Real-time in situ X-ray micro-computed tomography study of the effect of impurities on the crystallization of amorphous nifedipine.

Controlling the physical stability of noncrystalline active pharmaceutical ingredients remains a major challenge in the development of amorphous formulations such as amorphous solid-dispersion (ASD) formulations. To establish new evaluation and formulation strategies, the spatial distribution of the crystal phase in bulk amorphous nifedipine (NFD) was investigated as a model. The crystallization of amorphous NFD and the effect of a deliberately added impurity were investigated using powder X-ray diffraction (PXRD), differential scanning calorimetry and real-time in situ X-ray micro-computed tomography (X-ray CT). The stability data of amorphous samples, i.e., NFD and a mixture of NFD with an oxidative degradation product of NFD, impurity A (Imp A), at a weight ratio of 90:10, presented as percent amorphous remaining, suggests that Imp A accelerates the bulk crystal growth of NFD. Real-time in situ X-ray CT results showed surface-enhanced crystal growth and cavity formation in solid NFD samples. Moreover, the crystals were heterogeneous in density. These results suggest that Imp A affects the physical stability of the amorphous NFD. X-ray CT equipped with a heating unit can aid in-situ evaluation and assessment of physicochemical properties and physical stability of amorphous samples and formulations.

Exploring an experimental combination of analytical quality by design and green analytical chemistry approaches for development of HPTLC densitometric protocol for the analysis of barnidipine hydrochloride.

An experimental combination of analytical quality by design and green analytical chemistry approaches is introduced to develop an high-performance thin-layer chromatography (HPTLC) approach to quantify barnidipine hydrochloride in the pharmaceutical matrix. The analytical quality by design approach was introduced to green analytical chemistry to enhance protocol knowledge while ensuring efficiency and reducing environmental impacts, energy consumption and analyst visibility. This analytical approach was systematically addressed by exploring failure mode effect analysis, risk assessment and optimization design. Subsequently, a screening of primary variables was performed to select the aptest proportion of solvents in the mobile phase resulting from the principles of green analytical chemistry. Failure mode effect analysis and a risk assessment study were attempted to estimate the critical method parameters (CMPs). The influence of the CMPs on critical analytical attributes, i.e. retention factor and peak area, was assessed through a screening design. A response surface methodology was then executed for the critical analytical attributes as a concern of the determined CMPs, and the conditions for excellent resolution were determined using a desirability procedure. The established protocol was validated in compliance with the International Conference on Harmonization guideline Q2(R1) and showed excellent specificity and sensitivity.

Selective Laser Sintering of a Photosensitive Drug: Impact of Processing and Formulation Parameters on Degradation, Solid State, and Quality of 3D-Printed Dosage Forms.

This research study utilized a light-sensitive drug, nifedipine (NFD), to understand the impact of processing parameters and formulation composition on drug degradation, crystallinity, and quality attributes (dimensions, hardness, disintegration time) of selective laser sintering (SLS)-based three-dimensional (3D)-printed dosage forms. Visible lasers with a wavelength around 455 nm are one of the laser sources used for selective laser sintering (SLS) processes, and some drugs such as nifedipine tend to absorb radiation at varying intensities around this wavelength. This phenomenon may lead to chemical degradation and solid-state transformation, which was assessed for nifedipine in formulations with varying amounts of vinyl pyrrolidone-vinyl acetate copolymer (Kollidon VA 64) and potassium aluminum silicate-based pearlescent pigment (Candurin) processed under different SLS conditions in the presented work. After preliminary screening, Candurin, surface temperature (ST), and laser speed (LS) were identified as the significant independent variables. Further, using the identified independent variables, a 17-run, randomized, Box-Behnken design was developed to understand the correlation trends and quantify the impact on degradation (%), crystallinity, and quality attributes (dimensions, hardness, disintegration time) employing qualitative and quantitative analytical tools. The design of experiments (DoEs) and statistical analysis observed that LS and Candurin (wt %) had a strong negative correlation on drug degradation, hardness, and weight, whereas ST had a strong positive correlation with drug degradation, amorphous conversion, and hardness of the 3D-printed dosage form. From this study, it can be concluded that formulation and processing parameters have a critical impact on stability and performance; hence, these parameters should be evaluated and optimized before exposing light-sensitive drugs to the SLS processes.

