High-performance liquid chromatographic determination of the antifungal drug fluconazole in plasma and saliva of human immunodeficiency virus-infected patients

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.

Saliva for Precision Dosing of Antifungal Drugs: Saliva Population PK Model for Voriconazole Based on a Systematic Review

Precision dosing for many antifungal drugs is now recommended. Saliva sampling is considered as a non-invasive alternative to plasma sampling for therapeutic drug monitoring (TDM). However, there are currently no clinically validated saliva models available. The aim of this study is firstly, to conduct a systematic review to evaluate the evidence supporting saliva-based TDM for azoles, echinocandins, amphotericin B, and flucytosine. The second aim is to develop a saliva population pharmacokinetic (PK) model for eligible drugs, based on the evidence. Databases were searched up to July 2019 on PubMed® and Embase®, and 14 studies were included in the systematic review for fluconazole, voriconazole, itraconazole, and ketoconazole. No studies were identified for isavuconazole, posaconazole, flucytosine, amphotericin B, caspofungin, micafungin, or anidulafungin. Fluconazole and voriconazole demonstrated a good saliva penetration with an average S/P ratio of 1.21 (± 0.31) for fluconazole and 0.56 (± 0.18) for voriconazole, both with strong correlation (r = 0.89-0.98). Based on the evidence for TDM and available data, population PK analysis was performed on voriconazole using Nonlinear Mixed Effects Modeling (NONMEM 7.4). 137 voriconazole plasma and saliva concentrations from 11 patients (10 adults, 1 child) were obtained from the authors of the included study. Voriconazole pharmacokinetics was best described by one-compartment PK model with first-order absorption, parameterized by clearance of 4.56 L/h (36.9% CV), volume of distribution of 60.7 L, absorption rate constant of 0.858 (fixed), and bioavailability of 0.849. Kinetics of the voriconazole distribution from plasma to saliva was identical to the plasma kinetics, but the extent of distribution was lower, modeled by a scale factor of 0.5 (4% CV). A proportional error model best accounted for the residual variability. The visual and simulation-based model diagnostics confirmed a good predictive performance of the saliva model. The developed saliva model provides a promising framework to facilitate saliva-based precision dosing of voriconazole.

A descriptive systematic review of salivary therapeutic drug monitoring in neonates and infants

AIMS

Saliva, as a matrix, offers many benefits over blood in therapeutic drug monitoring (TDM), in particular for infantile TDM. However, the accuracy of salivary TDM in infants remains an area of debate. This review explored the accuracy, applicability and advantages of using saliva TDM in infants and neonates.

METHODS

Databases were searched up to and including September 2016. Studies were included based on PICO as follows: P: infants and neonates being treated with any medication, I: salivary TDM vs. C: traditional methods and O: accuracy, advantages/disadvantages and applicability to practice. Compounds were assessed by their physicochemical and pharmacokinetic properties, as well as published quantitative saliva monitoring data.

RESULTS

Twenty-four studies and their respective 13 compounds were investigated. Four neutral and two acidic compounds, oxcarbazepine, primidone, fluconazole, busulfan, theophylline and phenytoin displayed excellent/very good correlation between blood plasma and saliva. Lamotrigine was the only basic compound to show excellent correlation with morphine exhibiting no correlation between saliva and blood plasma. Any compound with an acid dissociation constant (pKa) within physiological range (pH 6-8) gave a more varied response.

CONCLUSION

There is significant potential for infantile saliva testing and in particular for neutral and weakly acidic compounds. Of the properties investigated, pKa was the most influential with both logP and protein binding having little effect on this correlation. To conclude, any compound with a pKa within physiological range (pH 6-8) should be considered with extra care, with the extraction and analysis method examined and optimized on a case-by-case basis.

Utility of noninvasive biomatrices in pharmacokinetic studies

Blood and plasma are the biomatrices traditionally used for drug monitoring and their pharmacokinetic profiling. Blood is the circulating fluid in contact with all organs and tissues of body and thus is the most representative fluid for measuring systemic drug levels. However, venipuncture suffers from the caveat of being an invasive technique which often makes people reluctant to participate in clinical studies. Thus, there is a need for noninvasive bio-fluids that are ethically appropriate, cost-efficient and toxicologically relevant. These alternate bio-fluids may prove clinically useful as alternatives to plasma/serum in therapeutic drug monitoring, pharmacokinetic and toxicokinetic studies, doping control in sports medicine and to monitor local adverse effects. These may be of particular interest in the case of special population groups such as neonates, children, the elderly, terminally ill patients and pregnant or lactating women, and offer the advantage of circumvention of the demand for specialized personnel for sample collection. This review describes such noninvasive bio-fluids (saliva, sweat, tears and milk) that have been considered for pharmacokinetic drug analysis, emphasizing their sample preparation, its associated difficulties and their correlation with plasma.

A validated assay by liquid chromatography-tandem mass spectrometry for the simultaneous quantification of elvitegravir and rilpivirine in HIV positive patients

Because of the large variability in the pharmacokinetics of anti-HIV drugs, therapeutic drug monitoring in patients may contribute to optimize the overall efficacy and safety of antiretroviral therapy. An LC-MS/MS method for the simultaneous assay in plasma of the novel antiretroviral agents rilpivirine (RPV) and elvitegravir (EVG) has been developed to that endeavor. Plasma samples (100 μL) extraction is performed by protein precipitation with acetonitrile, and the supernatant is subsequently diluted 1:1 with 20-mM ammonium acetate/MeOH 50:50. After reverse-phase chromatography, quantification of RPV and EVG, using matrix-matched calibration samples, is performed by electrospray ionization-triple quadrupole mass spectrometry by selected reaction monitoring detection using the positive mode. The stable isotopic-labeled compounds RPV-(13) C6 and EVG-D6 were used as internal standards. The method was validated according to FDA recommendations, including assessment of extraction yield, matrix effects variability (<6.4%), as well as EVG and RPV short and long-term stability in plasma. Calibration curves were validated over the clinically relevant concentrations ranging from 5 to 2500 ng/ml for RPV and from 50 to 5000 ng/ml for EVG. The method is precise (inter-day CV%: 3-6.3%) and accurate (3.8-7.2%). Plasma samples were found to be stable (<15%) in all considered conditions (RT/48 h, +4°C/48 h, -20°C/3 months and 60°C/1 h). Selected metabolite profiles analysis in patients' samples revealed the presence of EVG glucuronide, that was well separated from parent EVG, allowing to exclude potential interferences through the in-source dissociation of glucuronide to parent drug. This new, rapid and robust LCMS/MS assay for the simultaneous quantification of plasma concentrations of these two major new anti-HIV drugs EVG and RPV offers an efficient analytical tool for clinical pharmacokinetics studies and routine therapeutic drug monitoring service.

