Effect of Roux-En-Y Gastric Bypass in the Pharmacokinetics of (R)-Carvedilol and (S)-Carvedilol.

Roux-en-Y gastric bypass is one of the most common surgical treatments for obesity due to the effective long-term weight loss and remission of associated comorbidities. Carvedilol, a third-generation ß-blocker, is prescribed to treat cardiovascular diseases. This drug is a weak base with low and pH-dependent solubility and dissolution and high permeability. As the changes in the gastrointestinal tract anatomy and physiology after roux-en-Y gastric bypass can potentially affect drug pharmacokinetics, this study aimed to assess the effect of roux-en-Y gastric bypass on the pharmacokinetics of carvedilol enantiomers. Nonobese (n = 15, body mass index < 25 kg/m2 ), obese (n = 19, body mass index ≥ 30), and post-roux-en-Y gastric bypass subjects submitted to surgery for at least 6 months (n = 19) were investigated. All subjects were administered a single oral dose of 25-mg racemic carvedilol, and blood was sampled for up to 24 hours. Plasma concentrations of (R)- and (S)-carvedilol were determined by liquid chromatography-tandem mass spectrometry. The maximum plasma concentration (Cmax ) and the area under the plasma concentration-time curve (AUC) of (R)-carvedilol were 2- to 3-fold higher than (S)-carvedilol in all groups. Obese subjects have shown reduced Cmax of (R)- and (S)-carvedilol without changing the AUC. Post-roux-en-Y gastric bypass subjects presented a 3.5-fold reduction in the Cmax of the active (S)-carvedilol and a 1.9 reduction in the AUC from time 0 to infinity compared to nonobese subjects. The time to reach Cmax of (S)-carvedilol increased 2.5-fold in post-roux-en-Y gastric bypass subjects compared to obese or nonobese. Although the ß-blockade response was not assessed, the reduced exposure to carvedilol in subjects post-roux-en-Y gastric bypass may be clinically relevant and require dose adjustment.

Towards the advance of a novel iontophoretic patch for needle-free buccal anesthesia.

The aim of this work was to develop a mucoadhesive iontophoretic patch for anesthetic delivery in the buccal epithelium. The patch was comprised of three different layers, namely i) drug release (0.64 cm2); ii) mucoadhesive (1.13 cm2); and iii) backing (1.13 cm2). Prilocaine and lidocaine hydrochlorides were used as model drugs (1:1 ratio, 12.5 mg per unit). An anode electrode (0.5 cm2 spiral silver wire) was placed in between the drug release and mucoadhesive/backing layers to enable iontophoresis. Surface microscopy; mechanical and in vitro mucoadhesive properties; drug release kinetics and mechanism; and drug permeation through the porcine esophageal epithelium were assessed. Topographic analysis evidenced differences in the physical structures for the several layers. All layers presented suitable handling properties i.e., flexibility, elasticity and resistance. Both the release and mucoadhesive layers presented features of a soft and tough material, while the backing layer matched the characteristics of a hard and brittle material. A synergy between the drug release and mucoadhesive layers on the mucoadhesive force and work of adhesion of the tri-layered patch was observed. Passive drug release of both drugs fitted to First-order, Hixson-Crowell and Weibull kinetic models; and the release mechanism was attributed to anomalous transport. Iontophoresis remarkably enhanced the permeation of both drugs, but mainly prilocaine through the mucosa as evidenced by the permeability coefficient parameter (3.0-fold). The amount of these amino amide salts retained in the mucosa were also equally enhanced (4.7-fold), while the application of a tiny constant electric current (1 mA·cm-2·h-1) significantly decreased the lag time for lidocaine permeation by about 45%. In view of possible in vitro / in vivo correlations, the buccal iontophoretic patch displays a promising strategy for needle-free and patient-friendly local anesthesia in dentistry.

Characterization of Casearin X Metabolism by Rat and Human Liver Microsomes.

