Fluconazole. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic potential in superficial and systemic mycoses

Ethynyl-substituted benzosiloxaboroles: the role of C(π)⋯B interactions in their crystal packing and use in Cu(i)-catalyzed 1,3-dipolar cycloaddition

The synthesis and characterization of two novel 6-ethynyl-7-halogen substituted benzosiloxaboroles (Hal = F, Cl) is reported. The crystal structures of these compounds show a unique type of supramolecular assembly dictated by distinctive C(π)⋯B interactions resulting in the formation of columnar networks involving alternating ethynyl groups and boron atoms. The QTAIM, NBO and NCI analyses were performed in order to obtain a deeper quantitative insight into the nature of these interactions including energy and charge density distribution. The fluoro derivative 1c was used as a starting material in Cu-catalyzed 1,3-dipolar cycloaddition reactions with substituted benzenesulfonyl azides giving rise to benzosiloxaboroles with pendant 1-(arylsulfonyl)-1,2,3-triazole-4-yl functionalities or analogous ionic species, i.e., 1,2,3-triazolium arylsulfonates. Screening of antimicrobial activity of obtained derivatives against a wide selection of Gram-positive and Gram-negative bacteria as well as fungi strains was performed and the obtained results were compared with the data obtained previously for related benzosiloxaborole derivatives.

Antimicrobial Peptide Synergies for Fighting Infectious Diseases

Antimicrobial peptides (AMPs) are essential elements of thehost defense system. Characterized by heterogenous structures and broad-spectrumaction, they are promising candidates for combating multidrug resistance. Thecombined use of AMPs with other antimicrobial agents provides a new arsenal ofdrugs with synergistic action, thereby overcoming the drawback of monotherapiesduring infections. AMPs kill microbes via pore formation, thus inhibitingintracellular functions. This mechanism of action by AMPs is an advantage overantibiotics as it hinders the development of drug resistance. The synergisticeffect of AMPs will allow the repurposing of conventional antimicrobials andenhance their clinical outcomes, reduce toxicity, and, most significantly,prevent the development of resistance. In this review, various synergies ofAMPs with antimicrobials and miscellaneous agents are discussed. The effect ofstructural diversity and chemical modification on AMP properties is firstaddressed and then different combinations that can lead to synergistic action,whether this combination is between AMPs and antimicrobials, or AMPs andmiscellaneous compounds, are attended. This review can serve as guidance whenredesigning and repurposing the use of AMPs in combination with other antimicrobialagents for enhanced clinical outcomes.

Antifungal Susceptibility Pattern of Candida glabrata from a Referral Center and Reference Laboratory: 2012-2022

The prevalence of invasive candidiasis caused by non-Candida albicans has rapidly increased. Candida glabrata (Nakaseomyces glabrata) is an important pathogen associated with substantial mortality. Our study examined the antifungal temporal susceptibility of C. glabrata and cross-resistance/non-wild-type patterns with other azoles and echinocandins. Laboratory data of all adult patients with C. glabrata isolated from clinical specimens at the Mayo Clinic, Rochester, from 2012 to 2022 were collected. Clinical and Laboratory Standards Institute (CLSI) and European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints were used. We obtained 1046 C. glabrata isolates from 877 patients. Using CLSI and EUCAST breakpoints, 187 (17.9%) isolates and 256 (24.5%) isolates were fluconazole-resistant, respectively. Focusing on C. glabrata bloodstream infections, fluconazole-resistance ranged from 16 to 22%. Among those 187 fluconazole-resistant isolates, 187 (100%) and 184 (98.4%) isolates were also voriconazole and posaconazole non-wild-type, respectively, with 97 (51.9%) isolates deemed non-wild type for itraconazole. The fluconazole susceptibility pattern has not changed over the past decade. The proportion of fluconazole-resistant C. glabrata is relatively high, which could be due to the complexity of patients and fluconazole exposure. Itraconazole appears to be a compelling step-down therapy for fluconazole-resistant C. glabrata, given the high proportion of wild-type isolates. Further research to examine clinical outcomes is warranted.

First Synthesis of DBU-Conjugated Cationic Carbohydrate Derivatives and Investigation of Their Antibacterial and Antifungal Activity

The emergence of drug-resistant bacteria and fungi represents a serious health problem worldwide. It has long been known that cationic compounds can inhibit the growth of bacteria and fungi by disrupting the cell membrane. The advantage of using such cationic compounds is that the microorganisms would not become resistant to cationic agents, since this type of adaptation would mean significantly altering the structure of their cell walls. We designed novel, DBU (1,8-diazabicyclo[5.4.0]undec-7-ene)-derived amidinium salts of carbohydrates, which may be suitable for disturbing the cell walls of bacteria and fungi due to their quaternary ammonium moiety. A series of saccharide-DBU conjugates were prepared from 6-iodo derivatives of d-glucose, d-mannose, d-altrose and d-allose by nucleophilic substitution reactions. We optimized the synthesis of a d-glucose derivative, and studied the protecting group free synthesis of the glucose-DBU conjugates. The effect of the obtained quaternary amidinium salts against Escherichia coli and Staphylococcus aureus bacterial strains and Candida albicans yeast was investigated, and the impact of the used protecting groups and the sugar configuration on the antimicrobial activity was analyzed. Some of the novel sugar quaternary ammonium compounds with lipophilic aromatic groups (benzyl and 2-napthylmethyl) showed particularly good antifungal and antibacterial activity.

Azole Resistance in Candida albicans Isolates from Oropharyngeal Candidiasis is Associated with ERG11 Mutation and Efflux Overexpression

Background: Azole resistance rates are rising in Candida species. Fluconazole is one of the most important antifungal drugs used in candidiasis treatment. Objectives: We identified the molecular mechanisms of fluconazole resistance of Candida albicans oropharyngeal candidiasis (OPC) isolates obtained from head and neck cancer patients, a study carried out between 2018 and 2020. Methods: One hundred and twenty-five Candida albicans clinical isolates were collected. Antifungal susceptibilities were determined by the CLSI- M27-A3 method. The ERG11 gene was amplified and sequenced to discover SNP mutation. Moreover, real-time PCR was carried out to measure the mRNA levels of ERG11, CDR1, CDR2, and MDR1. Results: Resistance to fluconazole was found in 15 C. albicans isolates. Amino acid substitutions E266D and D116E were observed in resistant, sensitive dose-dependent (SDD), and susceptible C. albicans isolates. K128T, G465S, A114S, Y257H and V488I were in relation to fluconazole resistance. D504A, P375A, W520C, G59S, and V51L were novel substitutions detected in the isolates; except for D504A, other mutations were observed only in resistance isolates. The expression levels of CDR2, CDR1, MDR1, and ERG11 were increased compared to susceptible isolates, respectively. Conclusions: ERG11 mutation was the principal mechanism for fluconazole resistance in C. albicans isolated from oropharyngeal candidiasis patients, and caspofungin can be used as the effective antifungal substance in fluconazole resistance situation for C. albicans infection.

