Urinary metabolic markers reflect on hepatic, not intestinal, CYP3A activity in healthy subjects.

Intestinal cytochrome P450 3A (CYP3A) plays an important role in oral drug metabolism, but only endogenous metabolic markers for measuring hepatic CYP3A activity were identified. Our study evaluated whether hepatic CYP3A markers reflected intestinal CYP3A activity. An open-label, three-period, six-treatment, one-sequence clinical trial was performed in 16 healthy Korean males. In the control phase, all subjects received a single dose of intravenous (IV) and oral midazolam (1 mg and 5 mg, respectively). Clarithromycin (500 mg) was administered twice daily for 4 days to inhibit hepatic and intestinal CYP3A, and 500 mL of grapefruit juice was given to inhibit intestinal CYP3A. Clarithromycin significantly inhibited total CYP3A activity, and the clearance of IV and apparent clearance of oral midazolam decreased by 0.15- and 0.32-fold, respectively. Grapefruit juice only reduced the apparent clearance of oral midazolam by 0.84-fold, which indicates a slight inhibition of intestinal CYP3A activity. Urinary markers, including 6ß-OH-cortisol/cortisol and 6ß-OH-cortisone/cortisone, were significantly decreased 0.5-fold after clarithromycin administration but not after grapefruit juice. The fold changes in 6ß-OH-cortisol/cortisol and 6ß-OH-cortisone/cortisone did not correlate to changes in intestinal availability but did correlate to hepatic availability. In conclusion, endogenous metabolic markers are only useful to measure hepatic, but not intestinal, CYP3A activity.

Effects of steady-state clarithromycin on the pharmacokinetics of zolpidem in healthy subjects.

Zolpidem is extensively metabolized by CYP3A4, CYP2C9 and CYP1A2. Previous studies demonstrated that pharmacokinetics of zolpidem was affected by CYP inhibitors, but not by short-term treatment of clarithromycin. The objective of this study was to investigate the effects of steady-state clarithromycin on the pharmacokinetics of zolpidem in healthy subjects. In the control phase, 33 subjects received a single dose of zolpidem (5 mg). One week later, in the clarithromycin phase, the subjects received clarithromycin (500 mg) twice daily for 5 days to reach steady state concentrations, followed by zolpidem (5 mg) and clarithromycin (500 mg). In each phase, plasma concentrations of zolpidem were evaluated up to 12 h after drug administration by using liquid chromatography-tandem mass spectrometry method. In the clarithromycin phase, mean total area under the curve of zolpidem (AUCinf) was 1.62-fold higher and the time to reach peak plasma concentration of zolpidem (tmax) was prolonged by 1.95-fold compared to the control phase. In addition, elimination half-life (t1/2) of zolpidem was 1.40-fold longer during co-administration with clarithromycin and its apparent oral clearance (CL/F) was 36.2% lower with clarithromycin administration. The experimental data demonstrate the significant pharmacokinetic interaction between zolpidem and clarithromycin at steady-state.

The modulation of drug-loading stability within lipid membranes via medium chain triglycerides incorporation.

The current research aimed to explore medium chain triglycerides (MCT) incorporation in liposomes to overcome stability challenges when drugs with high molecular weight and payload are loaded within lipid membranes. A model drug clarithromycin was loaded in lipid dispersions with various MCT/phospholipids ratios (RM/P = 0, 0.5, 1.75 and 7.5 w/w). TEM images demonstrated a liposome-to-emulsion structural transformation by MCT incorporation to cause increased particle size (104.3-167.7 nm) but decreased zeta potential (-63.6 to -44.4 mV) of lipid particles. MCT incorporation produced biphasic release in PBS and accelerated released in plasma. The tolerance of liposomes for thermal sterilization, high temperature test and freeze-thaw cycles were significantly improved by MCT incorporation. However, MCT incorporation produced adverse effects on colloidal stability in plasma and pharmacokinetics behavior in vivo to some extent. MCT stabilizing mechanism attributes to the modulation of drug loading area and stability improvement of lipid carriers. MCT incorporated liposomes achieved 2-3 fold cellular uptake level than traditional liposomes without significant cytotoxicity. These results indicated that MCT incorporation could be a promising strategy to apply in liposome production to achieve stable drug loading.