Casearin X (CAS X) is the major clerodane diterpene isolated from the leaves of Casearia sylvestris and has been extensively studied due to its powerful cytotoxic activity at low concentrations. Promising results for in vivo antitumor action have also been described when CAS X was administered intraperitoneally in mice. Conversely, loss of activity was observed when orally administered. Since the advancement of natural products as drug candidates requires satisfactory bioavailability for their pharmacological effect, this work aimed to characterize the CAS X metabolism by employing an in vitro microsomal model for the prediction of preclinical pharmacokinetic data. Rat and human liver microsomes were used to assess species differences. A high-performance liquid chromatography with diode-array detection (HPLC-DAD) method for the quantification of CAS X in microsomes was developed and validated according to European Medicines Agency guidelines. CAS X was demonstrated to be a substrate for carboxylesterases via hydrolysis reaction, with a Michaelis-Menten kinetic profile. The enzyme kinetic parameters were determined, and the intrinsic clearance was 1.7-fold higher in humans than in rats. The hepatic clearance was estimated by in vitro-in vivo extrapolation, resulting in more than 90% of the hepatic blood flow for both species. A qualitative study was also carried out for the metabolite identification by mass spectrometry and indicated the formation of the inactive metabolite CAS X dialdehyde. These findings demonstrate that CAS X is susceptible to first-pass metabolism and is a substrate for specific carboxylesterases expressed in liver, which may contribute to a reduction in antitumor activity when administered by the oral route.

Determination of topiramate by capillary electrophoresis with capacitively-coupled contactless conductivity detection: A powerful tool for therapeutic monitoring in epileptic patients.

Topiramate (TPM) is the main antiepileptic drug used for the control of partial and generalized seizures in both adults and children. In association with clinical observations, the analysis of plasmatic concentration of TPM is of utmost importance for the individual adjustment of the administered dose to the patient. In the present work, a bioanalytical method was developed and validated for TPM analysis in plasma samples by capillary electrophoresis with capacitively-coupled contactless conductivity detection (CE-C4 D). A simple background electrolyte composed of 15 mmol/L triethylamine, hydrodynamic injections (0.8 psi for 5 s) and a moderate separation voltage (20 kV) were used, rendering relatively short analysis times (<3 min). The sample pre-treatment was carried out by liquid-liquid extraction using methyl terc-butyl ether as solvent and 200 µL of plasma. The method was validated according to the official guidelines from the European Medicine Agency and showed linearity in plasmatic concentration range from 1 to 30 µg/mL, which covers the clinically-relevant interval. The lower limit of quantification of 1 µg/mL obtained also allows following patients with low dosage of the drug. The method was successfully applied to analysis of plasma samples and allowed the identification of 80% under-medicated patients in the analyzed patient pool.

Combining amino amide salts in mucoadhesive films enhances needle-free buccal anesthesia in adults.

Needle-phobia is usually a great concern in dentistry, and the replacement of painful injections by patient-friendly needle-free topical formulations would bring several advantages in dental practice worldwide. In this pursuit, the effects of combining prilocaine hydrochloride (PCL) and lidocaine hydrochloride (LCL) in different proportions in mucoadhesive films on their in vitro permeation and retention through porcine esophageal mucosa was studied. Complementarily, the permeation and retention of isolated LCL was investigated. The in vitro model used for evaluating buccal anesthetic penetration and retention in buccal epithelium was validated. In addition, the feasibility of a novel in vivo model to evaluate the painful sensation due to puncture "needle-shaped" gum jaw of adults at shallow and deep levels was demonstrated. The in vivo clinical survey revealed the efficiency of the films, which had onset of anesthesia at 5min, peak of anesthetic effect within 15 and 25min and anesthesia duration of 50min after being placed in maxillary sites. The in vitro drug flux, permeability coefficient and retention in the epithelium significantly correlated with in vivo onset, peak and extent of shallow and deep anesthetic effect. At shallow level, the permeation of LCL has shown to be closely related to the onset of anesthesia, while the penetration of PCL has a significant impact in the peak of anesthetic effect. Concerning the deep level, the penetration of PCL is required to attain the onset of anesthetic effect. The total amount of drug retained in the epithelium showed to modulate the extent of both shallow and deep anesthesia. Thus, the combination of LCL and PCL in mucoadhesive films may offer dentists and their patients a safe improvement for pain management during dental procedures.