Fluconazole as Schistosoma mansoni cytochrome P450 inhibitor: In vivo murine experimental study

Schistosomiasis is a chronic disease caused by blood flukes of the Schistosoma spp. New approaches against this morbid infection are needed. In this study, we investigated fluconazole (FLZ) as an inhibitor of Schistosoma mansoni cytochrome P450 (S. mansoni CYP450) enzyme at different life cycle stages. We compared FLZ (10 mg/kg for two days) effects when administrated early 5 days post-infection (dpi) (Early I) and 21 dpi (Early II) versus late administration 60 dpi on S. mansoni CYP450 gene expression. These different FLZ treatment regimens were evaluated in experimentally infected mice with S. mansoni. This study showed that administration of FLZ, whether early or late during schistosomal infection, resulted in significant inhibition of S. mansoni CYP450 expression in the adult stage (P < 0.001). Early exposure to FLZ during the first week of infection significantly decreased the number of schistosomula that reached the adult stage compared to the infected control group and resulted in significant inhibition of S. mansoni CYP450 expression (P < 0.001) in the adult stage. In the Early I group, the fewest number of eggs per liver tissue gram was recorded. Our data suggested that FLZ is a S. mansoni CYP450 gene expression inhibitor with greater effect on schistosomula stages.

Total bodyweight and sex both drive pharmacokinetic variability of fluconazole in obese adults

BACKGROUND

Fluconazole is commonly used to treat or prevent fungal infections. It is typically used orally but in critical situations, IV administration is needed. Obesity may influence the pharmacokinetics and therapeutic efficacy of a drug. In this study, we aim to assess the impact of obesity on fluconazole pharmacokinetics given orally or IV to guide dose adjustments for the obese population.

METHODS

We performed a prospective pharmacokinetic study with intensive sampling in obese subjects undergoing bariatric surgery (n = 17, BMI ≥ 35 kg/m2) and non-obese healthy controls (n = 8, 18.5 ≤ BMI < 30.0 kg/m2). Participants received a semi-simultaneous oral dose of 400 mg fluconazole capsules, followed after 2 h by 400 mg IV. Population pharmacokinetic modelling and simulation were performed using NONMEM 7.3.

RESULTS

A total of 421 fluconazole concentrations in 25 participants (total bodyweight 61.0-174 kg) until 48 h after dosing were obtained. An estimated bioavailability of 87.5% was found for both obese and non-obese subjects, with a 95% distribution interval of 43.9%-98.4%. With increasing total bodyweight, both higher CL and Vd were found. Sex also significantly impacted Vd, being 27% larger in male compared with female participants.

CONCLUSIONS

In our population of obese but otherwise healthy individuals, obesity clearly alters the pharmacokinetics of fluconazole, which puts severely obese adults, particularly if male, at risk of suboptimal exposure, for which adjusted doses are proposed.

A detailed insight on the molecular and cellular mechanism of action of the antifungal drugs used in the treatment of superficial fungal infections

Background:

Dermatomycosis, a type of fungal infection that can infect human skin, hair, and nails; day by day the growth of fungal infections ranging from superficial to systemic infection is alarming. Common causative agents included are Candida, Cryptococcus, Aspergillus, and Pneumocystis species.

Objective:

The effective treatment of the fungal infection includes the use of proper antifungal drug therapy. Antifungal drugs are classified into various classes. This paper focuses on understanding and interpreting the detailed molecular and cellular mechanism of action of various classes of an anti-fungal drug along with their important characteristics along with the safety and efficacy data of individual drugs of the particular class.

Methods:

The data selection for carrying out the respective study has been done by studying the combination of review articles and research papers from different databases like Research Gate, PubMed, MDPI, Elsevier, Science Direct, and Med Crave ranging from the year 1972 to 2019 by using the keywords like “anti-fungal agents”, “dermatophytes”, “cutaneous candidiasis”, “superficial fungal infections”, “oral candidiasis”, “amphotericin”, “echinocandins”, “azoles”, “polyenes” “ketoconazole”, “terbinafine”, “griseofulvin”, “azoles”.

Result:

Based on interpretation, we have concluded that the different classes of antifungal drugs follow the different mechanisms of action and target the fungal cell membrane, and are efficient in reducing fungal disease by their respective mechanism.

Conclusion:

The prevention and cure of fungal infections can be done by oral or topical antifungal drugs that aim to destroy the fungal cell membrane. These drugs show action by their respective pathways that are either preventing the formation of ergosterol or squalene or act by inhibiting β-1,3-glucan synthase enzyme. All the drugs are effective in treating fungal infections.

Interaction of Antifungal Drugs with CYP3A- and OATP1B-Mediated Venetoclax Elimination

Venetoclax, a BCL-2 inhibitor used to treat certain hematological cancers, exhibits low oral bioavailability and high interpatient pharmacokinetic variability. Venetoclax is commonly administered with prophylactic antifungal drugs that may result in drug interactions, of which the underlying mechanisms remain poorly understood. We hypothesized that antifungal drugs may increase venetoclax exposure through inhibition of both CYP3A-mediated metabolism and OATP1B-mediated transport. Pharmacokinetic studies were performed in wild-type mice and mice genetically engineered to lack all CYP3A isoforms, or OATP1B2 that received venetoclax alone or in combination with ketoconazole or micafungin. In mice lacking all CYP3A isoforms, venetoclax AUC was increased by 1.8-fold, and pretreatment with the antifungal ketoconazole further increased venetoclax exposure by 1.6-fold, despite the absence of CYP3A. Ensuing experiments demonstrated that the deficiency of OATP1B-type transporters is also associated with increases in venetoclax exposure, and that many antifungal drugs, including micafungin, posaconazole, and isavuconazole, are inhibitors of this transport mechanism both in vitro and in vivo. These studies have identified OATP1B-mediated transport as a previously unrecognized contributor to the elimination of venetoclax that is sensitive to inhibition by various clinically-relevant antifungal drugs. Additional consideration is warranted when venetoclax is administered together with agents that inhibit both CYP3A-mediated metabolism and OATP1B-mediated transport.