Population pharmacokinetics of fluconazole after administration of fosfluconazole and fluconazole in critically ill patients

WHAT IS KNOWN AND OBJECTIVE

Fluconazole is an antifungal agent that is commonly used to treat patients with serious systemic fungal infections in intensive care units. Fosfluconazole is a phosphate prodrug of fluconazole, which was developed to reduce the volume of fluid required to administer fluconazole by intravenous injection. The objective of this study was to characterize the pharmacokinetics of the antifungal fluconazole after the intravenous administration of the prodrug fosfluconazole or fluconazole in critically ill patients with serious systemic fungal infections, by population pharmacokinetic analysis using the nonmem software package.

METHODS

Clinical biochemical data including serum fluconazole levels were obtained from 57 patients treated in the intensive care unit along with two naïve pooled patients gleaned from previous reports. The pharmacokinetic model of fluconazole was estimated using a one-compartment model. The probability that the area under the concentration-time curve is higher than 800 μg h/mL was determined by simulation.

RESULTS

It was assumed that all the administered fosfluconazole was converted to fluconazole with an estimated fosfluconazole-fluconazole conversion rate constant of 2·05/h. The significant covariates for clearance for fluconazole (CL) and volume of distribution for fluconazole (Vd) were resulted in creatinine clearance (CLcr) and body weight (BW), respectively, in the final pharmacokinetic model equations: CL (L/h) = 0·799 × [CLcr (mL/min)/92·7](0·685) and Vd (L) = 48·1 × [BW (kg)/65](1·40) , where the interpatient variabilities in CL and Vd and the intrapatient variability were 44·8%, 79·7% and 19·8%, respectively. On the basis of the results of the Monte Carlo simulation, the probabilities of target attainment were 60%, 26% and 11% for 400 mg/day administration as fluconazole equivalent at CLcr values of 40, 70 and 100 mL/min, respectively.

WHAT IS NEW AND CONCLUSION

The present population pharmacokinetic analysis strongly indicates that fosfluconazole (and fluconazole) dosage should be optimized in terms of CLcr in critically ill patients.

The pharmacokinetics of fluconazole in healthy Chinese adult volunteers: influence of ethnicity and gender

OBJECTIVE

The purpose of the present study was to investigate and compare the influence of ethnicity (including Han, Mongolian, Korean, Hui and Uygur) and gender on the pharmacokinetics of fluconazole in healthy adult volunteers after administration of 200-mg fluconazole tablet.

METHODS

Ten healthy subjects (five males and five females) of each ethnicity were recruited and given a single 200-mg dose of fluconazole in tablet form. Blood samples were obtained before dosing and at various predetermined time points after administration up to 96 h. Drug levels were measured by high-performance liquid chromatography. The blood concentration-time profiles were analyzed using a non-compartmental approach to estimate the absorption parameters (AUC((0-96)), C(max) and t(max)), the distribution parameter (V(d)) and the disposition parameters (t(1/2) and CL).

RESULTS

Ethnicity did not affect the parameter estimates, but gender did. However, the gender differences in pharmacokinetic parameter could be accounted for by differences in weight. There was a high linear correlation between weight and ln C(max), ln AUC (ln means natural logarithmic transformation), V(d) and CL.

CONCLUSIONS

Ethnicity (Chinese Han, Mongolian, Korean, Hui and Uygur) influences the pharmacokinetics of fluconazole tablet. However, there were statistically significant gender differences in AUC, C(max), V(d) and CL. But these could be accounted for by weight differences. If fluconazole dose-adjustment is deemed necessary, this can be done on a weight basis rather than gender basis.

A rapid and sensitive LC-MS/MS method for determination of fluconazole in human plasma and its application in infants with Candida infections

A rapid and sensitive LC-MS/MS method was developed to quantify fluconazole in human plasma. Seventy microliters of plasma were treated with protein precipitation procedures. Chromatographic separation was achieved on a C18 column using a gradient mobile phase of acetonitrile and water in 0.1% formic acid. Fluconazole and its deuterium-labeled internal standard were monitored in positive mode using electrospray ionization source. The method was fully validated over the range of 0.01 to 10 microg/mL. Intraday and interday precision ranged from 2.84% to 10.8% and 5.27% to 11.5%, respectively. The process recovery efficiency for fluconazole ranged from 98.6% to 104.4%. No carryover and minimal matrix effects were observed. Acceptable stability of fluconazole in blood at room temperature for up to 72 hours guaranteed that fluconazole concentrations in scavenged blood specimens were usable for infant PK analysis and model development. This method has been utilized for a fluconazole pharmacokinetic trial with 55 preterm and term infants younger than 90 days of age. The fast sample preparation cycle and lower limit of quantitation make this method a potential tool for therapeutic drug monitoring of fluconazole to optimize pediatric antifungal therapy. Optimal dose regimen of fluconazole in neonates and young infants might be achieved with application of TDM and pharmacometric approach designed to achieve AUC/MIC >50 for most Candida species with a MIC90 less than 8 microg/mL.