Fluconazole Non-susceptible Cryptococcus neoformans, Relapsing/Refractory Cryptococcosis and Long-term Use of Liposomal Amphotericin B in an AIDS Patient.

The treatment of cryptococcosis is hampered by inefficacy or intolerance to the recommended antifungal agents. A patient diagnosed with AIDS had multiple relapses of cryptococcal infection, which became refractory to antifungal agents during the course of therapy. During the follow-up, the patient developed renal toxicity due to amphotericin B use and non-susceptibility of isolated Cryptococcus neoformans to fluconazole was detected. Thereafter, antifungal treatment was performed exclusively with liposomal amphotericin B, reaching a cumulative dose of 19,180 mg over 46 months. The final relapse of cryptococcosis occurred during the maintenance phase with liposomal formulation in a once-weekly dose. Measurement of the minimum serum concentrations of amphotericin B, determined sequentially before and after this relapse, suggested the importance of monitoring drug levels when the liposomal formulation is used for a long period.

Determination of Levetiracetam in Human Plasma by Dispersive Liquid-Liquid Microextraction Followed by Gas Chromatography-Mass Spectrometry.

Levetiracetam (LEV) is an antiepileptic drug that is clinically effective in generalized and partial epilepsy syndromes. The use of this drug has been increasing in clinical practice and intra- or -interindividual variability has been exhibited for special population. For this reason, bioanalytical methods are required for drug monitoring in biological matrices. So this work presents a dispersive liquid-liquid microextraction method followed by gas chromatography-mass spectrometry (DLLME-GC-MS) for LEV quantification in human plasma. However, due to the matrix complexity a previous purification step is required. Unlike other pretreatment techniques presented in the literature, for the first time, a procedure employing ultrafiltration tubes Amicon® (10 kDa porous size) without organic solvent consumption was developed. GC-MS analyses were carried out using a linear temperature program, capillary fused silica column, and helium as the carrier gas. DLLME optimized parameters were type and volume of extraction and dispersing solvents, salt addition, and vortex agitation time. Under chosen parameters (extraction solvent: chloroform, 130 µL; dispersing solvent: isopropyl alcohol, 400 µL; no salt addition and no vortex agitation time), the method was completely validated and all parameters were in agreement with the literature recommendations. LEV was quantified in patient's plasma sample using less than 550 µL of organic solvent.

In vitro enantioselective human liver microsomal metabolism and prediction of in vivo pharmacokinetic parameters of tetrabenazine by DLLME-CE.

A new capillary electrophoresis method for the enantioselective analysis of cis- and trans- dihydrotetrabenazine (diHTBZ) after in vitro metabolism by human liver microsomes (HLMs) was developed. The chiral electrophoretic separations were performed by using tris-phosphate buffer (pH 2.5) containing 1% (w/v) carboxymethyl-ß-CD as background electrolyte with an applied voltage of +15kV and capillary temperature kept at 15°C. Dispersive liquid-liquid microextraction was employed to extract the analytes from HLMs. Dichloromethane was used as extraction solvent (75µL) and acetone as disperser solvent (150µL). The method was validated according to official guidelines and showed to be linear over the concentration range of 0.29-19.57µmolL(-1) (r=0.9955) for each metabolite enantiomer. Within- and between-day precision and accuracy evaluated by relative standard deviation and relative error were lower than 15% for all enantiomers. The stability assay showed that the analytes kept stable under handling, storage and in metabolism conditions. After method validation, an enantioselective in vitro metabolism and in vivo pharmacokinetic prediction was carried out. This study showed a stereoselective metabolism and the observed kinetic profile indicated a substrate inhibition behavior. DiHTBZ enantiomers were catalyzed mainly by CYP2C19 and the predicted clearance suggests that liver metabolism is the main route for TBZ elimination which supports the literature data.

