Degradation studies of quetiapine fumarate by liquid chromatography-diode array detection and tandem mass spectrometry methods.

Quetiapine fumarate (QUE) is an antipsychotic agent with a chemical structure that is susceptible to degradation; therefore, it is important to study its stability using appropriate analytical tools. Knowledge of the stability profile of a drug is important because chemical degradation of its active component often results in a loss of potency, affecting its efficacy and safety. This current work reports degradation studies of QUE as drug substance, under different stress conditions such as oxidation, hydrolysis, heat, humidity and photolysis, by a stability-indicating LC method. The chemical stability was evaluated using a simple HPLC/diode array detection method, with a core-shell C18 column under isocratic conditions, which allows the separation of all primary degradation products (DPs) in a short run time. QUE was mainly degraded under oxidative and hydrolytic conditions, with the formation of three and two DPs, respectively, which were identified by electrospray ionization-tandem mass spectrometry. The method was properly validated in terms of linearity, accuracy, precision, selectivity, robustness and quantitation limit. Commercial tablets containing 25 mg of QUE were quantified, with results obtained within the United States Pharmacopeia limits. The proposed method is suitable to assess the stability and perform routine analysis of QUE in pharmaceutical samples.

Determination of vortioxetine and its degradation product in bulk and tablets, by LC-DAD and MS/MS methods.

Vortioxetine hydrobromide (VOR), is a novel antidepressant used for the treatment of major depressive disorder. It has a chemical structure susceptible to degradation, therefore it is important to have suitable analytical methods to determine VOR in presence of its main degradation products (DP), because if the compound degrades, this could result in diminution of the therapeutic activity and safety. A simple HPLC method with photodiode array detection was developed and validated for determination of VOR in bulk and tablets, in the presence of its major DP. The drug was subjected to oxidative, hydrolytic, and photolytic stress conditions, showing significant degradation under oxidation with the formation of one DP, which was identified by ESI-MS/MS. A C18 column was used, with mobile phase consisting of acetonitrile and water with acetic acid and triethylamine in isocratic elution mode, with detection at 228 nm and 1.0 mL/min flow rate. The assay was linear in the 25-125 µg/mL concentration range. For precision, the RSD was <1.8%, the recovery was 100.0-101.6%, and the method demonstrated adequate selectivity. The method was successfully applied to quantify VOR in tablets. The results showed that the method is useful for routine analysis and for quality control purposes.

Optimization of rhein-loaded polymeric nanoparticles using a factorial design and evaluation of the cytotoxic and anti-inflammatory effects.

The aim of the work was to develop rhein loaded polymeric nanoparticles (R-PNPs). Nanoparticles were prepared by three methods, solvent emulsion-evaporation, double emulsion, and nanoprecipitation, by means of experimental design. Additionally, the effects of the best formulation on in vitro cytotoxicity and inflammation were evaluated. The solvent emulsion-evaporation method presented the highest encapsulation efficiency of the three techniques (38.41%), as well as had a mean diameter of 189.33 nm and a polydispersity index of less than 0.1. Despite efforts to optimize the encapsulation of rhein, the drug release from nanoparticles was close to 50% during the first 5 min, followed by a continuous release within 60 min. It was observed that macrophages exposed to the highest concentration of R-PNPs showed cell viability about 80% and at the lowest nanoparticle concentrations was closed to 100%. IL-1ß in cell culture supernatants was decreased in the presence of R-PNPs and TNFα concentrations were lower than the sensitivity of the assay. ROS production was only inhibited with R-PNPs at concentrations of 2.5 and 5 µM. In conclusion, the solvent emulsion-evaporation was the best method evaluated to obtain nanoparticles with the desired specifications. It was possible to assess R-PNPs with low cytotoxicity and anti-inflammatory properties showed by the inhibition of IL-1ß production and a low decrease in ROS production.

[Role of Mediterranean diet on the prevention of Alzheimer disease]. / Dieta mediterránea y sus efectos benéficos en la prevención de la enfermedad de Alzheimer.

