Ketoconazole: a review of its therapeutic efficacy in superficial and systemic fungal infections

Clinico-mycological and therapeutic updates on cutaneous dermatophytic infections in the era of Trichophyton indotineae

Trichophyton indotineae has emerged as a novel dermatophyte species resulting in treatment recalcitrant skin infections. While the earliest reports came from India, T. indotineae has now spread to many parts of the world and is rapidly becoming a global health concern. Accurate identification of T. indotineae requires elaborate mycological investigations which is beyond the domain of routine microbiology testing. Extensive, non-inflammatory and atypical presentations are commonly seen with this novel species. T. indotineae shows an alarmingly high rate of mutations in the squalene epoxidase gene leading to lowered in vitro susceptibility to terbinafine. This has also translated into a lowered clinical response and requirement of a higher dose and much longer durations of treatment with the drug. Although the species remains largely susceptible to itraconazole, prolonged treatment durations are required to achieve cure with itraconazole. Fluconazole and griseofulvin do not have satisfactory in vitro or clinical activity. Apart from requirement of prolonged treatment durations, relapse postsuccessful treatment is a distressing and yet unexplained consequence of this "species-shift." Use of third generation azoles and combinations of systemic antifungals is unwarranted as both have not demonstrated clear superiority over itraconazole given alone, and the former is an important class of drugs for invasive mycoses.

A Physiologically Based Pharmacokinetic Model of Ketoconazole and Its Metabolites as Drug-Drug Interaction Perpetrators

The antifungal ketoconazole, which is mainly used for dermal infections and treatment of Cushing's syndrome, is prone to drug-food interactions (DFIs) and is well known for its strong drug-drug interaction (DDI) potential. Some of ketoconazole's potent inhibitory activity can be attributed to its metabolites that predominantly accumulate in the liver. This work aimed to develop a whole-body physiologically based pharmacokinetic (PBPK) model of ketoconazole and its metabolites for fasted and fed states and to investigate the impact of ketoconazole's metabolites on its DDI potential. The parent-metabolites model was developed with PK-Sim^® and MoBi^® using 53 plasma concentration-time profiles. With 7 out of 7 (7/7) DFI AUC_last and DFI C_max ratios within two-fold of observed ratios, the developed model demonstrated good predictive performance under fasted and fed conditions. DDI scenarios that included either the parent alone or with its metabolites were simulated and evaluated for the victim drugs alfentanil, alprazolam, midazolam, triazolam, and digoxin. DDI scenarios that included all metabolites as reversible inhibitors of CYP3A4 and P-gp performed best: 26/27 of DDI AUC_last and 21/21 DDI C_max ratios were within two-fold of observed ratios, while DDI models that simulated only ketoconazole as the perpetrator underperformed: 12/27 DDI AUC_last and 18/21 DDI C_max ratios were within the success limits.

Design, Synthesis, Characterization, and Analysis of Antimicrobial Property of Novel Benzophenone Fused Azetidinone Derivatives through In Vitro and In Silico Approach

A sequence of novel 2-(4-benzoyl-2-methyl-phenoxy)-N-(3-chloro-2-oxo-4-phenyl-azetidin-1-yl)-acetamide analogues 9(a−n) were synthesized by multistep synthesis. The newly synthesized compounds were well characterized, and their antimicrobial activities were carried out by disc diffusion and broth dilution methods. Further, all the novel series of compounds (9a−n), were tested against a variety of bacterial and fungal strains in comparison to Ketoconazole, Chloramphenicol, and Amoxicillin as standard drugs, respectively. Compounds 9a, 9e, and 9g as a lead molecule demonstrated a good inhibition against tested strains. Further, molecular docking studies have been performed for the potent compounds to check the three-dimensional geometrical view of the ligand binding to the targeted proteins.

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.

Mechanistically Coupled PK (MCPK) Model to Describe Enzyme Induction and Occupancy Dependent DDI of Dabrafenib Metabolism

Dabrafenib inhibits the cell proliferation of metastatic melanoma with the oncogenic BRAF(V600)-mutation. However, dabrafenib monotherapy is associated with pERK reactivation, drug resistance, and consequential relapse. A clinical drug-dose determination study shows increased pERK levels upon daily administration of more than 300 mg dabrafenib. To clarify whether such elevated drug concentrations could be reached by long-term drug accumulation, we mechanistically coupled the pharmacokinetics (MCPK) of dabrafenib and its metabolites. The MCPK model is qualitatively based on in vitro and quantitatively on clinical data to describe occupancy-dependent CYP3A4 enzyme induction, accumulation, and drug–drug interaction mechanisms. The prediction suggests an eight-fold increase in the steady-state concentration of potent desmethyl-dabrafenib and its inactive precursor carboxy-dabrafenib within four weeks upon 150 mg b.d. dabrafenib. While it is generally assumed that a higher dose is not critical, we found experimentally that a high physiological dabrafenib concentration fails to induce cell death in embedded 451LU melanoma spheroids.

Does the circulating ketoconazole metabolite N-deacetyl ketoconazole contribute to the drug-drug interaction potential of the parent compound?

