A New Hyaluronic Emulgel of Hesperetin for Topical Application-An In Vitro Evaluation

The present study aimed to formulate and characterize a hesperetin formulation to achieve adequate deposition and retention of hesperetin in the epidermis as a target for some cosmetic/dermatological actions. To derive the final emulgel, various formulations incorporating different proportions of Polysorbate 80 and hyaluronic acid underwent testing through a Box-Behnken experimental design. Nine formulations were created until the targeted emulgel properties were achieved. This systematic approach, following the principles of a design of experiment (DoE) methodology, adheres to a quality-by-design (QbD) paradigm, ensuring a robust and purposeful formulation and highlighting the commitment to a quality-driven design approach. The emulsions were developed using the phase inversion method, optimizing the emulgel with the incorporation of hyaluronic acid. Physically stable optimized emulgels were evaluated for their globule size, surface charge, viscosity, pH, electrical conductivity, and hesperetin content. These assays, along with the temperature swing test, were used to select the optimal formulation. It was characterized by a droplet size, d[4,3], of 4.02 μm, a Z-potential of -27.8 mV, an O/W sign, a pH of 5.2, and a creamy texture and proved to be stable for at least 2 months at room temperature. Additionally, in vitro release kinetics from the selected emulgel exhibited a sustained release profile of hesperetin. Skin assays revealed adequate retention of hesperetin in the human epidermis with minimum permeation. Altogether, these results corroborate the promising future of the proposed emulgel in cosmetic or dermatological use on healthy or diseased skin.

Intranasal Drug Administration in Alzheimer-Type Dementia: Towards Clinical Applications

Alzheimer-type dementia (ATD) treatments face limitations in crossing the blood-brain barrier and systemic adverse effects. Intranasal administration offers a direct route to the brain via the nasal cavity's olfactory and trigeminal pathways. However, nasal physiology can hinder drug absorption and limit bioavailability. Therefore, the physicochemical characteristics of formulations must be optimized by means of technological strategies. Among the strategies that have been explored, lipid-based nanosystems, particularly nanostructured lipid carriers, are promising in preclinical investigations with minimal toxicity and therapeutic efficacy due to their ability to overcome challenges associated with other nanocarriers. We review the studies of nanostructured lipid carriers for intranasal administration in the treatment of ATD. Currently, no drugs for intranasal administration in ATD have marketing approval, with only three candidates, insulin, rivastigmine and APH-1105, being clinically investigated. Further studies with different candidates will eventually confirm the potential of the intranasal route of administration in the treatment of ATD.

American and European legislation on border medical devices

INTRODUCTION

Borderline medical devices are products in a "gray area", this means due to their characteristics, they could belong to different "legal products". In addition, regulation is a controversial topic and may change depending on the country which may put public health at risk and distort the market.

AREAS COVERED

This article analyzes how borderline medical devices are managed in the American and the European legislation. We compared the decisions made by both regulations on the devices of the "Manual on Borderline and Classification Medical Devices" of the European Commission for the first three sections, those which deal exclusively with medical devices.

EXPERT OPINION

Borderline medical devices do not have to be understood as something specific to each country. The different classification of products creates international borders. It is necessary to create working groups in international organizations in which global consensus is reached. Although a priori it seems that the American system could be more efficient, studies with quantitative data from authorized devices are needed to show that. Until EUDAMED is not fully operational and open access, it will not be possible to develop them.

Canthaxanthin Biofabrication, Loading in Green Phospholipid Vesicles and Evaluation of In Vitro Protection of Cells and Promotion of Their Monolayer Regeneration

In the present study, canthaxanthin was produced by biofermentation from Dietzia natronolimnaea HS-1 (D. natronolimnaea) and was loaded in phospholipid vesicles prepared with natural component using an easy and low dissipative method. Indeed, glycerosomes, hyalurosomes, and glycerohyalurosomes were prepared by direct hydration of both phosphatidylcholine and the biotechnological canthaxanthin, avoiding the use of organic solvents. Vesicles were sized from 63 nm to 87 nm and highly negatively charged. They entrapped a high number of the biomolecules and were stable on storage. Canthaxanthin-loaded vesicles incubated with fibroblasts did not affect their viability, proving to be highly biocompatible and capable of inhibiting the death of fibroblasts stressed with hydrogen peroxide. They reduced the nitric oxide expression in macrophages treated with lipopolysaccharides. Moreover, they favoured the cell migration in an in vitro lesion model. Results confirmed the health-promoting potential of canthaxanthin in skin cells, which is potentiated by its suitable loading in phospholipid vesicles, thus suggesting the possible use of these natural bioformulations in both skin protection and regeneration, thanks to the potent antioxidant, anti-inflammatory and antiageing effects of canthaxanthin.

Resveratrol and artemisinin eudragit-coated liposomes: A strategy to tackle intestinal tumors

Resveratrol and artemisinin, two naturally occurring compounds with a wide range of biological activities, have been reported to exert antitumor effects against several types of cancer. In this work, Eudragit-coated liposomes were developed to safely transport resveratrol and artemisinin through the gastrointestinal tract and target the intestine. The physico-chemical properties of the Eudragit-coated liposomes were assessed by light scattering and cryogenic transmission electron microscopy. Nanosized (around 100 nm), spherical or elongated, unilamellar vesicles were produced. The protective effect of the Eudragit coating was confirmed by assessing the physical stability of the vesicles in fluids mimicking the gastrointestinal environment. Furthermore, the vesicles were found to exert a pro-oxidant activity in intestinal adenocarcinoma cells, which resulted in a marked mortality due to the generation of reactive oxygen species (ROS). A time- and dose-dependent cell growth inhibitory effect was detected, with elevated ROS levels when resveratrol and artemisinin were combined. Therefore, the proposed formulations may represent a valuable means to counteract intestinal tumor growth.