Characterization of the contamination fingerprint of wastewater treatment plant effluents in the Henares River Basin (central Spain) based on target and suspect screening analysis

The interest in contaminants of emerging concern (CECs) has increased lately due to their continued emission and potential ecotoxicological hazards. Wastewater treatment plants (WWTPs) are generally not capable of eliminating them and are considered the main pathway for CECs to the aquatic environment. The number of CECs in WWTPs effluents is often so large that complementary approaches to the conventional target analysis need to be implemented. Within this context, multitarget quantitative analysis (162 compounds) and a suspect screening (>40,000 suspects) approaches were applied to characterize the CEC fingerprint in effluents of five WWTPs in the Henares River basin (central Spain) during two sampling campaigns (summer and autumn). The results indicated that 76% of the compounds quantified corresponded to pharmaceuticals, 21% to pesticides and 3% to industrial chemicals. Apart from the 82 compounds quantified, suspect screening increased the list to 297 annotated compounds. Significant differences in the CEC fingerprint were observed between summer and autumn campaigns and between the WWTPs, being those serving the city of Alcalá de Henares the ones with the largest number of compounds and concentrations. Finally, a risk prioritization approach was applied based on risk quotients (RQs) for algae, invertebrates, and fish. Azithromycin, diuron, chlortoluron, clarithromycin, sertraline and sulfamethoxazole were identified as having the largest risks to algae. As for invertebrates, the compounds having the largest RQs were carbendazim, fenoxycarb and eprosartan, and for fish acetaminophen, DEET, carbendazim, caffeine, fluconazole, and azithromycin. The two WWTPs showing higher calculated Risk Indexes had tertiary treatments, which points towards the need of increasing the removal efficiency in urban WWTPs. Furthermore, considering the complex mixtures emitted into the environment and the low dilution capacity of Mediterranean rivers, we recommend the development of detailed monitoring plans and stricter regulations to control the chemical burden created to freshwater ecosystems.

Inhibitory effect of polyunsaturated fatty acids alone or in combination with fluconazole on Candida krusei biofilms in vitro and in Caenorhabditis elegans

The incidence of infections by non-albicans Candida species, including Candida krusei, is increasing. Candida krusei exhibits intrinsic resistance to fluconazole and rapidly develops acquired resistance to other antifungals. Moreover, this yeast can form biofilm with increased resistance. Hence, there is a need to develop novel therapeutic strategies to combat infections caused by this pathogen. One such approach is through combination therapy with natural compounds, such as polyunsaturated fatty acids (PUFAs). This study aims to investigate the effect of PUFAs on fluconazole susceptibility of C. krusei biofilms, as well as the conserved nature of these effects in the Caenorhabditis elegans infection model. C. krusei biofilms were exposed to various fatty acids as well as combinations of fluconazole and linoleic acid (LA) or gamma-linolenic acid (GLA). The effect of these treatments on biofilm formation, cell ultrastructure, membrane integrity, oxidative stress and efflux pump activity was evaluated. In addition, the ability of the PUFAs to prolong survival and reduce the fungal burden of infected C. elegans, in the absence and presence of fluconazole, was assessed. Two P|UFAs, LA and GLA had he displayed significant inhibition of C. krusei biofilms and both of them increased the susceptibility of C. krusei biofilm to fluconazole in vitro via induction of oxidative stress, cell membrane damage, and disruption of efflux pump activity. These PUFAs also extended the lifespan of infected nematodes and displayed a potentiating effect with fluconazole in this model. This may pave the way for future studies into novel antifungal drug targets and treatment options.

LAY ABSTRACT

The pathogenic yeast, Candida krusei, is naturally resistant to the antifungal drug, fluconazole. This study finds that polyunsaturated fatty acids, linoleic and gamma-linolenic acid, can inhibit C. krusei and overcome this resistance of in vitro biofilms, as well as in a nematode infection model.

Update on Candida krusei, a potential multidrug-resistant pathogen

Although Candida albicans remains the main cause of candidiasis, in recent years a significant number of infections has been attributed to non-albicans Candida (NAC) species, including Candida krusei. This epidemiological change can be partly explained by the increased resistance of NAC species to antifungal drugs. C. krusei is a diploid, dimorphic ascomycetous yeast that inhabits the mucosal membrane of healthy individuals. However, this yeast can cause life-threatening infections in immunocompromised patients, with hematologic malignancy patients and those using prolonged azole prophylaxis being at higher risk. Fungal infections are usually treated with five major classes of antifungal agents which include azoles, echinocandins, polyenes, allylamines, and nucleoside analogues. Fluconazole, an azole, is the most commonly used antifungal drug due to its low host toxicity, high water solubility, and high bioavailability. However, C. krusei possesses intrinsic resistance to this drug while also rapidly developing acquired resistance to other antifungal drugs. The mechanisms of antifungal resistance of this yeast involve the alteration and overexpression of drug target, reduction in intracellular drug concentration and development of a bypass pathway. Antifungal resistance menace coupled with the paucity of the antifungal arsenal as well as challenges involved in antifungal drug development, partly due to the eukaryotic nature of both fungi and humans, have left researchers to exploit alternative therapies. Here we briefly review our current knowledge of the biology, pathophysiology and epidemiology of a potential multidrug-resistant fungal pathogen, C. krusei, while also discussing the mechanisms of drug resistance of Candida species and alternative therapeutic approaches.

Is Posaconazole Really Effective in Adolescent patients as a Prophylactic Agent: Experience of a Tertiary Care Center

BACKGROUND

Invasive fungal infections (IFIs) are a leading cause of morbidity and death in immunocompromised patients. Data on efficacy and pharmacokinetics of posaconazole in pediatric patients are rare (1 to 5). Herein, we retrospectively analyzed adolescent patients who had received posaconazole as antifungal prophylaxis.

METHODS

We retrospectively analyzed patients who received posaconazole as primary or secondary antifungal prophylaxis.