Clarithromycin laurate salt: physicochemical properties and pharmacokinetics after oral administration in humans.

OBJECTIVE: To prepare and characterize the physicochemical and pharmacokinetic properties of clarithromycin laurate (CLM-L), a fatty acid salt of clarithromycin (CLM). METHODS: CLM-L was prepared by a simple co-melting process. The formation of CLM-L was confirmed using FTIR, 1H NMR, and 13C NMR. Solubility, intrinsic dissolution rate (IDR), and partitioning properties of CLM-L were determined and compared to those of CLM. Bioavailability of CLM from CLM-L tablets was evaluated in healthy volunteers and compared to immediate release CLM tablets. RESULTS: CLM-L showed lower aqueous solubility, higher partitioning coefficient, and slower dissolution rate. Tablets of CLM-L also showed a significantly slower in vitro release in comparison to CLM tablets. Cmax, Tmax and AUC0→∞ of CLM-L tablets and immediate release CLM tablets did not show a significant difference. However, the AUC0→∞ for the CLM-L tablets tended to be higher than that of CLM tablets at all-time points. CONCLUSION: CLM-L was successfully prepared and its formation was confirmed. CLM-L was more hydrophobic than CLM. It exhibited a slight in vivo absorption enhancement in comparison to CLM. However, its pharmacokinetic behavior was comparable to that of CLM.

Assessment of potential interaction between simvastatin and clarithromycin in healthy adult male subjects.

Cardiac patients with weak immune system are susceptible to bacterial infections. Their prescriptions frequently contain simvastatin and clarithromycin together. The objective of present project was to assess the potential interaction between simvastatin and clarithromycin by evaluating the clarithromycin effects on the pharmacokinetics of simvastatin in healthy adult male subjects. The study design comprised of two phases, used at interval of one week. In first phase simvastatin 20 mg alone was administered to each volunteer. In second phase, co-administration of simvastatin 20 mg with clarithromycin 250 mg was made under similar specified conditions. Blood samples were collected at specified time intervals. Simvastatin plasma concentrations were analyzed through High Performance Liquid Chromatography with UV detector at 238 nm wavelength. Using one compartment open model, MW/PHARM version 3.02 software program was used by F. Rombut for pharmacokinetic parameters calculation. Clarithromycin co-treatment resulted in 2.3 fold increase in maximum plasma concentration Cmax (from 2.47±0.34 ng.mL-1 to 5.66±1.18 ng.mL-1; p<0.05) and 3.9 fold increase in area under time versus concentration curve from 0 to 10 hours AUC0-10 (from 15.10±3.73 ng.hr.mL-1 to 58.49±15.73 ng.hr.mL-1; p<0.05) of simvastatin. These results suggest that co-prescription of simvastatin and clarithromycin should be avoided to minimize the adverse events resulting from high simvastatin concentration, without sacrificing therapeutic worth of simvastatin.

Pharmacokinetic drug interaction and safety after coadministration of clarithromycin, amoxicillin, and ilaprazole: a randomised, open-label, one-way crossover, two parallel sequences study.