Stability of Reconstituted Fluconazole Oral Suspension in Plastic Bottles and Oral Syringes

Background:

Fluconazole for oral suspension is a dry powder with a beyond-use date of 14 days after being reconstituted. Dispensing fluconazole liquid in the inpatient setting would be much more efficient if prefilled oral syringes containing standard doses were readily available. In addition, if the beyond-use date could be extended, the resulting decreased waste would be economically beneficial.

Objective:

To determine the stability of reconstituted fluconazole oral suspension using high-performance liquid chromatography (HPLC).

Methods:

Diflucan lyophilized powder was reconstituted to fluconazole 40 mg/mL using Sterile Water for Irrigation, USP. Samples were stored at room temperature in both the original Diflucan plastic bottles and in amber polyethylene oral syringes with silicon elastomer plunger tips that were sealed with high-density polyethylene caps. Samples were analyzed immediately and at 14, 28, 42, 56, and 70 days. Fluconazole concentrations were measured using a modified stability-indicating HPLC method. At each test interval, the density of the suspension was determined gravimetrically and then used to calculate the exact volume of sample used for each analysis. Excessive degradation was defined as greater than 10% loss of the initial concentration.

Results:

The stock internal standard was stable for at least 77 days when stored in the dark at room temperature. The stock and working fluconazole standard solutions were prepared fresh at each test interval. Reconstituted oral suspension retained more than 90% of the initial fluconazole concentration for at least 70 days at 22–25 °C. No changes in color, odor, or visible microbiological growth were observed in any sample. The pH of the suspension was initially 4.2 and remained essentially unchanged throughout the study.

Conclusions:

Reconstituted fluconazole oral suspension is stable in both the product's original plastic bottles and in amber polyethylene oral syringes for at least 70 days when stored at 22-25 °C.

Design and in vitro/in vivo evaluation of novel mucoadhesive buccal discs of an antifungal drug: relationship between swelling, erosion, and drug release

Two groups of fluconazole mucoadhesive buccal discs were prepared: (a) Fluconazole buccal discs prepared by direct compression containing bioadhesive polymers, namely, Carbopol 974p (Cp), sodium carboxymethyl cellulose (SCMC), or sodium alginate (SALG) in combination with hydroxypropyl methylcellulose (HPMC) or hydroxyethyl cellulose (HEC). (b) Fluconazole buccal discs prepared by freeze drying containing different polymer combinations (SCMC/HPMC, Cp/HPMC, SALG/HPMC, and chitosan/SALG). The prepared discs were evaluated by investigating their release pattern, swelling capacity, mucoadhesion properties, and in vitro adhesion time. In vivo evaluation of the buccal disc and in vivo residence times were also performed. Fluconazole salivary concentration after application of fluconazole buccal systems to four healthy volunteers was determined using microbiological assay and high-performance liquid chromatography. SCMC/HPMC buccal disc prepared by direct compression could be considered comparatively superior mucoadhesive disc regarding its in vitro adhesion time, in vivo residence time, and in vitro/in vivo release rates of the drug. Determination of the amount of drug released in saliva after application of the selected fluconazole disc confirmed the ability of the disc to deliver the drug over a period of approximately 5 h and to reduce side effects and possibility of drug interaction encountered during systemic therapy of fluconazole, which would be beneficial in the case of oral candidiasis.

Determination of unbound antiretroviral drug concentrations by a modified ultrafiltration method reveals high variability in the free fraction

Total plasma concentrations are used for therapeutic drug monitoring of antiretroviral drugs, whereas antiviral activity is expected to depend on unbound concentrations. The determination of free (unbound) concentrations by ultrafiltration may be flawed by the irreversible adsorption of many drugs onto the membrane filters and plastic components of the device. The authors describe a modified ultrafiltration method enabling the accurate measurement of unbound concentrations of 10 antiretroviral drugs by liquid chromatography-tandem mass spectroscopy, which circumvents the problem of loss by adsorption in the early ultrafiltration fractions. The method was applied to assess the variability of free fractions of antiretroviral drugs during routine therapeutic drug monitoring in 144 patients with HIV. In in vitro experiments, ultrafiltrate collected in four fractions (0-8, 8-16, 16-24, and 24-30 minutes) gave much lower and more variable free drug concentrations in the first ultrafiltrate fraction than in the last three fractions for lopinavir, nelfinavir, saquinavir, tipranavir, and efavirenz. In the last two fractions, free concentrations remained constant, indicating saturable adsorption. The adsorption was modest for indinavir, amprenavir, and ritonavir, and unnoticeable for atazanavir and nevirapine. Free fraction values obtained with this modified ultrafiltration method reveal substantial interindividual variability, suggesting that monitoring unbound antiretroviral drug concentrations may increase its clinical usefulness, especially for lopinavir, saquinavir, and efavirenz.

Development and validation of a high-performance liquid chromatographic assay for the determination of fluconazole in human whole blood using solid phase extraction

A sensitive and specific high-performance liquid chromatographic ultraviolet method for the determination of fluconazole in human whole blood has been developed and validated. Whole blood samples were processed by a solid phase extraction procedure using an Oasis HLB extraction cartridge before chromatography. Phenacetin was used as the internal standard. Chromatography was performed using Waters C18 Symmetry analytical column, 5 microm, 4.6 x 250 mm, using an isocratic elution with a mobile phase consisting of acetonitrile and water (36:64, v/v) at a flow rate of 0.8 mL/min. The retention times of fluconazole and phenacetin were 4.7 and 8.3 minutes, respectively, and the total run time was 10 minutes. Quantitative analysis was performed using a Waters UV-VIS detector at a wavelength of 210 nm. The assay was linear over the concentration range of 0.5 to 15 microg/mL for fluconazole. The extraction recoveries at concentrations of 2.5, 5, and 10 microg/mL were 105.9%, 98.4%, and 95%, respectively. The method can quantify 0.5 microg/mL fluconazole using 300 microL of whole blood. At concentrations of 2.5, 5, and 10 microg/mL, the intraday precision expressed as coefficient of variation was 3.47%, 8.81%, and 1.14% and the interday precision was 5.21%, 5.48%, and 7.18%, respectively. This method is simple, uses a low blood volume for analysis, and allows reproducible and accurate measurement of fluconazole in whole blood samples from pediatric patients.