RESULTS

A total of 34 adolescent patients, 19 men (55.9%) and 15 women (44.1%) with a mean age of 15.8±2.1 years were included. Twenty-five of 34 (73.5%) patients were on primary and nine of 34 (26.5%) patients were on secondary antifungal prophylaxis. Diagnosis of the patients receiving posaconazole as primary antifungal prophylaxis were acute myeloid leukemia (n=12, 48%), hematopoietic stem cell transplantation (n=7, 28%), acute lymphoblastic leukemia (n=5, 20%), and Fanconi aplastic anemia (n=1, 4%). Five patients (55.6%) with hematopoietic stem cell transplantation, 1 patient with acute myeloid leukemia (11.1%), 1 patient with Fanconi aplastic anemia (11.1%), and 2 (22.2%) patients with chronic granulomatous disease received posaconazole as secondary antifungal prophylaxis. Twelve of 25 (48%) patients receiving posaconazole as primary antifungal prophylaxis were complicated by IFI; 4 of them were proven, 6 probable, and 2 with possible IFI. Three of 9 patients (33.3%) receiving posaconazole as secondary antifungal prophylaxis was complicated by IFI (P=0.29), 2 of them were probable and 1 was possible IFI. Five of 25 patients (20%) receiving posaconazole as primary prophylaxis died because of IFI.

CONCLUSION

Improvement of antifungal prophylaxis in patients with high risk of invasive infections seems clearly necessary, and analyzing serum posaconazole levels and individualizing dosing may be 1 approach to improve outcomes.

A preliminary study of the plasma concentrations of orally administered fluconazole in alpacas (Vicugna pacos)

Alpacas residing in the region endemic for Coccidioides spp. are susceptible to serious, disseminated coccidioidomycosis that may result in death. There is currently no oral antifungal dose recommendation for this species. We used a steady-state study design to assess the pharmacokinetics of oral generic fluconazole in alpacas dosed q 24 h for 14 days. Cohorts of 2-3 animals received fluconazole from 6 to 15 mg/kg/day, and pharmacokinetic analysis was performed after each group of animals in order to make dose adjustments for the next group. The final three animals were used as confirmation of our dose recommendation. The median T_max was 7 h, and the median C_max was 1.25 µg/ml per mg/kg dose. The mean dose-normalized 24-h AUC was 41.7 µg h/ml per mg/kg dose (CV = 72%). Based on these results, we recommend alpacas receive a starting dose of oral fluconazole at 10-15 mg/kg/day based on the fluconazole AUC in humans (313-625 µg h/ml). Testing to ascertain putative therapeutic plasma concentrations and monitoring of serum transaminases should be performed.

HPLC Method Validated for Quantification of Fluconazole Co-Encapsulated with Propolis Within Chitosan Nanoparticles

Considering the cases of fungal resistance to classic antifungals, it is necessary to develop more efficient and innovative therapies capable of reversing this situation. Fluconazole is an antifungal frequently used in the treatment of mycosis and some fungi developed resistance to its mechanism of action. In this work, fluconazole and green propolis were co-encapsulated in chitosan nanoparticles to be explored in order to promote a synergistic effect to enhance its therapeutic efficacy. However, because of the complexity of the chemical composition of green propolis, it was necessary to develop a simple and precise methodology to quantify fluconazole in the formulation. High Efficiency Liquid Chromatography methodology was developed and validated following the Brazilian regulatory guidelines (ANVISA, RDC 166/2017) for the separation of co-eluted peaks of fluconazole and green propolis in the nanoparticle supernatant. Applying the method developed, it was possible to quantify fluconazole in the same sample containing propolis. Thus, the results allow to affirm that it is a specific test, effective, precise and robust, which helped to determine the efficiency of association of the compounds within the nanoparticle. The method can be applied to quantify compounds that have similar chromatographic retention times.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12088-021-00954-2.

Influence of Fluconazole Administration on Gut Microbiome, Intestinal Barrier, and Immune Response in Mice

Antibiotics that can treat or prevent infectious diseases play an important role in medical therapy. However, the use of antibiotics has potentially negative effects on the health of the host. For example, antibiotics use may affect the host's immune system by altering the gut microbiota. Therefore, the aim of the study was to investigate the influence of antifungal (fluconazole) treatment on the gut microbiota and immune system of mice. Results showed that the gut microbial composition of mice receiving fluconazole treatment was significantly changed after the trial. Fluconazole did not affect the relative abundance of bacteria but significantly reduced the diversity of bacterial flora. In the bacteriome, Firmicutes and Proteobacteria significantly increased, while Bacteroidetes, Deferribacteres, Patescibacteria, and Tenericutes showed a remarkable reduction in the fluconazole-treated group compared with the control group. In the mycobiome, the relative abundance of Ascomycota was significantly decreased and Mucoromycota was significantly increased in the intestine of mice treated with fluconazole compared to the control group. Reverse transcription-quantitative PCR (RT-qPCR) results showed that the relative gene expression of ZO-1, occludin, MyD88, interleukin-1β (IL-1β), and IL-6 was decreased in the fluconazole-treated group compared to the control. Serum levels of IL-2, LZM, and IgM were significantly increased, while the IgG level was considerably downregulated in the fluconazole-treated compared to the control group. These results suggest that the administration of fluconazole can influence the gut microbiota and that a healthy gut microbiome is important for the regulation of the host immune responses.

Impact of Low-Dose Fluconazole on Tacrolimus Dosing in Renal Transplant

BACKGROUND

The interaction between azole antifungal therapy and immunosuppressant tacrolimus (TAC) is a barrier to use.

OBJECTIVE

This study quantified the drug interaction between low-dose fluconazole (LDF) and TAC to determine the appropriate TAC dose adjustment when used concurrently in renal transplant recipients.

METHODS

We conducted a single-center retrospective chart review of renal transplant patients >18 years who received LDF or nystatin (NYS), and TAC. The primary outcome was the difference in tacrolimus total daily dose (TAC TDD) for LDF versus NYS groups. Secondary outcomes included days with supratherapeutic, therapeutic and subtherapeutic tacrolimus levels, time to therapeutic level, incidence of adverse drug reactions and graft rejection.