PURPOSE: Ilaprazole, the latest proton pump inhibitor, can be used with clarithromycin and amoxicillin as a triple therapy regimen for eradicating Helicobacter pylori. The aim of this study was to evaluate pharmacokinetic drug interactions and safety profiles after coadministration of clarithromycin, amoxicillin, and ilaprazole. METHODS: A randomised, open-label, one-way crossover, two parallel sequences study was conducted in 32 healthy subjects. In part 1, the subjects received a single dose of ilaprazole 10 mg in period 1 and clarithromycin 500 mg and amoxicillin 1000 mg twice daily for 6 days in period 2. In part 2, the subjects received clarithromycin 500 mg and amoxicillin 1000 mg once in period 1 and ilaprazole 10 mg twice daily for 6 days in period 2. In both sequences, the three drugs were coadministrated once on day 5 in period 2. Pharmacokinetic evaluations of ilaprazole (part 1), and clarithromycin and amoxicillin (part 2) were conducted. RESULTS: Twenty-eight subjects completed the study. For ilaprazole, the peak concentration (Cmax) slightly decreased from 479 (ilaprazole alone) to 446 ng/mL (triple therapy) [Geometric least square mean ratio (90% confidence interval), 0.93 (0.70-1.22)]. The area under the concentration-time curve from 0 h to the last measurable concentration (AUClast) slightly increased from 3301 to 3538 µg·h/mL [1.07 (0.85-1.35)]. For clarithromycin, the Cmax slightly decreased from 1.87 to 1.72 µg/mL [0.90 (0.70-1.15)], and AUClast slightly increased from 14.6 to 16.5 µg·h/mL [1.09 (0.87-1.37)]. For amoxicillin, the Cmax slightly decreased from 9.37 to 8.14 µg/mL [0.86 (0.74-1.01)], and AUClast slightly decreased from 27.9 to 26.7 µg·h/mL [0.98 (0.83-1.16)]. These changes in the PK parameters of each drug were not statistically significant. CONCLUSIONS: The coadministration of ilaprazole, clarithromycin, and amoxicillin was tolerable and did not cause a significant PK drug interaction. Thus, a triple therapy regimen comprising ilaprazole, clarithromycin, and amoxicillin may be an option for the eradication of H. pylori. Clinicaltrials.gov number: NCT02998437.

Assessment of inter-racial variability in CYP3A4 activity and inducibility among healthy adult males of Caucasian and South Asian ancestries.

PURPOSE: Cytochrome P450 (CYP) 3A4 is responsible for the metabolism of more than 30% of clinically used drugs. Inherent between subject variability in clearance of CYP3A4 substrates is substantial; by way of example, midazolam clearance varies by > 10-fold between individuals before considering the impact of extrinsic factors. Relatively little is known about inter-racial variability in the activity of this enzyme. METHODS: This study assessed inter-racial variability in midazolam exposure in a cohort (n = 30) of CYP3A genotyped, age-matched healthy males of Caucasian and South Asian ancestries. Midazolam exposure was assessed at baseline, following 7 days of rifampicin and following 3 days of clarithromycin. RESULTS: The geometric mean baseline midazolam area under the plasma concentration curve (AUC0-6) in Caucasians (1057 µg/L/min) was 27% greater than South Asians (768 µg/L/min). Similarly, the post-induction midazolam AUC0-6 in Caucasians (308 µg/L/min) was 50% greater than South Asians (154 µg/L/min), while the post-inhibition midazolam AUC0-6 in Caucasians (1834 µg/L/min) was 41% greater than South Asians (1079 µg/L/min). The difference in baseline AUC0-6 between Caucasians and South Asians was statistically significant (p ≤ 0.05), and a trend toward significance (p = 0.067) was observed for the post-induction AUC0-6 ratio, in both unadjusted and genotype adjusted analyses. CONCLUSIONS: Significantly higher midazolam clearance was observed in healthy age-matched males of South Asian compared to Caucasian ancestry that was not explained by differences in the frequency of CYP3A genotypes.

The application of high-resolution mass spectrometry-based data-mining tools in tandem to metabolite profiling of a triple drug combination in humans.