Ocular distribution of intravenously administered micafungin in rabbits

The ocular distribution of micafungin (MCFG), which has antifungal activity against Candida and Aspergillus species, was followed after the systemic administration of MCFG in rabbits. After MCFG (10 mg/kg) plus fluconazole (FLCZ; 10 mg/kg) was administered intravenously, the rabbits were killed, and MCFG and FLCZ concentrations in retina-choroid, vitreous humor, and plasma were determined by high performance liquid chromatography or liquid chromatography/mass spectrometry. The mean concentrations of MCFG in the retina-choroid at 0.25, 0.75, 4, 8, and 24 h after administration were 20.18, 15.97, 13.19, 6.27, and 0.75 microg/g, respectively, and were comparable with the MCFG plasma concentrations. The MCFG concentrations in retina-choroid and plasma exceeded the minimal antifungal inhibitory concentrations for endophthalmitis, although MCFG was not detected in the vitreous humor. These results suggest that the intravenous administration of MCFG is an effective treatment for endogenous fungal endophthalmitis when the causative fungus is localized in the retina and choroid.

An optimized analytical method of fluconazole in human plasma by high-performance liquid chromatography with ultraviolet detection and its application to a bioequivalence study

A sensitive and accurate HPLC-UV method for the quantification of fluconazole (FLA) level in human plasma has been developed. The sample was prepared by one-step liquid-liquid extraction (LLE) of FLA from plasma using dichloromethane. Phenacetin was used as the internal standard. The chromatographic retention times of FLA and phenacetin were 4.6 and 8.3 min, respectively. The lower limit of quantitation (LLOQ) was 0.05 microg/mL, and no interferences were detected in the chromatograms. The devised HPLC-UV method was validated by evaluating its intra- and inter-day precisions and accuracies in a linear concentration range between 0.05 and 10.00 microg/mL. The devised method was successfully applied to a bioequivalence studies involving the oral administration of a single 150 mg FLA tablet and 3 x 50 mg FLA capsules in healthy Korean male volunteers.

Determination of aciclovir and ganciclovir in human plasma by liquid chromatography–spectrofluorimetric detection and stability studies in blood samples

A sensitive HPLC method has been developed for the assay of aciclovir and ganciclovir in human plasma, by HPLC coupled with spectrofluorimetric detection. Plasma (1000 microl), with 9-ethyl-guanine added as internal standard, is submitted to protein precipitation with trichloroacetic acid solution 20%. The supernatant, evaporated to dryness at 37 degrees C, is reconstituted in 100 microl of a solution of sodium heptanosulfonate 0.4% adjusted with acetic acid to pH 2.60 and a 30 microl volume is then injected onto a Nucleosil 100-5 microm C18 column. Aciclovir and ganciclovir are analysed by spectrofluorimetric detection set at 260 nm (excitation) and 380 nm (emission) using a gradient elution program with solvents constituted of acetonitrile and a solution of sodium heptanosulfonate 0.4% adjusted to pH 2.60. The calibration curves are linear between 0.1 and 10 microg/ml. The mean absolute recovery of aciclovir and ganciclovir are 99.2+/-2.5 and 100.3+/-2.5%, respectively. The method is precise (with mean inter-day C.V.s within 1.0-1.6% for aciclovir and 1.2-3.5% for ganciclovir), and accurate (range of inter-day deviations -1.6 to +1.6% for aciclovir and -0.4 to -1.4% for ganciclovir). The method has been applied in stability studies of ganciclovir in patients' blood samples, demonstrating its good stability in plasma at -20 degrees C and at room temperature. The distribution of ganciclovir and aciclovir in plasma and red blood cells was also investigated in vitro in spiking experiments with whole blood, which showed an initial drop of ganciclovir and aciclovir levels in plasma (about -25%) due to the cellular uptake of aciclovir and ganciclovir by red blood cells. The method has been validated and is currently applied in a clinical study assessing the ganciclovir plasma concentration variability after administration of valganciclovir in a population of solid organ transplant patients.

Radiochemical stability of fluconazole in the solid state

The effect of ionizing radiation in doses between 20 and 200 kGy on physicochemical properties of fluconazole (alpha-(2,4-diflurophenyl)-alpha-(1H-triazol-1-methyl)-1H-1,2,4-triazole-1-ethanol) in the solid state was examined. A number of qualitative and quantitative methods such as scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), ultraviolet (UV) and infrared (IR) spectroscopy, thin layer chromatography (TLC) and high pressure liquid chromatography (HPLC) and organoleptic analysis were used to determine and analyse any changes resulting from irradiation. A change in colour from white to cream was observed at even smallest dose (20 kGy) and as the dose increased the colour deepened from salmon pink to orange at the highest dose of 200 kGy. The UV method showed an increase in absorbance at lambda(max) and an appearance of an additional band in the range 280-310 nm for irradiated samples. These changes were associated with the appearance of one to two decomposition products observed by TLC. Depending on the dose of radiation, the HPLC method detected between 2 and 3 radiolysis products and the decreasing fluconazole content from 0.48 to 7.12%. The remaining analytical methods (SEM, IR and NMR) did not provide any conclusive information in respect of radiological stability of fluconazole. The results indicate that fluconazole is a compound of low radiological stability and should not be sterilized using gamma, beta or E-beam radiation.