Type 2 diabetes and obesity are possible risk factors for Alzheimer’s disease and these can be modified by physical activity and changes in dietary patterns, such as switching to a Mediterranean diet. This diet includes fruits, vegetables, olive oil, fish and moderate wine intake. These foods provide vitamins, polyphenols and unsaturated fatty acids. This diet should be able to reduce oxidative stress. The inflammatory response is also reduced by unsaturated fatty acids, resulting in a lower expression and a lower production of pro-inflammatory cytokines. The Cardiovascular protection is related to the actions of polyphenols and unsaturated fatty acids on the vascular endothelium. The Mediterranean diet also can improve cardiovascular risk factors such as dyslipidemia, hypertension and metabolic syndrome. These beneficial effects of the Mediterranean diet should have a role in Alzheimer’s disease prevention.

Morphological Effects Induced In Vitro by Propranolol on Human Erythrocytes.

Despite the extended use and well-documented information, there are insufficient reports concerning the effects of propranolol on the structure and functions of cell membranes, particularly those of human erythrocytes. Aimed to better understand the molecular mechanisms of its interactions with cell membranes, human erythrocyte and molecular models of the red cell membrane were utilized. The latter consisted of bilayers of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), representative of phospholipid classes located in the outer and inner monolayers of the human erythrocyte membrane, respectively. The capacity of propranolol to perturb the multibilayer structures of DMPC and DMPE was evaluated by X-ray diffraction. Moreover, we took advantage of the capability of differential scanning calorimetry to detect the changes in the thermotropic phase behavior of lipid bilayers resulting from propranolol interaction with DMPC and DMPE multilamellar vesicles. In an attempt to further elucidate their effects on cell membranes, the present work also examined their influence on the morphology of intact human erythrocytes by means of defocusing and scanning electron microscopy. Results indicated that propranolol induced morphological changes to human erythrocytes and interacted in a concentration-dependent manner with phospholipid bilayer.

Intramuscularly Administered PLGA Microparticles for Sustained Release of Rivastigmine: In Vitro, In Vivo and Histological Evaluation.

Rivastigmine is an acetylcholinesterase (AchE) and butyrylcholinesterase (BchE) inhibitor drug approved by the US Food and Drug Administration (FDA) for the treatment of mild to moderate dementia of Alzheimer's type. However, its first-pass metabolism and gastrointestinal side effects negatively affect the tolerability and efficacy of oral therapy. These adverse effects could be avoided with the use of a sustained -release formulation as an intramuscular (IM) administration system. The objective of this work was to develop polylactic co-glycolic acid (PLGA) microparticles for the sustained release of rivastigmine and to evaluate its stability during storage, tissue tolerance, in vitro release, and in vivo pharmacokinetics after its IM administration. The microparticles were made by the solvent evaporation emulsion method. A series of formulation parameters (the type of polymer used, the amount of polymer used, the initial amount of rivastigmine, and the volume of PVA 0.1% w/v) were studied to achieve an encapsulation efficiency (EE) and a rivastigmine load of 54.8 ± 0.9% and 3.3 ± 0.1%, respectively. The microparticles, whose size was 56.1 ± 2.8 µm, had a spherical shape and a smooth surface. FT-IR analysis showed that there is no chemical interaction between rivastigmine and the polymer. PLGA microparticles maintain rivastigmine retained and stable under normal (5 ± 3 °C) and accelerated storage (25 ± 2 °C and 60 ± 5 % RH) conditions for at least 6 months. The microparticles behaved as a sustained release system both in vitro and in vivo compared to non-encapsulated rivastigmine. The IM administration of the formulation in rats did not produce significant tissue damage. However, it is necessary to reproduce the experiments with multiple doses to rule out a negative effect in terms of tolerability in chronic treatment. To the best of our knowledge, this study is the only one that has obtained the sustained release of rivastigmine from PLGA microparticles after IM administration in an in vivo model.

Determination of the Chemical Stability of Dapagliflozin by LC/DAD and MS/MS Methods.

