineate its safety and efficacy profiles.

In-situ forming implants for the treatment of periodontal diseases: Simultaneous controlled release of an antiseptic and an anti-inflammatory drug

Different types of in-situ forming implants based on poly(lactic-co-glycolic acid) (PLGA) for the controlled dual release of an antiseptic drug (chlorhexidine) and an anti-inflammatory drug (ibuprofen) were prepared and thoroughly characterized in vitro. N-methyl-pyrrolidone (NMP) was used as water-miscible solvent, acetyltributyl citrate (ATBC) as plasticizer and hydroxypropyl methylcellulose (HPMC) was added to enhance the implants' stickiness/bioadhesion upon formation within the periodontal pocket. Different drug forms exhibiting substantially different solubilities were used: chlorhexidine dihydrochloride and digluconate as well as ibuprofen free acid and lysinate. The initial drug loadings were varied from 1.5 to 16.1%. In vitro drug release, dynamic changes in the pH of the surrounding bulk fluid and in the systems' wet mass as well as polymer degradation were monitored. Importantly, the release of both drugs, chlorhexidine and ibuprofen, could effectively be controlled simultaneously during several weeks. Interestingly, the tremendous differences in the drug forms' solubilities (e.g., factor >5000) did not translate into major differences in the resulting release kinetics. In the case of ibuprofen, this can likely (at least in part) be attributed to significant drug-polymer interactions (ibuprofen acts as a plasticizer for PLGA). In the case of chlorhexidine, the release of the much less soluble dihydrochloride was even faster compared to the more soluble digluconate (when combined with ibuprofen free acid). In the case of ibuprofen, at higher initial drug loadings also limited solubility effects within the implants seem to play a role, in contrast to chlorhexidine. In the latter case, instead, increased system porosity effects likely dominate at higher drug loadings.

Long lasting in-situ forming implant loaded with raloxifene HCl: An injectable delivery system for treatment of bone injuries

Bone injury is very serious in elder people or osteoporotic patients. In-situ forming implants (IFI) for bone rebuilding are usually poly-lactic-co-glycolic acid (PLGA)-based, which have a burst release effect. This study aimed to prepare novel liquid lipid-based PLGA-IFI loaded with raloxifene hydrochloride for prolonged non-surgical treatment of bone injuries by applying solvent-induced phase inversion technique. Labrasol® and Maisine® were added to the selected IFI forming long lasting lipid-based IFI (LLL-IFI). The formulations were characterized by analysing their in-vitro drug release, solidification time, injectability, rheological properties, and DSC in addition to their morphological properties. Results revealed that the LLL-IFI composed of 10%w/v PLGA with a lactide to glycolide ratio of 75:25 with ester terminal and 10% Maisine® possessed the most sustained drug release and lowest burst effect, as well as delayed pore formation compared to its counterpart lacking Maisine®. The selected LLL-IFI and PLGA-IFI formulations were tested for their capability to enhance bone regeneration in bone injuries induced in rats. Both formulations succeeded in healing the bones completely with the superiority of LLL-IFI in the formation of well-organized bone structures lacking fibrous tissues. The results suggest that LLL-IFI and PLGA-IFI are innovative approaches for treating critical and non-critical sized bone injuries.

Preparation and evaluation of injectable Rasagiline mesylate dual-controlled drug delivery system for the treatment of Parkinson's disease

A microsphere-gel in situ forming implant (MS-Gel ISFI) dual-controlled drug delivery system was applied to a high water-soluble small-molecule compound Rasagiline mesylate (RM) for effective treatment of Parkinson's disease. This injectable complex depot system combined an in situ phase transition gel with high drug-loading and encapsulation efficiency RM-MS prepared by a modified emulsion-phase separation method and optimized by Box-Behnken design. It was evaluated for in vitro drug release, in vivo pharmacokinetics, and in vivo pharmacodynamics. We found that the RM-MS-Gel ISFI system showed no initial burst release and had a long period of in vitro drug release (60 days). An in vivo pharmacokinetic study indicated a significant reduction (p < .01) in the initial high plasma drug concentration of the RM-MS-Gel ISFI system compared to that of the single RM-MS and RM-in situ gel systems after intramuscular injection to rats. A pharmacodynamic study demonstrated a significant reduction (p < .05) in 6-hydroxydopamine-induced contralateral rotation behavior and an effective improvement (p < .05) in dopamine levels in the striatum of the lesioned side after 28 days in animals treated with the RM-MS-Gel ISFI compared with that of animals treated with saline. MS-embedded in situ phase transition gel is superior for use as a biodegradable and injectable sustained drug delivery system with a low initial burst and long period of drug release for highly hydrophilic small molecule drugs.