Co-loading of finasteride and baicalin in phospholipid vesicles tailored for the treatment of hair disorders

Hair loss affects a large number of people worldwide and it has a negative impact on the quality of life. Despite the availability of different drugs for the treatment of hair disorders, therapeutic options are still limited and scarcely effective. An innovative strategy to improve the efficacy of alopecia treatment is presented in this work. Finasteride, the only oral synthetic drug approved by Unites States Federal Drug Administration, was loaded in phospholipid vesicles. In addition, baicalin was co-loaded as an adjuvant. Their effect on hair growth was evaluated in vitro and in vivo. Liposomes, hyalurosomes, glycerosomes and glycerol-hyalurosomes were manufactured by using a simple method that avoids the use of organic solvents. All the vesicles were small in size (∼100 nm), homogeneously dispersed (polydispersity index ≤0.27) and negatively charged (∼-16 mV). The formulations were able to stimulate the proliferation of human dermal papilla cells, which are widely used in hair physiology studies. The analysis of hair growth and hair follicles of C57BL/6 mice, treated with the formulations for 21 days, underlined the ability of the vesicles to improve hair growth by the simultaneous follicular delivery of finasteride and baicalin. Therefore, the developed nanosystems can represent a promising tool to ensure the efficacy of the local treatment of hair loss.

Mangiferin glycethosomes as a new potential adjuvant for the treatment of psoriasis

Mangiferin, a natural compound isolated from Mangifera indica L, was incorporated in glycerosomes, ethosomes and alternatively in glycerol-ethanol phospholipid vesicles (glycethosomes). Actually, only glycethosomes were able to stably incorporate the mangiferin that was loaded at increasing concentrations (2, 4, 6, 8 mg/mL). The morphology, size distribution, rheological properties, surface charge and entrapment efficiency of prepared vesicles were deeply measured. All vesicles were mainly spherical, oligolamellar, small in size (~145 nm) and negatively charged (~-40 mV), as confirmed by cryo-TEM observation and dynamic laser light scattering measurements. The higher concentration of mangiferin (8 mg/mL) allowed an increase of vesicle mean diameter up to ~288 nm. The entrapment efficiency was inversely proportional to the amount of loaded mangiferin. In vitro studies performed by using human abdominal skin, underlined that, the dose-dependent ability of vesicles to promote mangiferin retention in epidermis. In addition, glycethosomes were highly biocompatible and showed a strong ability to protect in vitro the fibroblasts against damages induced by hydrogen peroxide. In vivo results underlined the superior ability of mangiferin loaded glycethosomes respect to the mangiferin dispersion to promote the heal of the wound induced by TPA, confirming their potential application for the treatment of psoriasis or other skin disorders.

Relationship between rheological properties, in vitro release and in vivo equivalency of topical formulations of diclofenac

Determination of bioequivalence remains a challenge in generic topical drug development. To support pharmacokinetic studies, strategies to demonstrate microstructure sameness of the products being compared include in vitro evaluations, such as the comparison of rheological properties, droplet size and in vitro release rates. Nevertheless, defining the appropriate acceptance range to consider equivalence between test and reference formulation is complex. To shed more light into this issue, in vitro release and rheological properties were compared to in vivo bioequivalence data (systemic blood measurements within a clinical trial) after topical application of a single dose. Test and reference formulations of diclofenac diethylamine emulgels were evaluated. While the test formulation met the requirements for equivalence in both the in vivo bioequivalence and in vitro release study, the rheological properties were considered equivalent depending on the criteria used. The 90% confidence interval of the ratios between geometric mean values of both formulations were within the limits of 75-133%, but outside the 90-111% limit under discussion in the scientific community. Altogether these data indicate that differences beyond ±10% between rheological parameters of test and reference formulation might not translate into meaningful release nor bioavailability divergence.

Development of antibiotic loaded biodegradable matrices to prevent superficial infections associated to total knee arthroplasty

Development of a pharmaceutical form for the superficial infections related with arthroplasties would be helpful for clinical practice. In this context, we set out to evaluate ciprofloxacin and gentamicin elution from systems based on chitosan. Films and semisolid hydrogels containing chitosan alone (2%) or in combination with gelatin (6%) or different proportions (from 12% to 36%) of tetrakis-(hydroxymethyl)-phosphonium-chloride (THPC) were tested as delivery systems. Different antibiotic doses were assayed (0.5 mg/cm²,1 mg/cm² and 2 mg/cm²). Antibiotic release was studied for each formulation. In vitro cytocompatibility studies and a simulation exercise for bioactivity evaluation were performed. Samples containing chitosan or chitosan-gelatin released the antibiotics at very high rates. On the contrary, ciprofloxacin released was kept for 6 days from THPC-chitosan films and hydrogels. From hydrogel formulations release could be changed by varying the percentage of THPC. The system containing 12%-THPC-chitosan with 2 mg/cm² of ciprofloxacin showed that 100% of patient would be covered during 72 h post-surgery. The concentration of 12%-THPC did not show cytotoxicity in NIH3T3 mouse fibroblasts after 48 h. THPC is suitable as crosslinker for chitosan when ciprofloxacin is incorporated showing a sustained release during 6 days.

A novel lidocaine hydrochloride mucoadhesive films for periodontal diseases

Periodontal diseases are inflammatory disorders caused primarily by dental plaque microorganisms that even may need surgery to remove damaged tissue. Adhesive biocompatible films may be an adequate form in order to improve drug retention or prevent microbial infections by covering the surgical site. In recent years, much attention has been focused on biocompatible inexpensive polymers, for biomedical and pharmaceutical potential applications. The objective of this research is the development of a film for mucosal application containing lidocaine hydrochloride (5%, w/w) as anesthetic drug. Lidocaine films were prepared with three biopolymers: hydroxypropylmethylcellulose (HPMC), chitosan (CH), or xanthan gum (XG). Their thickness and uniformity content were characterized. Rheological behavior of the hydrated films was studied using flow curves, creep and recovery tests and dynamic oscillatory measurements with a rheometer. The mucoadhesive assays were carried out with cheeks of Wistar rat using a universal tensile tester to know their adhesiveness. Finally, lidocaine delivery through the films was investigated in Franz cells. All films (n = 3 for each polymer) showed flexibility, a drug content of 0.015 ± 0.001 g/cm² and a thickness of 0.25 ± 0.01 mm. The results of the maximum detachment force in tensile tests and work adhesion indicated that XG is the polymer that showed greater power of mucoadhesion (p < 0.05). These properties show a good correlation with the rheological characteristics. In all cases, the lidocaine amount released at 30 min is around 4 mg/cm². This amount could be considered sufficient to guarantee the anesthetic effect.

