Physicochemical Properties Of Drug Research Articles

Drug-drug salts of Naftopidil with non-steroidal anti-inflammatory drugs for potential multi-drug therapy

Drug-drug cocrystals (DDCs) are a subclass of pharmaceutical cocrystals in which both the components of a cocrystal are active drugs. DDCs are the recent advancement based on the crystal engineering approach to overcome the problems associated with conventional combination therapy. They also allow the modulation of the physicochemical properties of parent drugs. Four new drug-drug salts of Naftopidil (NFPD), a BCS class IV anti-cancer drug, were prepared by liquid-assisted grinding and solvent evaporation technique, with Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) such as Aspirin (ASP), Tolfenamic acid (TFA), Mefenamic acid (MFA) and Niflumic acid (NIFA) as coformers. The solids obtained were characterized by Single Crystal X-Ray diffraction (SCXRD), Powder X-ray Diffraction (PXRD), Thermo Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). Furthermore, the solubility of NFPD in the solids was determined by the shake flask method. SCXRD analysis showed that O–H···N hydrogen bond interactions found in the pure NFPD crystal structure are replaced by the N+–H···O- and O–H···O hydrogen bond interactions in the drug-drug solids. Additionally, the transfer of a proton from the carboxylic group of NSAIDs to piperazine nitrogen of NFPD is observed in all the drug-drug crystal structures, which suggests the nature of the solids as salts. NFPD-ASP salt exhibited improved solubility (33.2 µg/ml), which is eight-fold higher than the pure NFPD solubility (4.3 µg/ml). NFPD-MFA (0.6 µg/ml), NFPD-TFA (0.17 µg/ml), and NFPD-NIFA (1.35 µg/ml) showed reduced solubility than the pure NFPD. We anticipate that the current research will provide an alternate strategy to overcome the solubility issue of NFPD and provide potential candidates for designing combination therapy to treat complications in Benign Prostatic Hypertrophy (BPH), which involves pain and inflammation.

Cocrystal: A Review on the Design and Preparation of Pharmaceutical Cocrystals

The majority of the active pharmaceutical components have issues with poor solubility, bioavailability, chemical stability, and moisture absorption. Pharmaceutical crystals are a reliable way to change the aforementioned physicochemical properties of drugs without changing their pharmacological behaviour. However, the success of these approaches depends on the physical and chemical properties of the molecules being developed. The development of drug products with superior physicochemical characteristics, such as melting point, tablet ability, solubility, stability, bioavailability, and permeability, while preserving the pharmacological properties of the active pharmaceutical ingredient is greatly facilitated by co-crystallization of drug substances. All the components of a cocrystal, which is a stoichiometric homogeneous multicomponent system connected by non-covalent interactions, are solid under ambient conditions.

A pharmaceutical cocrystal of apigenin with piperazine: Preparation, structural characterization, and dissolution performance

As a natural flavonoid, apigenin (APG) has garnered considerable attention for its broad pharmacological properties. Unfortunately, the extremely poor aqueous solubility greatly restricts its clinical efficacy. Cocrystallization has been taken as an important approach to modulate physicochemical properties of parent drug. In this paper, piperazine (PIP) has been selected to assembly with APG and APG–PIP cocrystal has been successfully fabricated and characterized by single crystal X-ray diffraction and various analytical methods. Single-crystal X-ray diffraction analysis indicates APG–PIP crystallizes in the P21/c space group of monoclinic system and comprises neutral APG and PIP with the ratio of 1:1. APG and PIP are linked via O–H···N/N–H···O hydrogen bonds with a resulting 2D fes network. The 2D networks are further extended via π···π stacking interactions to afford its 3D architecture. The APG illustrates highly enhanced solubility and dissolving rate in APG–PIP cocrystal comparing with parent APG. It is notable that APG–PIP presents different equilibrium concentrations of APG along with insoluble residue when different dosages of APG–PIP are introduced. We speculate that APG and PIP may not be released equally within APG–PIP in aqueous medium due to their neutral nature and huge difference in solubility, and the existence of PIP can facilitate the dissolving of APG. This speculation has been further confirmed by investigation of relationship between equilibrium concentrations of APG and dosage of APG–PIP as well as powder dissolution experiment. The equilibrium concentrations are 0.118, 0.382, 0.556, 0.767, and 0.904 mg/mL when 5, 10, 15, 20, and 25 mg APG–PIP was put into 5 mL H2O and reveals good linear relation. The “spring and parachute” phenomenon and final similar solubility with parent APG in powder dissolution profile can be ascribed to the synergetic effect of metastable supersaturation and decreased PIP concentration due to withdrawing-replenishing operation.