Ketoconazole is a strong inhibitor of cytochrome P450 3A4 (CYP3A4) and of P-glycoprotein (P-gp) and is often used as an index inhibitor especially for CYP3A4-mediated drug metabolism. A preliminary physiologically based pharmacokinetic (PBPK) model for drug-drug interactions indicated possible involvement of a metabolite to the perpetrator potential of ketoconazole. Still unknown for humans, in rodents, N-deacetyl ketoconazole (DAK) has been identified as the major ketoconazole metabolite. We therefore investigated in vitro, whether DAK also inhibits the human CYPs and drug transporters targeted by ketoconazole and quantified DAK in human plasma from healthy volunteers after receiving a single oral dose of 400 mg ketoconazole. Our data demonstrated that DAK also inhibits CYP3A4 (2.4-fold less potent than ketoconazole), CYP2D6 (13-fold more potent than ketoconazole), CYP2C19 (equally potent), P-gp (3.4-fold less potent than ketoconazole), breast cancer resistance protein (more potent than ketoconazole) and organic anion transporting polypeptide 1B1 and 1B3 (7.8-fold and 2.6-fold less potent than ketoconazole). After a single oral dose of 400 mg ketoconazole, maximum concentrations of DAK in human plasma were only 3.1 ‰ of the parent compound. However, assuming that DAK also highly accumulates in the human liver as demonstrated for rodents, inhibition of the proteins investigated could also be conceivable in vivo. In conclusion, DAK inhibits several CYPs and drug transporters, which might contribute to the perpetrator potential of ketoconazole.

Clinical, clinicopathologic, and hepatic histopathologic features associated with probable ketoconazole-induced liver injury in dogs: 15 cases (2015-2018)

OBJECTIVE

To characterize clinical, clinicopathologic, and hepatic histopathologic features and outcome for dogs with probable ketoconazole-induced liver injury.

ANIMALS

15 dogs with suspected ketoconazole-induced liver injury that underwent liver biopsy.

PROCEDURES

Medical record data were summarized regarding signalment, clinical signs, clinicopathologic and hepatic histopathologic findings, concurrent medications, ketoconazole dose, treatment duration, and outcome.

RESULTS

Median age and body weight were 8.2 years (range, 5 to 15 years) and 13.0 kg (28.6 lb; range, 8.2 to 38.0 kg [18.0 to 83.6 lb]), respectively. The most common breed was Cocker Spaniel (n = 5). All dogs received ketoconazole to treat cutaneous Malassezia infections. Median daily ketoconazole dose was 7.8 mg/kg (3.5 mg/lb; range, 4.4 to 26.0 mg/kg [2.0 to 11.8 mg/lb]), PO. Treatment duration ranged from 0.3 to 100 cumulative weeks (intermittent cyclic administration in some dogs); 6 dogs were treated for ≤ 10 days. Common clinical signs included lethargy, anorexia, and vomiting. All dogs developed high serum liver enzyme activities. Hepatic histopathologic findings included variable lobular injury, mixed inflammatory infiltrates, and conspicuous aggregates of ceroid-lipofuscin-engorged macrophages that marked regions of parenchymal damage. Five dogs developed chronic hepatitis, including 3 with pyogranulomatous inflammation. Of the 10 dogs reported to have died at last follow-up, survival time after illness onset ranged from 0.5 to 165 weeks, with 7 dogs dying of liver-related causes.

CONCLUSIONS AND CLINICAL RELEVANCE

Findings for dogs with hepatotoxicosis circumstantially associated with ketoconazole treatment suggested proactive monitoring of serum liver enzyme activities is advisable before and sequentially after initiation of such treatment.

An Interlaboratory Evaluation of Five Pairs of Teratogens and Non-teratogens in Post-implantation Rat Embryo Culture

The usefulness of the post-implantation rat embryo culture method in screening xenobiotic compounds for developmental toxicity was validated in four laboratories with five pairs of compounds. This approach was chosen to provide information on the interlaboratory reproducibility of the results and to compare the effects of chemical analogues in embryo culture. By testing analogous compounds which are known to have different embryotoxic potencies in vivo, the discriminating power of the embryo culture method for the compound classes under study could be optimally assessed. The classes selected for testing were triazole antifungals, phthalic ester metabolites, substituted pyridines, sulphonamides and methylated xanthines. In summary, it was possible to distinguish between the compounds in three of the pairs, it was not possible to discriminate between the compounds of one pair, and it was possible to discriminate between the compounds of the other pair at two out of the four laboratories. The embryo culture results generally show a good correspondence with the embryotoxic properties of the compounds tested in vivo, although the embryo culture method appeared to be able to discriminate between only some of the pairs of chemical analogues. Some discrepancies may have arisen among the laboratories, because of methodological differences. These results suggest that the post-implantation rat embryo culture method may be a useful tool for screening xenobiotics within classes of compounds known to interfere with embryogenesis during the period of development represented in culture.