A simple and fast stability-indicating liquid chromatographic method with diode array detection (DAD) was developed and validated for the determination of dapagliflozin (DAPA) in bulk and tablets, in the presence of its major degradation products (DP). The drug was subjected to hydrolytic, oxidative, photolytic, thermal and humidity/thermal stress conditions, showing significant degradation under humidity/thermal with the formation of two DP, which were preliminarily identified by liquid chromatography with diode array detector coupled with electrospray ionization-tandem mass spectrometry (HPLC-DAD-ESI-MS/MS). Chromatographic separation of dapagliflozin and its DP was achieved with a core-shell RP-18 column, using acetonitrile and water as mobile phase in isocratic elution mode. The described method was linear over a range of 50-150 µg/mL. For precision, the relative standard deviation (RSD) was <1.3%, the recovery was 99.64-100.11%, and the assay demonstrated adequate selectivity. The degradation kinetics of dapagliflozin was evaluated corresponding to first-order under thermal and humidity/thermal stress conditions. Dapagliflozin was well resolved from its drug products showing the power of stability-indicating of the method. The results showed that the proposed method was found to be suitable for routine analysis, quantitative determination and the stability study of dapagliflozin in pharmaceutical samples.

Effects of phenylpropanolamine (PPA) on in vitro human erythrocyte membranes and molecular models.

Norephedrine, also called phenylpropanolamine (PPA), is a synthetic form of the ephedrine alkaloid. After reports of the occurrence of intracranial hemorrhage and other adverse effects, including several deaths, PPA is no longer sold in USA and Canada. Despite the extensive information about PPA toxicity, reports on its effects on cell membranes are scarce. With the aim to better understand the molecular mechanisms of the interaction of PPA with cell membranes, ranges of concentrations were incubated with intact human erythrocytes, isolated unsealed human erythrocyte membranes (IUM), and molecular models of cell membranes. The latter consisted in bilayers built-up of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), phospholipid classes present in the outer and inner monolayers of most plasmatic cell membranes, respectively. The capacity of PPA to perturb the bilayer structures of DMPC and DMPE was assessed by X-ray diffraction, DMPC large unilamellar vesicles (LUV) and IUM were studied by fluorescence spectroscopy, and intact human erythrocytes were observed by scanning electron microscopy (SEM). This study presents evidence that PPA affects human red cell membranes as follows: (a) in SEM studies on human erythrocytes it was observed that 0.5 mM PPA induced shape changes; (b) in IUM PPA induced a sharp decrease in the fluorescence anisotropy in the lipid bilayer acyl chains in a concentration range lower than 100 µM; (c) X-ray diffraction studies showed that PPA in the 0.1-0.5 mM range induced increasing structural perturbation to DMPC, but no effects on DMPE multibilayers were detected.

Carbamazepine Biosensor Development for Epilepsy Patient Screening.

The San Carlos population in Chile is an example of an underserved community due to lack of timely access to regular controls and laboratory results. One particular challenge is the adherence to treatment of Epilepsy patients. In this work, we present the design and proof-of-concept of a Point of Care Device (POCD) to measure carbamazepine levels in saliva to screen for correct dose prescription among epilepsy patients. We present the Screen Printed Electrode design and activating circuit and preliminary results to verify feasibility of the biosensor. Future steps include the fabrication of the device itself and validation with the target population.

Quantitative determination of fluoxetine in human serum by high performance thin layer chromatography.

A high performance thin layer chromatographic method was developed and validated for the quantification of fluoxetine in human serum. Fluoxetine was extracted by liquid-liquid extraction method with diethyl ether as extraction solvent. Imipramine was used as internal standard. The chromatographic separation was achieved on precoated silica gel F 254 high performance thin layer chromatographic plates using a mixture of toluene/acetic acid glacial (4:5 v/v) as mobile phase. 4-Dimethylamino-azobenzene-4-sulphonyl chloride was used as derivatization reagent. Densitometric detection was done at 272 nm. The method was linear between 12.5 and 87.5 ng/spot, corresponding to 0.05 and 0.35 ng/microL of fluoxetine in human serum after extraction process and applying 25 microL to the chromatographic plates. The method correlation coefficient was 0.999. The intra-assay and inter-assay precisions, expressed as the RSD, were in the range of 0.70-2.01% (n=3) and 0.81-3.90% (n=9), respectively. The LOD was 0.23 ng, and the LOQ was 0.70 ng. The method proved be accurate, with a recovery between 94.75 and 98.95%, with a RSD not higher than 3.61% and was selective for the active principle tested. This method was successfully applied to quantify fluoxetine in patient serum samples. In conclusion, the method is useful for quantitative determination of fluoxetine in human serum.