Photoelectrochemically driven bioconversion and determination of nifedipine based on a double photoelectrode system.

In the present work, a double photoelectrode system has been constructed for photoelectrochemically driven enzymatic bioconversion and determination of nifedipine. In which, the TiO2 nanotube arrays in-situ assembled with g-C3N4 (TNA/g-C3N4) was used as a photoanode, and a cytochrome P450 3A4 (CYP3A4) enzyme was immobilized in the porous ITO/CuO films to fabricate an ITO/CuO/CYP3A4 photocathode. The constructed double photoelectrode system had a significant photocurrent response compared to the single ITO/CuO/CYP3A4 or TNA/g-C3N4 under visible light irradiation. Under optimal conditions, the photocurrent of the double photoelectrode system had a high catalytic activity toward substrate nifedipine with kcat of 5.62 s-1 and catalytic efficiency with kcat/kmapp of 0.94 µM-1 s-1, and the bioconversion yield of nifedipine reached 22.1%. Furthermore, the constructed double photoelectrode system could be used to determine the nifedipine concentration with a high sensitivity of 2.46 µA µM-1 and a low detection limit of 0.015 µM. Therefore, the proposed double photoelectrode system can be used well for study enzyme biocatalysis for target bioconversion, and also has a potential application for toxicity analysis.

Ultrasonication-assisted synthesis of sphere-like strontium cerate nanoparticles (SrCeO3 NPs) for the selective electrochemical detection of calcium channel antagonists nifedipine.

In this work, strontium cerate nanoparticles (SrCeO3 NPs, SC NPs) were developed through facile synthetic techniques (Ultrasound-Assisted (UA) and Stirring-Assisted (SA) synthesis) and utilized as an electrocatalyst for the selective and sensitive electrochemical detection of calcium channel blocker nifedipine (NDF). The as-prepared UASC NPs and SASC NPs were characterized using XRD, Raman, TEM, EDS, mapping, XPS and BET analysis which exposed the formation of SC NPs in the form of spherical in shape and well crystalline in nature. BET studies reveal that UASC NPs have maximum surface area than that of SASC NPs. Further, the use of the as-developed UASC NPs and SASC NPs as an electrocatalyst for the detection of NDF. Interestingly, the UASC NPs modified screen printed carbon electrode (UASC NPs/SPCE) exhibited an excellent electrocatalytic activity in terms of lower reduction potential and enhanced reduction peak current when compared to SASC NPs and unmodified SPCE. Moreover, as-prepared UASC NPs/SPCE displayed wide linear response range (LR, 0.02-174 µM), lower detection limit (LOD, 5 nM) and good sensitivity (1.31 µA µM-1 cm-2) than that of SASC NPs (LR = 0.02-157 µM, LOD = 6.4 nM, sensitivity - 1.27 µA µM-1cm-2). Furthermore, UASC NPs/SPCE showed an excellent selectivity even in the existence of potentially co-interfering compounds such as similar functional group containing drugs, pollutants, biological substances and some common cations/anions. The developed sensor was successfully employed for the determination of NDF in real lake water, commercial NDF tablet and urine samples with acceptable recovery.

Development of a chromatographic method with multi-criteria decision making design for simultaneous determination of nifedipine and atenolol in content uniformity testing.

A new robust and reliable high-performance liquid chromatography (HPLC) method with multi-criteria decision making (MCDM) approach was developed to allow simultaneous quantification of atenolol (ATN) and nifedipine (NFD) in content uniformity testing. Felodipine (FLD) was used as an internal standard (I.S.) in this study. A novel marriage between a new interactive response optimizer and a HPLC method was suggested for multiple response optimizations of target responses. An interactive response optimizer was used as a decision and prediction tool for the optimal settings of target responses, according to specified criteria, based on Derringer's desirability. Four independent variables were considered in this study: Acetonitrile%, buffer pH and concentration along with column temperature. Eight responses were optimized: retention times of ATN, NFD, and FLD, resolutions between ATN/NFD and NFD/FLD, and plate numbers for ATN, NFD, and FLD. Multiple regression analysis was applied in order to scan the influences of the most significant variables for the regression models. The experimental design was set to give minimum retention times, maximum resolution and plate numbers. The interactive response optimizer allowed prediction of optimum conditions according to these criteria with a good composite desirability value of 0.98156. The developed method was validated according to the International Conference on Harmonization (ICH) guidelines with the aid of the experimental design. The developed MCDM-HPLC method showed superior robustness and resolution in short analysis time allowing successful simultaneous content uniformity testing of ATN and NFD in marketed capsules. The current work presents an interactive response optimizer as an efficient platform to optimize, predict responses, and validate HPLC methodology with tolerable design space for assay in quality control laboratories.