Fungal Peritonitis in Peritoneal Dialysis Patients

Peritonitis is one of the most frequent complications of peritoneal dialysis (PD) and 1% – 15% of episodes are caused by fungal infections. The mortality rate of fungal peritonitis (FP) varies from 5% to 53%; failure to resume PD occurs in up to 40% of patients. The majority of these FP episodes are caused by Candida species. Candida albicans has historically been reported to be a more common cause than non-albicans Candida species, but in recent reports a shift has been observed and non-albicans Candida may now be more common. Unusual, often “nonpathogenic,” fungi are being increasingly reported as etiologic agents in FP. Clinical features of FP are not different from those of bacterial peritonitis. Phenotypic identification of fungi in clinical microbiology laboratories is often difficult and delayed. New molecular diagnostic techniques ( e.g., polymerase chain reaction) are being developed and evaluated, and may improve diagnosis and so facilitate early treatment of infected patients. Abdominal pain, abdominal pain with fever, and catheter left in situ are risk factors for mortality and technique failure in FP. In programs with high baseline rates of FP, nystatin prophylaxis may be beneficial. Each program must examine its own history of FP to decide whether prophylaxis would be beneficial. Catheter removal is indicated immediately after fungi are identified by Gram stain or culture in all patients with FP. Prolonged treatment with antifungal agents to determine response and attempt clearance is not encouraged. Antifungals should be continued for 10 days to 2 weeks after catheter removal. Attempts at reinsertion should be made only after waiting for 4 – 6 weeks.

Ketoconazole Pharmacokinetics in Continuous Ambulatory Peritoneal Dialysis

Ketoconazole, a new oral drug, has minimal toxicity and a broad spectrum of antifungal activity. To determine its usefulness in fungal peritonitis associated with continuous ambulatory peritoneal dialysis (CAPD), we carried out nine pharmacokinetic studies in five patients on CAPD. Serum levels of ketoconazole in CAPD patients were lower than in normal controls, and some patients did not appear to absorb the drug. We did not detect ketoconazole in the peritoneal fluid of any patient, even in the presence of peritoneal inflammation. One should not use this agent in the treatment of fungal peritonitis at daily doses of 400 mg or less because such a dose achieves only poor peritoneal fluid concentrations.

Continuous ambulatory peritoneal dialysis (CAPD) has become an attractive alternative to hemodialysis for many patients with chronic renal failure. However, a major drawback with this technique is peritonitis (1). Although most of these infections are due to staphylococci (I), fungal peritonitis appears to be increasing as experience with CAPD grows (2,3). The treatment of such peritonitis is hampered by the poor penetration of amphotericin B into the peritoneal fluid (2), chemical peritonitis when amphotericin B is instilled directly into the cavity (3), and the limited spectrum of activity of flucytosine -a drug which readily penetrates into the peritoneal fluid (4).

Ketoconazole is less toxic than amphotericin B and easier to administer and it has a much broader antifungal spectrum than flucytosine. The value of ketoconazole in fungal peritonitis remains to be established, and we have only limited data concerning its penetration into the peritonal cavity (2, 5). In this study we assessed the serum and peritoneal-fluid levels of ketoconazole in patients on CAPD.

The Fungal CYP51s: Their Functions, Structures, Related Drug Resistance, and Inhibitors

CYP51 (Erg11) belongs to the cytochrome P450 monooxygenase (CYP) superfamily and mediates a crucial step of the synthesis of ergosterol, which is a fungal-specific sterol. It is also the target of azole drugs in clinical practice. In recent years, researches on fungal CYP51 have stepped into a new stage attributing to the discovery of crystal structures of the homologs in Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus. This review summarizes the functions, structures of fungal CYP51 proteins, and the inhibitors targeting these homologs. In particular, several drug-resistant mechanisms associated with the fungal CYP51s are introduced. The sequences and crystal structures of CYP51 proteins in different fungal species are also compared. These will provide new insights for the advancement of research on antifungal agents.

CYP51 as drug targets for fungi and protozoan parasites: past, present and future

The efficiency of treatment of human infections with the unicellular eukaryotic pathogens such as fungi and protozoa remains deeply unsatisfactory. For example, the mortality rates from nosocomial fungemia in critically ill, immunosuppressed or post-cancer patients often exceed 50%. A set of six systemic clinical azoles [sterol 14α-demethylase (CYP51) inhibitors] represents the first-line antifungal treatment. All these drugs were discovered empirically, by monitoring their effects on fungal cell growth, though it had been proven that they kill fungal cells by blocking the biosynthesis of ergosterol in fungi at the stage of 14α-demethylation of the sterol nucleus. This review briefs the history of antifungal azoles, outlines the situation with the current clinical azole-based drugs, describes the attempts of their repurposing for treatment of human infections with the protozoan parasites that, similar to fungi, also produce endogenous sterols, and discusses the most recently acquired knowledge on the CYP51 structure/function and inhibition. It is our belief that this information should be helpful in shifting from the traditional phenotypic screening to the actual target-driven drug discovery paradigm, which will rationalize and substantially accelerate the development of new, more efficient and pathogen-oriented CYP51 inhibitors.

