Redefining Statin Dosage Post-Gastric Bypass: Insights from a Population Pharmacokinetics-Pharmacodynamics Link Approach.

Roux-en-Y gastric bypass (RYGB) involves creating a small stomach pouch, bypassing part of the small intestine, and rerouting the digestive tract. These alterations can potentially change the drug exposure and response. Our primary aim was to assess the impact of RYGB on the pharmacokinetics of simvastatin lactone (SV) and its active metabolite, simvastatin hydroxy acid (SVA). Ultimately, we aimed to optimize dosing for this understudied population by employing a population pharmacokinetic-pharmacodynamic link approach. The study comprised patients who had undergone RYGB surgery and individuals without a previous history of RYGB. All participants received a single oral dose of simvastatin. Plasma concentration data were analyzed with a nonlinear mixed-effect modeling approach. A parent-metabolite model with first-order absorption, 2-compartments for SV and 1-compartment for SVA, linear elimination, and enterohepatic circulation best described the data. The model was linked to the turnover pharmacodynamic model to describe the SVA inhibition on LDL-cholesterol production. Our simulations indicated that following RYGB surgery, the exposure to SV and SVA decreased by 40%. Consequently, for low-intensity statin patients, we recommend increasing the dose from 10 to 20 mg in post-RYGB patients to maintain a comparable response to that of non-operated subjects. Moderate-intensity statin patients should require increasing doses to 40 or 60 mg or the addition of a non-statin medication to achieve similar therapeutic outcomes. In conclusion, individuals post-RYGB exhibit diminished exposure to SV and may benefit from increasing the dose or adjunctive therapy with non-statin drugs to attain equivalent responses and mitigate potential adverse events.

Rerouting cardiovascular management following gastric bypass surgery: Dose optimization of carvedilol using population-based analysis.

AIMS: A population-based pharmacokinetic (PK) modeling approach (PopPK) was used to investigate the impact of Roux-en-Y gastric bypass (RYGB) on the PK of (R)- and (S)-carvedilol. We aimed to optimize carvedilol dosing for these patients utilizing a pharmacokinetic/pharmacodynamic (PK/PD) link model. METHODS: PopPK models were developed utilizing data from 52 subjects, including nonobese, obese, and post- RYGB patients who received rac- carvedilol orally. Covariate analysis included anthropometric and laboratory data, history of RYGB surgery, CYP2D6 and CYP3A4 in vivo activity, and relative intestinal abundance of major drug- metabolizing enzymes and transporters. A direct effect inhibitory Emax pharmacodynamic model was linked to the PK model of (S)- carvedilol to simulate the changes in exercise- induced heart rate. RESULTS: A 2-compartmental model with linear elimination and parallel first-order absorptions best described (S)-carvedilol PK. RYGB led to a twofold reduction in relative oral bioavailability compared to nonoperated subjects, along with delayed absorption of both enantiomers. The intestinal ABCC2 mRNA expression increases the time to reach the maximum plasma concentration. The reduced exposure (AUC) of (S)-carvedilol post-RYGB corresponded to a 33% decrease in the predicted area under the effect curve (AUEC) for the 24-hour ß-blocker response. Simulation results suggested that a 50-mg daily dose in post-RYGB patients achieved comparable AUC and AUEC to 25-mg dose in nonoperated subjects. CONCLUSION: Integrated PK/PD modeling indicated that standard dosage regimens for nonoperated subjects do not provide equivalent ß-blocking activity in RYGB patients. This study highlights the importance of personalized dosing strategies to attain desired therapeutic outcomes in this patient cohort.

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.

Chemometric optimization of salting-out assisted liquid-liquid extraction (SALLE) combined with LC-MS/MS for the analysis of carvedilol enantiomers in human plasma: Application to clinical pharmacokinetics.

Carvedilol is a commonly used antihypertensive whose oral absorption is limited by low solubility and significant first-pass metabolism. This work aimed to apply chemometrics for the optimization of a salting-out assisted liquid-liquid extraction (SALLE) combined with LC-MS/MS to analyze carvedilol enantiomers in plasma samples. Method development and validation were driven for application in pharmacokinetic studies. Parameters that influence the efficiency of SALLE were evaluated using a fractional factorial 24-1 design with 4 factors and a central composite design was used to evaluate the optimal extraction condition. Carvedilol enantiomers and the internal standard lidocaine were separated on an Astec® Chirobiotic® V column and a mixture of methanol:ethanol (90:10, v/v) with 0.02% diethylamine and 0.18% acetic acid as mobile phase. The positive ion mode on electrospray ionization was used to monitor the transitions of m/z 407 > 100 and 235 > 86 for carvedilol enantiomers and lidocaine, respectively. Acetonitrile and ammonium acetate solution were selected for sample preparation by SALLE. Surface graphs and the desirability test were used to define the optimized SALLE conditions which resulted in 93% recovery for both carvedilol enantiomers. The method was linear in the range of 0.5 to 100 ng/mL in plasma, with a lower limit of quantification of 0.5 ng/mL. Within-run and between-run precision (as the relative standard deviation) were all < 9.74% and accuracy (as relative error) did not exceed ± 10.30%. Residual effect and matrix effect were not observed. Carvedilol enantiomers were stable in plasma under the storage, preparation, and analysis conditions. The validated method was successfully applied to analyze carvedilol in plasma samples from patients previously submitted to a Roux-en-Y gastric bypass surgery treated with a single oral dose of 25 mg racemic-carvedilol. Higher plasma concentrations were observed for (R)-(+)-carvedilol when compared to (S)-(-)-carvedilol in two patients post-bariatric surgery.

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.