Patients are usually exposed to multiple drugs, and metabolite profiling of each drug in complex biological matrices is a big challenge. This study presented a new application of an improved high resolution mass spectrometry (HRMS)-based data-mining tools in tandem to fast and comprehensive metabolite identification of combination drugs in human. The model drug combination was metronidazole-pantoprazole-clarithromycin (MET-PAN-CLAR), which is widely used in clinic to treat ulcers caused by Helicobacter pylori. First, mass defect filter (MDF), as a targeted data processing tool, was able to recover all relevant metabolites of MET-PAN-CLAR in human plasma and urine from the full-scan MS dataset when appropriate MDF templates for each drug were defined. Second, the accurate mass-based background subtraction (BS), as an untargeted data-mining tool, worked effectively except for several trace metabolites, which were buried in the remaining background signals. Third, an integrated strategy, i.e., untargeted BS followed by improved MDF, was effective for metabolite identification of MET-PAN-CLAR. Most metabolites except for trace ones were found in the first step of BS-processed datasets, and the results led to the setup of appropriate metabolite MDF template for the subsequent MDF data processing. Trace metabolites were further recovered by MDF, which used both common MDF templates and the novel metabolite-based MDF templates. As a result, a total of 44 metabolites or related components were found for MET-PAN-CLAR in human plasma and urine using the integrated strategy. New metabolic pathways such as N-glucuronidation of PAN and dehydrogenation of CLAR were found. This study demonstrated that the combination of accurate mass-based multiple data-mining techniques in tandem, i.e., untargeted background subtraction followed by targeted mass defect filtering, can be a valuable tool for rapid metabolite profiling of combination drugs in vivo.

In vitro and in vivo Evaluation of Synergism between Anti-Tubercular Spectinamides and Non-Classical Tuberculosis Antibiotics.

Spectinamides are new semi-synthetic spectinomycin derivatives with potent anti-tubercular activity. The reported synergism of the precursor spectinomycin with other antibiotics prompted us to examine whether spectinamides sensitize M. tuberculosis to other antibiotics not traditionally used in the treatment of tuberculosis to potentially expand therapeutic options for MDR/XDR Tuberculosis. Whole cell synergy checkerboard screens were performed using the laboratory strain M. tuberculosis H37Rv, lead spectinamide 1599, and a broad panel of 27 antibiotics. In vitro, 1599 synergized with 11 drugs from 6 antibiotic classes. The observed synergy was tested against clinical isolates confirming synergy with Clarithromycin, Doxycycline and Clindamycin, combinations of which were taken forward for in vivo efficacy determination. Co-administration of 1599 and clarithromycin provided additional bacterial killing in a mouse model of acute tuberculosis infection, but not in a chronic infection model. Further studies indicated that mismatched drug exposure profiles likely permitted induction of phenotypic clarithromycin resistance and subsequent loss of synergism. These studies highlight the importance of validating in vitro synergism and the challenge of matching drug exposures to obtain a synergistic outcome in vivo. Results from this study indicate that a 1599 clarithromycin combination is potentially viable, providing the drug exposures can be carefully monitored.

Simultaneous determination of triple therapy for Helicobacter pylori in human plasma by reversed phase chromatography with online wavelength switching.

The infection of gastric mucosa by Helicobacter pylori (HP) is an essential cofactor in the aetiology of gastroduodenal ulcer and gastric carcinoma. Because of the bacterial resistance, combination therapy containing omeprazole (OME), tinidazole (TNZ) and clarithromycin (CLA) is commonly used for eradication of HP. However, the simultaneous determination of the triple therapy in human plasma was not reported. A simple, reproducible, and selective HPLC method was developed for the simultaneous determination of the triple therapy mixture used for management of HP infections in human plasma. An HPLC procedure based on a liquid-liquid extraction, enrichment of the analytes and subsequent reversed-phase chromatography with UV detection was used. To enable sensitive and selective detection, the method involved the use of online wavelength switching detection, with two different detection wavelengths; 280nm for detection of OME and TNZ and 210nm for detection of CLA. Separations were performed on C18 analytical column with acetonitrile-10mM phosphate buffer of pH=3.0 at flow rate of 1.0mLmin(-1). The linear ranges in human plasma were 0.05-10µgmL(-1) with correlation coefficients >0.9990. The detection limits in human plasma were 0.02-0.07µgmL(-1). Validation parameters were assessed in compliance with US-FDA guidelines. The method proved to be valuable for the therapeutic drug monitoring after oral administration of triple therapy tablets.

