The effects of renal impairment on the pharmacokinetics and safety of fosfluconazole and fluconazole following a single intravenous bolus injection of fosfluconazole

Impact of tolerance to fluconazole on treatment response in Candida albicans bloodstream infection

BACKGROUND

Treatment of Candida albicans bloodstream infection with fluconazole is associated with significant mortality despite in vitro susceptibility to the drug.

OBJECTIVES

We sought to determine whether tolerance to fluconazole is predictive of treatment failure.

METHODS

We reviewed patients with monomicrobial C albicans bloodstream infection who received primary monotherapy with fluconazole. Tolerance to fluconazole, defined as the fraction of growth above the MIC, was quantified using the disc diffusion assay and digital image analyses. Survival analyses were performed with host and treatment factors as predictive variables.

RESULTS

Among 44 patients included in the study, all-cause mortality was 29.5% at 30 days and 43.1% at 12 weeks. Forty-one isolates (93%) were susceptible to fluconazole (MIC50, 0.5 mg/L). Fluconazole tolerance was strongly associated with death for patients treated with fluconazole within 24 h of candidemia onset (33.3% vs 0%; p = .007), but not among patients whose treatment was started later. MIC did not correlate with survival, regardless of treatment delay. A Cox regression model including time to treatment, tolerance to fluconazole, fluconazole exposure and Pitt bacteraemia score provided good prediction of treatment outcome (area under the receiver-operator curve, 0.82).

CONCLUSIONS

In patients with C albicans bloodstream infection, tolerance testing was predictive of fluconazole efficacy if the drug was started early. Further study is required to validate the utility of this metric to guide treatment choices.

The association between fluconazole dose and MIC with mortality and persistence in candidemia

To evaluate the association between fluconazole exposure parameters and clinical outcomes in patients with candidemia. We retrospectively included all adults with candidemia in a single center from January 2009 to December 2017, treated initially with fluconazole for fluconazole-susceptible candidemia. We assessed the association between fluconazole exposure parameters and 30-day mortality or 14-day clinical failure, a composite of mortality at day 14 or persistent candidemia ≥ 72 h, in all patients and in patients with C. glabrata candidemia. During the study period, 158 patients fulfilled the inclusion criteria. Main species were C. albicans 66 (41.8%), C. glabrata 35 (22.2%), and C. parapsilosis 31 (19.6%). Sixty patients (38%) died within 30 days. Sixty-one patients (38.6%) experienced 14-day failure. In 30-day survivors, the median AUC₂₄/MIC was 2279 [398, 5989] versus 1764 [238, 6714] h in non-survivors, p = 0.75. Median fluconazole MIC was 0.75 [0.25, 4] and 1 [0.22, 5.50] mg/L, p = 0.54, respectively. Similar non-significant differences were found for other fluconazole exposure parameters and in the 14-day clinical failure analysis. For C. glabrata, a higher AUC₂₄/MIC was observed among 30-day survivors with a median of 230 [77, 539] compared to 96 [75, 164] h in non-survivors, p = 0.008, in parallel with a trend for lower MIC values (median 7 [1, 2] versus 16 [8, 24] mg/L, p = 0.06, respectively). Currently used fluconazole dosing has no association with clinical outcome in Candida with low MIC values. For Candida species with high MICs, attention to dosing is needed.

Survival in Patients with Candida glabrata Bloodstream Infection Is Associated with Fluconazole Dose

