Gas chromatographic method for the determination of fluconazole, a novel antifungal agent, in human plasma and urine

Bio-analytical liquid chromatographic-based method with a mixed mode online solid phase extraction for drug monitoring of fluconazole in human serum

A simple, cost-effective and sensitive liquid chromatography-based bio-analytical method has been developed and validated for therapeutic drug monitoring of fluconazole (FLUC) in human serum. Integration of online mixed-mode solid-phase extraction (SPE) into the analytical system was the key for direct injection of untreated serum samples. A short protein-coated (PC) µBondapak CN silica column (PC-µB-CN-column) as a SPE tool and phosphate buffer saline (PBS) (pH 7.4) as an eluent were applied in the extraction step. PC-µB-CN-column operates in two different chromatographic modes. Using PBS, proteins were extracted from serum samples by size-exclusion liquid chromatography, while FLUC trapping was reversed-phase liquid chromatography dependent. FLUC was then eluted from the PC-µB-CN-column onto the quantification position using a mixture of acetonitrile-distilled deionized water (20:80, v/v) as an eluent and ODS analytical column. FLUC was separated at ambient temperature (22 ± 1 °C) and detected at 260 nm. The method was linear over the range of 200-10000 ng/mL. FLUC recovery in untreated serum samples ranged from 97.8 to 98.8% and showed good accuracy and precision. The reliability of the developed method was evaluated by studying the pharmacokinetic profile of FLUC in humans after an oral administration of a single 150 mg tablet.

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.

Validated HPLC method for the determination of fluconazole in human plasma

A high-performance liquid chromatographic assay with UV detection was developed for the determination of fluconazole in human plasma. The method utilized solid-phase extraction for sample clean-up. The separation was performed on a C18 column by isocratic elution with a mobile phase of 10 mM acetate buffer at pH 5.0 and methanol and UV detection at 210 nm. Validation was performed according to the current recommendations of the USFDA bioanalytical method validation guidance. The method proved to be specific, accurate, precise and linear between 200 and 10,000 ng/mL with correlation coefficients greater than 0.999. The coefficient of variation was within 11% and relative deviation was less than 10%.

On-line determination of fluconazole in blood and dermal rat microdialysates by microbore high-performance liquid chromatography

To study the distribution of fluconazole in the dermis of the rat, on-line microdialysis using double-site sampling coupled with a microbore HPLC system was developed. The chromatographic conditions consisted of a mobile phase of 20 mM diammonium phosphate-acetonitrile (75:25, v/v, pH 7.0) pumped through a microbore C(18) column at 40 microl/min. The eluent was monitored with UV detector with UZ flow cell (30 mm path length) at 210 nm. A microbore 10-port pneumatic valve fitted with two loops of 1 microl was used to collect and directly inject microdialysates from jugular and dermal probes. The retention time was 5.8 min for fluconazole and 10.1 min for its fluorinated analog, UK-54373 used as a retrodialysis marker. The assay was precise, with inter- and intra-assay relative standard deviation values of 0.64 and 0.71%, respectively, and with a good linearity (r=0.999) in the range of 0.15-20 microg/ml with only 1 microl injected onto the column. The LOD and LOQ values for fluconazole were 0.100 and 0.150 microg/ml, respectively. The applicability of the method was demonstrated by studying the disposition of fluconazole in blood and dermis following i.v. bolus at a dose of 10 mg/kg.

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.

Fluconazole concentrations in pulmonary tissue and pericardial fluid

In order to investigate the clinical efficacy of the triazole antifungal agent fluconazole (FCA) in the treatment of pulmonary mycosis, in the present study the concentrations of fluconazole in human pulmonary tissue, pericardial fluid and serum were determined at 1, 2, 12 and 13 h after intravenous administration of fluconazole 200 mg. The mean FCA concentrations in the serum were 4.04 mg/l (1 h), 3.82 mg/l (2 h), 2.35 mg/l (12 h) and 2.13 mg/l (13 h). The respective FCA levels in the pulmonary tissue were 4.64 mg/kg, 4.54 mg/kg; 3.50 mg/kg and 3.40 mg/kg and the concentrations in the pericardial fluid were 3.86 mg/l, 3.57 mg/l, 2.35 mg/l and 2.13 mg/l. The FCA concentrations in the pulmonary tissue that were statistically significant higher than the serum concentrations were found at 2 h, 12 h and 13 h after intravenous administration (p < 0.05).

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.

Serum level determination of fluconazole by high-performance liquid chromatography and bioassay

An HPLC method using a reverse phase system, an isocratic mobile phase and 1-phenyl-1,2 ethanediol as internal standard and a well diffusion bioassay using a strain of Candida pseudotropicalis were compared for the measurement of fluconazole in serum. Both methods permit determination of fluconazole in the range from 1 mg/L to 30 mg/L. The correlation between both methods was found to be r = 0.89. Both methods are useful for monitoring the serum level of fluconazole in clinical routine work.