CRISPR knockout rat cytochrome P450 3A1/2 model for advancing drug metabolism and pharmacokinetics research.

Cytochrome P450 (CYP) 3A accounts for nearly 30% of the total CYP enzymes in the human liver and participates in the metabolism of over 50% of clinical drugs. Moreover, CYP3A plays an important role in chemical metabolism, toxicity, and carcinogenicity. New animal models are needed to investigate CYP3A functions, especially for drug metabolism. In this report, Cyp3a1/2 double knockout (KO) rats were generated by CRISPR-Cas9 technology, and then were characterized for viability and physiological status. The Cyp3a1/2 double KO rats were viable and fertile, and had no obvious physiological abnormities. Compared with the wild-type (WT) rat, Cyp3a1/2 expression was completely absent in the liver of the KO rat. In vitro and in vivo metabolic studies of the CYP3A1/2 substrates indicated that CYP3A1/2 was functionally inactive in double KO rats. The Cyp3a1/2 double KO rat model was successfully generated and characterized. The Cyp3a1/2 KO rats are a novel rodent animal model that will be a powerful tool for the study of the physiological and pharmacological roles of CYP3A, especially in drug and chemical metabolism in vivo.

Promotion of cutaneous penetration of nifedipine for nanoemulsion

ABSTRACT This article reports the development and characterization of a nanoemulsion (NE) able to improve the cutaneous penetration of nifedipine. NE with nifedipine was development and characterized, presenting droplet size of 20 nm with low polydispersity index (IP<0.1), spherical shape without aggregation, pH compatible with typical skin levels and stability evaluated by seven months. In the permeation studies, a classical formulation based in an oil/water cream containing nifedipine was used for comparison with NE. Nanoemulsion promoted and improved the retention of nifedipine in the epidermis and dermis in relation to classical formulation. This promoting effect is related to the nanometric size of the droplets of the NE (20 nm), which give him a large superficial area, favoring the contact of the nanocarrier with the skin surface. The NE was efficient in promoting accumulation of nifedipine in the dermis, which is the site of vasodilation action. NE was not irritating according to the primary dermal irritation tests. NE is a promising release system to promote cutaneous penetration of nifedipine and can be used in the future in clinical trials to promote healing of lesions caused by peripheral vascular diseases.

Development of a HPLC-MS/MS method for the simultaneous determination of nifedipine and lidocaine in human plasma.

The method for simultaneous determination of nifedipine (NIF) and lidocaine (LID) in human plasma by one-step sample preparation has been developed for the first time. Due to the photosensitivity of nifedipine and its low plasma concentrations a precise and reliable method was required. The method involved liquid-liquid extraction (methyl tert-butyl ether, MTBE), and 10µL of the resulting sample was analyzed by HPLC-MS/MS. Chromatographic separation was achieved on an YMC-Triart C18 HPLC column (100×2.0mm; S-5µm 12nm). The mobile phase was methanol:water, 60:40 (v/v) and contained 0.15% acetic acid. The linearity of the method was established in the concentration ranges of 0.5-50ng/mL for NIF and 1.0-500ng/mL for LID. Photodestruction of NIF under ambient light was evaluated. The validated method was successfully applied to analyze human plasma samples after rectal application of the drug (1g) containing 2.0% LID and 0.3% NIF.

Analysis of nifedipine in human plasma and amniotic fluid by liquid chromatography-tandem mass spectrometry and its application to clinical pharmacokinetics in hypertensive pregnant women.

