Box-Behnken study design for optimization of bicalutamide-loaded nanostructured lipid carrier: stability assessment.

Bicalutamide (BCM) is an anti-androgen drug used to treat prostate cancer. In this study, nanostructured lipid carriers (NLCs) were chosen as a carrier for delivery of BCM using Box-Behnken (BB) design for optimizing various quality attributes such as particle size and entrapment efficiency which is very critical for efficient drug delivery and high therapeutic efficacy. Stability of formulated NLCs was assessed with respect to storage stability, pH stability, hemolysis, protein stability, serum protein stability and accelerated stability. Hot high-pressure homogenizer was utilized for formulation of BCM-loaded NLCs. In BB response surface methodology, total lipid, % liquid lipid and % soya lecithin was selected as independent variable and particle size and %EE as dependent variables. Scanning electron microscopy (SEM) was done for morphological study of NLCs. Differential scanning calorimeter and X-ray diffraction study were used to study crystalline and amorphous behavior. Analysis of design space showed that process was robust with the particle size less than 200 nm and EE up to 78%. Results of stability studies showed stability of carrier in various storage conditions and in different pH condition. From all the above study, it can be concluded that NLCs may be suitable carrier for the delivery of BCM with respect to stability and quality attributes.

Fabrication and optimization of chitosan-g-m-PEG-NH2 copolymer for advanced glioblastoma therapy using surface engineered lentinan loaded nanovesicles for nasal delivery.

Glioblastoma multiforme (GBM) exhibits a high mortality with an incidence rate of 3-5 per 100,000 each year, which demands existence of newer approach for its treatment. The current study focuses on synthesis of novel lipidic nanovesicles (LNs) loaded with highly potent macromolecule Lentinan (LNT) and surface modified with methoxy poly (ethylene glycol; PEG) amine (m-PEG-NH2)-grafted-chitosan (CS) for intranasal delivery. The grafting procedure was optimized using Box Behnken design (BBD) to limit the use of organic solvents. The fabricated polymer showed enhanced aqueous solubility, biodegradability and mucoadhesion, resulting in higher nasal mucosa permeation (z = 53.52 µm). The presence of PEG enabled the sustained release of LNT till 48 h and assisted in achieving higher accumulation of LNT in CSF (41.7 ± 3.1 µg/mL) and a higher brain targeting potential of 96.3 ± 2.31 % (p < 0.05). In-vitro cellular studies showed the enhanced anti-GBM effect of LNT on U87 MG cells by reducing the cell viability (~2 times reduction in IC50 value) accompanied with large number of cells undergoing late apoptosis and death (p < 0.05) because of the higher cellular uptake (63.22 ± 3.01 ng/100 cells) of novel formulation. The copolymer comprising LNs were biocompatible, stable and can be used as an effective tool in the management of GBM.

A bioanalytical assay for estimation of thymoquinone in rats cerebrospinal fluid and brain tissues of nasally administrated thymoquinone loaded lipo-polymeric nanoshells and its pharmacokinetic profiling.

Thymoquinone (TH) has been one of the major phytochemical used in the treatment of cancers since long time, especially in the management of glioblastoma multiforme (GBM). The formulation of lipo-polymeric nanoshells (LPNs) and their nasal delivery are fascinating approaches for overcoming the drawbacks of low solubility and poor bioavailability of TH. Hence targeting LPNs to the brain requires a validated bioanalytical method for the assessment of TH concentration in Cerebrospinal fluid (CSF) and brain tissue homogenates (BTH). Therefore, the current work focuses on the development and validation of high-performance liquid chromatography (HPLC) method in CSF by employing nasal simulated fluid (NSF) as one of the major components of the mobile phase. The developed method was checked for linearity in the range of 0.05 to 1.6 µg/mL, having an r2 value of 0.999 with mean % recovery >95% and % RSD values below <2.0%. The developed method gave a clear separation of TH at 6.021 ± 0.17 min with an internal standard at 4.102 ± 0.09 min and a CSF spike at 2.170 ± 0.12 min. The developed method assisted in determining the in-vitro and in-vivo drug release study of LPNs, pharmacokinetic profiling, qualitative in-vivo brain uptake study, in-vitro cellular uptake, and generating stability data of formulated LPNs proposed for intranasal administration in rats.