Implantable systems for drug delivery to the brain

Most diseases and disorders of the brain require long-term therapy and a constant supply of drugs. Implantable drug-delivery systems provide long-term, sustained drug delivery in the brain. The present review discusses different type of implantable systems such as solid implants, in situ forming implants, in situ forming microparticles, depot formulations, polymeric-lipid implants, sucrose acetate isobutyrate and N-stearoyl L-alanine methyl ester systems for continuous drug delivery into brain for various brain diseases including glioblastomas, medulloblastoma, epilepsy, stroke, schizophrenia and Alzheimer's diseases. Implantable neural probes and microelectrode array systems for brain are also discussed in brief.

Pharmacokinetics and Safety of Risperidone Subcutaneous Implants in Stable Patients With Schizophrenia

A subcutaneous risperidone implant (RI) formulation was developed to improve medication adherence in schizophrenia. Two phase 1 studies were conducted to evaluate the pharmacokinetics of RI in adult patients with schizophrenia. In study 1, all subjects were stable on 4 mg oral risperidone; subsequently, the first subject received 375 mg RI for 1 month, and the remaining subjects received 375 mg RI for 3 months. In study 2, all subjects were stable on oral risperidone 4 mg, 6 mg, or 8 mg and subsequently received RI 480 mg, 720 mg, or 960 mg, respectively, for 6 months. Blood samples were collected at prespecified time points. Various pharmacokinetic parameters were determined in both studies. In both studies risperidone total active moiety plasma concentrations following RI increased slowly, reached therapeutic levels within approximately 2 days, and remained relatively stable. In study 1, the average concentration for RI was 81.3% of the oral trough concentration and 27.5% of the oral peak concentration. In study 2, the steady-state concentration for RI was comparable to the oral trough concentration of the corresponding dose. Patient disease status remained stable with no major safety issues. RI may represent an alternative formulation for schizophrenia treatment with a lower peak-to-trough plasma drug ratio than oral risperidone.

Density functional theory study of structural and electronic properties of trans and cis structures of thiothixene as a nano-drug

The geometrical structure, electronic and optical properties, electronic absorption spectra, vibrational frequencies, natural charge distribution, MEP analysis and thermodynamic properties of the trans and cis structures of the drug thiothixene were investigated using density functional theory (DFT) and time-dependent DFT (TDDFT) methods with the B3LYP hybrid functional and 6-311 + G(d,p) basis set. The results of the calculations demonstrate that the cis structure of thiothixene has appropriate quantum properties that can act as an active medicine. The relative energies of trans and cis structures of thiothixene shows that the cis structure is more stable than the trans structure, with a small energy difference. TDDFT calculations show that the cis structure of thiothixene has the best absorption properties. The calculated NLO properties show that the NLO properties of the cis structure of thiothixene are higher than the trans structure, and the fact that the chemical hardness of the cis structure is lower than that of the trans structure that indicates that the reactivity and charge transfer of the cis isomer of thiothixene is higher than that of trans thiothixene. The molecular electrostatic potential (MEP) maps of both structures of thiothixene demonstrate that the oxygen atoms of the molecule are appropriate areas for electrophilic reactions. The vibrational frequencies of the two conformations of thiothixene demonstrate that both structures of thiothixene have almost similar modes of vibrations. The calculated thermodynamic parameters show that these quantities increase with enhancing temperature due to the enhancement of molecular vibrational intensities with temperature. Graphical abstract Trans/Cis isomerization of thiothixene drug.