The absorption kinetics of ketoconazole plays a major role in explaining the reported variability in the level of interaction with midazolam: Interplay between formulation and inhibition of gut wall and liver metabolism

The impact of different single oral doses of ketoconazole (KTZ) (100, 200 and 400 mg) and of staggering its dosage (400 mg at -12, -2, 0, 2 and 4 h), with respect to the administration of a single 5 mg oral dose of midazolam (MDZ) on the extent of inhibition of the metabolism of the latter, was evaluated in healthy subjects in two separate studies. Escalation of the ketoconazole dosage resulted in 2.3 (1.9), 2.7 (1.7) and 4.2 (2.5) -fold increases in the mean AUC_(0,12h) (and C_max ) values of midazolam. Dose-staggering was associated with 3.9 (2.5), 4.9 (2.9), 5.4 (2.8), 2.0 (1.3) and 1.2 (0.9) -fold increases in the mean AUC_(0,12h) (and C_max ) of midazolam. These findings could be predicted by physiologically based pharmacokinetic (PBPK) modelling using the ADAM (advanced dissolution absorption and metabolism) model within the Simcyp Simulator (Version 12 Release 2) to characterize the absorption kinetics of ketoconazole with respect to disintegration time, supersaturation ratio and precipitation rate. This study also emphasizes a need to account for inter-individual variability in the gut wall and systemic exposure of inhibitors with physicochemical properties similar to ketoconazole, in particular in their rate of oral absorption and when using different pharmaceutical formulations, in designing and evaluating the extent of drug-drug interactions. Copyright © 2016 John Wiley & Sons, Ltd.

Characterization of chemical-induced sterile inflammation in vitro: application of the model compound ketoconazole in a human hepatic co-culture system

Liver injury as a result of a sterile inflammation is closely linked to the activation of immune cells, including macrophages, by damaged hepatocytes. This interaction between immune cells and hepatocytes is as yet not considered in any of the in vitro test systems applied during the generation of new drugs. Here, we established and characterized a novel in vitro co-culture model with two human cell lines, HepG2 and differentiated THP-1. Ketoconazole, an antifungal drug known for its hepatotoxicity, was used as a model compound in the testing of the co-culture. Single cultures of HepG2 and THP-1 cells were studied as controls. Different metabolism patterns of ketoconazole were observed for the single and co-culture incubations as well as for the different cell types. The main metabolite N-deacetyl ketoconazole was found in cell pellets, but not in supernatants of cell cultures. Global proteome analysis showed that the NRF2-mediated stress response and the CXCL8 (IL-8) pathway were induced by ketoconazole treatment under co-culture conditions. The upregulation and ketoconazole-induced secretion of several pro-inflammatory cytokines, including CXCL8, TNF-α and CCL3, was observed in the co-culture system only, but not in single cell cultures. Taking together, we provide evidence that the co-culture model applied might be suitable to serve as tool for the prediction of chemical-induced sterile inflammation in liver tissue in vivo.

The Rise and Fall of Oral Ketoconazole

Background:

Ketoconazole was the first broad-spectrum oral antifungal agent available to treat systemic and superficial mycoses. Evidence of hepatotoxicity associated with its use emerged within the first few years of its approval. Growing evidence of serious side effects including endocrine dysregulation, several drug interactions, and death led to the review of oral ketoconazole in 2011.

Objective:

This article chronicles the use of oral ketoconazole from its introduction to its near replacement in medicine.

Conclusion:

Due to its hepatotoxic side effects, oral ketoconazole was withdrawn from the European and Australian markets in 2013. The United States imposed strict relabeling requirements and restrictions for prescription, with Canada issuing a risk communication echoing these concerns. Today, oral ketoconazole is only indicated for endemic mycoses, where alternatives are not available or feasible. Meanwhile, topical ketoconazole is effective, safe, and widely prescribed for superficial mycoses, particularly as the first-line treatment for tinea versicolor.

Drug safety assessment of oral formulations of ketoconazole

INTRODUCTION

Ketoconazole was the first broad-spectrum oral antifungal approved by the FDA in 1981. Post-marketing reports of drug-related hepatotoxicity, endocrine dysregulation and drug interactions resulted in market withdrawal of the drug in some countries and strict product relabeling in others.

AREAS COVERED

This drug safety review summarizes reports of oral ketoconazole-related adverse events retrieved from a search of the PubMed database using the search strategy 'ketoconazole OR Nizoral AND hepat*', references from relevant publications, and data from the FDA Adverse Event Reporting System.

EXPERT OPINION

Although oral ketoconazole is effective in treating fungal infections, the potential for drug interactions, endocrine dysregulation, and hepatotoxicity may outweigh its benefits. Newer oral antifungals have similar or greater efficacy in treating dermatologic conditions and are associated with less risk. Likewise, newer agents with specific targets and fewer drug interactions have been developed to treat systemic fungal infections. Therefore, by the time ketoconazole prescribing guidelines were amended, its use had already largely been replaced with newer antifungals. Being that ketoconazole was the first broad-spectrum oral antifungal, experience with the drug made patient safety, and especially hepatic safety, an important consideration in future antifungal development.

Antifungal drugs during pregnancy: an updated review

Antifungal prescription remains a challenge in pregnant women because of uncertainties regarding fetal toxicity and altered maternal pharmacokinetic parameters that may affect efficacy or increase maternal and fetal toxicity. We present updated data reviewing the available knowledge and current recommendations regarding antifungal prescription in pregnancy. Amphotericin B remains the first-choice parenteral drug in spite of its well-established toxicity. Topical drugs are used throughout pregnancy because of limited absorption. Recent data have clarified the teratogenic effect of high-dose fluconazole during the first trimester and provided reassuring cumulative data regarding its use at a single low dose in this key period. Recent data have also provided additional safety data on itraconazole and lipidic derivatives of amphotericin B. Regarding newer antifungal drugs, including posaconazole and echinocandins, clinical data are critically needed before considering prescription in pregnancy.