Baicalin and berberine ultradeformable vesicles as potential adjuvant in vitiligo therapy

0.5-1% of the world's population is affected by vitiligo, a disease characterized by a gradual depigmentation of the skin. Baicalin and berberine are natural compounds with beneficial activities, such as antioxidant, anti-inflammatory and proliferative effects. These polyphenols could be useful for the treatment of vitiligo symptoms, and their efficacy can be improved by loading in suitable carriers. The aim of this work was to formulate and characterize baicalin or berberine loaded ultradeformable vesicles, and demonstrate their potential as adjuvants in the treatment of vitiligo. The vesicles were produced using a previously reported simple, scalable method. Their morphology, size distribution, surface charge and entrapment efficiency were assessed. The ability of the vesicles to promote the permeation of the polyphenols was evaluated. The antioxidant and photoprotective effects were investigated in vitro using keratinocytes and fibroblasts. Further, the stimulation of melanin production and tyrosinase activity in melanocytes after treatment with the vesicles were assessed. Ultradeformable vesicles were small in size, homogeneously dispersed, and negatively charged. They were able to incorporate high amounts of baicalin and berberine, and promote their skin permeation. In fact, the polyphenols concentration in the epidermis was higher than 10%, which could be indicative of the formation of a depot in the epidermis. The vesicles showed remarkable antioxidant and photoprotective capabilities, presumably correlated with the stimulation of melanin production and tyrosinase activity. In conclusion, baicalin or berberine ultradeformable vesicles, and particularly their combination, may represent promising nanosystem-based adjuvants for the treatment of vitiligo symptoms.

Antibiotic-loaded Bone Cement as Prophylaxis in Total Joint Replacement

One of its most serious complications associated with arthroplasty is the development of infections. Although its prevalence is only between 0.5% and 3%, in some cases it can lead to death. Therefore, an important challenge in joint surgery is the prevention of infections when an arthroplasty is performed. The use of antibiotic-loaded cements could be a suitable tool due to numerous advantages. The main advantage of the use of antibiotic loading into bone cement derives directly from antibiotic release in the effect site, allowing achievement of high concentrations at the site of action, and minimal or no systemic toxicity. This route of administration was first described by Buchholz and Engelbrecht. In the case of infection treatment, this is an established method and its good results have been confirmed. However, its role in infection prevention, and, therefore, the use of these systems in clinical practice, has proved controversial because of the uncertainty about the development of possible antibiotic resistance after prolonged exposure time, their effectiveness, the cost of the systems, toxicity and loosening of mechanical properties. This review discusses all these topics, focusing on effectiveness and safety, antibiotic decisions, cement type, mixing method, release kinetics and future perspectives. The final objective is to provide the orthopaedic surgeons the right information in their clinical practice based on current evidence.

Nutriosomes: prebiotic delivery systems combining phospholipids, a soluble dextrin and curcumin to counteract intestinal oxidative stress and inflammation

Nutriosomes, new phospholipid nanovesicles specifically designed for intestinal protection were developed by simultaneously loading a water-soluble dextrin (Nutriose® FM06) and a natural antioxidant (curcumin). Nutriosomes were easily fabricated in a one-step, organic solvent-free procedure. The stability and delivery performances of the vesicles were improved by adding hydroxypropyl methylcellulose. All the vesicles were small in size (mean diameter ∼168 nm), negatively charged (zeta potential ∼-38 mV, irrespective of their composition), and self-assembled predominantly in unilamellar vesicles stabilized by the presence of Nutriose®, which was located in both the inter-lamellar and inter-vesicle media, as confirmed by cryo-TEM and SAXS investigation. The dextrin acted also as a cryo-protector, avoiding vesicle collapse during the lyophilization process, and as a protector against high ionic strength and pH changes encountered in the gastrointestinal environment. Thanks to the antioxidant properties of curcumin, nutriosomes provided an optimal protective effect against hydrogen peroxide-induced oxidative stress in Caco-2 cells. Moreover, these innovative vesicles showed promising efficacy in vivo, as they improved the bioavailability and the biodistribution of both curcumin and dextrin upon oral administration, which acted synergically in reducing colonic damage chemically induced in rats.

A novel ultradeformable liposomes of Naringin for anti-inflammatory therapy

Ultradeformable liposomes were formulated using naringin (NA), a flavanone glycoside, at different concentrations (3, 6 and 9mg/mL). Nanovesicles were small size (∼100nm), regardless of the NA concentration used, and monodisperse (PI<0.30). All formulations showed a high entrapment efficiency (∼88%) and a highly negative zeta potential (around -30mV). The selected formulations were highly biocompatible as confirmed by in vitro studies using 3T3 fibroblasts. In vitro assay showed that the amounts (%) of NA accumulated in the epidermis (∼10%) could explain the anti-inflammatory properties of ultradeformable liposomes. In vivo studies confirmed the higher effectiveness of ultradeformable liposomes respect to betamethasone cream and NA dispersion in reducing skin inflammation in mice. Overall, it can conclude that NA ultradeformable liposomes can be considered as a promising formulation for the treatment of skin inflammatory diseases.

Bioactivity of Ceftazidime and Fluconazole Included in Polymethyl Methacrylate Bone Cement for Use in Arthroplasty

BACKGROUND

The microorganisms that most frequently cause prosthetic joint infection are methicillin-resistant Staphylococcus aureus and gram-negative aerobic bacillus. Studies have documented the efficacy of mixing antibiotics with polymethyl methacrylate, but that of antifungal drugs has not received much attention. The objective of this in vitro study was to characterize the elution profile and bioactivity of ceftazidime and fluconazole when incorporated into bone cement in proportions intended for prophylaxis and treatment of bone infections.

METHODS

Antibiotic-loaded bone cement cylinders in a proportion of 1:40 and 4:40 (ratio of grams of antibiotic to grams of cement) were assayed. Drug delivery was investigated in a flow-through dissolution apparatus (SotaxCE7). To assess bioactivity, antibiotic concentrations were simulated in the joint space of 1000 patients. Antibacterial properties were evaluated by counting colony forming units and the inhibition-halo test.

RESULTS

The ratio of released ceftazidime and fluconazole was 453% and 648%, respectively, higher when used for treatment proportions than prophylaxis proportions. A bioactivity simulation exercise showed that the efficacy of ceftazidime/fluconazole determined as the amount of drug is released at the active site in the first 3 days after surgery would depend on the sensitivity of the microorganism and would increase substantially after drain removal. The microbiology study showed that biofilm formation by Pseudomonas aeruginosa could be a problem when ceftazidime was used in treatment or prophylaxis proportions.

CONCLUSION

Our in vitro findings suggest that ceftazidime and fluconazole can be added into polymethyl methacrylate for the prevention/treatment of infections associated to joint surgery. Their efficacy depends on the sensitivity of the microorganism causing the infection.