Structured solubility behaviour in fed simulated intestinal fluids

Intestinal drug solubility is a key parameter controlling absorption after the administration of a solid oral dosage form. The ability to measure fed state solubility in vitro is limited and multiple simulated intestinal fluid recipes have been developed but with no consensus which is optimal. This study has utilised nine bioequivalent simulated fed intestinal media recipes that cover over 90% of the compositional variability of sampled fed human intestinal fluid. The solubility of 24 drugs (Acidic; furosemide, ibuprofen, indomethacin, mefenamic acid, naproxen, phenytoin, piroxicam, valsartan, zafirlukast: Basic; aprepitant, atazanavir, bromocriptine, carvedilol, dipyridamole, posaconazole, tadalafil: Neutral; acyclovir, carbamazepine, felodipine, fenofibrate, griseofulvin, itraconazole, paracetamol, probucol) has been assessed to determine if structured solubility behaviour is present. The measured solubility behaviour can be split into four categories and is consistent with drug physicochemical properties and previous solubility studies. For acidic drugs (category 1) solubility is controlled by media pH and the lowest and highest pH media identify the lowest and highest solubility in 90% of cases. For weakly acidic, basic and neutral drugs (category 2) solubility is controlled by media pH and total amphiphile concentration (TAC), a consistent solubility pattern is evident with variation related to individual drug media component interactions. The lowest and highest pH × TAC media identify the lowest and highest solubility in 70% and 90% of cases respectively. Four drugs, which are non-ionised in the media systems (category 3), have been identified with a very narrow solubility range, indicating minimal impact of the simulated media on solubility. Three drugs exhibit solubility behaviour that is not consistent with the remainder (category 4). The results indicate that the use of two bioequivalent fed intestinal media from the original nine will identify in vitro the maximum and minimum solubility values for the majority of drugs and due to the media derivation this is probably applicable in vivo. When combined with a previous fasted study, this introduces interesting possibilities to measure a solubility range in vitro that can provide Quality by Design based decisions to rationalise drug and formulation development. Overall this indicates that the multi-dimensional media system is worthy of further investigation as in vitro tool to assess fed intestinal solubility.

Neural Network Models for Predicting Solubility and Metabolism Class of Drugs in the Biopharmaceutics Drug Disposition Classification System (BDDCS).

The biopharmaceutics drug disposition classification system (BDDCS) categorizes drugs into four classes on the basis of their solubility and metabolism. This framework allows for the study of the pharmacokinetics of transporters and enzymatic metabolization on biopharmaceuticals, as well as drug-drug interactions in the body. The objective of the present study was to develop computational models by neural network models and structural parameters and physicochemical properties to estimate the class of a drug in the BDDCS system. In this study, deep learning methods were utilized to explore the potential of artificial and convolutional neural networks (ANNs and CNNs) in predicting the BDDCS class of 721 substances. The structural parameters and physicochemical properties [Abraham solvation parameters, octanol-water partition (log P) and over the pH range 1-7.5 (log D), number of rotatable bonds, hydrogen bond acceptor numbers, as well as hydrogen bond donor count] are calculated with various software. These compounds were then split into a training set consisting of 602 molecules and a test set of 119 compounds to validate the models. The results of this study showed that neural network models using applied parameters of the drug, i.e., log D and Abraham solvation parameters, are able to predict the class of solubility and metabolism in the BDDCS system with good accuracy. Neural network models are well equipped to deal with the relations between the structural parameters and physicochemical properties of drugs and BDDCS classes. In addition, log D is a more suitable parameter compared with log P in predicting BDDCS.