Novel surface modified polymer-lipid hybrid nanoparticles as intranasal carriers for ropinirole hydrochloride: in vitro, ex vivo and in vivo pharmacodynamic evaluation.

Here we report fabrication and evaluation of novel surface modified polymer-lipid hybrid nanoparticles (PLN) as robust carriers for intranasal delivery of ropinirole hydrochloride (ROPI HCl). Sustained release, avoidance of hepatic first pass metabolism, and improved therapeutic efficacy are the major objectives of this experiment. PLN were fabricated by emulsification-solvent diffusion technique and evaluated for physicochemical parameters, in vitro mucoadhesion, in vitro diffusion, ex vivo permeation, mucosal toxicity and stability studies. Box-Behnken experimental design approach has been employed to assess the influence of two independent variables, viz. surfactant (Pluronic F-68) and charge modifier (stearylamine) concentration on particle size, ζ-potential and entrapment efficiency of prepared PLN. Numerical optimization techniques were used for selecting optimized formulation sample, further confirmed by three dimensional response surface plots and regression equations. Results of ANOVA demonstrated the significance of suggested models. DSC and SEM analysis revealed the encapsulation of amorphous form of drug into PLN system, and spherical shape. PLN formulation had shown good retention with no severe signs of damage on integrity of nasal mucosa. Release pattern of drug-loaded sample was best fitted to zero order kinetic model with non-Fickian super case II diffusion mechanism. In vivo pharmacodynamic studies were executed to compare therapeutic efficacy of prepared nasal PLN formulation against marketed oral formulation of same drug. In summary, the PLN could be potentially used as safe and stable carrier for intranasal delivery of ROPI HCl, especially in treatment of Parkinson's disease.

Solid lipid nanoparticles of ondansetron HCl for intranasal delivery: development, optimization and evaluation.

The present investigation deals with the development and statistical optimization of solid lipid nanoparticles (SLNs) of ondansetron HCl (OND) for intranasal (i.n.) delivery. SLNs were prepared using the solvent diffusion technique and a 2(3) factorial design. The concentrations of lipid, surfactant and cosurfactant were independent variables in this design, whereas, particle size and entrapment efficiency (EE) were dependent variables. The particle size of the SLNs was found to be 320-498 nm, and the EE was between 32.89 and 56.56 %. The influence of the lipid, surfactant and cosurfactant on the particle size and EE was studied. A histological study revealed no adverse response of SLNs on sheep nasal mucosa. Transmission electron microscopic analysis showed spherical shape particles. Differential scanning calorimetry and X-ray diffraction studies indicated that the drug was completely encapsulated in a lipid matrix. In vitro drug release studies carried out in phosphate buffer (pH 6.6) indicated that the drug transport was of Fickian type. Gamma scintigraphic imaging in rabbits after i.n. administration showed rapid localization of the drug in the brain. Hence, OND SLNs is a promising nasal delivery system for rapid and direct nose-to-brain delivery.

Formulation, optimization and evaluation of spray-dried mucoadhesive microspheres as intranasal carriers for Valsartan.

This investigation deals with the intranasal delivery of Valsartan, encapsulated in HPMC-based spray-dried mucoadhesive microspheres, with an aim to provide rapid absorption and quick onset of action for treating hypertension. A 2³-factorial design has been employed for the assessment of influence of three independent variables, namely inlet temperature, feed-flow rate and drug-polymer ratio on production yield, particle size and in vitro drug diffusion of the prepared microspheres. Microspheres were evaluated for particle size, entrapment efficiency, swelling property, in vitro mucoadhesion, in vitro drug diffusion, ex vivo drug permeation, histopathological examination and stability studies. The results of differential scanning calorimetry, X-ray diffraction and scanning electron microscopy revealed molecular dispersion of Valsartan into microspheres with spherical shape and smooth surface. Optimized formulation indicated good mucoadhesion with no severe sign of damage on nasal mucosa. Results of the non-invasive animal studies in dexamethasone-induced hypertensive rat model suggested the suitability of investigated drug delivery system for intranasal administration.

Development and characterization of amphotericin B nanoemulsion-loaded mucoadhesive gel for treatment of vulvovaginal candidiasis.