Involvement of intestinal permeability in the oral absorption of clarithromycin and telithromycin.

The involvement of intestinal permeability in the oral absorption of clarithromycin (CAM), a macrolide antibiotic, and telithromycin (TEL), a ketolide antibiotic, in the presence of efflux transporters was examined. In order independently to examine the intestinal and hepatic availability, CAM and TEL (10 mg/kg) were administered orally, intraportally and intravenously to rats. The intestinal and hepatic availability was calculated from the area under the plasma concentration-time curve (AUC) after administration of CAM and TEL via different routes. The intestinal availabilities of CAM and TEL were lower than their hepatic availabilities. The intestinal availability after oral administration of CAM and TEL increased by 1.3- and 1.6-fold, respectively, after concomitant oral administration of verapamil as a P-glycoprotein (P-gp) inhibitor. Further, an in vitro transport experiment was performed using Caco-2 cell monolayers as a model of intestinal epithelial cells. The apical-to-basolateral transport of CAM and TEL through the Caco-2 cell monolayers was lower than their basolateral-to-apical transport. Verapamil and bromosulfophthalein as a multidrug resistance-associated proteins (MRPs) inhibitor significantly increased the apical-to-basolateral transport of CAM and TEL. Thus, the results suggest that oral absorption of CAM and TEL is dependent on intestinal permeability that may be limited by P-gp and MRPs on the intestinal epithelial cells.

Simultaneous determination of rifampicin, clarithromycin and their metabolites in dried blood spots using LC-MS/MS.

INTRODUCTION: Rifampicin (RIF) and clarithromycin (CLR) are common drugs for the treatment of infections like Mycobacterium tuberculosis and Mycobacterium ulcerans. Treatment for these diseases are long-term and the individual pharmacokinetic variation, drug-drug interactions or non-adherence may introduce sub-therapeutic exposure or toxicity. The application of therapeutic drug monitoring (TDM) can be used to ensure efficacy and avoid toxicity. With the use of dried blood spot (DBS), TDM may be feasible in rural areas. During DBS method development, unexpected interactions or matrix effects may be encountered due to endogenous components in the blood. Another complication compared to plasma analysis is that RIF can form chelate complexes with ferric ions or can bind with hemes, which are potentially present in the extracts of dried blood spots. METHODS: The investigation focused on the interaction between RIF and the endogenous components of the DBS. The use of ethylenediaminetetraacetic acid (EDTA) and deferoxamine (DFX) as chelator agents to improve recoveries and matrix effects were investigated. A rapid analytical method was developed and validated to quantify RIF and CLR and their active metabolites desacetyl rifampicin (DAc-RIF) and 14-hydroxyclarythromcin (14OH-CLR) in DBS samples. A clinical application study was performed in tuberculosis patients by comparing DBS concentrations with plasma concentrations. RESULTS: The interaction between RIF and the DBS matrix was avoided using the complexing agents EDTA and DFX, which improved recoveries and matrix effects. The developed sample procedure resulted in a simple and fast method for the simultaneous quantification of RIF, CLR and their metabolites in DBS samples. High stability was observed as all four substances were stable at ambient temperature for 2 months. Deming regression analysis of the clinical application study showed no significant differences for RIF, DAc-RIF, CLR and 14OH-CLR between patient plasma and DBS analysis. The slopes of the correlation lines between DBS and plasma concentrations of RIF, DAc-RIF, CLR and 14OH-CLR were 0.90, 0.99, 0.80 and 1.09 respectively. High correlations between plasma and DBS concentrations were observed for RIF (R(2)=0.9076), CLR (R(2)=0.9752) and 14OH-CLR (R(2)=0.9421). Lower correlation was found for DAc-RIF (R(2) of 0.6856). CONCLUSION: The validated method is applicable for TDM of RIF, CLR and their active metabolites. The stability of the DBS at high temperatures can facilitate the TDM and pharmacokinetic studies of RIF and CLR even in resource limited areas. The role of EDTA and DFX as complexing agents in the extraction was well investigated and may provide a solution for potential applications to other DBS analytical methods.