Method and technology for drug repurposing based on changes in the physicochemical properties of dosage forms: experience of use in Russia

Controlled local hyperthermia and hypothermia are important factors in drug pharmacodynamics and pharmacokinetics because changing the temperature of drugs changes their physicochemical properties. In this regard, a controlled change in the temperature of the drug and/or the body part with which the drug interacts, relative to the level of human body temperature (hyperthermia or hypothermia) forms the basis of temperature pharmacology. To analyze the authors publications on the problem of methodology and technology for repurposing drugs based on changes in the physicochemical properties of dosage forms. A controlled change in the temperature of the drug and/or the part of the body with which the drug interacts; a change in acid (alkaline), osmotic activity, and the degree and quality of carbonation and/or oxygen-forming activity of medicinal solutions; and a change in the concentration of medicinal solution ingredients. On the basis of the used methods, the reprofiling of a number of drugs has been achieved. The author proposed reprofiling a 4% potassium chloride solution from the group of macroelements and microelements used to regulate acid-base balance with a resorptive effect (when administered intravenously to the whole body) into a group of vasoconstrictive drugs used to stop bleeding when applied to by a single irrigation of the bleeding surface. Cooling certain drugs and tissues at their interaction sites to 18C20C (via an ice pack or its substitute) inhibits metabolism and function, ensuring the conversion of many drugs into anti-ischemic drugs by reducing the need for tissues in oxygen. A targeted change in the physicochemical properties of known drugs combined with local hyperthermia allows them to be converted into expectorant, pyrolytic (astringent), hemolytic, thrombolytic (hemostatic), detergent, bleaching, cleaning, and other drugs, including antiseptic and cauterizing (necrotizing) drugs, very reliably, quickly, and inexpensively. Thus, 40 years ago, pharmacologists of the Russian Federation established the foundation for a novel method of drug development known today as repurposing of existing drugs. Today, it is evident that reprofiling may rapidly, inexpensively, and effectively give existing drugs a new purpose.

Quantum computations of non-steroidal anti-inflammatory drug molecules using Density Functional Theory

This paper addresses the electronic states and physicochemical properties of non-steroidal anti-inflammatory drug (NSAID) namely: Ibuprofen, Ketoprofen and Flufenamic acid. The molecular structures are quantum chemically treated and geometrically optimised using density functional theory (DFT). The computed geometrical parameters are compared with the experimental data. The Mulliken charge analysis is accomplished to understand the partial charge distribution in molecules. The molecular electrostatic potential analysis has been used to identify the appropriate location for an electrophilic and nucleophilic attacking site. Frontier molecular orbitals of the molecules are estimated and analysed. The HOMO-LUMO energy gaps have been used to estimate the different global reactivity descriptors of the selected molecules under investigation. The FT-IR spectra of molecules are recorded experimentally and are computed using DFT. The potential energy distribution (PED) assignment for the computed vibrations is carried out. The NBO analysis has been used to find the most intensive interaction in molecules based on the Fock-matrix sta3bilization energy. The NLO parameters have been computed for molecules to check their suitability towards NLO based applications. The UV-absorption spectra and ADME parameters for titled molecules are also simulated.

A quality by design framework for developing nanocrystal bioenabling formulations

The present study aims to outline a rational framework for the design and development of a 1.0% (w/v) hydrocortisone nanocrystal-based formulation, resorting to a simple, efficient, and scalable nanonization methodology, based on the high-pressure homogenization (HPH) technique. Accordingly, the innovative product was comprehensively optimized following a Quality by Design (QbD) approach. The thorough selection of formulation composition was driven by a dual purpose: improving skin permeation and stability. In the early stage of development, a Failure Mode, Effects and Criticality Analysis (FMECA) diagram was employed to identify the most impactful variables for the critical quality attributes (CQAs). In this sense, a rotatable, three-factor and five-level circumscribed central composite design (CCCD) was applied to investigate how squalene concentration (x1), soluplus concentration (x2) and HPH-time (x3) influence physicochemical properties, performance and physical stability of the formulation. A robust Design Space (DS) was defined, establishing the optimal settings for the critical variables, whose combination meets the requirements set in the quality target product profile (QTPP). Morphological analysis revealed the cuboidal shape of hydrocortisone nanocrystals. In what concerns colloidal properties, the most promising formulation disclosed a small particle size (Dx(50) = 311.8 ± 1.5 nm), along with narrow size distribution (span value = 1.91 ± 0.17). Zeta potential results (−2.19 ± 0.15 mV–−12.1 ± 0.4 mV) suggested a steric hindrance stabilization. FTIR spectra showed no chemical interactions between drug and formulation components. XRD diffractograms confirmed loss of crystallinity during the downsizing process. In vitro studies revealed an improvement on drug release rate (316 ± 21–516 ± 35 μg/cm2/√t), compared to the coarse suspension and commercial products, and a straight dependence on the stabilizer concentration and HPH time. The permeation flux across the skin (0.16 ± 0.02–1.2 ± 0.5 μg/cm2/h) appeared to be dependent on the drug physicochemical properties, in particular saturation solubility. Further characterization of the experimental formulations pointed out the role of the stabilizing component to prevent against physical instability phenomena. This organic solvent-free, and therefore “green” nanocrystal production technology offers great potential for pharmaceutical R&D and drug delivery by enabling the development of new forms of conventional drugs with optimal physicochemical properties and performance.