Inhibition of skin inflammation by baicalin ultradeformable vesicles

The topical efficacy of baicalin, a natural flavonoid isolated from Scutellaria baicalensis Georgi, which has several beneficial properties, such as antioxidative, antiviral, anti-inflammatory and antiproliferative, is hindered by its poor aqueous solubility and low skin permeability. Therefore, its incorporation into appropriate phospholipid vesicles could be a useful tool to improve its local activity. To this purpose, baicalin at increasing concentrations up to saturation, was incorporated in ultradeformable vesicles, which were small in size (∼67nm), monodispersed (PI<0.19) and biocompatible, regardless of the concentration of baicalin, as confirmed by in vitro studies using fibroblasts. On the other hand, transdermal flux through human epidermis was concentration dependent. The in vivo results showed the significant anti-inflammatory activity of baicalin loaded nanovesicles irrespective of the concentration used, as they were able to reduce the skin damage induced by the phorbol ester (TPA) application, even in comparison with dexamethasone, a synthetic drug with anti-inflammatory properties. Overall results indicate that ultradeformable vesicles are promising nanosystems for the improvement of cutaneous delivery of baicalin in the treatment of skin inflammation.

Development of curcumin loaded sodium hyaluronate immobilized vesicles (hyalurosomes) and their potential on skin inflammation and wound restoring

In the present work new highly biocompatible nanovesicles were developed using polyanion sodium hyaluronate to form polymer immobilized vesicles, so called hyalurosomes. Curcumin, at high concentration was loaded into hyalurosomes and physico-chemical properties and in vitro/in vivo performances of the formulations were compared to those of liposomes having the same lipid and drug content. Vesicles were prepared by direct addition of dispersion containing the polysaccharide sodium hyaluronate and the polyphenol curcumin to a commercial mixture of soy phospholipids, thus avoiding the use of organic solvents. An extensive study was carried out on the physico-chemical features and properties of curcumin-loaded hyalurosomes and liposomes. Cryogenic transmission electron microscopy and small-angle X-ray scattering showed that vesicles were spherical, uni- or oligolamellar and small in size (112-220 nm). The in vitro percutaneous curcumin delivery studies on intact skin showed an improved ability of hyalurosomes to favour a fast drug deposition in the whole skin. Hyalurosomes as well as liposomes were biocompatible, protected in vitro human keratinocytes from oxidative stress damages and promoted tissue remodelling through cellular proliferation and migration. Moreover, in vivo tests underlined a good effectiveness of curcumin-loaded hyalurosomes to counteract 12-O-tetradecanoilphorbol (TPA)-produced inflammation and injuries, diminishing oedema formation, myeloperoxydase activity and providing an extensive skin reepithelization. Thanks to the one-step and environmentally-friendly preparation method, component biocompatibility and safety, good in vitro and in vivo performances, the hyalurosomes appear as promising nanocarriers for cosmetic and pharmaceutical applications.

Study of the Influence of Bone Cement Type and Mixing Method on the Bioactivity and the Elution Kinetics of Ciprofloxacin

The objectives of this study were to examine ciprofloxacin release from three trademarks of bone cements (Simplex®, Lima® and Palacos®) and its bioactivity using as variables, the mixing method, the chemical form of the antibiotic and the antibiotic combination. The antibiotic amount released in base form represents 35% of antibiotic amount released when hydrochloride form is incorporated. Moreover, the combination (vancomycin and ciprofloxacin) shows a stronger release (132%) than hydrochloride ciprofloxacin alone. Three cements show equal drug release profile (P > 0.05). A bioactivity simulation exercise showed that until 72 hours post-surgery, ciprofloxacin concentrations in the implant would be higher than 0.1 μg/mL in 100% of the patients. After drain removal, it is expected that bioactivity would increase since drug clearance from implant would decrease.

Effects of ethanol and diclofenac on the organization of hydrogenated phosphatidylcholine bilayer vesicles and their ability as skin carriers

In this study, the effects of ethanol and/or diclofenac on vesicle bilayer structure have been studied. Liposomes with hydrogenated soy phosphatidylcholine, cholesterol and two different concentrations of diclofenac sodium (5 and 10 mg/ml) were obtained. In addition, ethanol was mixed in the water phase at different concentrations (5, 10 and 20 % v/v) to obtain ethosomes. To characterize vesicles, rehological analysis were carried out to investigate the intervesicle interactions, while bilayer structure was evaluated by small- and wide-angle X-ray scattering. Finally, the ethanol and/or diclofenac concentration-dependent ability to improve diclofenac skin delivery was evaluated in vitro. The addition of 20 % ethanol and/or diclofenac led to solid-like ethosome dispersion due to the formation of a new intervesicle structure, as previously found in transcutol containing vesicle dispersions. However, when using 5-10 % of ethanol the induction to form vesicle interconnections was less evident but the simultaneous presence of the drug at the highest concentration facilitated this phenomenon. Ethosomes containing the highest amount of both, drug (10 mg/ml) and ethanol (20 % v/v), improved the drug deposition in the skin strata and in the receptor fluid up to 1.5-fold, relative to liposomes. Moreover this solid-like formulation can easily overcome drawbacks of traditional liquid liposome formulations which undergo a substantial loss at the application site.

Exploring the co-loading of lidocaine chemical forms in surfactant/phospholipid vesicles for improved skin delivery

OBJECTIVES

The present study was aimed at targeting the skin to deliver lidocaine loaded in surfactant/phospholipid vesicles tailored for improved local delivery. The influence of different formulation parameters was explored to maximise drug efficacy.

METHODS

The vesicles were prepared using a mixture of soy lipids (Phospholipon 50) and a surfactant with penetration-enhancing properties (Oramix CG110, Labrasol, Labrafac PG or Labrafac CC), and loaded with lidocaine. The formulations were analysed in detail by cryo-TEM, SAXS, Turbiscan Lab, and tested in permeation experiments through new born pig skin, as a function of the chemical form and concentration of lidocaine (i.e. free base or salt, 12.5 or 25 mg/ml).

KEY FINDINGS

Small, spherical vesicles with good entrapment efficiency and exceptional long-term stability were produced. The lamellar organisation was affected by either the surfactant or the lidocaine form used. Permeation studies highlighted that the co-incorporation of lidocaine base + hydrochloride allowed the achievement of a superior deposition in the skin layers, especially when surfactant vesicles were used, as their content was presumably saturated with the maximum amount of loadable anaesthetic.