Interaction of ambrisentan with clarithromycin and its modulation by polymorphic SLCO1B1.

PURPOSE: We assessed the effect of cytochrome P450 (CYP) 3A4 and the OATP1B1 inhibitor clarithromycin on ambrisentan steady-state kinetics and its relationship to the SLCO1B1 15 haplotype in healthy volunteers. METHODS: In this open-label, monocenter, one-sequence crossover clinical trial ten male healthy participants were stratified according to CYP2C19 and SLCO1B1 (encoding for OATP1B1) genotype into two groups: group 1 (n = 6), with CYP2C19 1/1 (extensive metabolizer, EM) and SLCO1B1 wild-type; group 2 (n = 4), with CYP2C19 EM and homozygous (n = 3) or heterozygous for SLCO1B1 15 (n = 1). The participants were administered a once-daily oral dose of 5 mg ambrisentan on study days 1 and days 3-14 and twice-daily oral doses of 500 mg clarithromycin on study days 11-14. To monitor CYP3A activity 3 mg midazolam was given orally 1 day before the first ambrisentan administration and on days 1, 10, and 14 of ambrisentan treatment. Ambrisentan plasma kinetics was assessed on days 1 (single dose), 10 (steady-state), and 14 (CYP3A4/OATP1B1 inhibition by clarithromycin). RESULTS: Consistent with the expectation that ambrisentan does not induce its own metabolism, ambrisentan exposure and peak concentration (Cmax) were similar after the first dose and at steady-state. Clarithromycin increased the area under the plasma concentration-time curve of ambrisentan by 41 % and Cmax by 27 % (n = 10, both p < 0.05). No contribution of SLCO1B1*15 to the extent of this interaction was observed. CONCLUSIONS: Clarithromycin increased ambrisentan exposure to a similar extent to ketoconazole, namely, clinically minor and likely irrelevant.

Method development, validation and bioequivalence of varenicline in human plasma by liquid chromatography tandem mass spectrometry.

A method based on liquid chromatography coupled to tandem mass spectrometry was developed for quantitative determination of varenicline in human plasma. Varenicline and the internal standard (25.0ng/mL of Clarithromycin) were extracted from human plasma by liquid-liquid extraction, using methyl tertiary butyl ether as the organic solvent. The chromatographic separation was achieved using C8 column with isocratic elution using a mixture of acetonitrile:0.001M ammonium acetate (adjusted to pH 4.0) (70:30%, v/v). The method was validated over the concentration range of 0.1-10.0ng/mL by investigating specificity, sensitivity, linearity, precision, accuracy, recovery, matrix effect and stability according to United State Food and Drug Administration guideline. The validated bioanalytical method was successfully applied to evaluate bioequivalence of two commercial products of 1mg varenicline single dose.

Clinical validation of the analysis of linezolid and clarithromycin in oral fluid of patients with multidrug-resistant tuberculosis.

Linezolid plays an increasingly important role in the treatment of multidrug-resistant tuberculosis (MDR-TB). However, patients should be carefully monitored due to time- and dose-dependent toxicity. Clarithromycin plays a more modest role. Therapeutic drug monitoring may contribute to assessment of treatment regimens, helping to reduce toxicity while maintaining adequate drug exposure. Oral fluid sampling could provide a welcome alternative in cases where conventional plasma sampling is not possible or desirable. The aim of this study was to clinically validate the analysis of linezolid and clarithromycin and its metabolite hydroxyclarithromycin in oral fluid of patients with multidrug-resistant tuberculosis. Serum and oral fluid samples were simultaneously obtained and analyzed by using validated methods, after extensive cross-validation between the two matrices. Passing-Bablok regressions and Bland-Altman analysis showed that oral fluid analysis of linezolid and clarithromycin appeared to be suitable for therapeutic drug monitoring in MDR-TB patients. No correction factor is needed for the interpretation of linezolid oral fluid concentrations with a ratio of the linezolid concentration in serum to that in oral fluid of 0.97 (95% confidence interval [CI], 0.92 to 1.02). However, the clarithromycin concentration serum/clarithromycin concentration in oral fluid ratio is 3.07 (95% CI, 2.45 to 3.69). Analysis of hydroxyclarithromycin in oral fluid was not possible in this study due to a nonlinear relationship between the concentration in serum and that in oral fluid. In conclusion, the analysis of linezolid (no correction factor) and clarithromycin (correction factor of 3) in oral fluid is applicable for therapeutic drug monitoring in cases of multidrug-resistant tuberculosis as an alternative to conventional serum sampling. Easy sampling using a noninvasive technique may facilitate therapeutic drug monitoring for specific patient categories.