Crystallinity: A Complex Critical Quality Attribute of Amorphous Solid Dispersions.

Does the performance of an amorphous solid dispersion rely on having 100% amorphous content? What specifications are appropriate for crystalline content within an amorphous solid dispersion (ASD) drug product? In this Perspective, the origin and significance of crystallinity within amorphous solid dispersions will be considered. Crystallinity can be found within an ASD from one of two pathways: (1) incomplete amorphization, or (2) crystal creation (nucleation and crystal growth). While nucleation and crystal growth is the more commonly considered pathway, where crystals originate as a physical stability failure upon accelerated or prolonged storage, manufacturing-based origins of crystallinity are possible as well. Detecting trace levels of crystallinity is a significant analytical challenge, and orthogonal methods should be employed to develop a holistic assessment of sample properties. Probing the impact of crystallinity on release performance which may translate to meaningful clinical significance is inherently challenging, requiring optimization of dissolution test variables to address the complexity of ASD formulations, in terms of drug physicochemical properties (e.g., crystallization tendency), level of crystallinity, crystal reference material selection, and formulation characteristics. The complexity of risk presented by crystallinity to product performance will be illuminated through several case studies, highlighting that a one-size-fits-all approach cannot be used to set specification limits, as the risk of crystallinity can vary widely based on a multitude of factors. Risk assessment considerations surrounding drug physicochemical properties, formulation fundamentals, physical stability, dissolution, and crystal micromeritic properties will be discussed.

Effect of Cyclodextrin Complex Formation on Solubility Changes of Each Drug Due to Intermolecular Interactions between Acidic NSAIDs and Basic H2 Blockers.

One of the solubilization of poorly water-soluble drugs is the use of cyclodextrin (CD)-based inclusion complexes. On the other hand, few studies have investigated how CD functions on the solubility of drugs in the presence of multiple drugs that interact with each other. In this study, we used indomethacin (IND) and diclofenac (DIC) as acidic drugs, famotidine (FAM) and cimetidine (CIM) as basic drugs, and imidazole (IMZ), histidine (HIS), and arginine (ARG) as compounds structurally similar to basic drugs. We attempted to clarify the effect of β-CD on the solubility change of each drug in the presence of multiple drugs. IND and DIC formed a eutectic mixture in the presence of CIM, IMZ, and ARG, which greatly increased the intrinsic solubility of the drugs as well as their affinity for β-CD. Furthermore, the addition of high concentrations of β-CD to the DIC-FAM combination, which causes a decrease in solubility due to the interaction, improved the solubility of FAM, which was decreased in the presence of DIC. These results indicate that β-CD synergistically improves the solubility of drugs in drug-drug combinations, where the solubility is improved, whereas it effectively improves the dissolution rate of drugs in situations where the solubility is reduced by drug-drug interactions, such as FAM-DIC. This indicates that β-CD can be used to improve the physicochemical properties of drugs, even when they are administered in combination with drugs that interact with each other.

Study on Sulfamethoxazole-Piperazine Salt: A Mechanistic Insight into Simultaneous Improvement of Physicochemical Properties.