Despite being recognized as the "gold standard" for treating azole-resistant vulvovaginal candidiasis, amphotericin B (AmB), an amphoteric molecule, has not been widely used due to serious issues with solubility and permeability. In light of the aforementioned, the objective of the present study was to increase AmB's therapeutic efficacy by formulating it into an o/w nanoemulsion (AmB-NE) system. Furthermore, to facilitate AmB-NE's retention within the vaginal cavity, it was loaded into a mixture of Carbopol® 974P and Aloe vera-based gel (CA gel). Briefly, in the present study, a kinetically stable batch of formulated AmB-NE having a globule size of 76.52 ± 3.11 nm, PDI of 0.342 ± 0.032, and zeta potential of -22.32 ± 0.88 mV was incorporated into the CA gel base. This AmB-NE loaded gel (AmB-NE gel) exhibited a non-Fickian/anomalous diffusion from the hydrophilic matrix. The texture analysis of AmB-NE gel revealed that the prepared gel was a non-drip, soft, easy to spread, and sufficiently cohesive gel that could reside in the vaginal cavity, which was confirmed by our ex-vivo retention test, which revealed that AmB-NE loaded gel could stay in the vaginal cavity for approximately 11 h. Ex-vivo skin permeation studies revealed that AmB-NE is 4.26 times more permeable than AmB-coarse gel, implying that AmB-NE facilitates AmB entry into the vaginal epithelial layers. Furthermore, in-vivo vaginal lavage studies revealed that AmB-NE gel permeated 7.03-fold more than AmB-coarse gel. Prepared AmB-NE gel was stable in refrigerated condition and showed no histopathological toxicity. Thus, the present study suggests that AmB-NE gel could eliminate the existing problem of AmB and that it could serve as an alternative option to treat vulvovaginal candidiasis.

Solubility, dissolution rate and bioavailability enhancement of irbesartan by solid dispersion technique.

The objective of present work was to enhance the solubility and bioavailability of poorly aqueous soluble drug Irbesartan (IBS). The solid dispersions were prepared by spray drying method using low viscosity grade HPMC E5LV. Prepared solid dispersions were characterized by dissolution study, fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and X-ray diffraction studies (XRD). Results of the SEM, DSC and XRD study showed the conversion of crystalline form of IBS to amorphous form. The dissolution rate was remarkably increased in case of solid dispersion compared to pure IBS. Solubility and stability of solid dispersion was increased due to surfactant and wetting property, slowing devitrification and having anti-plasticization effect of HPMC E5LV. In vivo studies were performed in healthy rabbits (New Zealand grey) and compared with plain IBS. Solid dispersions showed increase in relative bioavailability than the plain IBS suspension. In conclusion, the prepared solid dispersions showed remarkable increase in solubility, dissolution rate and hence bioavailability of poorly water soluble drug Irbesartan.

Design and development of oral mucoadhesive multiparticulate system containing atenolol: in vitro-in vivo characterization.

The aim of the present study was to prepare mucoadhesive multiparticulate system for oral drug delivery using ionic gelation technique. Microspheres of different mucoadhesive polymers including hydroxypropyl methylcellulose (HPMC) K15M and carbopol 971P were prepared. In this technique cross linking of sodium alginate with calcium chloride was done which retarded the release of drug from the mucoadhesive polymer. In the present work atenolol was used as model drug. Interaction studies performed using FT-IR spectroscopy revealed that there was no drug to polymer interactions. Multiparticulates so prepared were discrete, bulky, free flowing and showed an average encapsulation efficiency ranging from 23-74%. Particle size of the multiparticulates as determined by the scanning electron microscopic analysis (SEM) studies was found to be between 561-831 microm. The prepared formulations also exhibited a good mucoadhesive strength which was determined in in vitro conditions through falling film technique. The multiparticulate so prepared also exhibited a good swelling index which confirmed the strong mucoadhesive property of the formulation. Atenolol release from the multiparticulate system was regulated and extended until 12 h and exhibited a non-Fickian anomalous transport from the swellable microspheres, as evident from the release rate exponent values which varied between 0.569-0.622. The stability studies performed on the optimized batch at 40 degrees C/75% RH for 90 d indicated no significant change in the physicochemical properties. In vivo radioimaging studies in rabbits showed the residence of mucoadhesive microspheres for 6-8 h in upper part of gastrointestinal tract (GIT).

Floating-mucoadhesive beads of clarithromycin for the treatment of Helicobacter pylori infection.