RESULTS

We evaluated 94 patients and included 81. Low-dose fluconazole received a greater TAC TDD prior to post-operative day (POD) 10 (10.5 ± 4.7 mg vs. 7.1 ± 4.5 mg, p < 0.001), but a decreased TAC TDD POD 10 - 30 (8.6 ± 2.2 mg vs. 9.8 ± 0.8 mg, p < 0.001) and following LDF discontinuation (6.9 ± 0.1 mg vs. 9.0 ± 0.4 mg, p < 0.001). Low-dose fluconazole had more patient-days with supratherapeutic (17.9 ± 7.0 vs. 13.9 ± 8.5; p = 0.02) but fewer with subtherapeutic (6.7 ± 5.7 vs. 12.9 ± 7.2; p < 0.01) TAC levels. There was no difference in patient-days with therapeutic TAC levels (15.9 ± 5.8 vs. 14.4 ± 6.6, p = 0.28), meanwhile LDF required less patient-days to therapeutic TAC level (7.1 ± 2.7 vs. 11.5 ± 7.7; p < 0.01). There was no difference in adverse drug reactions between groups and no incidence of graft rejection.

CONCLUSION

A 20% reduction in TAC TDD is warranted in renal transplant patients when used concomitantly with LDF to achieve therapeutic levels.

Antifungal use in the surgical ICU patient

PURPOSE OF REVIEW

The successful treatment of surgical fungal infections depends of a timely and adequate source control alongside with the use of prompt systemic antifungals. The main challenge of antifungal use in critically ill surgical patients is to find a balance between rational versus indiscriminate use in order to accomplish an antifungal stewardship program.

RECENT FINDINGS

Surgical fungal infections represent an important burden in the daily clinical activity in many ICUs. The efficacy of the available antifungal drugs has not been adequately assessed in randomized controlled trials with surgical fungal infections in ICU patients. Most clinical experience is limited to case reports or uncontrolled case series. Due to the lack of adequate scientific evidence to assess the role of the different antifungals in surgical ICU patients, it is usually suggested to follow the recommendations for invasive candidiasis and candidemia.

SUMMARY

Antifungal use in the surgical patients admitted to an ICU is a complex matter and there are several elements to consider like the presence of septic shock and multiorgan failure, local epidemiology and antifungal resistance, among others. The proper use of antifungals alongside early recognition and prompt source control, are critical factors for improved outcomes.

Intracellular and Intraorgan Concentrations of Small Molecule Drugs: Theory, Uncertainties in Infectious Diseases and Oncology, and Promise

The distribution of a drug within the body should be considered as involving movement of unbound drug between the various aqueous spaces of the body. At true steady state, even for a compound of restricted lipoidal permeability, unbound concentrations in all aqueous compartments (blood, extracellular, and intracellular) are considered identical, unless a compartment has a clearance/transport process. In contrast, total drug concentrations may differ greatly, reflecting binding or partitioning into constituents of each compartment. For most highly lipid permeable drugs, this uniform unbound concentration is expected to apply. However, many compounds have restricted lipoidal permeability and are subjected to transport/clearance processes causing a gradient between intracellular and extracellular unbound concentrations even at steady state. Additional concerns arise where the drug target resides in a site of limited vascularity. Many misleading assumptions about drug concentrations and access to drug targets are based on total drug. Correction, if made, is usually by measuring tissue binding, but this is limited by the lack of homogenicity of the organ or compartment. Rather than looking for technology to measure the unbound concentration it may be better to focus on designing high lipoidal permeable molecules with a high chance of achieving a uniform unbound drug concentration. It is hoped this paper will stimulate greater understanding of the path from circulation to cell interior, and thereby in part avoid or minimize the need to provide the experimentally very determining, and sometimes still questionable, answer to this problem.

Therapy of Skin, Hair and Nail Fungal Infections

Treatment of superficial fungal infections has come a long way. This has, in part, been through the development and evaluation of new drugs. However, utilising new strategies, such as identifying variation between different species in responsiveness, e.g., in tinea capitis, as well as seeking better ways of ensuring adequate concentrations of drug in the skin or nail, and combining different treatment methods, have played equally important roles in ensuring steady improvements in the results of treatment. Yet there are still areas where we look for improvement, such as better remission and cure rates in fungal nail disease, and the development of effective community treatment programmes to address endemic scalp ringworm.

Fluconazole Pharmacokinetics in Galleria mellonella Larvae and Performance Evaluation of a Bioassay Compared to Liquid Chromatography-Tandem Mass Spectrometry for Hemolymph Specimens

The invertebrate model organism Galleria mellonella can be used to assess the efficacy of treatment of fungal infection. The fluconazole dose best mimicking human exposure during licensed dosing is unknown. We validated a bioassay for fluconazole detection in hemolymph and determined the fluconazole pharmacokinetics and pharmacodynamics in larval hemolymph in order to estimate a humanized dose for future experiments. A bioassay using 4-mm agar wells, 20 μl hemolymph, and the hypersusceptible Candida albicans DSY2621 was established and compared to a validated liquid chromatography-tandem mass spectrometry (LC-MS-MS) method. G. mellonella larvae were injected with fluconazole (5, 10, and 20 mg/kg of larval weight), and hemolymph was harvested for 24 h for pharmacokinetics calculations. The exposure was compared to the human exposure during standard licensed dosing. The bioassay had a linear standard curve between 1 and 20 mg/liter. Accuracy and coefficients of variation (percent) values were below 10%. The Spearman coefficient between assays was 0.94. Fluconazole larval pharmacokinetics followed one-compartment linear kinetics, with the 24-h area under the hemolymph concentration-time curve (AUC_{24 h}) being 93, 173, and 406 mg · h/liter for the three doses compared to 400 mg · h/liter in humans under licensed treatment. In conclusion, a bioassay was validated for fluconazole determination in hemolymph. The pharmacokinetics was linear. An exposure comparable to the human exposure during standard licensed dosing was obtained with 20 mg/kg.

Pharmacodynamic Optimization for Treatment of Invasive Candida auris Infection

Candida auris is an emerging multidrug-resistant threat. The pharmacodynamics of three antifungal classes against nine C. auris strains was explored using a murine invasive candidiasis model. The total drug median pharmacodynamic (PD) target associated with net stasis was a fluconazole AUC/MIC (the area under the concentration-time curve over 24 h in the steady state divided by the MIC) of 26, an amphotericin B C_max/MIC (maximum concentration of drug in serum divided by the MIC) of 0.9, and a micafungin AUC/MIC of 54. The micafungin PD targets for C. auris were ≥20-fold lower than those of other Candida species in this animal model. Clinically relevant micafungin exposures produced the most killing among the three classes.