A three phase hollow fiber liquid-phase microextraction for quantification of lamotrigine in plasma of epileptic patients by capillary electrophoresis.

A three phase hollow fiber liquid-phase microextraction technique combined with capillary electrophoresis was developed to quantify lamotrigine (LTG) in plasma samples. The analyte was extracted from 4.0 mL of a basic donor phase (composed of 0.5 mL of plasma and 3.5 mL of sodium phosphate solution pH 9.0) through a supported liquid membrane composed of 1-octanol immobilized in the pores of the hollow fiber, and to an acidic acceptor phase (hydrochloric acid solution pH 4.0) placed in the lumen of the fiber. The extraction was carried out for 30 min at 500 rpm. The eletrophoretic analysis was carried out in 130 mmol/L MES buffer, pH 5.0 with a constant voltage of +15 kV and 20°C. Sample injections were performed for 10 s, at a pressure of 0.5 psi. The detection was performed at 214 nm for both LTG and the internal standard lidocaine. Under the optimized conditions, the method showed a limit of quantification of 1.0 µg/mL and was linear over the plasmatic concentration range of 1.0-20.0 µg/mL. Finally, the validated method was applied for the quantification of LTG in plasma samples of epileptic patients.

Evaluation of the Intestinal Absorption Mechanism of Casearin X in Caco-2 Cells with Modified Carboxylesterase Activity.

The clerodane diterpene casearin X (1), isolated from the leaves of Casearia sylvestris, is a potential new drug candidate due to its potent in vitro cytotoxic activity. In this work, the intestinal absorption mechanism of 1 was evaluated using Caco-2 cells with and without active carboxylesterases (CES). An LC-MS method was developed and validated for the quantification of 1. The estimation of permeability coefficients was possible only under CES-inhibited conditions in which 1 is able to cross the Caco-2 cell monolayer. The mechanism is probably by active transport, with no significant efflux, but with a high retention of the compound inside the cells. The enzymatic hydrolysis assay demonstrates the susceptibility of 1 to first-pass metabolism as substrate for specific CES expressed in human intestine.

Needle-free buccal anesthesia using iontophoresis and amino amide salts combined in a mucoadhesive formulation.

Iontophoresis is a strategy to increase the penetration of drugs through biological membranes; however, its use has been underexplored in mucosa. The aim of this work was to investigate the influence of iontophoresis in the mucosal penetration of prilocaine hydrochloride (PCL) and lidocaine hydrochloride (LCL), which are largely used in dentistry as local anesthetics, when combined in the same formulation. Semisolid hydrogels containing these drugs either alone or in combination were developed at two different pHs (7.0 and 5.8) and presented adequate mechanical and mucoadhesive properties for buccal administration. The distribution coefficients between the mucosa and the formulations (Dm/f) and the in vitro mucosa permeation and retention rates were evaluated for both PCL and LCL. At pH 7.0, the combination of the drugs decreased the Dm/f of PCL by approximately 3-fold but did not change the Dm/f of LCL; iontophoresis increased the permeation rate of PCL by 12-fold and did not significantly change LCL flux compared with the passive permeation rate of the combined drugs. Combining the drugs also resulted in an increase in both PCL (86-fold) and LCL (12-fold) accumulation in the mucosa after iontophoresis at pH 7.0 compared with iontophoresis of the isolated drugs. Therefore, applying iontophoresis to a semisolid formulation of this drug combination at pH 7.0 can serve as a needle-free strategy to speed the onset and prolong the duration of buccal anesthesia.

Quantitative determination of lercanidipine enantiomers in commercial formulations by capillary electrophoresis.