A comparison between solid phase extraction and supercritical fluid extraction for the determination of fluconazole from animal feed

The application of supercritical fluid extraction with carbon dioxide and modified carbon dioxide for the determination of fluconazole from an animal feed was studied. A fractional factorial design approach was used to examine the significant experimental variables for quantitative extraction of fluconazole. Gas chromatography with either flame ionisation or mass selective detection was used for quantitation of the extracts. The results indicated that modifier (methanol) had the greatest effect on the recovery of fluconazole from the animal feed.

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

A high-performance liquid chromatographic (HPLC) assay has been developed for the determination of the antifungal drug fluconazole in saliva and plasma of patients infected with the human immunodeficiency virus (HIV). Samples can be heated at 60 degrees C for 30 min to inactivate the virus without loss of the analyte. The sample pretreatment involves a liquid-liquid extraction with chloroform-1-propanol (4:1, v/v). The chromatographic analysis is performed on a Lichrosorb RP-18 (5 microns) column by isocratic elution with a mobile phase of 0.01 M acetate buffer (pH 5.0)-methanol (70:30, v/v) and ultraviolet (UV) detection at 261 nm. The lower limit of is 100 ng/ml in plasma (using 500-microliters samples) and 1 microgram/ml in saliva (using 250-microliters samples) and the method is linear up to 100 micrograms/ml in plasma and saliva. At a concentration of 5 micrograms/ml the within-day and between-day precision in plasma are 7.1 and 5.7%, respectively. In saliva the within-day and between-day precision is 10.8% (at 5 micrograms/ml). The methodology is now being used in pharmacokinetic studies in HIV-infected patients in our hospital.

Gas chromatographic and high-performance liquid chromatographic methods for the determination of genaconazole in biological fluids

Gas chromatographic (GC) and high-performance liquid chromatographic (HPLC) methods were developed for the determination of genaconazole in biological fluids. Both methods involved organic solvent extraction followed by solid-phase extraction on a C18 column. GC analysis utilized a megabore column (DB-17) with 63Ni electron-capture detection, whereas HPLC analysis utilized separation on a reversed-phase column with a methanol-phosphate buffer mixture as the mobile phase and quantitation by UV absorbance at 208 nm. Both methods yielded good linearity, accuracy and precision. The limit of quantitation (LOQ) was 0.025 microgram per ml of serum for GC and 0.2 microgram per ml of serum or 0.5 microgram per ml of urine for HPLC analysis. Both GC and HPLC methods were used for the determination of serum concentration-time curves of genaconazole in man following oral administration of a 50-mg dose.

Clinical pharmacokinetics of fluconazole

Fluconazole was recently developed for the treatment of superficial and systemic fungal infections. Triazole groups and insertion of 2 fluoride atoms increase the polarity and hydrosolubility of the drug, allowing it to be used in a parenteral form. Bioassay methods using Candida pseudotropicalis as a test organism were the first techniques used for the determination of fluconazole in body fluids. Gas chromatographic and high performance liquid chromatographic methods were later developed with better accuracy and sensitivity. Prediction of efficacious concentrations in patients from the minimum inhibitory concentrations in vitro seems to be uncertain because of low efficacy of the drug on some yeasts in vitro compared with efficacy in vivo in animal models. Oral forms (capsule and solution) are quickly absorbed and bioavailability is nearly complete (about 90%). Plasma protein binding is low (11 to 12%) and fluconazole circulates as active drug. Distribution is extensive throughout the tissues and allows the treatment of a variety of systemic fungal infections. The average elimination half-life (t1/2) of 31.6 +/- 4.9h is long, with a minimum of 6 days needed to reach steady-state; thus, a loading dose (equal to double the maintenance dose) is recommended. The metabolism of fluconazole is not qualitatively or quantitatively significant. The main route of elimination is renal. The mean +/- SD (calculated from published data) total and renal clearance values are 19.5 +/- 4.7 and 14.7 +/- 3.7 ml/min (1.17 +/- 0.28 and 0.88 +/- 0.22 L/h), respectively. Concentrations of fluconazole in blood after administration of single doses correlated well with the administered dose. There was very little interassay variation between the data reported in literature. Concentrations in blood after multiple doses also exhibit little variation and the accumulation factor was between 2.1 and 2.8. Fluconazole was found in many body fluids, especially in cerebrospinal fluid and dialysis fluid, allowing the treatment of systemic fungal infections such as coccidioidal meningitis and fungal peritonitis. Concentrations of 1 to 3 mg/L and 20 mg/L are the extreme values expected in clinical practice. In renal insufficiency the fluconazole t1/2 is longer, requiring dosage adjustment in relation to creatinine clearance. In continuous ambulatory peritoneal dialysis a 150mg dose in a 2L dialysis solution every 2 days has been proposed. In haemodialysis, a dose of 100 or 200mg should be given at the end of each dialysis session. Neither old age nor irradiation affect fluconazole pharmacokinetics, but the t1/2 was shorter in children.(ABSTRACT TRUNCATED AT 400 WORDS)