Robust pharmacodynamic indices that align fluconazole dose or exposure with outcomes in invasive candidiasis due to Candida glabrata remain elusive. The purpose of this retrospective multicenter study was to evaluate a cohort of 127 patients with C. glabrata fungemia treated with fluconazole, using adjusted analyses to identify risk factors for 28-day death. No significant correlations were found between fluconazole area under the curve (AUC), AUC/MIC ratio, or MIC and survival. In multivariate logistic regression analyses, however, higher average fluconazole dose (odds ratio [OR], 1.006 [95% confidence interval [CI], 1.001 to 1.010]; P = 0.008), average fluconazole dose of ≥400 mg (OR, 3.965 [95% CI, 1.509 to 10.418]; P = 0.005), and higher fluconazole dose on day 1 of therapy (OR, 1.007 [95% CI, 1.002 to 1.011]; P = 0.002) were found to be independent predictors of 28-day survival. Additionally, the presence of a central venous catheter at the time of infection was found to be a significant risk factor for death. In conclusion, we found fluconazole dose to be an independent predictor of 28-day survival for patients with C. glabrata fungemia, with doses of ≥400 mg/day being associated with 28-day survival rates approaching 90%. These data indicate the use and efficacy of fluconazole in the treatment of this serious infection. Aggressive dosing appears to be necessary when fluconazole is used for the treatment of C. glabrata fungemia, irrespective of MIC.

Fluconazole levels in serum and cerebrospinal fluid according to daily dosage in patients with cryptococcosis and other fungal infections

Fluconazole is extensively used for the treatment of candidiasis and cryptococcosis. Among other factors, successful treatment is related to appropriate fluconazole levels in blood and cerebrospinal fluid. In the present study, fluconazole levels were determined in 15 patients, 14 of whom had AIDS and 13 had neurocryptococcosis. The only selection criterion was treatment with fluconazole, which was performed with a generic or similar form of the drug. Fluconazole level was determined by high performance liquid chromatography and the susceptibility profile of Cryptococcus spp. isolated from the patients was assessed by broth microdilution. Blood and cerebrospinal fluid fluconazole levels were found to be related to the fluconazole daily dose, and exceeded the minimum inhibitory concentration of this antifungal for the Cryptococcus spp. isolates. A good correlation was observed between serum and cerebrospinal fluid drug concentration. In conclusion, treatment with non-original fluconazole under usual medical practice conditions results in appropriate blood and cerebrospinal fluid levels of the drug for inhibiting Cryptococcus spp. susceptible to this antifungal drug. The relatively common failures of neurocryptococcosis treatment appear not to be due to insufficient fluconazole levels in the cerebrospinal fluid, especially with the use of daily doses of 400-800mg.

Effects of fluconazole based medicated feed on haemato-immunological responses and resistance of Labeo rohita against Saprolegnia parasitica

Fluconazole (FLZ) is a new azole antifungal drug having no earlier record of its utilization for the treatment of fish diseases. A 55-days experiment was carried out to delineate the role of FLZ based medicated feed on haemato-immunological responses and prevention of fungal infection in Labeo rohita fingerlings. Three hundred and sixty fingerlings were randomly distributed into four experimental groups in triplicates. Four iso-caloric and iso-nitrogenous purified medicated feeds were prepared with 0, 100, 200 and 300 mg FLZ 100 g^-1 feed. Haemato-immunological parameters like erythrocyte counts (EC), haemoglobulin (Hb), leucocyte counts (LC), packed cell volume (PCV), mean corpuscular haemoglobin (MCH), mean corpuscular volume (MCV), mean corpuscular haemoglobin concentration (MCHC), nitro-blue tetrazolium (NBT), albumin, globulin, total plasma protein were studied. The present study revealed that the continuous feeding of FLZ based feed for 15-30 days significantly (P < 0.05) increases the erythropoiesis, heme-synthesis, as well as the leucocytosis in rohu. However, all the doses exhibited equal protection from the infectious S. parasitica after 45 days of continuous feeding.