CONCLUSIONS

The proposed systems based on surfactant/phospholipid vesicles co-loaded with both lidocaine forms are an effective approach for improving its local delivery.

Chitosan-xanthan gum microparticle-based oral tablet for colon-targeted and sustained delivery of quercetin

CONTEXT

Quercetin (QUE) is a flavonoid with antioxidant/anti-inflammatory properties, poorly absorbed when orally administered.

OBJECTIVES

To prepare chitosan/xanthan gum microparticles to increase QUE oral bioavailability and optimize its release in the colon.

MATERIALS AND METHODS

Chitosan/xanthan gum hydrogel embedding QUE was spray-dried to obtain microparticles characterized by size, scanning electron microscopy, differential scanning calorimetry and X-ray diffraction. Microparticles were compressed into tablets, coated with Eudragit® to further prevent degradation in acidic pH. The swelling degree and QUE release in simulated gastric and intestinal pH were investigated.

RESULTS

Microparticles were smooth and spherical, around 5 µm, with successful QUE loading. Microparticle tablets provided resistance to acidic conditions, allowing complete drug release in alkaline pH, mimicking colonic environment. The release was controlled by non-Fickian diffusion of the dissolved drug out of the swollen polymeric tablet.

DISCUSSION AND CONCLUSION

Microparticle tablets represent a promising dosage form for QUE delivery to the colon in the oral therapy of inflammatory-based disorders.

Fabrication of quercetin and curcumin bionanovesicles for the prevention and rapid regeneration of full-thickness skin defects on mice

In the present work biocompatible quercetin and curcumin nanovesicles were developed as a novel approach to prevent and restore skin tissue defects on chronic cutaneous pathologies. Stable and suitable quercetin- and curcumin-loaded phospholipid vesicles, namely liposomes and penetration enhancer-containing vesicles (PEVs), were prepared. Vesicles were made from a highly biocompatible mixture of phospholipids and alternatively a natural polyphenol, quercetin or curcumin. Liposomes were obtained by adding water, while PEVs by adding polyethylene glycol 400 and Oramix®CG110 to the water phase. Transmission electron microscopy, cryogenic-transmission electron microscopy and small- and wide-angle X-ray scattering showed that vesicles were spherical, oligo- or multilamellar and small in size (112-220 nm). In vitro and in vivo tests underlined a good effectiveness of quercetin and curcumin nanovesicles in counteracting phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) induced lesions and inflammation. Myeloperoxydase activity, used to gauge inflammation, was markedly inhibited by quercetin liposomes (59%) and curcumin liposomes and polyethylene glycol (PEG)-PEVs (∼ 68%). Histology showed that PEG-PEVs provided an extensive re-epithelization of the TPA-damaged skin, with multiple layers of thick epidermis. In conclusion, nanoentrapped polyphenols prevented the formation of skin lesions abrogating the various biochemical processes that cause epithelial loss and skin damage.

Improving oral bioavailability and pharmacokinetics of liposomal metformin by glycerolphosphate-chitosan microcomplexation

The purpose of this study was to develop a new delivery system capable of improving bioavailability and controlling release of hydrophilic drugs. Metformin-loaded liposomes were prepared and to improve their stability surface was coated with chitosan cross-linked with the biocompatible β-glycerolphosphate. X-ray diffraction, differential scanning calorimetry, as well as rheological analysis were performed to investigate interactions between chitosan and β-glycerolphosphate molecules. The entrapment of liposomes into the chitosan-β-glycerolphosphate network was assessed by scanning electron microscopy and transmission electron microscopy. Swelling and mucoadhesive properties as well as drug release were evaluated in vitro while the drug oral bioavailability was evaluated in vivo on Wistar rats. Results clearly showed that, compared to control, the proposed microcomplexes led to a 2.5-fold increase of metformin T(max) with a 40% augmentation of the AUC/D value.

Hydroxypropylmethylcellulose films for the ophthalmic delivery of diclofenac sodium

OBJECTIVES

The aim of this study was to prepare diclofenac/hydroxypropylmethylcellulose (HPMC) and diclofenac-loaded nanoparticles/HPMC films as potential systems for ocular delivery.

METHODS

Two different concentration of the polymer were used: 1.5 and 2.0% w/v. Chitosan-hyaluronic acid nanoparticles were prepared by the ionotropic gelation technique. Nanoparticles were characterized by transmission electron microscopy, dynamic light scattering, drug encapsulation efficiency and rheological studies. In-vitro drug studies and corneal penetration release studies were carried out. Drug release mechanism was finally evaluated by fitting the Ritger and Peppas equation to data. In addition corneal hydration level was calculated to determine whether films could damage the corneas.

KEY FINDINGS

Diclofenac HPMC films presented a faster drug release and a higher drug penetration than nanoparticles; on the contrary nanoparticles containing films were able to give a more sustained release of the drug and thus a slower diclofenac permeation through the cornea than HPMC films.

CONCLUSIONS

Nanoparticles loaded with diclofenac sodium in HPMC films may be a valuable alternative for the treatment of ocular inflammatory diseases, since these formulations offer the benefit of sustained releasing directly to the site of action.

Animal model of undernutrition for the evaluation of drug pharmacokinetics

BACKGROUND

Protein energy malnutrition is a public health problem affecting a great number of people. Pathophysiological imbalances in malnourished individuals have a profound impact on drug pharmacokinetics.

OBJECTIVE

To develop an animal model of undernutrition using male Wistar rats to be used to assess, in further studies, the impact of nutritional status on the oral bioavailability and pharmacokinetics of drugs.

DESIGN

[corrected] Animals were randomly assigned to one of two groups and fed different diets for 26 days: WN (well-nourished/regular diet, N = 61) and UN (under-nourished/protein-calorie restricted diet, N = 72). Assessment of the animals' nutritional status was performed taking into account serum albumin, total cholesterol level and total body weight. A kinetic model incorporating population kinetic analysis (NONMEM) was developed to analyze body weight versus time profiles in the adaptation period following administration of the two aforementioned diets.