The pharmacokinetics of fluconazole during haemodialysis in uraemic patients

We have studied the pharmacokinetics of fluconazole in five patients on long-term haemodialysis. The single-pass extraction rate of the dialyzer was 59 (3.5)% (n = 4), and the serum concentration was reduced by haemodialysis for 3 or 4 h by 26 (3.2)% (n = 5) and 39 (2.2)% (n = 9) respectively. The estimated amount extracted by a dialysis of 4 h was 33 (3.2)% (n = 4) of the dose. During repeated administration the serum fluconazole concentration increased, reaching a plateau at about 4 times the peak concentration after the first dose. After discontinuing administration the serum fluconazole concentration fell by 25% in every 3 h dialysis session. We conclude that fluconazole should be given in the usual dose of 100 or 200 mg at the end of every haemodialysis session.

Safety and pharmacokinetics of fluconazole in children with neoplastic diseases

To evaluate the safety, tolerance, and pharmacokinetics of fluconazole in children with neoplastic diseases, we studied fluconazole in 26 children, aged 5 to 15 years, with normal renal function who were receiving treatment for cancer. The patients received fluconazole, 2, 4, or 8 mg/kg per day for 7 days intravenously for a 2-hour period. Patients had no nausea or vomiting related to fluconazole; three patients had an asymptomatic rise in hepatic aminotransferase values after four to six doses (one patient at 2 mg/kg per day and two patients at 8 mg/kg per day), which returned to normal within 2 weeks after discontinuation of the drug. Fluconazole showed linear first-order kinetics over the dosage range tested and during multiple dosing. After the first dose, mean clearance was 22.8 +/- 2.3 ml/min, volume of distribution 0.87 +/- 0.06 L/kg, and terminal elimination half-life 16.8 +/- 1.1 hours. Similarly, after the last dose, clearance was 19.4 +/- 1.3 ml/min, volume of distribution 0.84 +/- 0.04 L/kg, and terminal elimination half-life 18.1 +/- 1.2 hours. Patients receiving their first fluconazole dose of 8 mg/kg achieved peak serum levels of 9.5 +/- 0.4 microgram/ml and trough levels of 2.7 +/- 0.5 microgram/ml 24 hours later, and an area under the serum concentration-time curve from time zero to infinity of 186 +/- 16 micrograms.hr per milliliter. Renal clearance of fluconazole was 65% +/- 5% of total clearance and demonstrated the predominantly renal excretion of this drug. We suggest that the shorter serum half-life and the higher frequency of aminotransferase elevations in comparison with those of adults warrant careful investigation of fluconazole in controlled clinical trials.

Rapid and sensitive assay for fluconazole which uses gas chromatography with electron capture detection

Fluconazole, an orally active antifungal agent, has been shown to be clinically beneficial for maintenance therapy of cryptococcal meningitis. A sensitive gas-liquid chromatographic assay with electron capture detection, which required only a single extraction step and precluded any pretreatment of the chromatographic column, was developed for fluconazole. The assay was linear from 0.1 to 20 micrograms/ml, with a correlation coefficient of 0.999. The intraassay and interassay coefficients of variation were less than 9%. The measured values on average were within 8% of the target values. The extraction recoveries ranged from 87 to 106%. Steady-state plasma fluconazole levels (mean +/- standard deviation) in three AIDS patients with cryptococcal meningitis receiving 200 mg of fluconazole per day ranged from 8.95 +/- 1.32 to 11.41 +/- 0.63 micrograms/ml and were within the expected range for this dosing rate, on the basis of previous studies. The ratio of fluconazole concentration in cerebrospinal fluid to fluconazole concentration in plasma in one patient receiving 400 mg/day was 0.73 at steady state and was consistent with published reports.

Standardization of a fluconazole bioassay and correlation of results with those obtained by high-pressure liquid chromatography

An improved bioassay for fluconazole was developed. This assay is sensitive in the clinically relevant range (2 to 40 micrograms/ml) and analyzes plasma, serum, and cerebrospinal fluid specimens; bioassay results correlate with results obtained by high-pressure liquid chromatography (HPLC). Bioassay and HPLC analyses of spiked plasma, serum, and cerebrospinal fluid samples (run as unknowns) gave good agreement with expected values. Analysis of specimens from patients gave equivalent results by both HPLC and bioassay. HPLC had a lower within-run coefficient of variation (less than 2.5% for HPLC versus less than 11% for bioassay) and a lower between-run coefficient of variation (less than 5% versus less than 12% for bioassay) and was more sensitive (lower limit of detection, 0.1 micrograms/ml [versus 2 micrograms/ml for bioassay]). The bioassay is, however, sufficiently accurate and sensitive for clinical specimens, and its relative simplicity, low sample volume requirement, and low equipment cost should make it the technique of choice for analysis of routine clinical specimens.