Multidrug salts represent more than one drug in a crystal lattice and thus could be used to deliver multiple drugs in a single dose. It showcases unique physicochemical properties in comparison to individual components, which could lead to improved efficacy and therapeutic synergism. This study presents the preparation and scale-up of sulfamethoxazole-piperazine salt, which has been thoroughly characterized by X-ray diffraction and thermal and spectroscopic analyses. A detailed mechanistic study investigates the impact of piperazine on the microenvironmental pH of the salt and its effect on the speciation profile, solubility, dissolution, and diffusion profile. Also, the improvement in the physicochemical properties of sulfamethoxazole due to the formation of salt was explored with lattice energy contributions. A greater ionization of sulfamethoxazole (due to pH changes contributed by piperazine) and lesser lattice energy of sulfamethoxazole-piperazine contributed to improved solubility, dissolution, and permeability. Moreover, the prepared salt addresses the stability issues of piperazine and exhibits good stability behavior under accelerated stability conditions. Due to the improvement of physicochemical properties, the sulfamethoxazole-piperazine salt demonstrates better pharmacokinetic parameters in comparison to sulfamethoxazole and provides a strong suggestion for the reduction of dose. The following study suggests that multidrug salts can concurrently enhance the physicochemical properties of drugs and present themselves as improved fixed-dose combinations.

Topological indices of molecular graphs of monkeypox drugs for QSPR analysis to predict physicochemical and ADMET properties

AbstractNumerous viral diseases endure to develop causing serious community health issues. One of such diseases is monkeypox, which is a viral zoonotic disease, found primarily in remote areas of Central and West African countries and is sporadically spread to other countries. The virus is transmitted to people through contact with infected animals and also from person to person through respiratory droplets, bodily fluids and skin lesions of infected individuals. There are no specific drugs to treat monkeypox virus. This virus is similar to smallpox and belongs to Orthopoxvirus family. The smallpox drugs are recommended to treat monkeypox disease. There are few antiviral drugs such as Cidofovir, Valacyclovir, Famciclovir, Acyclovir, Tecovirimat, and Brincidofovir used for treating monkeypox disease. A chemical molecule/structure can be considered as a graph where is the set of atoms and is the set of bonds between the atoms. A molecular descriptor of the molecular graph/structure is a numerical value of . The numerical values of molecular descriptors are used to quantitatively describe the physical and chemical information of the molecules. In this article, density based topological descriptors are computed for the molecular graphs of the above aforesaid drugs to treat monkeypox disease to carry out QSPR analysis through the quadratic regression to predict physicochemical and ADMET properties of monkeypox drugs.

Analytical and Clinical Validation of Assays for Volumetric Absorptive Microsampling (VAMS) of Drugs in Different Blood Matrices: A Literature Review.

Volumetric absorptive microsampling (VAMS) is the newest and most promising sample-collection technique for quantitatively analyzing drugs, especially for routine therapeutic drug monitoring (TDM) and pharmacokinetic studies. This technique uses an absorbent white tip to absorb a fixed volume of a sample (10-50 µL) within a few seconds (2-4 s), is more flexible, practical, and more straightforward to be applied in the field, and is probably more cost-effective than conventional venous sampling (CVS). After optimization and validation of an analytical method of a drug taken by VAMS, a clinical validation study is needed to show that the results by VAMS can substitute what is gained from CVS and to justify implementation in routine practice. This narrative review aimed to assess and present studies about optimization and analytical validation of assays for drugs taken by VAMS, considering their physicochemical drug properties, extraction conditions, validation results, and studies on clinical validation of VAMS compared to CVS. The review revealed that the bio-analysis of many drugs taken with the VAMS technique was optimized and validated. However, only a few clinical validation studies have been performed so far. All drugs that underwent a clinical validation study demonstrated good agreement between the two techniques (VAMS and CVS), but only by Bland-Altman analysis. Only for tacrolimus and mycophenolic acid were three measurements of agreement evaluated. Therefore, VAMS can be considered an alternative to CVS in routine practice, especially for tacrolimus and mycophenolic acid. Still, more extensive clinical validation studies need to be performed for other drugs.

Generating Potential Protein-Protein Interaction Inhibitor Molecules Based on Physicochemical Properties.