An enantioselective method based on capillary electrophoresis (CE) using cyclodextrin (CD) as chiral selector was developed and validated for determination of lercanidipine (LER) enantiomers, a drug calcium channel blocker which exerts antihypertensive effects of long duration, in a pharmaceutical formulation. Optimum separation of LER enantiomers was obtained on a 50 cm × 50 µm id capillary using a sodium acetate buffer solution 200 mmol/L pH 4.0 containing 10 mmol/L of 2,3,6-o-methyl-ß-cyclodextrin (TM-ß-CD) as background electrolyte. The capillary temperature and voltage were 15°C and 25 kV, respectively, hydrodynamic injection and detection at 237 nm. Linearity was obtained in the range 12.5-100 µg/mL for both enantiomers (r ≥ 0.995). The RSD (%) and relative errors (E, %) obtained in precision and accuracy studies (intraday and interday) were lower than 5%. After validation, the method was applied to quantify the enantiomers of LER in commercial tablets and the results were satisfactory in terms of accuracy and precision, both less than 5%. Therefore, this method was found to be appropriate for enantioselective quality control of LER enantiomers in pharmaceutical formulations.

A new and fast DLLME-CE method for the enantioselective analysis of zopiclone and its active metabolite after fungal biotransformation.

Zopiclone (ZO) is a chiral drug that undergoes extensive metabolism to N-desmethylzopiclone (N-Des-ZO) and zopiclone-N-oxide (N-Ox-ZO). Pharmacological studies have shown (S)-N-Des-ZO metabolite presents anxiolytic activity and a patent for this metabolite was requested for anxiety treatment and related disorders. In this context, biotransformation employing fungi may be a promising strategy to obtain N-Des-ZO. To perform the biotransformation study in this work, an enantioselective method based on capillary electrophoresis (CE) and dispersive liquid-liquid microextraction (DLLME) was developed. CE analyses were carried out in sodium phosphate buffer (pH 2.5; 50mmolL(-1)) containing 0.5% (w/v) carboxymethyl-ß-CD, at a constant voltage of +25kV. DLLME was conducted using 2mL of liquid culture medium pH 9.5. Chloroform (100µL) and methanol (300µL) were employed as extraction and disperser solvent, respectively. After CE and DLLME optimization, the analytical method was fully validated. The method was linear over a concentration range of 90-6000ngmL(-1) for each ZO enantiomer (r>0.999) and 50-1000ngmL(-1) for each N-Des-ZO enantiomer (r>0.998). Absolute recovery of 51 and 82% was achieved for N-Des-ZO and ZO, respectively. The accuracy and precision results agreed with the EMA (European Medicines Agency) guideline, and so did the stability study. Application of the developed method in a biotransformation study was conducted in order to investigate the ability of fungi, belonging to the genus Cunninghamella, in metabolizing ZO chiral drug. Fungi Cunninghamella elegans ATCC 10028B and Cunninghamella echinulata var elegans ATCC 8688A demonstrated to be able to enantioselectively biotransform ZO to its active metabolite, N-Des-ZO. Therefore, the proposed goals of this work, i.e. a fast DLLME-CE method and an outstanding strategy to obtain N-Des-ZO, were successfully attained.

Evaluation of dispersive liquid-liquid microextraction in the stereoselective determination of cetirizine following the fungal biotransformation of hydroxyzine and analysis by capillary electrophoresis.

We developed a capillary electrophoresis (CE) and dispersive liquid-liquid microextraction (DLLME) method to stereoselectively analyze hydroxyzine (HZ) and cetirizine (CTZ) in liquid culture media. The CE analyses were performed on an uncoated fused-silica capillary; 50mmolL(-1) sodium borate buffer (pH 9.0) containing 0.8% (w/v) S-ß-CD was used as the background electrolyte. The applied voltage and temperature were +6 kV and 15 °C, respectively, and the UV detector was set to 214 nm. Chloroform (300 µL) and ethanol (400 µL) were used as the extraction and disperser solvents, respectively, for the DLLME. Following the formation of a cloudy solution, the samples were subjected to vortex agitation at 2000 rpm for 30s and to centrifugation at 3000 rpm for 5 min. The recoveries ranged from 87.4 to 91.7%. The method was linear over a concentration range of 250-12,500 ng mL(-1) for each HZ enantiomer (r>0.998) and 125-6250 ng mL(-1) for each CTZ enantiomer (r>0.998). The limits of quantification were 125 and 250 ng mL(-1) for CTZ and HZ, respectively. Among the six fungi studied, three species were able to convert HZ to CTZ enantioselectively, particularly the fungus Cunninghamella elegans ATCC 10028B, which converted 19% of (S)-HZ to (S)-CTZ with 65% enantiomeric excess.