An objective of the present study was to develop alginate/hydroxypropyl methylcellulose (HPMC) based floating-mucoadhesive beads of clarithromycin to provide prolonged contact time of antibiotic to treat stomach ulcer. Floating-mucoadhesive beads were prepared and characterized for in vitro performance followed by investigation of ex vivo study in albino-wistar rats. Beads were prepared by ionic gelation technique where calcium chloride used as gelating agent and incorporated liquid paraffin for floating of the beads. Prepared beads were evaluated extensively for particle size, drug entrapment; swelling and surface morphology by using scanning electron microscopy. X-ray radioimaging study in rabbits, in vitro mucoadhesion using rat stomach mucosal membrane and in vitro drug release studies were carried out. Ex vivo performance of alginate-HPMC beads were studied using albino rats in comparison to simple alginate-calcium beads. Alginate-HPMC beads may be suitable floating-muco-adhesive drug delivery system for delivering clarithromycin to treat stomach ulcers.

Rapidly disintegrating tablets containing taste masked metoclopramide hydrochloride prepared by extrusion-precipitation method.

The purpose of this study was to mask the intensely bitter taste of metoclopramide HCl and to formulate a rapid disintegrating tablet (RDT) of the taste-masked drug. Taste masking was done by complexing metoclopramide HCl with aminoalkyl methacrylate copolymer (Eudragit EPO) in different ratio by the extrusion-precipitation method. Drug-polymer complexes (DPCs) were tested for drug content, in vitro taste in simulated salivary fluid (SSF) of pH 6.8, taste evaluation in oral cavity and molecular property. The complex having drug-polymer ratio of 1 : 2 shows significant taste masking, confirmed by drug release in SSF and in-vivo taste evaluation; therefore, it was selected for further study. Taste evaluation of DPCs in human volunteers revealed considerable taste masking with the degree of bitterness below threshold value (0.5) within 10 s, whereas, metoclopramide HCl was rated intensely bitter with a score of +3 for 10 s. Tablets were evaluated for various parameters like tensile strength, wetting time, water absorption ratio, in-vitro disintegration time, and disintegration in oral cavity. The effect of diluents, lubricants and sweetening agent (Xylisorb) on the disintegration time was also evaluated. Tablets of batch F3 containing mannitol and microcrystalline cellulose in the ratio 1 : 1 and 8% w/w crosspovidone showed faster disintegration (within 20 s) than the marketed formulation (180 s). Good correlation between in vitro disintegration behavior and in the oral cavity was recognized. Tablets of batch F3 also revealed rapid drug release (t(90), 90 s) in SGF compared with marketed formulation (t(90), 600 s).

Formulation and evaluation of floating, pulsatile, multiparticulates using pH-dependent swellable polymers.

The objective of this study was to develop a floating, pulsatile, multiparticulate drug delivery system intended for chronopharmacotherapy of arthritis. The floating pulsatile drug delivery has the advantage that a drug can be released in the upper gastrointestinal tract after a definite time period of no drug release, i.e. lag time. Cross-linked beads were prepared using low methoxylated pectin (LM104AS), sodium alginate, and low methoxylated pectin (LM104AS) along with sodium alginate by acid- base reaction during ionotropic gelation. Beads were dried in oven at 50 degrees C for 4 h. Aceclofenac was used as a model drug for encapsulation. Drug loaded multiparticulates were subjected to various characterization and evaluation parameters like entrapment efficiency, surface topography, size analysis and in vitro release study. It was found that calcium pectinate beads show maximum drug entrapment. Hence, pectin containing formulation was further studied for buoyancy, DSC and radio imaging study. Drug release study was performed in acidic environment using pH 1.2 buffer solution for 6 h and then at 7.4 pH for 60 min. The total drug release ranges from 5-10% and 90-94% in acidic and basic media, respectively.

Formulation and evaluation of oral mucoadhesive multiparticulate system containing metoprolol tartarate: an in vitro-ex vivo characterization.