RESULTS

Serum albumin plasma levels were lower than 2.3 g/dL in 80% (60/72) of malnourished animals at the end of the adaptation period. The range of the total serum cholesterol was similar in both groups at the end of the adaptation period. Total body weight in all cases was less than 230 g for malnourished animals and higher than 240 g for well-nourished animals. The kinetic model assayed was confirmed to be an expansion module characterized by linear weight gain and a decline module characterized by exponential weight loss, where the weight loss rate constant is an exponential function of time. The bootstrap resampling method confirmed the stability of the model eventually selected.

CONCLUSIONS

The animal model developed in this study is reliable and could be of use in evaluating the impact of nutritional state on the pharmacokinetics of drugs. The proposed mathematical model allows the body weight of animals to be predicted at a given time taking into account the diet followed in the experimental period.

Enhancement of nortriptyline penetration through human epidermis: influence of chemical enhancers and iontophoresis

Different known percutaneous chemical enhancers and iontophoresis have been tested in-vitro to study their ability to increase transdermal absorption of nortriptyline hydrochloride (20 mg mL−1). The chemicals 1-dodecanol, Span 20, Azone, (R)-(+)-limonene or isopropyl myristate were used as an overnight pretreatment at 5% (w/w) in ethanol. Furthermore, isopropyl myristate (20%, w/w) and propylene glycol (15%, w/w) were tested in the same vehicle. Iontophoresis was applied directly to the nortriptyline hydrochloride donor solution for three different concentrations (20, 2 and 0.5 mgmL−1). The chemical enhancers slightly increased the nortriptyline transdermal flux but iontophoresis was more efficient. In this case, nortriptyline transdermal flux was concentration dependent, having a higher flux when the concentration was lowered. Therefore, iontophoresis was the most suitable technique to increase transdermal absorption of nortriptyline and it could be an alternative method to provide therapeutic concentrations of this drug in smoking cessation treatment.

A dopamine transport inhibitor with markedly low abuse liability suppresses cocaine self-administration in the rat

RATIONALE

N-substituted benztropine analogs are potent dopamine uptake inhibitors that display pharmacokinetic/dynamic properties consistent with the profile of a substitute medication for cocaine addiction.

OBJECTIVES

The purpose of the present experiments was to characterize in rats the addictive-like properties of one such analog, 3 alpha-[bis(4'-fluorophenyl)methoxy]-tropane (AHN-1055), incorporating probes of its stimulant and incentive/motivational effects and of its ability to influence cocaine self-administration.

METHODS

We used open field activity and drug self-administration assays. To examine the effects of AHN-1055 on locomotor behavior, the analog was administered alone (0, 1, 3, and 10 mg/kg intraperitoneally) and in combination with cocaine (15 mg/kg i.p.). The influence of AHN-1055 on cocaine's intake was studied by administering the analog (0, 3, and 10 mg/kg i.p.) before the start of the self-administration sessions. To compare the addictive-like properties of AHN-1055 and cocaine, progressive ratio performance and abstinence-induced context-conditioned relapse were evaluated.

RESULTS

AHN-1055 evoked robust and sustained locomotor activity when administered alone and increased cocaine-induced locomotor stimulation. Notably, the analog showed by comparison to cocaine weak reinforcing efficacy in a modified progressive ratio schedule of drug reinforcement, and contrary to cocaine, it showed no ability to promote context-conditioned relapse to drug seeking following stable self-administration and abstinence. Further, AHN-1055 treatment blocked cocaine intake dose-dependently in rats with a steady history of cocaine self-administration without reducing responding for sucrose, a natural reward.

CONCLUSIONS

These findings demonstrate essential psychopharmacological differences between AHN-1055 and cocaine and highlight important properties of the analog as a possible pharmacotherapy in cocaine addiction.

Bioavailability and Pharmacokinetic Model for Ritonavir in the Rat

The aim of this study is to investigate in vivo the oral bioavailability of ritonavir and to evaluate the pharmacokinetic model that best describes the plasma concentration behavior after oral and intravenous administration. Male Wistar rats were intravenously administered at 3 mg dose of pure ritonavir and oral administered at 4.6 +/- 2.5 mg of diluted Norvir. Blood samples were taken by means of the jugular vein for a 24 h period of time. An analytical high-performance liquid chromatography (HPLC) technique was developed in order to quantify ritonavir plasma concentrations. A nonlinear modeling approach was used to estimate the pharmacokinetic parameters of interest. Results showed that a two-compartmental model with zero-order kinetic in the incorporation process of ritonavir into the body better fitted intravenous and oral data. The estimated oral bioavailability by means of noncompartmental and compartmental approaches resulted in 74% and 76.4%, respectively. These values confirm the ones obtained by other authors in the rat. In conclusion, a zero-order kinetic in the incorporation process at the administered doses suggests the saturation of the possible specialized transport mechanisms involved in the incorporation of ritonavir into the body. These results could justify the use of low doses of ritonavir when improving the bioavailability of other protease inhibitors (PIs) is required.

Population modelling to describe pharmacokinetics of amiodarone in rats: Relevance of plasma protein and tissue depot binding

The objective of this paper was to characterize the disposition phase of AM in rats, after different high doses and modalities of i.v. administration. Three fitting programs, WINNONLIN, ADAPT II and NONMEM were employed. The two-stage fitting methods led to different results, none of which can adequately explain amiodarone's behaviour, although a great amount of data per subject is available. The non-linear mixed effect modelling approach allows satisfactory estimation of population pharmacokinetic parameters, and their respective variability. The best model to define the AM pharmacokinetic profile is a two-compartment model, with saturable and dynamic plasma protein binding and linear tissular depot dynamic binding. These results indicate that peripheral tissues act as depots, causing an important fall in AM plasma levels in the first moment after dosing. Later, the return of the drug from these depots causes a slow increase in serum concentration whenever the dose is reduced.

Labetalol absorption kinetics: Rat small intestine and colon studies

Labetalol is a widely used drug for the management of hypertension, which is preferably administered by the oral route despite its low bioavailability. The objective of this study is to ascertain the mechanisms underlying its absorption as an approach to help in predicting the influence of dosage changes, possible drug-drug and drug-fruit juice interactions. Perfusion experiments have been performed in rats in two sites of absorption: the intestine and the colon. The nonlinearity of the process has been established by means of the assay of a wide range of concentrations (2-2000 microM). Fitting of the concentration versus time data allows the estimation of passive diffusion constant in the intestine (1.42 +/- 0.05/h) and the colon (1.13 +/- 0.06/h), V(m) and K(m) of the input process (9.85 +/- 4.98 microM/h, and 10.44 +/- 26.16 microM, respectively) and K(m) of an efflux system (0.53 +/- 1.16 microM) and V(m) in both intestinal segments (2.60 +/- 11.37 microM . /h in the intestine and 0.66 +/- 1.38 microM . /h in the colon). The efflux carrier implicated is identified by means of several inhibition experiments, whose inhibition ability is mathematically estimated. Results suggest the p-glycoprotein as responsible for the efflux of labetalol.