Identification and characterization of a novel antimicrobial protein from the housefly Musca domestica

Antimicrobial peptides/proteins are immune-related molecules that are widely distributed in bacteria, fungi, plants, invertebrates and higher animals. They have exhibited great potential to be developed into antimicrobial drugs. The housefly, Musca domestica, lives in a highly contaminated environment and has adapted a robust immune system against various pathogens. As an effort to search for new antimicrobial molecules in the housefly, we investigated the function of an uncharacterized gene firstly by confirming that its expression was induced by infection in M. domestica. The corresponding protein was then shown to have potent antimicrobial activity. Scanning Electron Microscopy data showed that treatment of C. albicans cells with the protein caused cell size decreasing and cell elongation. The results here suggest the protein a novel class of antimicrobial protein and provide new insights into the immunological mechanisms by which M. domestica combats invading C. albicans.

Hepatotoxicity induced by antifungal drugs itraconazole and fluconazole in rats: a comparative in vivo study

Itraconazole and fluconazole are oral antifungal drugs, which have a wide spectrum antifungal activity and better efficacy than the older drugs. However, both drugs have been associated with hepatotoxicity in susceptible patients. The mechanism of antifungal drug-induced hepatotoxicity is largely unknown. Therefore, the aim of this present study was to investigate and compare the hepatotoxicity induced by these drugs in vivo. Rats were treated intraperitoneally with itraconazole or fluconazole either single (0, 10, l00 and 200 mg/kg) or subchronic (0, 10, 50 and loo mg/kg per day for 14 days) doses. Plasma and liver samples were taken at the end of the study. A statistically significant and dose dependent increase of plasma alanine aminotransferase (ALT) and alkaline phosphatase (ALP) activities were detected in the subchronic itraconazole-treated group. In addition, dose-dependent hepatocellular necrosis, degeneration of periacinar and mizonal hepatocytes, bile duct hyperplasia and biliary cirrhosis and giant cell granuloma were observed histologically in the same group. Interestingly, fluconazole treated rats had no significant increase in transaminases for both single and subchronic groups. In the subchronic fluconazole treated rats, only mild degenerative changes of centrilobular hepatocytes were observed. These results demonstrated that itraconazole was a more potent hepatotoxicant than fluconazole in vivo in rats.

Antifungal agents and liver toxicity: a complex interaction

INTRODUCTION

The number of antifungal agents has sharply increased in recent decades. Antifungals differ in their spectrum of activity, pharmacokinetic/pharmacodynamic properties, dosing, safety-profiles and costs. Risk of developing antifungal associated hepatotoxicity is multifactorial and is influenced by pre-existing liver disease, chemical properties of the drug, patient demographics, comorbidities, drug-drug interactions, environmental and genetic factors. Antifungal related liver injury typically manifests as elevations in serum aminotransferase levels, although the clinical significance of these biochemical alterations is not always clear. Incidence rates of hepatotoxicity induced by antifungal therapy range widely, occurring most frequently in patients treated with azole antifungals for documented fungal infections.

AREAS COVERED

This review provides an update regarding the hepatotoxicity profiles of the modern systemic antifungals used in treatment of invasive fungal infections. Expert commentary: Understanding the likelihood and pattern of hepatotoxicity for all suspected drugs can aid the clinician in early detection of liver injury allowing for intervention and potential mitigation of liver damage. Therapeutic drug monitoring is emerging as a potential tool to assess risk for hepatotoxicity.

In vitro activity of five antifungal agents against Candida albicans isolates, Sari, Iran

Background and Purpose:

Candidaalbicans is the most common causative agent of candidiasis. Candidiasis management is dependent on the immune status of the host, severity of disease, and the choice of antifungal drug. Antifungals, specifically triazoles, are widely administered for the treatment of invasive fungal infections. Herein, we aimed to evaluate the invitro susceptibility of C. albicans isolates to fluconazole (FLZ), itraconazole (ITZ), voriconazole (VRZ), amphotericin B (AMB), and Caspofungin (CAS).

Materials and Methods:

A total of 44 clinical strains of C. albicans were collected from 36 patients admitted to four hospitals in Mazandaran Province, Iran. The invitro antifungal susceptibility testing was performed based on the Clinical and Laboratory Standards Institute methods.

Results :

Generally, 34 isolates were susceptible to all the five antifungal drugs, while four isolates were susceptible or susceptible dose-dependent (SDD) and six isolates were SDD or resistant to these antifungals. The lowest minimum inhibitory concentration (MIC; 0.016 µg/ml) belonged to AMB and the highest MIC was for FLZ )16 µg/ml). The lowest MIC (₅₀ 0.063 µg/ml) was related to ITZ and the lowest MIC (₉₀ 0.25 µg/ml) pertained to CAS, in addition , the highest MIC (₅₀ 1 µg/ml) and MIC (₉₀ 4 µg/ml) were for FLZ. Four of the isolates showed resistance to both FLZ and VRZ, separately, and five isolates were resistant to ITZ. Caspofungin showed potent activity against more than %95 of the C. albicans isolates.

Conclusion:

Overall, we reported %9.1 resistance to FLZ and VRZ ,%11.3 resistance to ITZ and AMB, and %4.6 resistance to caspofungin .Our finding is in agreement with previous observations proposing that C. albicans isolates develop resistance to some antifungal drugs such as FLZ since they are widely used as prophylaxis.

Drug resistance mechanisms and their regulation in non-albicans Candida species

Fungal pathogens use various mechanisms to survive exposure to drugs. Prolonged treatment very often leads to the stepwise acquisition of resistance. The limited number of antifungal therapeutics and their mostly fungistatic rather than fungicidal character facilitates selection of resistant strains. These are able to cope with cytotoxic molecules by acquisition of appropriate mutations, re-wiring gene expression and metabolic adjustments. Recent evidence points to the paramount importance of the permeability barrier and cell wall integrity in the process of adaptation to high drug concentrations. Molecular details of basal and acquired drug resistance are best characterized in the most frequent human fungal pathogen, Candida albicans Effector genes directly related to the acquisition of elevated tolerance of this species to azole and echinocandin drugs are well described. The emergence of high-level drug resistance against intrinsically lower susceptibility to azoles in yeast species other than C. albicans is, however, of particular concern. This is due to their steadily increasing contribution to high mortality rates associated with disseminated infections. Recent findings concerning underlying mechanisms associated with elevated drug resistance suggest a link to cell wall and plasma membrane metabolism in non-albicans Candida species.

In Vitro Susceptibilities of Candida albicans Isolates to Antifungal Agents in Tokat, Turkey

Background:

Candida albicans is the pathogenic species most commonly isolated from fungal infections. Management of these infections depends on the immune status of the host, severity of disease, and the choice of antifungal drug. In spite of the development of new antifungal drugs, epidemiological studies have shown that resistance to antifungal drugs in C. albicans strains is becoming a serious problem.