Pharmacokinetics of fluconazole and fosfluconazole after intraperitoneal administration to peritoneal dialysis rats

Fluconazole (FLCZ) is an antifungal agent that is efficacious in the treatment of fungal peritonitis. Fosfluconazole (F-FLCZ) is the phosphate prodrug of FLCZ, which is highly soluble compared with FLCZ. F-FLCZ is useful against fungal peritonitis in continuous ambulatory peritoneal dialysis (CAPD) patients because it has a high water solubility. The aims of the present study were to characterize the peritoneal permeability of FLCZ and the pharmacokinetics of FLCZ and F-FLCZ after intraperitoneal (i.p.) administration to peritoneal dialysis rats. FLCZ or F-FLCZ was administered intravenously and intraperitoneally. After the i.p. administration of F-FLCZ, FLCZ was detected in circulating blood and the dialyzing fluid in peritoneal dialysis rats. The concentration of plasma FLCZ after the i.p. F-FLCZ administration was lower than that after the intravenous (i.v.) F-FLCZ administration. It is considered that the dose should be increased appropriately when F-FLCZ is administered intraperitoneally. The profiles of plasma FLCZ after i.v. and i.p. administrations were analyzed using a two-compartment model in which the distribution volume of the peripheral compartment was fixed at a volume of the dialyzing fluid (peritoneal dialysis PK model). The peritoneal dialysis PK model could describe the profiles of plasma and dialyzing fluid FLCZ. These results suggest that FLCZ and F-FLCZ could be administered intraperitoneally for the treatment of fungal peritonitis in CAPD patients.

Determination of the novel non-peptidic HIV-protease inhibitor tipranavir by HPLC–UV after solid-phase extraction

An HPLC method previously described for the assay of amprenavir (APV), ritonavir (RTV), indinavir (IDV), saquinavir (SQV), nelfinavir (NFV), lopinavir (LPV), atazanavir (ATV), nevirapine (NVP) and efavirenz (EFV) can be also conveniently applied, with minor gradient program adjustment, for the determination of the novel non-peptidic HIV protease inhibitor tipranavir (TPV) in human plasma, by off-line solid-phase extraction (SPE) followed by HPLC coupled with UV-diode array detection (DAD). After viral inactivation by heat, the plasma is diluted with phosphate buffer (pH 7), and subjected to a SPE on a C18 cartridge. Matrix components are eliminated with a solution of 0.1% H3PO4 solution neutralised to pH 7, and TPV is eluted with MeOH. The resulting eluate is evaporated and reconstituted in 100 microl MeOH/H2O 50/50. A 40 microl volume is injected onto a Nucleosil C18 AB column and TPV is analysed by UV detection at 201 nm using a gradient elution program constituted of MeCN and phosphate buffer adjusted to pH 5.12 and containing 0.02% sodium heptanesulfonate. The calibration curves are linear up to 75 microg/ml, with a lower limit of quantification of 0.125 microg/ml. The mean absolute recovery of TPV is 77.1+/-4.0%. The method is precise with mean inter-day coefficient of variations (CVs) within 2.2-3.4%, and accurate (range of inter-day deviations from 0.7 to 1.2%). The method has been validated and is currently applied to the monitoring of TPV plasma levels in HIV patients.

Evaluation of the bioequivalence of capsules containing 150 mg of fluconazole

Fluconazole is an antifungal agent. The purpose of this study was to evaluate bioequivalence of two commercial 150 mg capsule formulations of fluconazole available in the Brazilian market. The study was an open, randomized, two-period, two-group crossover trial with a 2-week washout interval. Blood samples were collected throughout a 96-h period after administration of reference product (R) and test product (T) to 28 fasting volunteers. A simple, accurate, precise and sensitive high-performance liquid chromatographic (HPLC) method with ultraviolet detection was developed and validated for quantification of fluconazole in plasma samples after liquid-liquid extraction. Bioequivalence between the products was determined by calculating 90% confidence intervals (90% C.I.) for the ratio of C(max), AUC(0-t) and AUC(0-infinity) values for the test and reference products, using logarithmic transformed data. The 90% confidence intervals for the ratio of C(max) (101.06-105.45%), AUC(0-t) (97.11-104.69%) and AUC(0-infinity) (97.96-103.36%) values for the test and reference products are within the 80-125% interval, proposed by FDA and EMEA. It was concluded that the two fluconazole formulations are bioequivalent in their rate and extent of absorption.

A New, Rapid, Fully Automated Method for Determination of Fluconazole in Serum by Column-Switching Liquid Chromatography

A sensitive and rapid HPLC assay for the determination of fluconazole in serum is described. HPLC-integrated sample preparation allows direct injection of serum samples without any pretreatment. The in-line extraction technique is carried out by automatically switching from the extraction column (Lichrospher ADS C8) to the analytic column (Nucleosil C18). After 6 minutes the matrix passes the extraction column, and the retained analyte is quantitatively transferred to the analytic column, where separation by isocratic HPLC is performed. The extraction eluent is sodium dihydrogen phosphate buffer, pH 5.0 (50 mM), and the analytic eluent is acetonitrile/sodium dihydrogen phosphate buffer, pH 5.0 (50 mM) (26.8/73.2, vol/vol). Fluconazole is detected according to its absorption maximum at 210 nm. The lower limit of quantification (LLOQ) is 0.65 microg/mL, the limit of detection (LOD) is 0.2 microg/mL, and the quantification range is 0.65-23.3 microg/mL. The assay was precise with a between-run coefficient of variation of < or = 5.59%. The within-run accuracy was 99.8% and 103.4%, and the between-run accuracy was 99.2% and 99.7%, respectively, for the concentrations 23.3 microg/mL and 1.3 microg/mL. The recovery was 78%. The described procedure allows sample cleanup and determination within 20 minutes, thereby facilitating drug monitoring in clinical routine. The method was applied successfully.