Differential association of fluconazole dose and dose/MIC ratio with mortality in patients with Candida albicans and non-albicans bloodstream infection

Targeting fluconazole therapy to achieve predefined pharmacodynamic goals has been suggested as a means of optimizing the treatment of patients with candidaemia. However, data regarding species-specific dosing targets are inconclusive. We retrospectively analysed a cohort of 75 adult patients with Candida bloodstream infection (BSI) who received initial treatment with fluconazole for ≥48 h (36 Candida albicans and 39 non-albicans Candida (NAC)). Fluconazole dose, the dose/MIC ratio and the 24-h area under the concentration-time curve (AUC24)/MIC ratio were determined for each patient, and classification and regression tree analysis was used to determine breakpoints for significant interactions with 30-day survival. Both fluconazole exposure parameters and patient-related and disease-related variables were assessed in univariable and multivariable survival models. The crude 30-day mortality rate was 32% (44% and 21% for C. albicans and NAC, respectively). An average fluconazole dose of >200 mg/day, a dose/MIC ratio of >400 and an AUC24/MIC ratio of >400 were associated with a higher 30-day survival rate and better microbiological response in patients with C. albicans BSI but not in those with NAC BSI. Baseline chronic kidney disease was a risk factor for fluconazole underdosing and mortality. Severity of sepsis (Sequential Organ Failure Assessment score) was the only significant predictor of death in patients with NAC BSI. We conclude that, although pharmacodynamic target-directed fluconazole dosing may help to optimize outcomes for patients with C. albicans BSI, additional studies are needed to define the role of fluconazole in the treatment of NAC BSI.

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.

Discovery of a potent tubulin polymerization inhibitor: synthesis and evaluation of water-soluble prodrugs of benzophenone analog

Prodrugs have proven to be very useful in enhancing aqueous solubility of sparingly water-soluble drugs, thereby increasing in vivo efficacy without a need of special excipients. In vitro and in vivo evaluations of a number of amino acid prodrugs of 1, a previously identified potent tubulin polymerization inhibitor and cytotoxic against various cancer cell lines led to the discovery of 3·HCl (l-valine attached) which is highly efficacious in mouse xenografts bearing human cancer. Pharmacokinetic analysis in rats revealed that compound 1 was released immediately upon administration of 3·HCl intravenously, with rapid clearance of 3·HCl indicating the effective cleavage of prodrug. Compound 3·HCl (CKD-516) has now been progressed to phase 1 clinical trial.

Prodrug strategies to overcome poor water solubility

Drug design in recent years has attempted to explore new chemical spaces resulting in more complex, larger molecular weight molecules, often with limited water solubility. To deliver molecules with these properties, pharmaceutical scientists have explored many different techniques. An older but time-tested strategy is the design of bioreversible, more water-soluble derivatives of the problematic molecule, or prodrugs. This review explores the use of prodrugs to effect improved oral and parenteral delivery of poorly water-soluble problematic drugs, using both marketed as well as investigational prodrugs as examples. Prodrug interventions should be considered early in the drug discovery paradigm rather than as a technique of last resort. Their importance is supported by the increasing percentage of approved new drug entities that are, in fact, prodrugs.

Association of fluconazole area under the concentration-time curve/MIC and dose/MIC ratios with mortality in nonneutropenic patients with candidemia

The present study tested in vitro susceptibility of Candida bloodstream isolates to fluconazole to determine if the ratio of the fluconazole area under the concentration-time curve (AUC) or weight-normalized daily dose (dose(wn)) to MIC correlated with mortality. Fluconazole susceptibility and outcome data were determined for 77 patients with a positive Candida blood culture between 2002 and 2005. The most commonly isolated Candida species were C. albicans (64%), C. glabrata (14%), C. parapsilosis (8%), C. tropicalis (6%), and C. lusitaniae (4%). Only two isolates were classified as fluconazole resistant by the CLSI M27-A2 method. Fluconazole MICs were highest against C. glabrata relative to other Candida species. Overall the crude mortality assessed at hospital discharge was 19.4% (n = 15). Mortality rates by species were as follows: C. albicans, 16.3%; C. glabrata, 36.4%; C. parapsilosis, 0%; C. tropicalis, 0%; C. lusitaniae, 33.3%. A mortality rate of 50% was noted among patients infected with nonsusceptible isolates (MIC > or = 16 microg/ml) compared to 18% for patients infected with susceptible (MIC < or = 8 microg/ml) isolates (P = 0.17). The fluconazole dose(wn)/MIC (24-h) values were significantly higher for the 62 survivors (13.3 +/- 10.5 [mean +/- standard deviation]) compared to the 15 nonsurvivors (7.0 +/- 8.0) (P = 0.03). The fluconazole AUC/MIC (24 h) values also trended higher for survivors (775 +/- 739) compared to nonsurvivors (589 +/- 715) (P = 0.09). These data support the dose-dependent properties of fluconazole. Underdosing fluconazole against less-susceptible Candida isolates has the potential to increase the risk of mortality associated with candidemia.