Protein-protein interactions (PPIs) are associated with various diseases; hence, they are important targets in drug discovery. However, the physicochemical empirical properties of PPI-targeted drugs are distinct from those of conventional small molecule oral pharmaceuticals, which adhere to the "rule of five (RO5)". Therefore, developing PPI-targeted drugs using conventional methods, such as molecular generation models, is challenging. In this study, we propose a molecular generation model based on deep reinforcement learning that is specialized for the production of PPI inhibitors. By introducing a scoring function that can represent the properties of PPI inhibitors, we successfully generated potential PPI inhibitor compounds. These newly constructed virtual compounds possess the desired properties for PPI inhibitors, and they show similarity to commercially available PPI libraries. The virtual compounds are freely available as a virtual library.

Development of Successful Physiologically-Based Pharmacokinetic (PBPK) Models

Physiologically-based pharmacokinetic (PBPK) modeling is a strong mathematical tool that integrates body physiology, drug physicochemical properties and pharmacokinetics to predict detailed drug profiles in different parts of the body. PBPK modeling can also be used to predict the effects of drug-drug interactions and diseases on drug pharmacokinetics. The use of special modules enables the extrapolation to different routes and also different species. PBPK steps for successful modeling will be discussed with examples using GastroPlus program. Such in-silico work can minimize the number and risks of in vivo clinical studies done on healthy subjects or on patients.

Enzyme-Triggered Intestine-Specific Targeting Adhesive Platform for Universal Oral Drug Delivery.

Patient adherence to chronic therapies can be suboptimal, leading to poor therapeutic outcomes. Dosage forms that enable reduction in dosing frequency stand to improve patient adherence. Variation in gastrointestinal transit time, inter-individual differences in gastrointestinal physiology and differences in physicochemical properties of drugs represent challenges to the development of such systems. To this end, a small intestine-targeted drug delivery system is developed, where prolonged gastrointestinal retention and sustained release are achieved through tissue adhesion of drug pills mediated by an essential intestinal enzyme catalase. Here proof-of-concept pharmacokinetics is demonstrated in the swine model for two drugs, hydrophilic amoxicillin and hydrophobic levodopa. It is anticipated that this system can be applicable for many drugs with a diverse of physicochemical characteristics.

Amorphization versus cocrystallization of celecoxib-tramadol hydrochloride using CO2-assisted nano-spray drying

The manipulation of both solid-state form and particle size is a versatile means by which physicochemical properties of pharmaceutical drugs may be improved/fine-tuned. The work presented herein describes the solid-state and particle size control of the most recently FDA-approved pharmaceutical cocrystal, composed of two APIs, Celecoxib-Tramadol hydrochloride (Seglentis®), using a continuous atomization technique, namely supercritical CO2-assisted nano-spray drying. Using a three-factorial design of experiments, both (co)amorphous and cocrystalline samples were generated, depending on processing conditions. Mean particle sizes ranged from 120 nm to 1160 nm, with solution flow rate showing the most significant effect due to its impact on atomized droplet sizes. While all (co)amorphous samples displayed a similar morphology, one set of conditions produced a (co)amorphous sample with a larger degree of intermolecular interactions, comparable with the hydrogen bonding network observed in the cocrystalline samples. Tabletting of four formulations was carried out to investigate the impact of particle size and solid-state on tabletability, compactability and compressibility. While all formulations performed adequately in these critical quality attributes, the formulations which contained cocrystalline particles underperformed regarding tabletability and compactability due to their irregular shape and larger size. However, due to the increased prevalence of intermolecular interactions, the cocrystalline and (co)amorphous samples with a larger degree of hydrogen bonding led to improved compressibility.

μPESI-MS/MS System for Screening and Quantitating Drugs in Plasma Samples.

Recently, we developed a novel microprobe electrospray ionization (μPESI) source and its coupled MS (μPESI-MS/MS) system. Here, we aimed to widely validate the μPESI-MS/MS method for quantitative analysis of drugs in plasma samples. Furthermore, the relationship between the quantitative performance of the μPESI-MS/MS method and the physicochemical properties of target drugs was analyzed. The μPESI-MS/MS methods for quantitative analysis of 5 representative drugs with a relatively wide range of molecular weight, pKa, and log P values were developed and validated. The results showed that the linearity, accuracy, and precision of these methods met the requirements of the European Medicines Agency (EMA) guidance. Then a total of 75 drugs from plasma samples were primarily detected using the μPESI-MS/MS methods, among which 48 drugs could be quantitatively measured. Logistics regression suggested that drugs with significantly greater log P and physiological charge had better quantitative performance using the μPESI-MS/MS method. Collectively, these results clearly demonstrate the practical application of the μPESI-MS/MS system as a rapid approach to the quantitative analysis of drugs in plasma samples.