Role of clove oil in solvent exchange-induced doxycycline hyclate-loaded Eudragit RS in situ forming gel

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Role of clove oil (CO) in doxycycline hyclate (DH)-loaded Eudragit RS (ERS) in situ forming gel (ISG) was investigated.

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CO could solubilize ERS and increase the viscosity of ISG and also minimize DH burst release with sustainable DH release.

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ISGs comprising CO could expel through the 27-gauge needle and transform into matrix depot in simulated crevicular fluid.

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Antimicrobial activities against all test bacterias were increased when increasing CO and N-methyl pyrrolidone (NMP) ratio.

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DH-loaded ERS ISG comprising CO could be used as a local drug delivery system for periodontitis treatment.

Solvent exchange induced in situ forming gel (ISG) is the promising drug delivery system for periodontitis treatment owing to the prospect of maintaining an effective high drug level in the gingival crevicular fluid. In the present study, the influence of clove oil (CO) on the characteristics of doxycycline hyclate (DH)-loaded ISG comprising Eudragit RS (ERS) was investigated including viscosity/rheology, syringeability, in vitro gel formation/drug release, matrix formation/solvent diffusion and antimicrobial activities. CO could dissolve ERS and increase the viscosity of ISG and its hydrophobicity could also retard the diffusion of solvent and hinder the drug diffusion; thus, the minimization of burst effect and sustained drug release were achieved effectively. All the prepared ISGs comprising CO could expel through the 27-gauge needle for administration by injection and transform into matrix depot after exposure to the simulated gingival crevicular fluid. The antimicrobial activities against Staphylococcus aureus, Escherichia coli, Streptococcus mutans and Porphyromonas gingivalis were increased when the ratio of CO and N-methyl pyrrolidone (NMP) was decreased from 1:1 to 1:10 owing to higher diffusion of DH except that for C. albicans was increased as CO amount was higher. Therefore, CO could minimize the burst while prolonging the drug release of DH-loaded ERS ISG for use as a local drug delivery system for periodontitis treatment.

Characterization of Antimicrobial Agent Loaded Eudragit RS Solvent Exchange-Induced In Situ Forming Gels for Periodontitis Treatment

Eudragit RS (ERS), a quaternary polyacrylate positively charged polymer, exhibits a very low permeability and swells in aqueous media independently of pH without dissolving. Owing to its high solubility in N-methyl pyrrolidone (NMP), it was interesting to apply as polymer matrix for solvent-exchanged in situ forming gel. The aim of this research was to prepare in situ forming gels from ERS to deliver the antimicrobial agents (doxycycline hyclate, metronidazole, and benzoyl peroxide) for periodontitis treatment. They were evaluated for viscosity and rheology, gel formation, syringeability, drug release, and antimicrobial activities. The solvent exchange between NMP and an external aqueous simulated gingival crevicular fluid stimulated the dissolved ERS transforming into the opaque rigid gel. Antimicrobial agent loaded ERS systems exhibited Newtonian flow with acceptable syringeability. The higher-loaded ERS promoted the more prolongation of drug release because of the retardation of water diffusion into the precipitated matrix. Antimicrobial activities against Staphylococcus aureus, Escherichia coli, Candida albicans, Streptococcus mutans, and Porphyromonas gingivalis depended on type of drugs and test microorganisms. Doxycycline hyclate loaded ERS systems showed these activities greater than the others; however, all of them could inhibit all test microorganisms. Thus, the solvent exchange-induced in situ forming gels comprising ERS-antimicrobial drugs exhibited potential use as localized delivery systems for periodontitis treatment.

Hydrophobic mixed solvent induced PLGA-based in situ forming systems for smooth long-lasting delivery of Radix Ophiopogonis polysaccharide in rats

To obtain a sustained in vivo release of Radix Ophiopogonis polysaccharide, hydrophobic solvent-induced in situ forming systems were investigated, including the factors affecting drug release and anti-myocardial ischemic activity of a formulation.