Instrumental planar chromatographic method for determination of carbamazepine in human serum.

An instrumental planar chromatographic (HPTLC) method for quantification of carbamazepine in human serum was developed using liquid-liquid extraction with dichloromethane, fluorescence activation with perchloric acid 60%/ethanol/water (1:1:1, v/v) and fluorescence detection. Planar chromatographic separation was performed on precoated silica gel F254 HPTLC plates using a mixture of ethyl acetate/toluene/methanol/acetic acid glacial (5:4:0.5:0.5, v/v) as mobile phase. Densitometric detection was done at 366 nm. The method was validated for linearity, precision and accuracy. Linear calibration curves in the range of 3 and 20 ng/microL showed correlation coefficient of 0.998. The intra-assay and inter-assay precision, expressed as the RSD, were in the range of 0.41-1.24% (n = 3) and 2.17-3.17% (n = 9), respectively. The LOD was 0.19 ng, and the LOQ was 0.57 ng. Accuracy, calculated as percentage recovery, was between 98.98 and 101.96%, with a RSD not higher than 1.52%. The method was selective for the active principle tested. In conclusion, the method is useful for quantitative determination of carbamazepine in human serum.

Stability-Indicating Liquid Chromatographic Methods with Photodiode Array Detection and Light Scattering Detection for Simultaneous Determination of Candesartan and Hydrochlorothiazide.

Development, validation and comparison of two stability-indicating LC methods, one with photodiode array detector (DAD) and the other with evaporative light scattering detector (ELSD), were performed for simultaneous determination of candesartan cilexetil (CANC) and hydrochlorothiazide (HCTZ), in pharmaceutical samples. A RP-18 column (125 mm × 4 mm, 5 µm) was used for separation of CANC, HCTZ and its major degradation products, using acetonitrile and phosphate buffer (pH 6.0) for DAD method and acetonitrile and water with acetic acid and triethylamine (pH 4.1) for ELSD method, as mobile phase in a gradient mode. The response with ELSD was fitted to a power function and the DAD response by a linear model over a range of 32-160 µg/mL for CANC and 25-125 µg/mL for HCTZ. The precision and accuracy of the methods were similar, with RSD below 3.0% and recovery between 98.1% and 103.9%. The drugs were subjected to stress conditions of hydrolysis, oxidation, photolysis, humidity and temperature. The degradation products were satisfactory separated from the main peaks and from each other. Both drugs mainly degrade by hydrolysis, showing the formation of one degradation product for HCTZ and two for CANC; its identification was conducted by LC/MS/MS. The methods were successfully applied to the analysis of CANC and HCTZ in combined commercial tablets. The performance of DAD and ELSD methods are comparable, therefore both methods are suitable for stability study and determination of CANC and HCTZ in pharmaceutical samples.

The antiepileptic drug carbamazepine affects sodium transport in toad epithelium.

The present work investigates the effects of the antiepileptic drug carbamazepine (CBZ) on sodium transport in the isolated skin of the toad Pleurodema thaul. A submaximal concentration of the drug (0.2 mM) applied to the outer surface of the epithelium increased the electrical parameters short-circuit current (Isc) and potential difference (PD) by over 28%, whereas only a higher concentration (1 mM) induced over a 45% decrease in these parameters when applied to the inner surface. The amiloride test showed that the outer surface stimulatory effect was accompanied by an increase and the inner surface inhibitory effect by a decrease in the sodium electromotive force (ENa). Exploration of these effects of CBZ on the outer surface showed that 0.2 mM increased net Na+ (22Na) influx by 20% and 0.6 mM CBZ decreased Na+ mucosa-serosa flux by 19%, a result in agreement with the finding that higher concentrations of CBZ applied to the inner surface not only decreased ENa but also sodium conductance (GNa).

Effects of the antiepileptic drug carbamazepine on human erythrocytes.