Nifedipine is a dihydropyridine calcium channel blocker used for the treatment of hypertension in pregnant women. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for analysis of nifedipine in human plasma and amniotic fluid. Separation of nifedipine and nitrendipine (IS) was performed using a LiChroCART(®) RP-Select B column and a mixture of water:acetonitrile:glacial acetic acid (30:70:0.5 v/v) as the mobile phase. Aliquots of 500µL of biological samples were extracted at pH 13 using dichloromethane:n-pentane (3:7 v/v). The validated method was applied to a study of the pharmacokinetics of nifedipine in human plasma and amniotic fluid samples collected up to 12h after administration of the last slow-release nifedipine (20mg/12h) dose to 12 hypertensive pregnant women. The estimated pharmacokinetic parameters of nifedipine showed a mean AUC(0-12) of 250.2ngh/mL, ClT/F of 89.2L/h, Vd/F of 600.0L and t1/2 5.1h. The mean amniotic fluid/plasma concentration ratio was 0.05. The methods proved to be highly sensitive by showing a lower quantification limit of 0.1ng/mL for both matrices. And this study reports for the first time the complete development and validation of the method to quantify nifedipine in amniotic fluid using LC-MS-MS.

Métodos indicativos de estabilidade para determinação do besilato de anlodipino, nifedipino e nimodipino considerados inibidores do canal de cálcio / Determination of calcium channel blockers amlodipine besylate, nifedipine and nimodipine by stability assays

A hipertensão é uma doença crônica não transmissível e mais freqüente na população sendo o principal fator de risco para complicações cardiovasculares, tais como acidente vascular cerebral e infarto agudo do miocárdio. Na presente pesquisa estão sendo estudados os fármacos utilizados no tratamento da hipertensão mais especificamente, os bloqueadores do canal de cálcio do grupo diidropiridínicos: besilato de anlodipino, nifedipino e nimodipino. O objetivo desse trabalho foi verificar a estabilidade intrínseca dos fármacos besilato de anlodipino, nifedipino e nimodipino, para isto foram utilizadas as seguintes técnicas: testes indicativos de estabilidade utilizando as técnicas de espectrofotometria na região do Ultravioleta/Visível (UV/VIS) e Cromatografia em fase Líquida de Alta Eficiência (CLAE). Termogravimetria/ Termogravimetria Derivada (TG/DTG), Calorimetria Exploratória Diferencial (DSC), Difração de Raios X (DRX), Espectroscopia de absorção na região do Infravermelho com Transformada de Fourier (FTIR) e Microscopia Eletrônica de Varredura (MEV). Para o fármaco besilato de anlodipino (AB) pelo método de degradação forçada, analisado por espectrofotometria no UV/VIS, as condições para a análise espectrofotométrica foram metanol e água a uma proporção de (5:45 v/v) e a segunda diluição com água. A leitura foi efetuada a 364,4nm. A linearidade foi estabelecida na faixa de 40,0-65,0 µg/mL e o coeficiente de correlação foi (r) 0,9992. O método cromatográfico, mostrou o diferente comportamento das substâncias nifedipino e nimodipino diante dos meios básicos, ácido, neutro e oxidativo. As condições para a substância nifedipino foram coluna LiChrospher®100 RP-18 (5µm) Merck® fase móvel constituída por metanol e água (45:55v/v), fluxo 1.0 mL/min, tempo de retenção 5,1min, detecção UV a 234nm e vazão de 1.0 mL/min. Foi obtida uma linearidade no intervalo de 5.0-55.0 µg/mL coeficiente de correlação (r) =0,9964. E para a substância nimodipino foram coluna LiChrospher®100 RP-18 (5µm) Merck® fase móvel constituída por acetonitrila e água (55:45v/v), fluxo 1.0mL/min, tempo de retenção 5,8 min, detecção UV a 235 nm e vazão de 1.0mL/min. Foi obtida uma linearidade no intervalo de 5.0-55.0 µg/mL coeficiente de correlação (r) =0,9964. Os resultados obtidos das curvas TG/DTG e DSC mostraram o perfil da decomposição térmica das substâncias estudadas pela Calorimetria Exploratória Diferencial. A análise dos resultados de DRX e DSC mostraram que não há evidências de polimorfismo nessas substâncias. No entanto nas análises de Espectroscopia de absorção na região do infravermelho com Transformada de Fourier (FTIR) não foram encontradas diferenças significativas na matéria-prima e no padrão de referência. As análises de MEV permitiram observar a cristalinidade das substâncias estudadas