Modelling intestinal absorption of salbutamol sulphate in rats

The objective was to develop a semiphysiological population pharmacokinetic model that describes the complex salbutamol sulphate absorption in rat small intestine. In situ techniques were used to characterize the salbutamol sulphate absorption at different concentrations (range: 0.15-18 mM). Salbutamol sulphate at concentration of 0.29 mM was administered in presence of verapamil (10 and 20 mM), grapefruit juice and sodium azide (NaN3) (0.3, 3 and 6 mM). Different pharmacokinetic models were fitted to the dataset using NONMEM. Parametric and non-parametric bootstrap analyses were employed as internal model evaluation techniques. The validated model suggested instantaneous equilibrium between salbutamol sulphate concentrations in lumen and enterocyte, and the salbutamol sulphate absorption was best described by a simultaneous passive diffusion (ka = 0.636 h(-1)) and active absorption (VMax = 0.726 mM/h, Km = 0.540 mM) processes from intestinal lumen to enterocyte, together with an active capacity-limited P-gp efflux (V'max = 0.678 mM/h, K'm = 0.357 mM) from enterocyte to intestinal lumen. The extent of salbutamol sulphate absorption in rat small intestine can be improved by NaN3, grapefruit juice and verapamil.

Use of nonlinear mixed effect modeling for the intestinal absorption data: Application to ritonavir in the rat

The aim of this study is to investigate in situ the mechanisms involved in the gastrointestinal absorption of ritonavir in the rat, as an animal model for preclinical studies of anti-HIV agents in vivo. Four ritonavir solutions (40, 27, 13 and 7 microM) in the presence of 1% dimethylsulfoxide (DMSO) were perfused in the small intestine of anaesthetised rats. Effects of DMSO on the intestinal permeability were investigated using solutions containing antipyrine 1.33 mM and ritonavir 7 microM with and without 1% of DMSO. Antipyrine and ritonavir transport was not modified in the presence of 1% of DMSO. The population pharmacokinetic parameters of the ritonavir intestinal transport were obtained by means of nonlinear mixed effect modelling approach according to a nonlinear absorption and nonlinear secretion. The absorption and secretion kinetic parameters for ritonavir were: Vm=47.6 microM/h; Km=8.77 microM; Vms=3.66 microM/h and Kms=0 microM. The interindividual variability found to ritonavir Vm 13.1%, and the residual variability was 8.98%. The Kms value support the saturation of the carrier at the range of concentrations of ritonavir assayed. The interindividual variability value of the Vm could explain, at least in part, the variability in absorption rate constants observed.

Profile of P‐glycoprotein Distribution in the Rat and Its Possible Influence on the Salbutamol Intestinal Absorption Irocess

The intrinsic absorption of salbutamol in different intestinal segments of the rat was measured and related with the corresponding intestinal P-glycoprotein (P-gp) expression levels. The apparent absorption rate constants (k(a), h(-1)) observed in each fraction by means of the "in situ" rat gut absorption method after perfusion of a 0.29-mM isotonic solution of salbutamol were used as absorption indexes. In a separate series of studies, a semiquantitative analysis of the mRNA expression of P-gp by means of polymerase chain reaction and Western blot with an antibody raised against the P-gp were also performed. The "in situ" k(a) values determined in the different segments (h(-1)) showed that the absorption is not homogeneous along the intestinal tract, that is, 0.499 +/- 0.054 for colon, 0.474 +/- 0.052 for the proximal segment, 0.345 +/- 0.014 for the mean, and 0.330 +/- 0.023 for the distal fraction. Addition of verapamil to the perfusion fluid did provide a better absorption of salbutamol in the distal segment. The analysis of the mRNA expression and levels of P-gp showed that the enzyme content in each section of the intestine was inversely related to salbutamol absorption.

Pharmacokinetic models for the saturable absorption of cefuroxime axetil and saturable elimination of cefuroxime

Since oligopeptidic drugs such as beta-lactam antibiotics share the same carriers in humans and animals, the absorption and elimination kinetics of cefuroxime (C) were investigated in rats. Plasma C concentrations were measured by liquid chromatography. Pharmacokinetics and bioavailability of C in the rat were examined after intravenous (i.v.) administration at three doses (1.78, 8.9 and 17.8mg) of cefuroxime sodium and oral administration at two doses (2.02 and 8.9mg) of cefuroxime axetil (CA). Preliminary fits using data from intravenous administration of C showed that the drug disposition kinetics were clearly nonlinear, with an increase in plasma clearance as the intravenous dose increased. After oral administration of CA, normalized C(max) was higher for smaller dose than for the largest dose. The population pharmacokinetic parameters were obtained by means of nonlinear mixed effect modelling approach according to a nonlinear elimination and nonlinear absorption two-compartment model. The nonlinear elimination could be attributed to a saturable renal tubular reabsorption of the antibiotic and nonlinear intestinal absorption of CA mediated by carrier system. The oral bioavailability of C, calculated by numeric integration of an amount of CA drug absorbed was 22 and 17% for 2.02 and 8.9mg of prodrug administered orally.

The influence of active secretion processes on intestinal absorption of salbutamol in the rat

Salbutamol was perfused in the small intestine of rat using a standard rat gut "in situ" preparation: (1) in inhibitor-free solution at seven different concentrations (0.15, 0.29, 1.20, 5.0, 9.0, 13.0 and 18.0mM); (2) at a 0.29mM concentration - thought to be close to the allometric dose in man - in the presence of a non-specific enzyme inhibitor, sodium azide (0.3, 3.0 and 6.0mM); and (3) at 0.29mM in the presence of a selective secretion inhibitor, verapamil (10.0 and 20.0mM). In free solution, the mixed-order rate constants, k'(a), of salbutamol increase as the solute concentration increases until an apparent asymptotic value is reached. This could be due to the saturation of enzymatic systems responsible for the secretion of the drug from the enterocyte to the luminal fluid, a process that could explain the poor absorption of salbutamol. In the presence of sodium azide, the k(a) values increased about 1.5-fold, whereas in the presence of verapamil they increased two- to three-fold. These results indicate that salbutamol can act as a substrate of an intestinal secretory transport, which probably includes--at least in part--the enzyme P-glycoprotein, since verapamil has been shown to inhibit this enzyme by dose-dependent competition. This leads to a secretion-limited peroral absorption of salbutamol, which contributes to the poor oral bioavailability of the drug. The possible options for improving salbutamol absorption are discussed.