Periodontal tissue and serum concentration of clarithromycin after systemic administration in patients affected by chronic periodontitis.

BACKGROUND: During the past two decades, dentists and microbiologists have relied on periodontal antibiotic therapy in the management of periodontitis. This association has accumulated and strengthened exponentially. Macrolides attain high therapeutic concentrations in infected tissue, so they are potentially a good choice for inhibiting invasive periodontal pathogens. Clarithromycin accumulates in phagocytes, monocytes, fibroblasts, polymorphonuclear cells, macrophages, and lymphocytes. These cells are more numerous at inflamed sites, so it is reasonable to expect clarithromycin levels to be higher in periodontally diseased sites. This study determines the distribution profile of clarithromycin in the gingiva of patients with periodontitis compared to serum after systemic administration of clarithromycin. METHODS: Twenty patients (14 males and six females, aged 25 to 45 years) with chronic periodontitis were enrolled in the study. Gingival index and plaque index were recorded at baseline and 3 days after administration of 500 mg clarithromycin, twice daily, for 3 days. Intravenous blood and biopsy of periodontal tissue samples were taken on the third day. These samples were analyzed for detection of clarithromycin concentration using high-performance liquid chromatography. RESULTS: Approximately 6 hours after the last dose of clarithromycin, mean clarithromycin concentrations in serum and periodontal tissue were 0.465 µg/mL and 2.61 µg/g, respectively, and the difference was statistically significant. CONCLUSIONS: Clarithromycin can attain higher levels in gingiva than serum of patients with periodontitis. This distribution profile of clarithromycin can thus be advantageous in the management of periodontal lesions.

Troubleshooting carry-over of LC-MS/MS method for rifampicin, clarithromycin and metabolites in human plasma.

Clarithromycin and rifampicin are used for the treatment of Mycobacteria. Pharmacokinetic drug interaction is possibly due to the influence of the two drugs on the liver enzymes. Using a Hypurity Aquastar C18 column (50mm×2.1mm×5µm) for liquid chromatography including a polar end-capped phase for the determination of clarithromycin, rifampicin and their metabolites together in plasma using LC-MS/MS resulted in a substantial carry-over. As a consequence, the throughput of the method is not assured. Using a step-by-step troubleshooting procedure, such carry-over was found originating from column memory effect. With the use of another type of C18 column, the carry-over is eliminated. Due to the absence of carry-over, the analytical concentration ranges are extended and are therefore more appropriate for the analysis of patient samples. The method was re-validated for linearity, reproducibility and dilution integrity.

Determination and stability assessment of clarithromycin in human plasma using RP-LC with electrochemical detection.

A selective, sensitive and stability-indicating reversed-phase high-performance liquid chromatography method was developed and validated for the determination of clarithromycin antibiotic in human plasma. Liquid chromatography was performed on a 5-µm (100 × 4.6 mm) C8 column at 40°C. The mobile phase consisted of acetonitrile with 0.045M H(3)PO(4) (37:63, v/v) adjusted to pH 6.7 and pumped at a flow rate of 1.2 mL/min. Detections were monitored on an electrochemical detector operated at a potential of 0.85 V with glassy carbon electrode against Ag/AgCl reference electrode. Each analysis required 13 min and quantification over the range of 0.05-5.0 µg/mL of plasma was linear, as indicated by a correlation coefficient (R(2)), 0.9999. The method was validated according to international guidelines. Data with respect to accuracy, within-run and between run, were close to 100% with 4% precision. Absolute recovery was 95%. The limit of quantification was 0.05 µg/mL. Neither endogenous substances nor commonly used drugs were found to interfere with the retention times of analytes. Stock solutions and calibration standards of the drug and quality control preparations were demonstrated to be stable at room temperature and -20°C for long and short periods of time. Eventually, the proposed method was successfully applied to quantify clarithromycin in spiked human plasma and real samples from healthy volunteers, indicating the utility and throughput of this method for clinical and bioavailability studies.