The aim of the present study was to prepare mucoadhesive multiparticulate system for oral drug delivery using ionic gelation technique. Microspheres composed of various mucoadhesive polymers including HPMC of various grades like K4M, K15M, K100M, E50LV, Carbopol of grades 971P, 974P and polycarbophil were prepared. In this technique cross linking of sodium alginate with calcium chloride was done which retarded the release of drug from the mucoadhesive polymer. In the present work Metoprolol tararate was used as a model drug. Interaction studies performed using FTIR spectroscopy revealed that there was no drug to polymer interactions. The preliminary mucoadhesive strength studies performed for various polymers using rotating cylindrical method showed that HPMC had greater mucoadhesive properties than carbopol and polycarbophil. Microspheres so prepared were discrete, bulky, free flowing and showed an average encapsulation efficiency ranging from 50-60%. Particle size of the microspheres, as determined by the optical microscopy was found to be between 400-650 microm. The prepared formulations also exhibited a good mucoadhesive strength which was determined in in vitro conditions through falling film technique and was compared with ex vivo studies. The microspheres so prepared also exhibited a good swelling index which confirmed the strong mucoadhesive property of the formulation. Metoprolol release from the multiparticulate system was regulated and extended until 12 hours and exhibited a non fickian drug release kinetics approaching to zero order, as evident from the release rate exponent values which varied between 0.57 to 0.73. The stability studies performed on the optimized batches at 40 degrees C /75% RH for 90 days indicated no significant change in the physicochemical properties.

Formulation and evaluation of in situ gelling system of dimenhydrinate for nasal administration.

Nasal drug delivery has a variety of advantages. Drugs can be rapidly absorbed through the nasal mucosa, giving rapid onset of action, and avoiding presystemic metabolism. In present study; the nasal mucoadhesive in situ gels of anti-emetic drug Dimenhydrinate were formulated using Gellan gum and Carbopol 934P. The in situ gels so prepared were characterized for gelation, viscosity, gel strength, mucoadhesion, drug content, drug diffusion, ex vivo permeation and histopathological studies. The optimized formulation passing from above tests was further subjected to accelerated stability study. It retained the good stability over the period of 90 days. From the overall performance this in situ gel seems to be an effective delivery system for the nasal route.

N,N,N­trimethyl chitosan modified flaxseed oil based mucoadhesive neuronanoemulsions for direct nose to brain drug delivery.

Here we fabricated flaxseed oil-based neuronanoemulsions (NNEs) which were further surface-modified with a mucoadhesive polymer, N,N,N­trimethyl chitosan (TMC) to form mucoadhesive neuronanoemulsions (mNNEs). The NNEs were loaded with high partitioning ropinirole-dextran sulfate (ROPI-DS) nanoplex and fabricated using hot high-pressure homogenization (HPH) technique. NNEs were optimized using Central Composite experimental design. TMC modified mNNE have not been prepared yet for direct nose to brain drug delivery. Here, an objective to provide controlled drug release with prolonged residence on the nasal mucosa for the treatment of Parkinson's disease (PD) is at prime consideration. Enhanced brain targeting through BBB bypass drug delivery, improved therapeutic efficacy through enhanced retention of mNNE formulation over nasal mucosal membrane, reduced dose and frequency of administration, and safety were further expected outcomes of this experiment. The mNNE formulation was subjected to 6 month stability assessment. The mNNE formulation was administered to the Swiss albino mice model via intranasal route and both, the plasma and brain pharmacokinetics were estimated. The in vivo studies performed on mice exhibited high brain targeting efficiency of mNNE formulation through nose to brain delivery via olfactory pathway. The prepared intranasal mNNEs could be on the clinics, if investigated more for behavioral and neurotoxicity studies.

Ropinirole-dextran sulfate nanoplex for nasal administration against Parkinson's disease: in silico molecular modeling and in vitro-ex vivo evaluation.

Dextran sulfate sodium (DS) was allowed to interact ionically with ropinirole hydrochloride (ROPI HCl, an anti-Parkinsonian agent) to synthesize self-assembled ROPI-DS nanoplex. The preliminary objective behind ROPI-DS complexation was to enhance the partitioning of ROPI HCl and thereby its encapsulation into nanocarriers and to improve the nasal membrane permeability. Molecular interactions were computed using in silico molecular modeling. Nanoplex were characterized for physicochemical and partitioning behavior. Optimized ROPI-DS nanoplex was further characterized by spectroscopic and thermal analysis, diffraction studies, morphological and histopathological analysis. In summary, ROPI-DS nanoplex represents a promising nanocarrier material for intranasal administration.

N,N,N-Trimethyl chitosan: An advanced polymer with myriad of opportunities in nanomedicine.