Monitoring of ractopamine concentration in the mixture of this feed additive with vitamin mineral complex and with swine feed by HPLC.

Ractopamine (RAC) analysis at all stages in the feed chain until its final mixing into swine feed is necessary to ensure the safety of all meat consumers and to decrease waste and the cost of supplementation of feed. Two suitable HPLC methods were developed and validated for RAC determination in vitamin mineral complex (VMC) and in swine feed. Both methods employed reverse-phase (C18 column at 40°C) and isocratic elution, but with some modifications to the methods. Validation parameters, such as selectivity, linearity, precision, trueness and robustness, were shown to be within the acceptable range. Therefore, the developed methods can be successfully applied for the monitoring of RAC concentrations in samples of VMC and swine feed ensuring economy to producers and security to consumers of swine meat.

Solid phase microextraction and LC-MS/MS for the determination of paliperidone after stereoselective fungal biotransformation of risperidone.

The present work describes for the first time the use of SPME coupled to LC-MS/MS employing the polar organic mode in a stereoselective fungal biotransformation study to investigate the fungi ability to biotransform the drug risperidone into its chiral and active metabolite 9-hydroxyrisperidone (9-RispOH). The chromatographic separation was performed on a Chiralcel OJ-H column using methanol:ethanol (50:50, v/v) plus 0.2% triethylamine as the mobile phase at a flow rate of 0.8 mL min(-1). The SPME process was performed using a C18 fiber, 30 min of extraction time and 5 min of desorption time in the mobile phase. The method was completely validated and all parameters were in agreement with the literature recommendations. The Cunninghamella echinulata fungus was able to biotransform risperidone into the active metabolite, (+)-9-RispOH, resulting in 100% of enantiomeric excess. The Cunninghamella elegans fungus was also able to stereoselectively biotransform risperidone into (+)- and (-)-9-RispOH enantiomers at different rates.

(-)-Hinokinin-loaded poly(D,-lactide-co-glycolide) microparticles for Chagas disease.

The (-)-hinokinin display high activity against Trypanosoma cruzi in vitro and in vivo. (-)-Hinokinin-loaded poly(D,L-lactide-co-glycolide) microparticles were prepared and characterized in order to protect (-)-hinokinin of biological interactions and promote its sustained release for treatment of Chagas disease. The microparticles contain (-)-hinokinin were prepared by the classical method of the emulsion/solvent evaporation. The scanning electron microscopy, light-scattering analyzer were used to study the morphology and particle size, respectively. The encapsulation efficiency was determined, drug release studies were kinetically evaluated, and the trypanocidal effect was evaluated in vivo. (-)-Hinokinin-loaded microparticles obtained showed a mean diameter of 0.862 microm with smooth surface and spherical shape. The encapsulation efficiency was 72.46 +/- 2.92% and developed system maintained drug release with Higuchi kinetics. The preparation method showed to be suitable, since the morphological characteristics, encapsulation efficiency, and in vitro release profile were satisfactory. In vivo assays showed significant reduction of mice parasitaemia after administration of (-)-hinokinin-loaded microparticles. Thus, the developed microparticles seem to be a promising system for sustained release of (-)-hinokinin for treatment of Chagas disease.

Development and validation of a simple method for routine analysis of ractopamine hydrochloride in raw material and feed additives by HPLC.