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.

The effects of hepatic impairment on the pharmacokinetics of fosfluconazole and fluconazole following a single intravenous bolus injection of fosfluconazole

AIMS

Fosfluconazole is a phosphate pro-drug of fluconazole (FLCZ). This study was conducted to determine the pharmacokinetics of fosfluconazole and FLCZ following a single intravenous injection of fosfluconazole in subjects with hepatic impairment and to compare them with healthy subjects.

METHODS

Twenty-four subjects (12 with normal hepatic function and 12 with chronic stable mild to moderate impaired hepatic function) received a single 1000-mg bolus intravenous injection of fosfluconazole. Concentrations of fosfluconazole and FLCZ were determined in plasma and urine samples taken up to 192 h and 48 h postdose, respectively.

RESULTS

The total clearance of fosfluconazole was higher and the t(1/2,Z) and mean residence time were shorter in hepatically impaired subjects than in normal subjects. This may reflect more rapid conversion to FLCZ. The degree of protein binding of fosfluconazole (> 90%) and the amount of fosfluconazole excreted in the urine were similar in both groups. Slightly higher mean plasma concentrations of FLCZ were observed in the impaired group than in the normal group; however, hepatic impairment had no statistically significant effect on the FLCZ pharmacokinetic parameters apart from t(max). The t(max) values were 4.8 h and 3.1 h in the normal and impaired subjects, respectively. The shorter t(max) for FLCZ is also consistent with the more rapid conversion in the impaired subjects. The ratios (95% confidence intervals) for C(max) and AUC of FLCZ (impaired/normal) were 106.0% (92.8, 121.2) and 115.6% (86.4, 154.7), respectively. There were no serious adverse events, and no discontinuations due to adverse events or laboratory test abnormalities. The adverse events reported were mostly mild in severity and no trend could be discerned between the groups.

CONCLUSIONS

Fosfluconazole was more rapidly converted to FLCZ in the hepatically impaired subjects but the FLCZ pharmacokinetic parameters (except t(max)) were not statistically significantly affected by hepatic impairment. Fosfluconazole was well tolerated by both groups. These results suggest that there is no requirement to adjust the dose of fosfluconazole when administered to subjects with mild to moderate hepatic impairment.

[Nonclinical studies and clinical studies on fosfluconazole, a triazole antifungal agent (Prodif)]

Fosfluconazole is a phosphate prodrug of fluconazole that has been developed to reduce the volume of fluid required to administer fluconazole by the intravenous route. Fosfluconazole is hydrolyzed by alkaline phosphatase to fluconazole and phosphoric acid. Fosfluconazole had no significant antifungal activity in vitro. However, in rat models of acute systemic candidiasis and intracranial cryptococcosis, fosfluconazole retained the antifungal potency and efficacy of fluconazole. This reflects the effective conversion of the prodrug to the parent during the course of the experiments. The 2-day-loading dose regimen led to earlier achievement of target fluconazole steady state plasma concentrations compared to use of the 1-day- or no-loading dose regimen of fosfluconazole. The efficacy and safety of fosfluconazole were investigated with the 2-day-loading dose regimen in patients with deep-seated mycosis caused by Candida and Cryptococcus species. The efficacy rates were 73.8% in the domestic Phase III study and 91.7% in the foreign Phase III study. Adverse events were observed in 31 cases (19.4%) out of 160 in both studies. These results indicate that fosfluconazole is effective for the treatment of deep-seated mycosis and shows no clinically significant adverse events in the Phase III studies