Objectives:

The aim of this study was to evaluate the in vitro susceptibility of C. albicans isolates to ketoconazole, fluconazole, itraconazole, voriconazole, posaconazole, amphotericin B, caspofungin, and anidulafungin.

Materials and Methods:

A total of 201 C. albicans isolates were collected from clinical specimens. Antifungal susceptibility tests were performed using the Etest.

Results:

All the tested C. albicans isolates were found to be susceptible to amphotericin B and anidulafungin. Although none of the isolates showed resistance to caspofungin, 15% of the isolates were classified as showing intermediate resistance. The resistance rates of C. albicans isolates to ketoconazole, fluconazole, itraconazole, voriconazole and posaconazole were 32%, 34%, 21%, 14% and 14%, respectively.

Conclusions:

Our findings indicate that resistance of C. albicans strains to azoles is more common in Tokat, Turkey. Therefore, a strategy to control the inappropriate and widespread use of antifungal drugs is urgently needed. Fungal culturing and antifungal susceptibility testing will be useful in patient management as well as resistance surveillance.

Antifungal prophylaxis with posaconazole vs. fluconazole or itraconazole in pediatric patients with neutropenia

Pediatric patients with hemato-oncological malignancies and neutropenia resulting from chemotherapy have a high risk of acquiring invasive fungal infections. Oral antifungal prophylaxis with azoles, such as fluconazole or itraconazole, is preferentially used in pediatric patients after chemotherapy. During this retrospective analysis, posaconazole was administered based on favorable results from studies in adult patients with neutropenia and after allogeneic hematopoietic stem cell transplantation. Retrospectively, safety, feasibility, and initial data on the efficacy of posaconazole were compared to fluconazole and itraconazole in pediatric and adolescent patients during neutropenia. Ninety-three pediatric patients with hemato-oncological malignancies with a median age of 12 years (range 9 months to 17.7 years) that had prolonged neutropenia (>5 days) after chemotherapy or due to their underlying disease, and who received fluconazole, itraconazole, or posaconazole as antifungal prophylaxis, were analyzed in this retrospective single-center survey. The incidence of invasive fungal infections in pediatric patients was low under each of the azoles. One case of proven aspergillosis occurred in each group. In addition, there were a few cases of possible invasive fungal infection under fluconazole (n = 1) and itraconazole (n = 2). However, no such cases were observed under posaconazole. The rates of potentially clinical drug-related adverse events were higher in the fluconazole (n = 4) and itraconazole (n = 5) groups compared to patients receiving posaconazole (n = 3). Posaconazole, fluconazole, and itraconazole are comparably effective in preventing invasive fungal infections in pediatric patients. Defining dose recommendations in these patients requires larger studies.

Pharmacokinetics and pharmacodynamics of antifungals in children and their clinical implications

Invasive fungal infections are a significant cause of morbidity and mortality in children. Successful management of these systemic infections requires identification of the causative pathogen, appropriate antifungal selection, and optimisation of its pharmacokinetic and pharmacodynamic properties to maximise its antifungal activity and minimise toxicity and the emergence of resistance. This review highlights salient scientific advancements in paediatric antifungal pharmacotherapies and focuses on pharmacokinetic and pharmacodynamic studies that underpin current clinical decision making. Four classes of drugs are widely used in the treatment of invasive fungal infections in children, including the polyenes, triazoles, pyrimidine analogues and echinocandins. Several lipidic formulations of the polyene amphotericin B have substantially reduced the toxicity associated with the traditional amphotericin B formulation. Monotherapy with the pyrimidine analogue flucytosine rapidly promotes the emergence of resistance and cannot be recommended. However, when used in combination with other antifungal agents, therapeutic drug monitoring of flucytosine has been shown to reduce high peak flucytosine concentrations, which are strongly associated with toxicity. The triazoles feature large inter-individual pharmacokinetic variability, although this pattern is less pronounced with fluconazole. In clinical trials, posaconazole was associated with fewer adverse effects than other members of the triazole family, though both posaconazole and itraconazole display erratic absorption that is influenced by gastric pH and the gastric emptying rate. Limited data suggest that the clinical response to therapy may be improved with higher plasma posaconazole and itraconazole concentrations. For voriconazole, pharmacokinetic studies among children have revealed that children require twice the recommended adult dose to achieve comparable blood concentrations. Voriconazole clearance is also affected by the cytochrome P450 (CYP) 2C19 genotype and hepatic impairment. Therapeutic drug monitoring is recommended as voriconazole pharmacokinetics are highly variable and small dose increases can result in marked changes in plasma concentrations. For the echinocandins, the primary source of pharmacokinetic variability stems from an age-dependent decrease in clearance with increasing age. Consequently, young children require larger doses per kilogram of body weight than older children and adults. Routine therapeutic drug monitoring for the echinocandins is not recommended. The effectiveness of many systemic antifungal agents has been correlated with pharmacodynamic targets in in vitro and in murine models of invasive candidiasis and aspergillosis. Further study is needed to translate these findings into optimal dosing regimens for children and to understand how these agents interact when multiple antifungal agents are used in combination.

Considerations in the pharmacologic treatment and prevention of neonatal sepsis

The management of neonatal sepsis is challenging owing to complex developmental and environmental factors that contribute to inter-individual variability in the pharmacokinetics and pharmacodynamics of many antimicrobial agents. In this review, we describe (i) the changing epidemiology of early- and late-onset neonatal sepsis; (ii) the pharmacologic considerations that influence the safety and efficacy of antibacterials, antifungals, and immunomodulatory adjuvants; and (iii) the recommended dosing regimens for pharmacologic agents commonly used in the treatment and prevention of neonatal sepsis. Neonatal sepsis is marked by high morbidity and mortality, such that prompt initiation of antimicrobial therapy is essential following culture collection. Before culture results are available, combination therapy with ampicillin and an aminoglycoside is recommended. When meningitis is suspected, ampicillin and cefotaxime may be considered. Following identification of the causative organism and in vitro susceptibility testing, antimicrobial therapy may be narrowed to provide targeted coverage. Therapeutic drug monitoring should be considered for neonates receiving vancomycin or aminoglycoside therapies. For neonates with invasive fungal infections, the development of new antifungal agents has significantly improved therapeutic outcomes in recent years. Liposomal amphotericin B has been found to be safe and efficacious in patients with renal impairment or toxicity caused by conventional amphotericin B. Antifungal prophylaxis with fluconazole has also been reported to dramatically reduce rates of neonatal invasive fungal infections and to improve long-term neurodevelopmental outcomes among treated children. Additionally, several large multicenter studies are currently investigating the safety and efficacy of oral lactoferrin as an immunoprophylactic agent for the prevention of neonatal sepsis.