A simple method was optimized and validated for determination of ractopamine hydrochloride (RAC) in raw material and feed additives by HPLC for use in quality control in veterinary industries. The best-optimized conditions were a C8 column (250 x 4.6 mm id, 5.0 microm particle size) at room temperature with acetonitrile-100 mM sodium acetate buffer (pH 5.0; 75 + 25, v/v) mobile phase at a flow rate of 1.0 mL/min and UV detection at 275 nm. With these conditions, the retention time of RAC was around 5.2 min, and standard curves were linear in the concentration range of 160-240 microg/mL (correlation coefficient > or = 0.999). Validation parameters, such as selectivity, linearity, limit of detection (ranged from 1.60 to 2.05 microg/mL), limit of quantification (ranged from 4.26 to 6.84 microg/mL), precision (relative standard deviation < or = 1.87%), accuracy (ranged from 96.97 to 100.54%), and robustness, gave results within acceptable ranges. Therefore, the developed method can be successfully applied for the routine quality control analysis of raw material and feed additives.

Hypotensive effect of the nitrosyl ruthenium complex nitric oxide donor in renal hypertensive rats.

We have described a new compound (trans-[RuCl([15]aneN(4))NO](2+)), which in vitro releases NO by the action of a reducing agent such as catecholamines. We investigated the effect of this NO donor in lowering the mean arterial pressure (MAP) in severe and moderate renal hypertensive 2K-1C rats. MAP was measured before and after intravenous in bolus injection of the compound in conscious 2K-1C and normotensive (2K) rats. In the hypertensive rats (basal 196.70+/-8.70mmHg, n=5), the MAP was reduced in -34.25+/-13.50mmHg (P<0.05) 6h after administration of 10mmol/L/Kg of the compound in bolus. In normotensive rats the compound had no effect. We have also studied the effect of the injection of 0.1mmol/L/Kg in normotensive (basal 118.20+/-11.25mmHg, n=4), moderate (basal 160.90+/-2.30mmHg, n=6), and severe hypertensive rats (basal 202.46+/-16.74 mmHg, n=6). The compound at the dose of 0.1mmol/L/Kg did not have effect (P>0.05) on MAP of normotensive and moderate hypertensive rats. However, in the severe hypertensive rats (basal 202.46+/-16.70mmHg, n=6) there was a significant reduction on the MAP of -28.64+/-12.45mmHg. The NO donor reduced the MAP of all hypertensive rats in the dose of 10mmol/L/Kg and in the severe hypertensive rats at the dose of 0.1mmol/L/Kg. The compound was not cytotoxic to the rat aortic vascular smooth muscle cells in the concentration of 0.1mmol/L/Kg that produced the maximum relaxation.

Degradation and configurational changes of thioridazine 2-sulfoxide.

Thioridazine (THD) is a phenothiazine neuroleptic drug used for the treatment of psychiatric disorders. After oral administration THD is extensively biotransformed to thioridazine 2-sulfone (THD 2-SO(2)), thioridazine 5-sulfoxide (THD 5-SO) and thioridazine 2-sulfoxide (THD 2-SO). THD 2-SO and THD 5-SO have two chiral centres and therefore exist as two diastereoisomeric pairs. The degradation and epimerization of THD 2-SO in human plasma, buffer and methanolic solutions were studied using an enantioselective HPLC method. The samples were prepared by liquid-liquid extraction with diethyl ether and the chiral resolution of the enantiomers was carried out on a Chiralpak AD column using a mobile phase consisting of hexane:ethanol:2-propanol (90:7:3, v/v/v) containing 0.2% diethylamine. The method was validated and used to study the degradation and epimerization under different conditions of incubation. Our results showed that both enantiomers were stable at varying temperatures, pH and ionic strengths; however, solubility problems were observed, mainly at pH 8.5. The influence of light on stability was studied using methanolic solutions and degradation and epimerization of the THD 2-SO enantiomers were observed under UV light of 366 and 254nm, respectively.