Cytochrome P450 3A-mediated microsomal biotransformation of 1α,25-dihydroxyvitamin D3 in mouse and human liver: drug-related induction and inhibition of catabolism

The biological activities of vitamin D(3) are exerted through the dihydroxy metabolite of vitamin D(3) [1α,25(OH)(2)D(3)]. Hepatic biotransformation of 1α,25(OH)(2)D(3) by cytochrome P450 (P450) enzymes could be an important determinant of bioavailability in serum and tissues. In the present study, we investigated the comparative biotransformation of 1α,25(OH)(2)D(3) in mouse and human liver microsomes and determined the effects of commonly used drugs on the catabolism of 1α,25(OH)(2)D(3). Severe symptoms of vitamin D deficiency have historically been observed in patients who received dexamethasone. To compare the effects of clinically important glucocorticoids with hepatic biotransformation of 1α,25(OH)(2)D(3), adult male CD-1 mice were given intraperitoneal injections of either vehicle (50% ethanol), dexamethasone (80 mg/kg per day), or prednisone (80 mg/kg per day) for three consecutive days. Hydroxy metabolite formation pattern and the extent of substrate depletion were similar in mouse liver microsomes (MLM) from vehicle- or prednisone-treated mice, whereas treatment with dexamethasone led to the emergence of additional metabolites and increased substrate depletion, as determined by liquid chromatography/mass spectrometry. The metabolite formation profile in vehicle-treated mice was different from that of human liver microsomes (HLM). Selective P450 chemical inhibitors have demonstrated that CYP3A isoforms are responsible for the microsomal biotransformation of 1α,25(OH)(2)D(3) in MLM. Coincubation of 1α,25(OH)(2)D(3) with commonly used drugs led to approximately 60 to 100% inhibition of CYP3A4-mediated catabolism of 1α,25-(OH)(2)D(3) in HLM. A species-based difference was identified between CYP3A-mediated hepatic microsomal metabolism of 1α,25(OH)(2)D(3) in humans and mice. We have shown that the clinical importance of glucocorticoids differentially modulates catabolism of active vitamin D(3) and that commonly used drugs could affect vitamin D homeostasis.

Molecular complexes of ketaconazole and oxatomide with p-chloranil: spectroscopic and spectrofluorimetric studies

The molecular complexes of the donors ketaconazole (KTZ) and oxatomide (OXA) drugs with 2,3,5,6-tetrachloro-1,4-benzoquinone (p-chloranil, p-CHL) have been investigated spectroscopically (UV-vis, FT-IR and 1H NMR) and spectrofluorimetrically in different solvents and temperatures. The stoichiometry of the complexes was found to be 1:1. The data are discussed in terms of formation constant, molar extinction coefficient, oscillator strength, dipole moment, ionization potential, dissociation energy and thermodynamic parameters. The results indicated that the formation of molecular complex is spontaneous and endothermic. The fluorescence quenching studies indicated that the interaction of the donors is spontaneous and the fluorescence quenching increased with an increase in the intensity of complexation with the acceptor.

Prediction of the intestinal first-pass metabolism of CYP3A substrates in humans using cynomolgus monkeys

To select high bioavailability compounds, it is necessary to predict the first-pass metabolism in the intestine. However, in vitro-in vivo predictions of the intestinal metabolism have proven both challenging and less definitive. The purpose of this study was to investigate prediction of intestinal first-pass metabolism in humans using cynomolgus monkeys. First, we investigated intrinsic metabolic activities in intestinal microsomes of monkeys (MIM) and humans (HIM) (CL(int, MIM) and CL(int, HIM), respectively) of 18 CYP3A substrates. The CL(int, MIM) values were found to be relatively high and showed excellent correlation with the CL(int, HIM) values. Subsequently, we determined the plasma concentrations of 9 CYP3A substrates (buspirone, carbamazepine, diazepam, felodipine, midazolam, nicardipine, nifedipine, saquinavir, and verapamil) in monkeys after an oral dose of 2 mg/kg with or without an oral dose of 5 mg/kg ketoconazole and calculated AUC((+vehicle))/AUC((+ketoconazole)), defined as F(g, monkey(observed)); we confirmed that the dose of ketoconazole inhibited only intestinal CYP3A metabolism by preliminary in vitro and in vivo experiments using ketoconazole. The F(g, monkey(observed)) was lower than the F(g, human(observed)) for most compounds, but moderate correlation was observed. Furthermore, using these data, we established a new methodology to estimate F(g, human(predicted)) more precisely on the basis of the assumption that intestinal physiological conditions other than intrinsic metabolic activity would be the same between monkeys and humans. In conclusion, the in vivo model using cynomolgus monkeys in this study is useful for prediction of intestinal first-pass metabolism by CYP3A in humans because it was able to predict F(g, human) of all nine compounds investigated.

Conazoles

This review provides a historical overview of the analog based drug discovery of miconazole and its congeners, and is focused on marketed azole antifungals bearing the generic suffix “conazole”. The antifungal activity of miconazole, one of the first broad-spectrum antimycotic agents has been mainly restricted to topical applications. The attractive in vitro antifungal spectrum was a starting point to design more potent and especially orally active antifungal agents such as ketoconazole, itraconazole, posaconazole, fluconazole and voriconazole. The chemistry, in vitro and in vivo antifungal activity, pharmacology, and clinical applications of these marketed conazoles has been described.