Porous microspheres as promising vehicles for the topical delivery of poorly soluble asiaticoside accelerate wound healing and inhibit scar formation in vitro &in vivo

Asiaticoside is a natural compound possessing diverse pharmacological effects with great potential for clinical use. However, the low solubility and oil-water partition coefficient of asiaticoside lead to reduced effect and limited application. This study aims to construct a porous microsphere for the sustained release of asiaticoside to improve its absorption and enhance the therapeutic effects. Parameters of the formulations, including the drug to polymer ratio, solvent amounts of the inner and external phases, the stirring speed for preparation, and the drug entrapment efficiency were investigated and optimized. Particle size, morphology, pores structure, and Fourier transform infrared spectrum of the microsphere were characterized. The release kinetics and cellular uptake profiles of the asiaticoside-microspheres were examined. The therapeutic effects of asiaticoside-microspheres on wound healing and skin appendages regeneration were investigated in vitro & in vivo. Results showed that the optimized asiaticoside-microspheres possess spherical spongy structure with cylindrical holes. Asiaticoside can be loaded in the microsphere with high efficiency and released with sustained manner. The cellular uptake of asiaticoside from the microspheres was increased with 9.1 folds higher than that of free solution. Asiaticoside-microspheres expressed the strong promotion in the proliferation, migration of keratinocytes and wound scratching healing in vitro. More importantly, they significantly accelerated the re-epithelization, collagen synthesis and pro-angiogenesis in the rat full-skin wound healing. Porous microsphere was shown a novel carrier for the sustained delivery of poorly soluble asiaticoside, with absorption and therapeutic effects improved. Asiaticoside-microsphere is a promising topical preparation with excellent regenerative effects for the wound therapy.

Mechanistic analysis of Zein nanoparticles/PLGA triblock in situ forming implants for glimepiride

Objectives

The study aims at applying pharmaceutical nanotechnology and D-optimal fractional factorial design to screen and optimize the high-risk variables affecting the performance of a complex drug delivery system consisting of glimepiride–Zein nanoparticles and inclusion of the optimized formula with thermoresponsive triblock copolymers in in situ gel.

Methods

Sixteen nanoparticle formulations were prepared by liquid–liquid phase separation method according to the D-optimal fractional factorial design encompassing five variables at two levels. The responses investigated were glimepiride entrapment capacity (EC), particle size and size distribution, zeta potential, and in vitro drug release from the prepared nanoparticles. Furthermore, the feasibility of embedding the optimized Zein-based glimepiride nanoparticles within thermoresponsive triblock copolymers poly(lactide-co-glycolide)-block-poly(ethylene glycol)-block-poly(lactide-co-glycolide) in in situ gel was evaluated for controlling glimepiride release rate.

Results

Through the systematic optimization phase, improvement of glimepiride EC of 33.6%, nanoparticle size of 120.9 nm with a skewness value of 0.2, zeta potential of 11.1 mV, and sustained release features of 3.3% and 17.3% drug released after 2 and 24 hours, respectively, were obtained. These desirability functions were obtained at Zein and glimepiride loadings of 50 and 75 mg, respectively, utilizing didodecyldimethylammonium bromide as a stabilizer at 0.1% and 90% ethanol as a common solvent. Moreover, incorporating this optimized formulation in triblock copolymers-based in situ gel demonstrated pseudoplastic behavior with reduction of drug release rate as the concentration of polymer increased.

Conclusion

This approach to control the release of glimepiride using Zein nanoparticles/triblock copolymers-based in situ gel forming intramuscular implants could be useful for improving diabetes treatment effectiveness.

Solvent exchange-induced in situ forming gel comprising ethyl cellulose-antimicrobial drugs

Solvent-exchanged in situ forming gel is a drug delivery system which is in sol form before administration. When it contacts with the body fluid, then the water miscible organic solvent dissipates and water penetrates into the system, leading the polymer precipitation as in situ gel at the site of injection. The aim of this research was to study the parameters affecting the gel properties, drug release and antimicrobial activities of the in situ forming gels prepared from ethyl cellulose (EC) dissolved in N-methyl pyrrolidone (NMP) to deliver the antimicrobial agents (doxycycline hyclate, metronidazole and benzyl peroxide) for periodontitis treatment. The gel appearance, pH, viscosity, rheology, syringeability, gel formation, rate of water diffusion into the gels, in vitro degradation, drug release behavior and antimicrobial activities against Staphylococcus aureus, Escherichia coli, Candida albicans, Streptococcus mutans and Porphyrommonas gingivalis were determined. Increasing the amount of EC increased the viscosity of system while still exhibiting Newtonian flow and increased the work of syringeability whereas decreased the releasing of drug. The system transformed into the rigid gel formation after being injected into the simulated gingival crevicular fluid. The developed systems containing 5% w/w antimicrobial agent showed the antimicrobial activities against all test bacteria. Thus the developed solvent exchange-induced in situ forming gels comprising EC-antimicrobial drugs exhibited potential use for periodontitis treatment.