The structural effects of the antiepileptic drug carbamazepine (CBZ) on the human erythrocyte membrane and molecular models have been investigated in the present work. This report presents the following evidence that CBZ interacts with red cell membranes: (a) X-ray diffraction and fluorescence spectroscopy of phospholipid bilayers showed that CBZ perturbed a class of lipids found in the outer moiety of the erythrocyte membrane; (b) in isolated unsealed human erythrocytes (IUM) the drug induced a disordering effect on the polar head groups and acyl chains of the membrane lipid bilayer; (c) in scanning electron microscopy (SEM) studies on human erythrocytes the formation of echinocytes was observed, due to the preferential insertion of CBZ in the outer monolayer of the red cell membrane. The effects of the drug detected in the present work were observed at concentrations of the order of those currently appearing in serum when it is therapeutically administered. This is the first time that toxic effects of carbamazepine on the human erythrocyte membrane have been described.

Comparison of Stability-Indicating LC Methods Using Light Scattering and Photodiode Array Detection with Monolithic Column for Determination of Quinapril and Hydrochlorothiazide.

Rapid stability-indicating LC methods for simultaneous analysis of quinapril and hydrochlorothiazide were developed, validated and compared using evaporative light scattering detection (ELSD) and diode array detection (DAD). For the separation of quinapril, hydrochlorothiazide and its major degradation products, a monolithic column was used and the analytes were eluted within 7 min, applying gradient mobile phase in both methods. Quinapril was subjected to hydrolytic, oxidative, thermal, humidity and photolytic stress conditions. Degradation products were well resolved from main peaks and from each other, proving the stability-indicating power of the methods. The response with DAD was linear and the response with ELSD was fitted to a power function, for quinapril and hydrochlorothiazide concentrations of 20-160 and 12.5-100 µg mL(-1), respectively. DAD method achieved better precision than ELSD method, the LOQ of DAD was lower and the accuracy of the methods was similar. Quinapril degrade by hydrolysis and thermal stress, showing the formation of quinaprilat and quinapril diketopiperazine as degradants, which were identified by MS-MS. The methods were successfully applied to quantify quinapril and hydrochlorothiazide in commercial tablets. LC-DAD and LC-ELSD methods are suitable to assess the stability and routine analysis of quinapril and hydrochlorothiazide in pharmaceutical industry.

[Pediculicide effect of a Eucaliptus globulus L formulation]. / Efecto pediculicida de una formulación en base a Eucaliptus globulus L.

INTRODUCTION: Pediculosis capitis is a public health problem with a high prevalence. The emergence of parasite resistance to conventional pediculicide is of great concern worldwide. OBJECTIVE: To develop alternatives pediculicide, effective and safe, based on the essential oil of Eucaliptus globulus. METHOD: Through bioassays active concentrations ranges of the essential oil were established, and proceeded to develop a standardized, stable, pharmaceutical form, evaluating its effects on our population. RESULTS: The results showed 100% effectiveness; short time of death, ovicidal action, activity on the adhesion of the egg, and low toxicity. DISCUSSION: In addition to great effect, the inability of the parasite to become resistant to the chemical composition of the essential oil makes this formulation an alternative to the problem of head lice solution.

The antiepileptic drug diphenylhydantoin affects the structure of the human erythrocyte membrane.

Phenytoin (diphenylhydantoin) is an antiepileptic agent effective against all types of partial and tonic-clonic seizures. Phenytoin limits the repetitive firing of action potentials evoked by a sustained depolarization of mouse spinal cord neurons maintained in vitro. This effect is mediated by a slowing of the rate of recovery of voltage activated Na+ channels from inactivation. For this reasons it was thought of interest to study the binding affinities of phenytoin with cell membranes and their perturbing effects upon membrane structures. The effects of phenytoin on the human erythrocyte membrane and molecular models have been investigated in the present work. This report presents the following evidence that phenytoin interacts with cell membranes: a) X-ray diffraction and fluorescence spectroscopy of phospholipid bilayers showed that phenytoin perturbed a class of lipids found in the outer moiety of cell membranes; b) in isolated unsealed human erythrocyte membranes (IUM) the drug induced a disordering effect on the polar head groups and acyl chains of the erythrocyte membrane lipid bilayer; c) in scanning electron microscopy (SEM) studies on human erythrocytes the formation of echinocytes was observed, due to the insertion of phenytoin in the outer monolayer of the red cell membrane. This is the first time that an effect of phenytoin on the red cell shape is described. However, the effects of the drug were observed at concentrations higher than those currently found in plasma when phenytoin is therapeutically administered.