Hypertension is the most frequent non-communicable chronic disease in the population being the main factor of risk for cardiovascular complications, such as stroke and acute myocardial infarction. In this work, active pharmaceutical ingredients used to treat hypertension were studied, more specifically the blockers calcium channel dihydropyridine group: amlodipine besylate, nifedipine and nimodipine. The aim of this study was to determine the intrinsic stability of amlodipine besylate, nifedipine and nimodipine. For this purpose the following stability test techniques were used: UV/VIS spectrophotometry and chromatography Net phase High Performance. Thermogravimetry/Derivative Thermogravimetry (TG/ DTG), Differential Scanning Calorimetry (DSC), X-Ray Diffraction (XRD), Fourier Transformed Infrared absorption (FTIR) and Scanning Electron Microscopy (MEV). For drug amlodipine besylate (AB) by forced degradation method analyzed by spectrophotometry UV/VIS spectrophotometric conditions for the analysis were methanol and water at a ratio (5:45v/v) and the second dilution with water. The reading was made at 364,4nm. The linearity was established in the range of 40.0 to 65.0 mg/mL and the correlation coefficient was (r) 0.9992. The chromatographic method showed different behavior of nifedipine and nimodipine substances on the basic means, acid, neutral and oxidative. The conditions for nifedipine were LiChrospher®100 RP-18 column (5µm) Merck® mobile phase consisting of methanol and water (45:55v/v), flow 1.0 mL/min, retention time 5,1min, UV detection at 234 nm and flow of 1.0 mL/min. Linearity was obtained within the range of 5.0-55.0 mg/mL correlation coefficient (r) = 0.9964. And for nimodipine the parameters were: LiChrospher®100 RP-18 column (5µm) Merck® mobile phase consisted of acetonitrile: water (55:45v/v), flow 1.0 mL/min, retention time 5,8min, UV detection at 235nm and flow of 1.0 mL/min. The linearity was obtained within the range of 5.0- 55.0 mg/mL correlation coefficient (r) = 0.9964. The results of TG/DTG and DSC curves presented the profile of the thermal decomposition of the substances studied by DSC. The results of XRD and DSC presented no evidence of polymorphism in these analyzes, however, according to analyzes of absorption spectroscopy in the infrared (FTIR) there were no significant differences in the raw materials and standard reference. SEM analyzes allowed to observe the crystallinity of the studied substances

Enhanced dissolution and oral bioavailability of nifedipine by spontaneous emulsifying powders: effect of solid carriers and dietary state.

The objective of this study was to prepare spontaneous emulsifying powder (SEP) for improving dissolution and enhancing oral bioavailability of a poorly water-soluble drug, nifedipine (NDP). In order to investigate the effects of solid carrier properties, such as surface area and pore size, and a concurrent food intake on absorption of NDP in rats, different SEP formulations were prepared by adsorbing liquid spontaneous emulsifying formulation (SEF), composing of polyoxyl 35 castor oil, caprylic/capric glyceride and diethylene glycol monoethyl ether at a ratio of 1:1:8, onto various solid carriers (i.e., silica (FS), porous calcium silicate (PCS) and porous silicon dioxide). The solid characterization by scanning electron microscopy, differential scanning calorimetry and powder X-ray diffraction revealed the absence of crystalline NDP in the formulations. SEP also demonstrated excellent spontaneous emulsification properties similar to SEF. The droplet size of emulsions formed after dilution was less than 200 nm. The solid carriers (particularly PCS) had significant and positive effect in drug dissolution; the mean dissolution time of SEP containing PCS was considerably improved. SEP also provided a good stability after storage in accelerated and long-term conditions for 6 months. The bioavailability study resulted in enhanced values of C(max) and AUC for SEP formulations, when tested in both fasted and fed rats. Furthermore, comparing the AUC in fasted and fed rats, NDP powder exhibited a significant food effect. The difference in bioavailability of NDP in fed compared to fasted state can be avoided by using SEP.

Method development and validation study for quantitative determination of nifedipine and related substances by ultra-high-performance liquid chromatography.