Fluconazole for the treatment of candidiasis: 15 years experience

Candidia spp. are responsible for contributing to the increasing global prevalence of fungal infections. Fluconazole (Diflucan((R)), Pfizer) is a triazole that has established an exceptional therapeutic record for candida infections including oropharyngeal and esophageal candidiasis, vulvovaginal candidiasis, candidemia and disseminated candidiasis. It is both an oral and parenteral fungistatic agent that inhibits ergosterol synthesis in yeasts. Extensive clinical studies have demonstrated fluconazole's remarkable efficacy, favorable pharmacokinetics and reassuring safety profile, all of which have contributed to its widespread use. Fluconazole became the first antifungal with worldwide sales exceeding billions of dollars, therefore providing an incentive for the pharmaceutical industry to develop new antifungals. This review will examine the contributions and limitations of fluconazole in the treatment of superficial and invasive candidiasis syndromes.

Safety of fluconazole in paediatrics: a systematic review

PURPOSE

To determine the safety of fluconazole in neonates and other paediatric age groups by identifying adverse events (AEs) and drug interactions associated with treatment.

METHODS

A search of EMBASE (1950-January 2012), MEDLINE (1946-January 2012), the Cochrane database for systematic reviews and the Cumulative Index to Nursing and Allied Health Literature (1982-2012) for any clinical study about fluconazole use that involved at least one paediatric patient (≤17 years) was performed. Only articles with sufficient quality of safety reporting after patients' exposure to fluconazole were included.

RESULTS

We identified 90 articles, reporting on 4,209 patients, which met our inclusion criteria. In total, 794 AEs from 35 studies were recorded, with hepatotoxicity accounting for 378 (47.6 %) of all AEs. When fluconazole was compared with placebo and other antifungals, the relative risk (RR) of hepatotoxicity was not statistically different [RR 1.36, 95 % confidence interval (CI) 0.87-2.14, P = 0.175 and RR 1.43, 95 % CI 0.67-3.03, P = 0.352, respectively]. Complete resolution of hepatoxicity was achieved by 84 % of patients with follow-up available. There was no statistical difference in the risk of gastrointestinal events of fluconazole compared with placebo and other antifungals (RR 0.81, 95 % CI 0.12-5.60, P = 0.831 and RR 1.23, 95 %CI 0.87-1.71, P = 0.235, respectively). There were 41 drug withdrawals, 17 (42 %) of which were due to elevated liver enzymes. Five reports of drug interactions occurred in children.

CONCLUSION

Fluconazole is relatively safe for paediatric patients. Hepatotoxicity and gastrointestinal toxicity are the most common adverse events. It is important to be aware that drug interactions with fluconazole can result in significant toxicity.

Sequential antibiotic therapy: Effective cost management and patient care

The escalating costs associated with antimicrobial chemotherapy have become of increasing concern to physicians, pharmacists and patients alike. A number of strategies have been developed to address this problem. This article focuses specifically on sequential antibiotic therapy (sat), which is the strategy of converting patients from intravenous to oral medication regardless of whether the same or a different class of drug is used. Advantages of sat include economic benefits, patient benefits and benefits to the health care provider. Potential disadvantages are cost to the consumer and the risk of therapeutic failure. A critical review of the published literature shows that evidence from randomized controlled trials supports the role of sat. However, it is also clear that further studies are necessary to determine the optimal time for intravenous to oral changeover and to identify the variables that may interfere with the use of oral drugs. Procedures necessary for the implementation of a sat program in the hospital setting are also discussed.

Candida urinary tract infections--treatment

In many instances a report from the clinical laboratory indicating candiduria represents colonization or procurement contamination of the specimen and not invasive candidiasis. Even if infection of the urinary tract by Candida species can be confirmed, antifungal therapy is not always warranted. Further investigation may reveal predisposing factors, which if corrected or treated, result in the resolution of the infection. For those with symptomatic urinary tract infections (UTIs), the choice of antifungal agent will depend upon the clinical status of the patient, the site of infection, and the pharmacokinetics and pharmacodynamics of the agent. Because of its safety, achievement of high concentrations in the urine, and availability in both an oral and intravenous formulation, fluconazole is preferred for the treatment of Candida UTIs. Flucytosine is concentrated in urine and has broad activity against Candida spp, but its use requires caution because of toxicity. Low-dose amphotericin B may be useful for Candida UTIs in selected patients. The role of echinocandins and azoles that do not achieve measurable concentrations in the urine is not clear. Small case series note some success, but failures have also occurred. Irrigation of the bladder with antifungal agents has limited utility. However, with fungus balls, irrigation of the renal pelvis through a nephrostomy tube can be useful in combination with systemic antifungal agents.

Evidence of CYP3A allosterism in vivo: analysis of interaction between fluconazole and midazolam

The allosteric effect of fluconazole (effector) on the formation of 1’-hydroxymidazolam (1’-OH-MDZ) and 4-hydroxymidazolam (4-OH-MDZ) from the CYP3A4/5 substrate, midazolam (MDZ), was examined in healthy volunteers. Following pre-treatment of fluconazole, AUC_4-OH/AUC_MDZ increased 35–62%, while AUC_1’-OH/AUC_MDZ decreased 5–37%; AUC_1’-OH/AUC_4-OH ratio decreased 46–58% by fluconazole and had no association with CYP3A5 genotype. 1’-OH-MDZ formation in vitro was more susceptible than 4-OH-MDZ formation to inhibition by fluconazole. Fluconazole decreased the intrinsic formation clearance ratio of 1’-OH-MDZ/4-OH-MDZ to an extent that was quantitatively comparable to in vivo observations. The elimination clearance of midazolam metabolites appeared unaffected by fluconazole. This study demonstrated that fluconazole alters midazolam product formation both in vivo and in vitro in a manner consistent with an allosteric interaction. The 1'-OH-MDZ/4-OH-MDZ ratio may serve as a biomarker of such interactions between midazolam, CYP3A4/5 and other putative effectors.