3-ketocholanoic acid is the major in vitro human hepatic microsomal metabolite of lithocholic acid

3alpha-Hydroxy-5 beta-cholan-24-oic (lithocholic) acid is a relatively minor component of hepatic bile acids in humans but is highly cytotoxic. Hepatic microsomal oxidation offers a potential mechanism for effective detoxification and elimination of bile acids. The aim of the present study was to investigate the biotransformation of lithocholic acid by human hepatic microsomes and to assess the contribution of cytochrome P450 (P450) enzymes in human hepatic microsomes using human recombinant P450 enzymes and chemical inhibitors. Metabolites were identified, and metabolite formation was quantified using a liquid chromatography/mass spectrometry-based assay. Incubation of lithocholic acid with human liver microsomes resulted in the formation of five metabolites, which are listed in order of their rates of formation: 3-oxo-5 beta-cholan-24-oic (3-ketocholanoic) acid, 3 alpha,6 alpha-dihydroxy-5 beta-cholan-24-oic (hyodeoxycholic) acid, 3 alpha,7 beta-dihydroxy-5 beta-cholan-24-oic (ursodeoxycholic) acid, 3 alpha,6 beta-dihydroxy-5 beta-cholan-24-oic (murideoxycholic) acid, and 3 alpha-hydroxy-6-oxo-5 beta-cholan-24-oic (6-ketolithocholic) acid. 3-Ketocholanoic acid was the major metabolite, exhibiting apparent K(m) and V(max) values of 22 muM and 336 pmol/min/mg protein, respectively. Incubation of lithocholic acid with a of human recombinant P450 enzymes revealed that all five metabolites were formed by recombinant CYP3A4. Chemical inhibition studies with human liver microsomes and recombinant P450 enzymes confirmed that CYP3A4 was the predominant enzyme involved in hepatic microsomal biotransformation of lithocholic acid. In summary, the results indicate that oxidation of the third carbon of the cholestane ring is the preferred position of oxidation by P450 enzymes for lithocholic acid biotransformation in humans and suggest that formation of lithocholic acid metabolites leads to enhanced hepatic detoxification and elimination.

Pharmacokinetic interaction between efavirenz and ketoconazole in rats

1. It is well known that efavirenz and ketoconazole act as an inducer and inhibitor of CYP3A4, respectively. As a result of these actions, co-administration of these drugs may result in changes in the pharmacokinetic parameters of one or both of them. 2. Duodenum-cannulated rats have been used to compare the effect of intraduodenal (KC(i.d.)) and intravenous administration of ketoconazole (KC(i.v.)) on the pharmacokinetics of efavirenz after intraduodenal administration, as well as the potential effect of efavirenz as a CYP450 inducer on ketoconazole pharmacokinetic profile. 3. While KC(i.v.) did not show any significant effect on efavirenz pharmacokinetic profile, KC(i.d.) increased significantly (p < 0.05) the peak concentration (C(max)) and the area under the plasma concentration-time curve (AUC) of efavirenz by 25.5% and 44.5%, respectively. In addition, the time necessary to reach peak concentration (T(max)) increased markedly by 71%. However, the mean total clearance (CL/F) of efavirenz was significantly decreased by 45%. Efavirenz did not produce any alteration in ketoconazole pharmacokinetics. 4. These findings suggest that when the treatment starts with enteral administration of ketoconazole, the inhibitor effect on CYP450 prevails over the inducer effect of efavirenz.

Pharmacokinetics of topical and oral antifungals

By principle both topical and systemic antifungals are available for oral candidosis. As therapeutic results have not yet reached an optimum these modalities deserve further consideration. This especially applies to bioavailability. As candidosis in general very often is a disease confined to other tissues than blood especially to cutaneous and mucosal surfaces, it is helpful to determine the drug level found at these sites. Both total and free drug levels should be looked at. The skin blistering techniques make this possible. In vitro simulation of the level profiles of various antifungals including in particular ketoconazole found in the skin can be simulated in vitro using Grasso's model. If this is done only a very limited candidacidal effect is to be seen. Taking this fact into account as well as a limited clinical efficacy of conventional treatment protocols it looks rewarding to use conventional antifungal drugs such as ketoconazole at comparatively high doses.

Update on terbinafine with a focus on dermatophytoses

Since terbinafine was introduced on the world market 17 years ago, it has become the leading antifungal for the treatment of superficial fungal infections, aided by unique pharmacologic and microbiologic profiles. This article reviews mode of action, antimycotic spectrum and disposition profile of terbinafine. It examines the data, accumulated over 15 years, on the comparative efficacy of terbinafine (vs griseofulvin, itraconazole, fluconazole) in the management of the infections for which it is primarily indicated (eg, dermatophytoses) and provides a brief discussion on its use for the treatment of non-dermatophyte infections. Finally, the available data on the newest topical and systemic formulations are introduced.