A novel stability-indicating reversed phase ultra-high performance liquid chromatography (UPLC) coupled photodiode array gradient method was developed for determination of the nifedipine and related compounds. Furthermore, based on the chromatographic conditions and forced degradation studies performed through the development of the related substances method a UPLC isocratic method was validated for the determination of the assay of this active substance. An Acquity Shield RP18 (50 × 3.0 mm 1.7 µm) column was used for separation of nifedipine and its five potential impurities within 11 min, which is 5-fold less than the official method. A mobile phase consisting of 10 mm ammonium formate (pH 4.5) and methanol, delivered at a flow rate 0.5 mL/min, was employed to achieve a minimum resolution of 2.0 for all consecutive pairs of compounds. The precision value expressed as percentage relative standard deviation for method repeatability and reproducibility was <5.0%. The recoveries for all the related compounds were in the range of 99-105.0%. Linearity was found to be acceptable over the concentration range of 0.25-1.5 µg/mL for nifedipine and its impurities. The limit of quantification for nifedipine was 0.05 µg/mL, which is much less than the European Pharmacopoeia method.

Pharmacopoieal quality of non-expired and expired nifedipine formulations from Estonian and Russian Federation medicinal products market.

The pharmacopoeial quality of non-expired and expired nifedipine tablets of the same batches purchased from the Estonian and Russian Federation medicinal product markets was evaluated. The IR spectroscopy, HPLC analysis for quantitative content and purity of the active pharmaceutical ingredient (API), and dissolution test techniques were applied. In the experiments with non-expired nifedipine tablets, in all Estonian (n = 8, label claims 10, 20, and 40 mg) and Russian Federation (n = 4, label claim 10 mg) registered formulations the API was identified and quantified as nifedipine in amounts set by the European Pharmacopoeia and without exceeding the tolerance limits for the impurities. The dissolution rate was variable but all 10 and 20 mg non-expired nifedipine tablets released at least 80% of API in 12 h. The expiration of the nifedipine tablets led to somewhat increased dissolution rate while only traces of the nifedipine degradation products were discovered in the dissolution medium. In conclusion, our present study shows that with minor variations the Estonian and Russian Federation registered nifedipine tablets are comparable, the API preserves well beyond the expiration date but the expired nifedipine tablets may release the API faster than the non-expired tablets.

Analysis of single particle photodegradation using photothermal infrared microspectroscopy.

The increasing use of high throughput methods, coupled with the need to develop approaches to anticipate long term stability issues, has necessitated the introduction of testing approaches whereby extremely small samples may be rapidly analysed. A novel method is described whereby the UV light-induced degradation of single particles of a model drug, nifedipine, may be rapidly and simply monitored using photothermal infrared microspectroscopy (PTMS). The technique involves the contact attachment of individual particles to a heated probe tip composed of a modified Wollaston wire which enables temperature fluctuations to be measured. Application of a focused IR beam to excite the sample allows measurement and subsequent Fourier transformation of the resultant interferogram to produce an IR spectrum which is in good agreement with that obtained from conventional IR methods. By application of a UV source to the assembly for specified time periods, we demonstrate that it is possible to monitor the appearance of peaks associated with degradation products as a function of time. The technique is critically evaluated in terms of practical issues associated with volatilization, particle size effects and orientation to the light source as well as more general issues associated with the sensitivity, resolution and quantitative interpretation of data from the PTMS technique. Overall the method has been shown to be capable of rapid measurement of photo-instability on individual particles, with important implications for development of the approach as a rapid screening or high throughput technique, although there are practical and theoretical limitations to reliable quantitative analysis at the present time.

Solubility enhancement, physicochemical characterization and formulation of fast-dissolving tablet of nifedipine-betacyclodextrin complexes

The main objective of the study was to enhance the dissolution of nifedipine, a poorly water soluble drug by betacyclodextrin complexation and to study the effect of the preparation method on the in vitro dissolution profile. The stoichiometric ratio determined by phase solubility analysis for inclusion complexation of nifedipine with β-cyclodextrin was 1:1. Binary complex was prepared by different methods and was further characterized using XRD, DSC and FT-IR. A saturation solubility study was carried out to evaluate the increase in solubility of nifedipine. The optimized complex was formulated into fast-dissolving tablets by using the superdisintegrants Doshion P544, pregelatinized starch, crospovidone, sodium starch glycolate and croscarmellose sodium by direct compression. Tablets were evaluated for friability, hardness, weight variation, disintegration and in vitro dissolution. Tablets showed an enhanced dissolution rate compared to pure nifedipine.