Metrodidazole In Situ Forming Eudragit RS Gel Comprising Different Solvents

In situforming gel with solvent exchange mechanism is one of drug delivery systems for periodontitis treatment. The system is injected into the desired site then transforms into a gel state when the solvent diffuses out and aqueous diffuses in. Thein situforming Eudragit RSgels loading 1, 5 and 10%w/w metronidazole (MT) were developed in this study usingN-methyl pyrrolidone (NMP), 2-pyrrolidone and dimethyl sulfoxide (DMSO) as solvent. The viscosity of the gel systems in all solvents were increased as drug or polymer amount was increased with Newtonian flow behavior. Transformation into gel was evident after initiated the systems in phosphate buffer pH 6.8. NMP systems exhibited the lowest work of syringeability through 18 G syringe. Drug release from dialysis tube of DMSO systems was slower than that of NMP and 2-pyrrolidone systems, respectively. Antimicrobial activity againstStaphylococcus aureusof the systems comprising MT using NMP as solvent was greater than that using 2-pyrrolidone and DMSO, respectively, which the antimicrobial activity was increased as the drug amount was increased. Therefore, the solvent type affected the viscosity, gel formation, syringeability, drug release and antimicrobial activity of Eudragit RS systems. These developed systems sustained the drug release and inhibited the bacterial growth hence they were interesting systems for periodontitis treatment.

The anti-melanoma efficiency of the intratumoral injection of cucurbitacin-loaded sustained release carriers: in situ-forming implants

Our previous studies revealed that the PLGA-based particulate systems loaded with cucurbitacin showed limited anti-melanoma efficiency in xenograft animal models after intratumoral injection, which was due to the undesirable initial burst release and the leakage of the particulate carriers from the injection site through the pinhole. In this paper, two categories of in situ-forming implants (ISFIs) for intratumoral injection, PLGA ISFIs and SAIB ISFIs, were systemically evaluated for their potentials for on solid tumor treatment via intratumoral injection. The in vitro drug release profiles of these two ISFIs were different due to the different sol-gel transition properties. The pharmacodynamics results revealed that SAIB ISFIs displayed obvious therapeutic efficiencies to melanoma, and multi-points injection of SASIB ISFIs displayed better efficiency than single-point injection. The different sol-gel transition properties and mechanism for PLGA ISFIs and SAIB ISFIs affected both the drug release and strongly impacted the pharmacokinetic parameters and pharmacodynamic effectiveness. Also, the adhesive property of SAIB to the local tissue could extend the retention and inhibit the leakage of the SAIB ISFIs, thus enhanced the anticancer effectiveness. Comparison of the various intratumoral injection systems, appropriate drug release profiles (lower initial burst and steady release) and good retention (minimum leakage from the injection site) would benefit to the antitumor effects of the intratumoral depots.

Injectable long-acting systems for Radix Ophiopogonis polysaccharide based on mono-PEGylation and in situ formation of a PLGA depot

Background

Radix Ophiopogonis polysaccharide (ROP), a highly hydrophilic macromolecule, has a unique anti-ischemic action in the myocardium. One of the main problems with its use is its relatively short half-life in vivo. To solve this problem, injectable long-acting drug delivery systems, which combine mono-PEGylation (PEG, polyethylene glycol) with the in situ formation of poly(_d,l-lactide-co-glycolide) copolymer (PLGA) depots, were tested in this study.

Methods

Through a moderate coupling reaction between 20 kDa amino-terminated methoxy-PEG and excessive ROP with activated hydroxyls, a long-circulating and bioactive mono-PEGylated ROP was prepared and characterized. A reasonable and applicable range of PLGA formulations loaded with the mono-PEGylated ROP were prepared, characterized, and evaluated in vivo.