Dispersive liquid-liquid microextraction followed by green high-performance liquid chromatography for fluconazole determination in cerebrospinal fluid with the aid of chemometric tools.

A new method, simple and fast, for fluconazole (FLU) quantification in cerebrospinal fluid (CSF) samples using dispersive liquid-liquid microextraction (DLLME) and an eco-friendly mobile phase for HPLC-PDA was developed. The study of DLLME extraction condition covered the investigation of 12 combinations of extraction and disperser solvents followed by a fractional factorial design 2(7-3) to determine the influence of seven factors. After this stage, a central composite design was performed for three factors and a response surface was obtained. Aiming a compromise between a good recovery and a low organic solvent use it was established an extraction condition that consists of: 100 µL of chloroform, 100 µL of isopropyl alcohol, 200 µL of CSF, 200 µL of 50 mM phosphate buffer pH 7.3 and centrifugation for 5 min at 2200g and 4 °C. The HPLC analysis used an Ascentis® Express C18 column (100 mm × 4.6 mm, 2.7 µm) and an Ascentis® Express C18 guard column (3 mm × 4.6 mm, 2.7 µm), ethanol : water (15 : 85, v/v) as mobile phase, temperature of 45 °C, flow rate of 0.8 mL min-1 and phenacetin as internal standard. The method validation was performed according to European Agency's Guideline on Bioanalytical Validation Methodology and a linear range was obtained from 0.25 to 62.5 µg mL-1, with precision and accuracy within the recommended limits and recovery of 70% for FLU and 81% for phenacetin. Samples were stable in the studies performed and the method showed to be selective and with no carryover effect. The feasibility of the obtained method was confirmed by FLU determination at a CSF from a patient who was treated for neuromycosis. Therefore, here is described a method that meets many principles of green analytical chemistry and is useful for FLU therapeutic monitoring.

Synergy between surfactants and mucoadhesive polymers enhances the transbuccal permeation of local anesthetics from freeze-dried tablets.

We report on the advance of freeze-dried mucoadhesive orodispersible tablets (ODTs) loaded with prilocaine (PRC) and lidocaine (LDC) hydrochlorides, aiming to promote noninvasive buccal anesthesia. The influences of combining biocompatible polymers (pullulan and HPMC K100 LV) and a blend of surfactants (oleic acid, polysorbate 80 and propylene glycol) acting as chemical enhancers on the permeation of such drugs through the esophageal porcine epithelium and in vitro mucoadhesion were investigated. The ODTs were also characterized in terms of average weight, thickness, pH, drug content, in vitro release, thermal behavior and scanning electronic microscopy. A dissolution test showed fast drug release within one hour. The drug release data for all ODTs fitted first order. No significant influence of the type of mucoadhesive polymer on release was observed, while the drug release from ODTs decreased in the presence of chemical enhancers. For the ODT containing pullulan the drug release mechanism was anomalous transport, whist for all others it was case-II transport. A remarkable synergic effect between pullulan and chemical enhancers on the permeation flux, lag time, and permeability coefficient of both drugs, but mainly for PRC was observed. Pullulan together with permeation enhancers also substantially improved the work of mucoadhesion as compared to HPMC. In contrast, HPMC improved drug retention in the epithelium. The novel drug delivery platform achieved by combining a freeze-drying technique, mucoadhesive biocompatible polymers, and chemical permeation enhancers displayed an effective strategy for the transbuccal delivery of PRC and LDC that can be used to improve needle-free buccal anesthesia.

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.

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.

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.

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.

A simple and high-resolution HPLC-PDA method for simultaneous quantification of local anesthetics in in vitro buccal permeation enhancement studies.

A simple, isocratic, high-resolution and prompt HPLC-PDA method was developed and validated for the simultaneous quantification of prilocaine (PCL) and lidocaine (LCL) hydrochlorides in in vitro buccal iontophoresis-driven permeation studies. A reversed-phase C18 column (250 mm x 4.6 mm, 3µm, 110Å) was used for the chromatographic separation. The mobile phase contained acetonitrile: 0.1M sodium phosphate buffer, pH 7.0 (1:1, v/v), plus 0.05% (v/v) diethylamine. The isocratic flow rate was set at 1 mL/min and the detection wavelength was 203 nm. PCL and LCL eluted in 8.9 min and 13 min, respectively, and the system suitability parameters varied within an acceptable range. The method was selective, sensitive, precise, accurate and robust, producing a linear plot at the concentration range of 0.25 to 10 µg/mL. The application of this method was demonstrated by a significant enhancement of the permeation of PCL and LCL with the application of iontophoresis (1 mA/cm(2) per 1 h) through isolated porcine esophageal epithelium. The amount of the drug retained in the epithelium also increased with the application of an electrical current. Copyright © 2015 John Wiley & Sons, Ltd.

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.

Simultaneous determination of dipyrone metabolites in rat hypothalamus, cerebrospinal fluid and plasma samples by LC-MS/MS.

BACKGROUND: After oral administration dipyrone is rapidly hydrolyzed to 4-methylaminoantipyrine, which is absorbed and further metabolized to 4-formylaminoantipyrine and to 4-aminoantipyrine, which is acetylated by a polymorphic N-acetyltransferase system to 4-acetylaminoantipyrine. To evaluate the presence of dipyrone metabolites in different rat matrices after intraperitoneal administration, an analytical method was developed and validated. METHODOLOGY: The four main dipyrone metabolites were extracted from plasma, cerebrospinal fluid and hypothalamus samples by LLE prior to LC-MS/MS. RESULTS: Standard calibration graphs for all metabolites were linear (r > 0.99). The intra- and inter-day precision and accuracy values were both inferior to 15%. CONCLUSION: This method is simple and specific for studying dipyrone metabolites after intraperitoneal administration.