Liquid chromatography–tandem mass spectrometric method for the analysis of fluconazole and evaluation of the impact of phenolic compounds on the concentration of fluconazole in Candida albicans

A bioanalytical method using liquid chromatography-tandem mass spectrometry was developed for the analysis of fluconazole in Candida albicans after incubation with phenolic compounds, which have been proved possessing antifungal properties and have synergetic activity against C. albicans when in combination with fluconazole. Samples of C. albicans thallus obtained by centrifuging the mixed culture after 24 h incubation were saponified and centrifuged. The supernatant was evaporated to dryness, reconstituted, and injected on a C18 column using an organic-aqueous mobile phase. The chromatographic run time was 3.5 min per injection, with retention times of 2.4 min for fluconazole. The detection was by monitoring fluconazole at m/z 305-->191. The standard curve range was 1.0-100.0 ng ml(-1) with a mean correlation coefficient 0.9992. The precision and accuracy of the quality control (QC) samples were R.S.D < 5.5%, R.E. <3% for intra-day and R.S.D. <6.2%, R.E. <4% for inter-day. The concentration of fluconazole in C. albicans was found to be increased with the increment of the tested compounds concentration when they were in combination.

Liquid/liquid extraction using 96-well plate format in conjunction with hydrophilic interaction liquid chromatography-tandem mass spectrometry method for the analysis of fluconazole in human plasma

A bioanalytical method using automated sample transferring, automated liquid/liquid extraction (LLE) and hydrophilic interaction liquid chromatography-tandem mass spectrometry was developed for the determination of fluconazole in human plasma. Samples of 0.05 ml were transferred into 96-well plate using automatic liquid handler (Multiprobe II). Automated LLE was carried out on a 96-channel programmable liquid handling workstation (Quadra 96) using methyl-tetra butyl ether as the extraction solvent. The extract was evaporated to dryness, reconstituted, and injected onto a silica column using an aqueous-organic mobile phase. The chromatographic run time was 2.0 min per injection, with retention times of 1.47 and 1.44 min for fluconazole and internal standard (IS) ritonavir, respectively. The detection was by monitoring fluconazole at m/z 307-->238 and IS at m/z 721-->296, respectively. The standard curve range was 0.5-100 ng ml(-1). The inter-day precision and accuracy of the quality control samples were <7.1% relative standard deviation and <2.2% relative error.

Hepatobiliary excretion of fluconazole and its interaction with cyclosporin A in rat blood and bile using microdialysis

In order to investigate the hepatobiliary excretion of Fluconazole, we develop a rapid and sensitive method using high-performance liquid chromatography coupled with microdialysis for the simultaneous determination of unbound fluconazole in rat blood and bile. Microdialysis probes were inserted into both the jugular vein toward the right atrium and bile duct of male Sprague-Dawley rats for biological fluid sampling after administration of fluconazole at 10 mg/kg through the femoral vein. Fluconazole and dialysates were separated using a Zorbax phenyl column maintained at ambient temperature. The detection limit of fluconazole was 50 ng/ml. Biological fluid sampling thereby allowed the simultaneous determination of fluconazole levels in blood and bile. The disposition of fluconazole in the blood and bile fluid suggests that there was rapid exchange and equilibration between the blood and hepatobiliary system. In addition, to investigate the mechanism of P-glycoprotein related hepatobiliary excretion of fluconazole, we examined the drug-drug interaction of fluconazole and cyclosporin A in the aspect of pharmacokinetics. These results indicate that the plasma level of fluconazole was no different than that in bile, and that fluconazole undergoes hepatobiliary excretion, maybe unrelated to the P-glycoprotein transported system.

Determination of lopinavir and nevirapine by high-performance liquid chromatography after solid-phase extraction: application for the assessment of their transplacental passage at delivery

An adaptation of the HPLC method previously described for the simultaneous assay of amprenavir, ritonavir, indinavir, saquinavir, nelfinavir and efavirenz after solid-phase extraction is proposed here for the separate analysis of the newer PI lopinavir (LPV) and the NNRTI nevirapine (NVP). After viral inactivation by heat (60 degrees C for 60 min), plasma (600 microl), with clozapine added as internal standard, is diluted 1+1 with phosphate buffer pH 7 and subjected to a solid-phase extraction on a C(18) cartridge. Matrix components are eliminated with 2 x 500 microl of a solution of 0.1% H(3)PO(4) neutralised with NaOH to pH 7. LPV and NVP are eluted with 3 x 500 microl MeOH. The resulting eluate is evaporated under nitrogen at room temperature and is reconstituted in 100 microl MeOH 50%. A 40-microl volume is injected onto a Nucleosil 100, 5 microm C(18) AB column. LPV and NVP are analysed separately using a gradient elution program with solvents constituted of MeCN and phosphate buffer adjusted to pH 5.07 and containing 0.02% sodium heptanesulfonate. LPV and NVP are detected by UV at 201 and 282 nm, respectively. The calibration curves are linear up to 10 microg/ml. The mean absolute recovery of LPV and NVP is 91% and 88%, respectively. The method is precise with mean inter-day C.V.s within 2.1-6.6% and 0.9-1.7% for LPV and NVP, and accurate (range of inter-day deviations -1.1 to +2.4%, and -1.9 to +0.8%, for LPV and NVP, respectively). The method has been validated and is currently applied to the monitoring of LPV and NVP in HIV patients, and has been notably applied in a study aimed at assessing the extent of transplacental passage of nevirapine and PIs, notably lopinavir, at the time of delivery in pregnant HIV-infected women.

Single-step extraction of fluconazole from plasma by ultra-filtration for the measurement of its free concentration by high performance liquid chromatography