Role of Metabolism in Drug-Induced Idiosyncratic Hepatotoxicity

Rare adverse reactions to drugs that are of unknown etiology, or idiosyncratic reactions, can produce severe medical complications or even death in patients. Current hypotheses suggest that metabolic activation of a drug to a reactive intermediate is a necessary, yet insufficient, step in the generation of an idiosyncratic reaction. We review evidence for this hypothesis with drugs that are associated with hepatotoxicity, one of the most common types of idiosyncratic reactions in humans. We identified 21 drugs that have either been withdrawn from the U.S. market due to hepatotoxicity or have a black box warning for hepatotoxicity. Evidence for the formation of reactive metabolites was found for 5 out of 6 drugs that were withdrawn, and 8 out of 15 drugs that have black box warnings. For the other drugs, either evidence was not available or suitable studies have not been carried out. We also review evidence for reactive intermediate formation from a number of additional drugs that have been associated with idiosyncratic hepatotoxicity but do not have black box warnings. Finally, we consider the potential role that high dosages may play in these adverse reactions.

Effects of ketoconazole on the pharmacokinetics and pharmacodynamics of morphine in healthy Greyhounds

OBJECTIVE

To assess pharmacokinetics and pharmacodynamics of morphine and the effects of ketoconazole on the pharmacokinetics and pharmacodynamics of morphine in healthy Greyhounds.

ANIMALS

6 healthy Greyhounds, 3 male and 3 female.

PROCEDURES

Morphine sulfate (0.5 mg/kg. IV) was administered to Greyhounds prior to and after 5 days of ketoconazole (12.7 +/- 0.6 mg/kg, PO) treatment. Plasma samples were obtained from blood samples that were collected at predetermined time points for measurement of morphine and ketoconazole concentrations by mass spectrometry. Pharmacokinetics of morphine were estimated by use of computer software.

RESULTS

Pharmacodynamic effects of morphine in Greyhounds were similar to those of other studies in dogs and were similar between treatment groups. Morphine was rapidly eliminated with a half-life of 1.28 hours and a plasma clearance of 32.55 mL/min/kg. The volume of distribution was 3.6 L/kg. No significant differences in the pharmacokinetics of morphine were found after treatment with ketoconazole. Plasma concentrations of ketoconazole were high and persisted longer than expected in Greyhounds.

CONCLUSIONS AND CLINICAL RELEVANCE

Ketoconazole had no significant effect on morphine pharmacokinetics, and the pharmacodynamics were similar between treatment groups. Plasma concentrations of ketoconazole were higher than expected and persisted longer than expected in Greyhounds.

Drug interaction prediction using ontology-driven hypothetical assertion framework for pathway generation followed by numerical simulation

BACKGROUND

In accordance with the increasing amount of information concerning individual differences in drug response and molecular interaction, the role of in silico prediction of drug interaction on the pathway level is becoming more and more important. However, in view of the interferences for the identification of new drug interactions, most conventional information models of a biological pathway would have limitations. As a reflection of real world biological events triggered by a stimulus, it is important to facilitate the incorporation of known molecular events for inferring (unknown) possible pathways and hypothetic drug interactions. Here, we propose a new Ontology-Driven Hypothetic Assertion (OHA) framework including pathway generation, drug interaction detection, simulation model generation, numerical simulation, and hypothetic assertion. Potential drug interactions are detected from drug metabolic pathways dynamically generated by molecular events triggered after the administration of certain drugs. Numerical simulation enables to estimate the degree of side effects caused by the predicted drug interactions. New hypothetic assertions of the potential drug interactions and simulation are deduced from the Drug Interaction Ontology (DIO) written in Web Ontology Language (OWL).

RESULTS

The concept of the Ontology-Driven Hypothetic Assertion (OHA) framework was demonstrated with known interactions between irinotecan (CPT-11) and ketoconazole. Four drug interactions that involved cytochrome p450 (CYP3A4) and albumin as potential drug interaction proteins were automatically detected from Drug Interaction Ontology (DIO). The effect of the two interactions involving CYP3A4 were quantitatively evaluated with numerical simulation. The co-administration of ketoconazole may increase AUC and Cmax of SN-38(active metabolite of irinotecan) to 108% and 105%, respectively. We also estimates the potential effects of genetic variations: the AUC and Cmax of SN-38 may increase to 208% and 165% respectively with the genetic variation UGT1A1*28/*28 which reduces the expression of UGT1A1 down to 30%.

CONCLUSION

These results demonstrate that the Ontology-Driven Hypothetic Assertion framework is a promising approach for in silico prediction of drug interactions. The following future researches for the in silico prediction of individual differences in the response to the drug and drug interactions after the administration of multiple drugs: expansion of the Drug Interaction Ontology for other drugs, and incorporation of virtual population model for genetic variation analysis, as well as refinement of the pathway generation rules, the drug interaction detection rules, and the numerical simulation models.

Effect of efavirenz on the pharmacokinetics of ketoconazole in HIV-infected patients

OBJECTIVE

To investigate the effect of efavirenz on the ketoconazole pharmacokinetics in HIV-infected patients.

METHODS

Twelve HIV-infected patients were assigned into a one-sequence, two-period pharmacokinetic interaction study. In phase one, the patients received 400 mg of ketoconazole as a single oral dose on day 1; in phase two, they received 600 mg of efavirenz once daily in combination with 150 mg of lamivudine and 30 or 40 mg of stavudine twice daily on days 2 to 16. On day 16, 400 mg of ketoconazole was added to the regimen as a single oral dose. Ketoconazole pharmacokinetics were studied on days 1 and 16.