Interaction of taurine on baclofen intestinal absorption: a nonlinear mathematical treatment using differential equations to describe kinetic inhibition models

Previous studies showed that the in situ absorption of baclofen in rat jejunum was inhibited by beta-alanine, a nonessential amino acid, and therefore mediated, at least in part, by some beta-amino acid carrier. In this paper a similar study was undertaken using taurine, a sulfonic beta-amino acid, in order to evaluate its effect and to establish a general inhibition model. To achieve this goal, remaining concentrations of inhibitor were also measured and incorporated into the model. Previously, kinetic absorption in situ parameters for taurine in free solution were obtained: Vm = 27.73 +/- 9.99 mM h-1, K(m) = 8.06 +/- 2.82 mM, Ka (passive difussion component) = 0.40 +/- 0.28 h-1. Isotonic solutions containing 0.5 mM baclofen with starting taurine concentrations ranging from 0 to 100 mM were perfused in rat jejunum, and the remaining concentrations of both compounds were measured. The apparent rate pseudoconstant of the drug clearly decreased as the remaining taurine concentration increased. The interaction can be described as a complete competitive inhibition plus a second component, K, noninhibited, K = 0.58 (+/- 0.03) h-1, Ki = 20.62 (+/- 4.04) mM, Vmi = 28.12 (+/- 6.12) mM h-1, Kmi = 11.71 (+/- 2.53) mM, Kai = 0.47 (+/- 0.10) h-1. A residual absorption of baclofen in the presence of high taurine concentrations was observed, which should be attributed to another transport system not associated with the taurine carrier. In order to elucidate whether or not taurine and beta-alanine carriers are two separate entities that baclofen can use for absorption, further experiments using beta-alanine and taurine together as inhibitors (baclofen, 0.5 mM; beta-alanine, 50 mM, and taurine, 50 mM) were developed. Results indicated that baclofen and both amino acids share the same carrier in the intestinal absorption process. We have completed studies using leucine, taurine, and GABA together as inhibitors of drug absorption. An isotonic perfusion solution of 0.5 mM baclofen in the presence of 50 mM leucine, 25 mM taurine, and 25 mM GABA was perfused. Under these conditions the absorption rate pseudoconstant of baclofen decreases until 0.080 h-1 (+/- 0.069). Practical implications of these phenomena are briefly discussed.

Influence of leucine on intestinal baclofen absorption as a model compound of neutral alpha-aminoacids

The inhibitory effect of the essential alpha-aminoacid L-leucine on the intestinal absorption of the antispastic drug baclofen was examined by means of an in situ rat gut perfusion technique. When 0.5 mM baclofen solutions were perfused in the presence of increasing concentrations of the aminoacid (5-100 mM), the apparent absorption rate constant of the drug decreased as the initial leucine concentration increased. Higher leucine concentrations however did not completely abolish the absorption of the drug (at 100 mM of leucine, only 76% inhibition was observed). The interaction can be mathematically described as a complete competitive inhibition with a second component, K = 0.35 (+/- 0.08)h-1, Ki = 0.25 (+/- 0.09)mM, AIC = -97.02. In the light of some of the absorption features of the drug, however, the residual absorption of baclofen in the presence of high leucine concentrations should be attributed to another transport system not used by leucine. Apparent parameters characterizing absorption of leucine in the presence of baclofen (0.5 mM) were Vm = 61.02 (+/- 5.46)mM h-1; Km = 8.04 (+/- 0.89)mM, and AIC = -62.25. The results indicate that baclofen and leucine share some carriers in the intestinal absorption processes. Since leucine is an essential dietary aminoacid, and therefore a normal food component, this finding could be relevant in preventing interactions that would lead to a reduced oral bioavailability during baclofen therapy.

Influence of gamma-aminobutyric acid on baclofen intestinal absorption

Since previous studies suggested that baclofen absorption in the rat middle intestine was inhibited by beta-alanine and therefore mediated, at least in part, by the beta-aminoacid carrier, we focused our new studies on the analysis of the possible inhibition of the drug by a gamma-aminoacid model compound, gamma-aminobutyric acid (GABA). A rat jejunum in situ study was undertaken in order to evaluate the effect of GABA on baclofen absorption and to establish the inhibition model. Assays using isotonic perfusion solutions of 0.5 mM baclofen with starting GABA concentrations ranging from 0 to 100 mM are reported. The results show that the absorption rate pseudoconstants of the drug decrease at the GABA concentration increases, with a limiting value of 0.65 h-1 (+/- 0.01). A partial competitive inhibition or complete competitive inhibition in the presence of a passive component could define the interaction phenomena between the two substances. Kinetic absorption parameters for GABA in the presence and absence of baclofen (Ki = 5.67 +/- 1.54, Km = 3.87 +/- 0.63) suggest the existence of more than one intestinal carrier system for baclofen or GABA.

Intestinal absorption pathway of gamma-aminobutyric acid in rat small intestine

Intestinal absorption of gamma-aminobutyric acid (GABA), as a model compound for gamma-aminoacids, has not been extensively studied from the kinetic viewpoint. Since data from our laboratory suggested that some competition arises between intestinal absorption of beta-alanine and GABA and since our intent was to maintain the aqueous stagnant diffusion layer in order to approach absorption tests to in vivo physiological conditions, a rat jejunum in situ study was undertaken in order to gain an insight into the mechanism of GABA absorption. In the present paper, results from assays using isotonic perfusion solutions with starting GABA concentrations ranging from 1 to 50 mM are reported. They show that the intestinal absorption of the gamma-aminoacid can be apparently described as a specialized transport mechanism which obeys Michaelis-Menten and first-order kinetics. Parameter values found were Vm = 13.99 +/- 2.37 mM h-1, Km = 3.87 +/- 0.63 mM, and ka(passive) = 0.362 +/- 0.120 h-1. Through the perfusion of 5 mM beta-alanine solutions containing variable concentrations of GABA (from 5 to 50 mM), a partially competitive inhibition of beta-alanine absorption was apparently characterized.