High performance liquid chromatography (HPLC) is the reference method for measuring concentrations of antimicrobials in blood. This technique requires careful sample preparation. Protocols using organic solvents and/or solid extraction phases are time consuming and entail several manipulations, which can lead to partial loss of the determined compound and increased analytical variability. Moreover, to obtain sufficient material for analysis, at least 1 ml of plasma is required. This constraint makes it difficult to determine drug levels when blood sample volumes are limited. However, drugs with low plasma-protein binding can be reliably extracted from plasma by ultra-filtration with a minimal loss due to the protein-bound fraction. This study validated a single-step ultra-filtration method for extracting fluconazole (FLC), a first-line antifungal agent with a weak plasma-protein binding, from plasma to determine its concentration by HPLC. Spiked FLC standards and unknowns were prepared in human and rat plasma. Samples (240 microl) were transferred into disposable microtube filtration units containing cellulose or polysulfone filters with a 5 kDa cut-off. After centrifugation for 60 min at 15000g, FLC concentrations were measured by direct injection of the filtrate into the HPLC. Using cellulose filters, low molecular weight proteins were eluted early in the chromatogram and well separated from FLC that eluted at 8.40 min as a sharp single peak. In contrast, with polysulfone filters several additional peaks interfering with the FLC peak were observed. Moreover, the FLC recovery using cellulose filters compared to polysulfone filters was higher and had a better reproducibility. Cellulose filters were therefore used for the subsequent validation procedure. The quantification limit was 0.195 mgl(-1). Standard curves with a quadratic regression coefficient > or = 0.9999 were obtained in the concentration range of 0.195-100 mgl(-1). The inter and intra-run accuracies and precisions over the clinically relevant concentration range, 1.875-60 mgl(-1), fell well within the +/-15% variation recommended by the current guidelines for the validation of analytical methods. Furthermore, no analytical interference was observed with commonly used antibiotics, antifungals, antivirals and immunosuppressive agents. Ultra-filtration of plasma with cellulose filters permits the extraction of FLC from small volumes (240 microl). The determination of FLC concentrations by HPLC after this single-step procedure is selective, precise and accurate.

Application of capillary zone electrophoresis with off-line solid-phase extraction to in vitro metabolism studies of antifungals

A simple and robust solid-phase extraction (SPE) procedure for the cleanup and sample preconcentration of antifungals (ketoconazole, clotrimazole, itraconazole, fluconazole, and voriconazole) and their metabolites after incubation with human liver microsomes, as well as a simplified capillary zone electrophoresis (CZE) method for their rapid analysis, have been developed to determine the stability of these compounds in in vitro samples. Three different sample pretreatment procedures using SPE with reversed-phase sorbents (100 mg C8, 100 mg C18, and 30 mg Oasis-HLB) were studied. The highest and most reproducible recoveries were obtained using a 30 mg Oasis-HLB sorbent and methanol containing 2% acetic acid as eluent. Enrichment by a factor of about four times was achieved by reconstituting the final SPE eluates to a small volume. For the CZE separation, good separations without interfering peaks due to the in vitro matrix were obtained with a simple running electrolyte using a fused-silica capillary. The best separation for all components originated by each tested drug after incubation with human liver microsomes (unmetabolized parent drug and its metabolites) was obtained using a 0.05 M phosphate running buffer (pH 2.2) without additives. The effect of the injection volume was also investigated in order to obtain the best sensitivity. Performance levels in terms of precision, linearity, limits of detection, and robustness were determined.

Can fluconazole concentrations in saliva be used for therapeutic drug monitoring?

The saliva/plasma concentration ratio of fluconazole was investigated in 22 HIV-1-infected individuals with an oropharyngeal Candida infection to determine whether saliva fluconazole concentrations could provide useful information for therapeutic drug monitoring in this population. Steady-state paired plasma and saliva samples were obtained after approximately 1 week of treatment with 50-or 100-mg fluconazole as capsules. A significant correlation between plasma and salivary levels of fluconazole was observed. The median saliva/plasma concentration ratio was 1.3 and was independent of the ingested dose and the plasma fluconazole concentration. The prediction of fluconazole concentrations in plasma from the concentrations in saliva was, although unbiased, not precise. From these findings, the authors conclude that although stimulated salivary fluconazole concentrations are significantly correlated with plasma concentrations, it is not possible to predict plasma fluconazole levels from the salivary concentrations with adequate precision. However, saliva fluconazole concentrations have sufficient value to test for compliance and even semiquantitative prediction of plasma concentrations.

Optimization of the separation of a group of antifungals by capillary zone electrophoresis

Two simple, rapid, and efficient methods for the analysis of seven antifungal compounds have been developed by capillary zone electrophoresis. Resolutions higher than 1.5 were obtained using 0.025 M phosphate buffer (pH 2.30) (analysis time close to 9 min) or 0.2 M formic acid (pH 2.15) (analysis time close to 6 min), with an applied voltage of 20 kV and a temperature of 30 degrees C. The highest sensitivity and selectivity can be obtained using phosphate buffer but the shortest analysis times are achieved in the formic system. The analytical characteristics of the optimized methods were investigated. The reproducibility obtained for migration times (RSD(n = 10) < or = 1.0%) and peak areas (RSD(n = 10) < or = 4.3%) was acceptable, but better reproducibilities were obtained when verapamil was used as internal standard (RSD(n = 10) < 0.4% for relative migration times and RSD(n = 10) < or = 2.2% for peak area ratios). The lowest limit of detection was obtained for clotrimazole (0.12 microg/ml) and the highest for fluconazole and voriconazole (0.90 microg/ml). The lowest and the highest limits of quantitation were, respectively, 0.40 microg/ml for clotrimazole and 3.00 microg/ml for fluconazole and voriconazole.

Simultaneous determination of the HIV protease inhibitors indinavir, amprenavir, saquinavir, ritonavir, nelfinavir and the non-nucleoside reverse transcriptase inhibitor efavirenz by high-performance liquid chromatography after solid-phase extraction