Este estudo teve por objetivo principal incrementar a dissolução do nifedipino, fármaco pouco solúvel em água, por meio de sua complexação com β-ciclodextrina e estudar o efeito do método de preparação sobre o perfil de dissolução in vitro. A razão estequiométrica, determinada por ensaio de solubilidade de fase, para a complexação de nifedipino por inclusão em β-ciclodextrina foi 1:1. O complexo binário foi preparado por diferentes métodos, sendo caracterizado utilizando-se difratometria de raios X (XRD), calorimetria diferencial de varredura (DSC) e espectroscopia no infravermelho com transformada de Fourier (FT-IR). Realizou-se estudo de solubilidade de saturação para avaliar o incremento da solubilidade do nifedipino. O complexo otimizado foi formulado em comprimidos de dissolução rápida preparados por compressão direta, nos quais se utilizaram os superdesintegrantes Doshion P544, amido pré-gelatinizado, crospovidona, amidoglicolato de sódio e croscarmelose sódica. Os comprimidos, que foram avaliados quanto à friabilidade, dureza, variação de peso, desintegração e dissolução in vitro, apresentaram taxa de dissolução superior à do nifedipino pura.

An electrochemical microfluidic platform for human P450 drug metabolism profiling.

This paper is the first report of a P450-electrode in a microfluidic format. A 30 µL microfluidic cell was made in poly(methyl methacrylate) containing the inlet, outlet, and reaction chamber with two electrode strips, one of which contains the human cytochrome P450 3A4 covalently bound to gold via a 6-hexanethiol and 7-mercaptoheptanoic acid (1:1) self-assembled monolayer. The electrochemical response of the P450-electrode in the microfluidic cell was tested using four drugs that are known substrates of P450 3A4: quinidine, nifedipine, alosetron and ondansetron. Titration experiments allowed the electrochemical measurements of K(M) for the four drugs, with values of 2.9, 29.1, 113.4, and 114.1 mM, respectively. The K(M) values are found to be in good agreement and correctly ranked with respect to the published literature on human liver microsomes and baculosomes: [ondansetron ≈ alosetron > nifedipine > quinidine]. The results presented in this paper represent a step forward for a rapid evaluation of the interaction of P450 and drug, requiring small volumes of new chemical entities to be tested.

Facile and efficient aromatization of 1,4-dihydropyridines with M(NO3)2.XH2O, TNCB, TBAP and HMTAI and preparation of deuterium labeled dehydronifedipine from nifedipine-d3.

The easy and efficient aromatization of various 1,4-dihydropyridines was investigated using various metal nitrates, trinitratocerium(IV) bromate (TNCB), and tetrabutyl ammonium periodate (TBAP) as oxidant in acetic acid at 100 degrees C, as well as hexamethylenetetramine-iodine (HMTAI) reflux in methanol. The efficient conversion of nifedipine-d(3) to dehydronifedipine-d(3) as an internal standard can be used in the measurement of nifedipine concentration in a body.

Microbial degradation of pharmaceuticals in estuarine and coastal seawater.

Microbial degradation rates were measured for 19 pharmaceuticals in estuarine and coastal surface water samples. Antipyrine, carbamazepine, cotinine, sulfamethoxazole, and trimethoprim were the most refractory (half-lives, t(1/2)=35 to >100 days), making them excellent candidates for wastewater tracers. Nicotine, acetaminophen, and fluoxetine were labile across all treatments (t(1/2)=0.68-11 days). Caffeine, diltiazem, and nifedipine were also and relatively labile in all but one of the treatments (t(1/2)=3.5-13 days). Microbial degradation of caffeine was further confirmed by production (14)CO(2). The fastest decay of non-refractory compounds was always observed in more sewage-affected Jamaica Bay waters. Degradation rates for the majority of these pharmaceuticals are much slower than reported rates for small biomolecules, such as glucose and amino acids. Batch sorption experiments indicate that removal of these soluble pharmaceuticals from the water column to sediments is a relatively insignificant removal process in these receiving waters.

Nifedipine preparations on the Belgian market: a comparative study.

Nifedipine preparations formulated as immediate-release capsules and prolonged-release tablets were evaluated with different tests, including in vitro dissolution, assay and content uniformity, and determination of related compounds. The analytical methods were previously validated according to international guidelines. All examined products complied with the postulated requirements but the dissolution test for prolonged-release tablets showed that these products cannot be interchanged.