Corneal Permeability and Uptake of Twenty-Five Drugs: Species Comparison and Quantitative Structure-Permeability Relationships.

The purpose of this study was to determine corneal permeability and uptake in rabbit, porcine, and bovine corneas for twenty-five drugs using an N-in-1 (cassette) approach and relate these parameters to drug physicochemical properties and tissue thickness through quantitative structure permeability relationships (QSPRs). A twenty-five-drug cassette containing β-blockers, NSAIDs, and corticosteroids in solution at a micro-dose was exposed to the epithelial side of rabbit, porcine, or bovine corneas mounted in a diffusion chamber, and the corneal drug permeability and tissue uptake were monitored using an LC-MS/MS method. Data obtained were used to construct and evaluate over 46,000 quantitative structure-permeability (QSPR) models using multiple linear regression, and the best-fit models were cross-validated by Y-randomization. Drug permeability was generally higher in rabbit cornea and comparable between bovine and porcine corneas. Permeability differences between species could be explained in part by differences in corneal thickness. Corneal uptake between species correlated with a slope close to 1, indicating generally similar drug uptake per unit weight of tissue. A high correlation was observed between bovine, porcine, and rabbit corneas for permeability and between bovine and porcine corneas for uptake (R2 ≥ 0.94). MLR models indicated that drug characteristics such as lipophilicity (LogD), heteroatom ratio (HR), nitrogen ratio (NR), hydrogen bond acceptors (HBA), rotatable bonds (RB), index of refraction (IR), and tissue thickness (TT) are of great influence on drug permeability and uptake. When data for all species along with thickness as a parameter was used in MLR, the best fit equation for permeability was Log (% transport/cm2·s) = 0.441 LogD - 8.29 IR + 8.357 NR - 0.279 HBA - 3.833 TT + 10.432 (R2 = 0.826), and the best-fit equation for uptake was Log (%/g) = 0.387 LogD + 4.442 HR + 0.105 RB - 0.303 HBA - 2.235 TT + 1.422 (R2 = 0.750). Thus, it is feasible to explain corneal drug delivery in three species using a single equation.

Prediction of Liquid-Liquid Phase Separation at the Dissolving Drug Salt Particle Surface.

During the dissolution of drug salt particles, liquid-liquid phase separation (LLPS) of a free form can occur within the unstirred water layer (UWL) of the particles (UWL-LLPS). Theoretically, UWL-LLPS occurs when the free form concentration at the salt particle surface (C0) exceeds the intrinsic LLPS concentration (S0LLPS) of the free form. In the present study, we attempted to predict UWL-LLPS based on the intrinsic physicochemical properties of drugs. Cyproheptadine hydrochloride (CPH-HCl), diclofenac sodium (DCF-Na), papaverine hydrochloride (PAP-HCl), and propafenone hydrochloride (PRF-HCl) were selected as model drug salts. The pH0 and C0 values at pHs 4.0-9.5 (citric acid, phosphoric acid, and boric acid, buffer capacity = ca. 4 mM/ΔpH) were calculated using the pKa, solubility product (Ksp), and diffusion coefficient (D) of a drug. S0LLPS was measured using the pH-shift method. UWL-LLPS was predicted to occur when C0 ≥ S0LLPS. The prediction result was then compared with UWL-LLPS observed at each pH by polarized light microscopy (PLM). The pH-LLPS concentration (SpHLLPS) profile of each drug was also measured. UWL-LLPS was approximately correctly predicted for CPH-HCl, DCF-Na, and PRF-HCl. However, UWL-LLPS was not observable when C0 was close to S0LLPS. Furthermore, UWL-LLPS was not accurately predicted in the case of PAP-HCl. The pH-SpHLLPS profile of PAP did not follow the Henderson-Hasselbalch equation, probably because of the formation of cationic aggregates. In conclusion, UWL-LLPS was approximately predictable for drug salts using their intrinsic physicochemical properties (Ksp, pKa, D, and S0LLPS), except for PAP-HCl.