Stability-indicating LC method for the simultaneous determination of lisinopril and hydrochlorothiazide.

A simple and rapid stability-indicating liquid chromatographic method was developed and validated for the simultaneous determination of lisinopril and hydrochlorotiazide (HCTZ) in drug substances and dosage forms in the presence of degradation products. Forced degradation studies were conducted on the pure drugs under hydrolytic, oxidative, thermal and photolytic conditions. A chromatographic separation of the two drugs and its degradation products was achieved with an RP-18 column, using methanol, acetonitrile and phosphate buffer (pH 7.1; 0.05 M) (15:15:70, v/v/v) as mobile phase at a flow rate of 0.8 mL min(-1) and UV detection at 210 nm. Lisinopril and HCTZ were well resolved from its degradation products showing the stability-indicating capability of the method. The described method was linear over a range of 40-200 µg mL(-1) for lisinopril and 25-175 µg mL(-1) for HCTZ. The assay was also selective, accurate and precise for lisinopril and HCTZ determination. This method represents an alternative to the United States Pharmacopeia (USP) method showing shorter retention time. The method was successfully applied for determination of lisinopril and HCTZ in combined commercial tablets. The results showed that the proposed method was found to be suitable for quantitative determination and the stability study of lisinopril and HCTZ in pharmaceutical samples.

Dieta mediterránea y sus efectos benéficos en la prevención de la enfermedad de Alzheimer / Role of Mediterranean diet on the prevention of Alzheimer disease

Type 2 diabetes and obesity are possible risk factors for Alzheimer’s disease and these can be modified by physical activity and changes in dietary patterns, such as switching to a Mediterranean diet. This diet includes fruits, vegetables, olive oil, fish and moderate wine intake. These foods provide vitamins, polyphenols and unsaturated fatty acids. This diet should be able to reduce oxidative stress. The inflammatory response is also reduced by unsaturated fatty acids, resulting in a lower expression and a lower production of pro-inflammatory cytokines. The Cardiovascular protection is related to the actions of polyphenols and unsaturated fatty acids on the vascular endothelium. The Mediterranean diet also can improve cardiovascular risk factors such as dyslipidemia, hypertension and metabolic syndrome. These beneficial effects of the Mediterranean diet should have a role in Alzheimer’s disease prevention.

Efecto pediculicida de una formulación en base a Eucaliptus globulus L / Pediculicide effect of a Eucaliptus globulus L formulation

Introduction: Pediculosis capitis is a public health problem with a high prevalence. The emergence of parasite resistance to conventional pediculicide is of great concern worldwide. Objective: To develop alternatives pediculicide, effective and safe, based on the essential oil of Eucaliptus globulus. Method: Through bioassays active concentrations ranges of the essential oil were established, and proceeded to develop a standardized, stable, pharmaceutical form, evaluating its effects on our population. Results: The results showed 100% effectiveness; short time of death, ovicidal action, activity on the adhesion of the egg, and low toxicity. Discussion: In addition to great effect, the inability of the parasite to become resistant to the chemical composition of the essential oil makes this formulation an alternative to the problem of head lice solution.

Introducción: La pediculosis capitis es un problema de salud pública con una alta prevalencia. La aparición de resistencia del parásito a los pediculicidas convencionales es de gran preocupación a nivel mundial. Objetivo: Desarrollar alternativas pediculicidas, efectivas y seguras, en base al aceite esencial de Eucaliptus globulus. Método: A través de bioensayos se establecieron rangos de concentraciones activas del aceite esencial, y se procedió al desarrollo de una forma farmacéutica, estandarizada, estable, evaluando sus efectos en nuestra población. Resultados: Los resultados mostraron 100% de efectividad; corto tiempo de muerte, acción ovicida, actividad sobre la adherencia del huevo, y baja toxicidad. Discusión: Además de la gran efectividad, la imposibilidad del parásito de adquirir resistencia a la composición química del aceite esencial hace de esta formulación una solución alternativa al problema de la pediculosis.