Results

Relative to ROP, the half-life of which was only 0.5 hours, the conjugate alone, following subcutaneous administration, showed markedly prolonged retention in the systemic circulation, with a mean residence time in vivo of approximately 2.76 days. In combination with in situ-forming PLGA depots, the residence time of the conjugate in vivo was prolonged further. In particular, a long-lasting and steady plasma exposure for nearly a month was achieved by the formulation comprising 40% 30 kDa PLGA in N-methyl-2-pyrrolidone.

Conclusion

Long-lasting and steady drug exposure could be achieved using mono-PEGylation in combination with in situ formation of PLGA depots. Such a combination with ROP would be promising for long-term prophylaxis and/or treatment of myocardial ischemia. For high-dose and highly hydrophilic macromolecular drugs like ROP, more than one preparation technology might be needed to achieve week-long or month-long delivery per dosing.

The role of long-acting injectable antipsychotics in schizophrenia: a critical appraisal

Despite their widespread use, long-acting injectable (LAI) antipsychotics (APs) are often regarded with some negativity because of the assumption of punishment, control and insufficient evolution towards psychosocial development of patients. However, LAI APs have proved effective in schizophrenia and other severe psychotic disorders because they assure stable blood levels, leading to a reduction of the risk of relapse. Therapeutic opportunities have also arisen after introduction of newer, second-generation LAI APs in recent years. Newer LAI APs are more readily dosed optimally, may be better tolerated and are better suited to integrated rehabilitation programmes. This review outlines the older and newer LAI APs available for the treatment of schizophrenia, with considerations of past and present pharmacological and therapeutic issues. Traditional, evidence-based approaches to systematic reviews and randomized clinical trials are of limited utility in this area so this paper's blending of experimental trials with observational research is particularly appropriate and effective.

Injectable long-acting in situ forming systems for Radix Ophiopogonis polysaccharide

In the area of injectable long-acting formulations, the in situ forming system (ISFS) is an attractive alternative for its various superiorities. In this study, both hydrophilic and hydrophobic in situ forming systems, using Poloxamer and sucrose acetate isobutyrate (SAIB) or poly(D,L-lactide-co-glycolide) copolymer (PLGA) as carrier, respectively, were investigated for Radix Ophiopogonis polysaccharide (ROP), a natural anti-myocardial ischemic fructan. A reasonable and applicable range of formulations were selected from each carrier for in vivo study by investigating their rheological property. The results from in vivo evaluation show that relatively promising sustained behaviors were achieved by formulations 24% P407/10% P188, 40% PLGA30k/NMP, and 30% PLGA50k/NMP. Significant differences of drug release kinetics were observed between in situ thermally-induced Poloxamer-based hydrogels and in situ solvent exchange-induced hydrophobic PLGA depots. This suggests that different ISFS could be chosen to provide different application purpose for polysaccharide drugs. In the case of ROP, Poloxamer-based ISFS is promising for short-term acute therapies; however, PLGA-based ISFS might be promising for long-term precaution or/and cure of myocardial ischemia.

Injectable long-term control-released in situ gels of hydrochloric thiothixene for the treatment of schizophrenia: preparation, in vitro and in vivo evaluation

Hydrochloric thiothixene (HT) is an antipsychotic drug used in the treatment of various psychoses including schizophrenia, mania, polar disorder, and in behavior disturbances. However, because the psychotics often could not control their behaviors, the independent administration of antipsychotic drug based on medical order was difficult. The omissions of the administration often brought an unsatisfactory therapeutic efficacy. A novel injectable long-term control-released in situ gel of HT for the treatment of schizophrenia was developed based on biodegradable material polylactic acid (PLA). The optimum formulation of the injectable PLA-based HT in situ gel containing 15% (w/w) HT and 45% (w/w) PLA with benzyl benzoate was used as a gelling solvent. The results of the in vitro and in vivo studies showed that this in situ gel had a long-term period of drug release for several weeks and a good histocompatibility without any remarkable inflammatory reactions.