Rapid quantitative analysis of clarithromycin in rat plasma by UPLC-MS/MS after intravenous injection of the clarithromycin-loaded ultrafine PLGA nanoparticles.

Nanoparticles were designed to encapsulate drugs to alter their pharmacological behaviors, therefore, it is very essential to monitor the pharmacokinetic profile of drug encapsulated in nanoparticles in order to clarify and predict their efficacy and side effects. In this paper, we reported a simple, rapid µ-elution 96-well solid phase extraction (µSPE) method combining with ultra high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) for determination of nanoformulated drug in rat plasma. This method presented satisfactory results in terms of sensitivity, precision, accuracy, and recovery, for the first time, of quantitatively analyzing clarithromycin (CLA) in rat plasma after intravenous administration CLA-loaded ultrafine PLGA nanoparticles for pharmacokinetic study. This method has been proved to be fast, reliable and reproducible to accurately analyze drug encapsulated in polymeric nanoparticles sample for a pharmacokinetic study.

Effect of cytochrome P450 3A5 genotype on atorvastatin pharmacokinetics and its interaction with clarithromycin.

Abstract Study Objective. To assess the effects of the cytochrome P450 (CYP) 3A genotype, CYP3A5, on atorvastatin pharmacokinetics and its interaction with clarithromycin. Design. Prospective, two-phase, randomized-sequence, open-label pharmacokinetic study. Setting. Clinical research center at a teaching hospital. Subjects. Twenty-three healthy volunteers who were screened for genotype: 10 subjects carried the CYP3A5*1 allele (expressors) and 13 subjects did not (nonexpressors). Intervention. In one phase, subjects received a single oral dose of atorvastatin 20 mg. In the other phase, subjects received clarithromycin 500 mg twice/day for 5 days; on day 4 after the morning dose, subjects also received a single oral dose of atorvastatin 20 mg. All subjects participated in both phases of the study, which were separated by at least 14 days. Measurements and Main Results. Pharmacokinetic parameters of both forms of atorvastatin-atorvastatin acid and atorvastatin lactone-were compared between CYP3A5 expressors and nonexpressors, both in the absence and presence of clarithromycin, a strong CYP3A inhibitor. The acid form is pharmacologically active, and the lactone form has been associated with the atorvastatin's muscle-related adverse effects. Atorvastatin acid exposure did not differ significantly between CYP3A5 genotype groups. When subjects had not received clarithromycin pretreatment, the area under the concentration-time curve from time zero extrapolated to infinity (AUC(0-∞)) of atorvastatin lactone was 36% higher in nonexpressors than in expressors (median 47.6 ng•hr/ml [interquartile range (IQR) 37.8-64.3 ng•hr/ml] vs 34.9 ng•hr/ml [IQR 21.6-42.2 ng•hr/ml], p=0.038). After clarithromycin pretreatment, changes in the pharmacokinetic parameters of atorvastatin acid and lactone were not significantly different between the nonexpressors versus the expressors; however, the increase in the AUC(0-∞) of atorvastatin lactone was 37% greater in expressors than in nonexpressors (geometric mean ± SD 3.59 ± 0.57 vs 2.62 ± 0.35, p=0.049). Conclusion. Our data suggest that the CYP3A5 genotype has minimal effects on the pharmacokinetic parameters of atorvastatin and its interaction with clarithromycin; these effects are unlikely to be clinically significant.