As part of an on-going study on the suitability of a formal therapeutic drug monitoring (TDM) of antiviral drugs for improving the management of HIV infection, a high-performance liquid chromatography method has been developed to quantify simultaneously in plasma five HIV protease inhibitors (PIs) (i.e., indinavir, amprenavir, saquinavir, ritonavir, nelfinavir) and the novel non-nucleoside reverse transcriptase inhibitor efavirenz. After viral inactivation by heat (60 degrees C for 60 min), plasma (600 microl), with clozapine added as internal standard, is diluted 1:1 with phosphate buffer, pH 7 and subjected to a solid-phase extraction on a C18 cartridge. Matrix components are eliminated with 2 x 500 microl of a solution of 0.1% H3PO4 neutralised with NaOH to pH 7. PIs and efavirenz are eluted with 3 x 500 microl MeOH. The resulting eluate is evaporated under nitrogen at room temperature and is reconstituted in 100 microl 50% MeOH. A 40-microl volume is subjected to HPLC analysis onto a Nucleosil 100, 5 microm C18 AB column, using a gradient elution of MeCN and phosphate buffer adjusted to pH 5.15 and containing 0.02% sodium heptanesulfonate: 15:85 at 0 min-->30:70 at 2 min-->32:68 at 8 min-->42:58 at 18 min-->46:54 at 34 min, followed by column cleaning with MeCN-buffer, pH 5.15 (90:10), onto which 0.3% AcOH is added. Clozapine, indinavir, amprenavir, saquinavir, ritonavir, efavirenz and nelfinavir are detected by UV at 201 nm at a retention time of 8.2, 13.0, 16.3, 21.5, 26.5, 28.7 and 31.9 min, respectively. The total run time for a single analysis is 47 min, including the washing-out and reequilibration steps. The calibration curves are linear over the range 100-10,000 ng/ml. The absolute recovery of PIs/efavirenz is always higher than 88%. The method is precise with mean inter-day relative standard deviations within 2.5-9.8% and accurate (range of inter-day deviations -4.6 to +4.3%). The in vitro stability of plasma spiked with PIs/efavirenz at 750, 3000 and 9000 ng/ml has been studied at room temperature, -20 degrees C and +60 degrees C. The method has been validated and is currently applied to the monitoring of PIs and efavirenz in HIV patients. This HPLC assay may help clinicians confronted to questionable compliance, side effects or treatment failure in elucidating whether patients are exposed to adequate circulating drug levels. The availability of such an assay represents an essential step in elucidating the utility of a formal TDM for the optimal follow-up of HIV patients.

Fluconazole bioequivalence study: quantification by tandem mass spectrometry

To develop a new method for quantifying fluoconazole in human plasma and to compare the bioavailability of two fluconazole capsule formulations, an open, randomized, two-period crossover study with a one-week washout interval was conducted in 24 healthy volunteers. Plasma samples were obtained up to 168 hours after drug administration and the serum fluconazole concentrations were analyzed using electrospray tandem mass spectrometry coupled to liquid chromatography using multiple reaction monitoring mode. The pharmacokinetic parameters obtained for fluconazole after the administration of each formulation included the Area under the curve (AUC)(0-168h), AUC(0-infinity), Cmax, Cmax/AUC(0-168h), Tmax, elimination rate constant (Ke), and half-life (T1/2). Within- and between-run imprecision was less than 2.3% and 8.2%, respectively. Inaccuracy within and between runs was -1.5% and -9.7%, respectively. The pharmacokinetic parameters for bioequivalence showed a normal distribution, and the variance of AUC(0-168h), AUC(0-infinity), and Cmax were homoscedastic. The geometric mean for the Fluconal/Zoltec (Fluconal; Libbs Farmacêutica Ltda, São Paulo, Brazil; Zoltec; Laboratórios Pfizer Ltda., São Paulo, Brazil) individual percent ratio was 94.9% for AUC(0-168h), 94.7% for AUC(0-infinity), 80.1% for Cmax, 102.6% for Ke, 97.5% for T1/2, and 0.93 for Tmax (arithmetic mean of individual differences). We have developed a method in which liquid chromatography is coupled with electrospray tandem mass spectrometry to improve the pharmacokinetic analysis of fluconazole. Because the 90% CI AUC is within the interval proposed for the Food and Drug Administration, we concluded that Fluconal is bioequivalent to Zoltec in terms of absorption. The CV was 27.5% for the Cmax parameter, indicating that fluconazole's absorption rate is highly variable. The European Union Regulatory Agency accepts an interval of 70-143%, and because the 90% CI for Cmax is within the interval proposed for the European Union agency, we conclude that Fluconal is bioequivalent to Zoltec for the rate of absorption.

High-performance liquid chromatographic determination of fluconazole in plasma

A high-performance liquid chromatographic method with ultraviolet absorbance detection at 260 nm was developed for the analysis of fluconazole in plasma. The method involves sample clean-up by liquid-liquid extraction. The proposed technique is reproducible, selective, reliable and sensitive. Calibration standards were prepared in the range 1.25-20 mg/l. The limit of quantitation was 0.4 mg/l. The coefficients of variation were 5% between measurements of a single extract injected in duplicate, and 7% between two extractions of spiked samples at the same concentrations. The separation between fluconazole and endogenous substances was satisfactory. This method was designed in order to minimise the risk of interference from substances that could be co-administered to critically ill patients undergoing hemodiafiltration. With a run time below 5 min, the present method is rapid and easy to use for later clinical studies, as well as for routine monitoring.

Pharmacokinetics of fluconazole in saliva and plasma after administration of an oral suspension and capsules

The concentrations of fluconazole were determined at steady state in the saliva and plasma of 10 healthy volunteers after ingestion of fluconazole as capsules and after flushing the mouth for 2 min with the same dose formulated as an oral suspension and swallowing of the drug. Saliva and plasma samples were analyzed by a validated high-performance liquid chromatographic assay. Flushing and swallowing of the oral suspension resulted in a significantly (P = 0.005) higher mean area under the concentration-versus-time curve (AUC) from 0 to 24 h in saliva (89.13 +/- 23.42 mg.h/liter) than that obtained after ingestion of the same dose as capsules (69.27 +/- 12.89 mg . h/liter). The calculated mean maximum concentration in saliva just after swallowing of the suspension was 97.99 +/- 6.12 mg/liter. The peak fluconazole concentration in saliva after the ingestion of the capsules was 3.55 +/- 0.40 mg/liter. The fluconazole oral suspension and capsules resulted in comparable concentrations and AUCs in plasma. Thus, because of a higher local level of drug exposure in terms of both higher peak concentrations in saliva and a higher salivary AUC, the fluconazole oral suspension has theoretical advantages over the capsule formulation in the treatment of oropharyngeal candidiases.