N,N,N-trimethyl chitosan (TMC), a quaternized hydrophilic derivative of chitosan (CHT), outperformed the well-known solubility issues raised by CHT. The excellent properties offered by TMC provide it a significant edge for nanoparticle (NP) formation over other nanocarrier materials. Recently, TMC NPs have been applied to various fields like pharmaceutical, biomedical, biomaterials, and biotechnological field. The aim of this review is, therefore, to bring the TMC into the limelight so as to appraise it as an attractive functional polymer for nanomedicine applications which is facing oversight, at present, by regulatory agencies and manufacturers. The versatility of surface-tailoring, the capability of further chemical modifications, and the feasibility of ligand-conjugations in TMC polymer will further assist the scientists for reaching new dimensions in the nano-assembly of novel structures based on TMC.

Xyloglucan: A functional biomacromolecule for drug delivery applications.

The near future of drug delivery system would lie in the search of a versatile and innocuous material, based mostly on the natural resources. The tamarind seed xyloglucan (XG) is a natural neutral hemicellulose and a hydrophilic polysaccharide consisting of a main chain of glucan backbone with xylose and galactose side chains. XG is endowed with idiosyncratic mucoadhesive and in situ gelling properties which rated XG as an attractive, functional polymer for numerous drug delivery applications. In milieu of this, the present review is designed to underline the plausible potential of XG or XG-based systems in drug delivery. The feasibility of surface-tailoring, the flexibility of chemical-modification, and the possibility as ligand-conjugations grant XG an extraordinary consideration in the scientific territory. The authors are hopeful that the versatility of XG would meet the expectations of regulatory authorities and the XG-based products will serve the therapeutic needs of the community in the future, if sufficiently investigated and promising outcomes are obtained in human subjects.

Controlled synthesis of N,N,N-trimethyl chitosan for modulated bioadhesion and nasal membrane permeability.

In an experiment to explore the bioadhesion, biocompatibility, and membrane permeation properties, the controlled synthesis of N,N,N-trimethyl chitosan (TMC) was carried out by two-step reductive methylation of chitosan (CHT). Methylation was confirmed by (1)H NMR (δ=3.1 ppm) and FTIR analysis (CH stretch at 1,485 cm(-1)). The TMC was further characterized by DSC, TGA, XRD, HR-TEM, SEM, and elemental analysis. Findings revealed improved solubility, enhanced viscosity, increased swelling index and higher molecular weight of TMC over CHT. Comparative evaluation validated increased bioadhesion potential, and improved ex vivo biocompatibility of TMC compared to CHT. Increased bioadhesion of TMC NPs over CHT NPs can be attributed to the strong electrostatic interactions between cationic amino groups with anionic sialic and sulfonic acid moieties contained in the mucin of the nasal mucus. Ex vivo biocompatibility studies suggested that the NP formulations of both biopolymers were biocompatible and could be applied safely on the nasal epithelium. Ex vivo permeation studies executed on excised cattle nasal mucosa illustrated improved permeability of TMC NPs over CHT NPs. In the author's opinion, two-step reductive methylation of CHT could be an attractive strategy to improve its solubility, bioadhesion, and permeation characteristics without affecting biocompatibility across the mucosal surfaces.

Brain-blood ratio: implications in brain drug delivery.

INTRODUCTION: The brain-blood ratio is an important model correlating the brain-targeting ability of neurotherapeutics with the CNS pharmacokinetics, which need to be presented before the scientific community for exploration of its scientific worth. The purpose of this article is to bring this key concept and its precise discussion to the attention of the researchers. AREAS COVERED: Three major points are discussed herein: First, the significance of brain-blood ratio with respect to investigational neurotherapeutics, and carrier systems and correlation of its research findings with the brain targeting efficiency. Second, the various factors influencing the brain-blood ratio. Third, the various strategies for enhancing the brain-blood ratio. In addition, the benchmark criteria for CNS-likeness of drug molecules and the correlation of brain-blood ratio with brain targeting ability of neurotherapeutics have been tabulated. EXPERT OPINION: The brain-blood ratio (also referred to as the brain-plasma ratio) represents one of the tools available today for estimation of CNS pharmacokinetics. It is preferred over other complicated techniques (in situ brain perfusion and microdialysis) due to its ease of use and practicality. We are optimistic that the brain-blood ratio offers an excellent way of evaluating brain-targeting efficiency of neurotherapeutics effectively. In our opinion, it is a very fundamental aspect of brain bioavailability and needs to be presented in a precise way.