Effect of oral antacid administration on the pharmacokinetics of oral fluconazole

Absorption and elimination of fluconazole after oral administration of a 100-mg capsule were unaffected by concomitant administration of an antacid containing aluminum and magnesium hydroxides.

Fluconazole levels in plasma and vaginal secretions of patients after a 150-milligram single oral dose and rate of eradication of infection in vaginal candidiasis

Mean peak concentrations of fluconazole in plasma and vaginal secretions of females after a 150-mg single oral dose were shown to be 2.82 micrograms/ml and 2.43 micrograms/g, respectively. Our results indicate that clinically efficacious concentrations of fluconazole in vaginal secretions are easily achieved after this single oral dose.

Sputum levels of fluconazole in humans

We measured fluconazole levels in sputum samples obtained from 11 bronchiectatic volunteers at 4 and 24 h after a single oral dose of 150 mg of fluconazole. Levels in sputum were similar to levels in plasma at both times.

Assay of fluconazole by megabore capillary gas-liquid chromatography with nitrogen-selective detection

A megabore column gas-liquid chromatographic method which uses nitrogen-phosphorus detection was developed for the analysis of fluconazole in plasma, serum, cerebrospinal fluid, or urine. The assay was linear from 0.2 to 200 micrograms/ml and had an average coefficient of variation of 7%. The suitability of the assay for pharmacokinetic studies was demonstrated.

Determination of fluconazole in biological fluids by capillary column gas chromatography with a nitrogen detector

Fluconazole concentrations in biological fluids were determined by high-performance gas chromatography. A simple extraction procedure with chloroform, under basic conditions and after the addition of UK-47,265 as the internal standard and with no evaporation stage, was carried out prior to analysis. A solid injector and a 15-m capillary column, coated with a nonpolar phase and connected to a nitrogen-selective detector that afforded an excellent selectivity and sensitivity, constituted the gas chromatographic system. The duration of each analysis was less than 4 min and the minimum detectable serum concentration was 50 ng/mL. In five patients undergoing chronic peritoneal dialysis, the mean serum concentrations +/- SD at 1, 6, and 48 h after the intraperitoneal administration of a single dose of fluconazole were, respectively, 325 +/- 75, 928 +/- 159, and 607 +/- 80 ng/mL.

Fluconazole and testosterone: in vivo and in vitro studies

Fluconazole (UK-49,858), a novel bis-triazole antifungal agent, was given orally to groups of 10 male volunteers at doses of 25 and 50 mg/day for 28 days. Blood samples for testosterone estimation were taken from these and from a placebo group at several time points on days 1, 14, and 28 of the study, and the assay results demonstrated that the compound had no significant effect on circulating testosterone levels. Similarly, in studies with rat Leydig cells in vitro, fluconazole at concentrations up to 10 micrograms/ml was found to be only a weak inhibitor of testosterone production, whereas ketoconazole caused more than 50% inhibition at 0.1 microgram/ml. It is concluded that fluconazole, in contrast to ketoconazole, has little effect on the biosynthesis of testosterone by mammalian cells.

Fluconazole penetration into cerebrospinal fluid in humans

One hour after intravenous doses of 50 mg/d fluconazole for 6 days or 100 mg/d for seven days to healthy subjects, the cerebrospinal fluid concentrations of fluconazole were 1.26 mg/L and 2.74 mg/L, respectively. These values were approximately 52% and 62% those of serum. Four patients with an initial clinical diagnosis of meningitis also had significant concentrations of fluconazole in the cerebrospinal fluid.

Overview of medically important antifungal azole derivatives

Fungal infections are a major burden to the health and welfare of modern humans. They range from simply cosmetic, non-life-threatening skin infections to severe, systemic infections that may lead to significant debilitation or death. The selection of chemotherapeutic agents useful for the treatment of fungal infections is small. In this overview, a major chemical group with antifungal activity, the azole derivatives, is examined. Included are historical and state of the art information on the in vitro activity, experimental in vivo activity, mode of action, pharmacokinetics, clinical studies, and uses and adverse reactions of imidazoles currently marketed (clotrimazole, miconazole, econazole, ketoconazole, bifonazole, butoconazole, croconazole, fenticonazole, isoconazole, oxiconazole, sulconazole, and tioconazole) and under development (aliconazole and omoconazole), as well as triazoles currently marketed (terconazole) and under development (fluconazole, itraconazole, vibunazole, alteconazole, and ICI 195,739).