RESULTS

Pretreatment with efavirenz significantly increased the clearance of ketoconazole by 201%. C(max) and AUC(0-24) were significantly decreased by 44 and 72%, respectively. The T ((1/2)) was significantly shorter by 58%.

CONCLUSION

Efavirenz has a strong inducing effect on the metabolism of ketoconazole.

Simultaneous determination of docetaxel and ketoconazole in rat plasma by liquid chromatography/electrospray ionization tandem mass spectrometry

A rapid and sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method has been developed and validated for simultaneous quantification of docetaxel and ketoconazole in rat plasma with paclitaxel as internal standard (IS). The analytes were extracted from rat plasma by using a liquid-liquid extraction technique with ethyl acetate and the LC separation was performed on a Cosmosil-C(18) analytical column (150 mm x 2.0 mm i.d., Nacalai Tesque Inc., Japan). The extracted samples were analyzed with LC/MS/MS, operating in selected reaction monitoring (SRM) mode. The SRM transitions of precursor ions to product ions were 830.3-->549.1 (m/z) for docetaxel, 531.2-->489.3 (m/z) for ketoconazole, and 876.7-->307.9 (m/z) for the IS. The calibration curves were linear over the range of 2-500 ng/mL for docetaxel and 50-20 000 ng/mL for ketoconazole, with coefficients of correlation above 0.999. The limits of quantification for docetaxel and ketoconazole were both 2 ng/mL. The limit of detection for each analyte was 1 ng/mL. The intra- and inter-day precision (CV) of analysis were within 7%, and the accuracy ranged from 95 to 110%. The overall recoveries for docetaxel and ketoconazole were about 89.0% and 91.1%, respectively. The total analysis time was only 9.0 min. This quantitation method was successfully applied to the simultaneous determination of docetaxel and ketoconazole in rat plasma and some potential interaction was found in the current coadministration pharmacokinetic study. This established method was also utilized in the in vitro and in vivo drug-drug interaction study of docetaxel and ketoconazole (to be published).

Optimization and validation of a high-performance liquid chromatographic method with UV detection for the determination of ketoconazole in canine plasma

An isocratic high-performance liquid chromatographic method with detection at 240 nm was developed, optimized and validated for the determination of ketoconazole in canine plasma. 9-Acetylanthracene was used as internal standard. A Hypersil BDS RP-C18 column (250 mm x 4.6 mm, 5 microm particle size), was equilibrated with a mobile phase composed of methanol, water and diethylamine 74:26:0.1 (v/v/v). Its flow rate was 1 ml/min. The elution time for ketoconazole and 9-acetylanthracene was approximately 9 and 8 min, respectively. Calibration curves of ketoconazole in plasma were linear in the concentration range of 0.015-10 microg/ml. Limits of detection and quantification in plasma were 5 and 15 ng/ml, respectively. Recovery was greater than 95%. Intra- and inter-day relative standard deviation for ketoconazole in plasma was less than 3.1 and 4.7%, respectively. This method was applied to the determination of ketoconazole plasma levels after administration of a commercially available tablet to dogs.

Cushing's syndrome during pregnancy secondary to adrenal adenoma: metyrapone treatment and laparoscopic adrenalectomy

Cushing's syndrome during pregnancy is a rare and difficult to diagnose disorder. We describe the case of a 30-yr-old woman presenting with symptoms and signs of mild hypercortisolism, in which ACTH-independent Cushing's syndrome was diagnosed. Urinary cortisol excretion was elevated and circadian rhythm of cortisol was absent. ACTH levels were low. In addition, plasma cortisol failed to suppress after a high dexamethasone dose. An abdominal computed tomography scan confirmed a left adrenal mass. While diagnosis work-up was still in progress, the patient became pregnant and wanted to carry her pregnancy to full-term. Hypercortisolism was successfully controlled with metyrapone, which was started at 8 weeks of gestation. At 16 weeks of gestation, a laparoscopic left adrenalectomy was performed. Pathologic examination of the gland showed a benign adrenocortical adenoma. The patient developed secondary adrenal insufficiency and was discharged on 20 mg hydrocortisone daily dose. At 30 weeks of gestation, the patient had a pre-term rupture of membranes and underwent spontaneous vaginal delivery. The newborn was a normal virilized male who weighed 1280 g. No apparent metyrapone-induced teratogenic effects were observed and there was no clinical or biochemical suppression of adrenocortical function. In conclusion, in adrenal Cushing's syndrome during pregnancy, medical treatment with metyrapone as soon as the diagnosis is made, in combination with laparoscopic surgery during the second trimester, are useful in preventing complications secondary to hypercortisolism and safe both for the mother and infant.

Synthesis and antimicrobial study of novel heterocyclic compounds from hydroxybenzophenones

The triazolothiadiazine analogues 6a-e were obtained via a multistep synthesis sequences beginning with the hydroxybenzophenones 1a-e. Hydroxybenzophenones on reaction with ethyl chloroacetate affords ethyl (2-aroylaryloxy)acetates 2a-e which on treatment with hydrazine hydrate yields 2-(2-aroylaryloxy)acetohydrazides 3a-e. Intramolecular cyclization of 3a-e with carbon disulfide affords 5-(2-aroylaryloxy)methyl-1,3,4-oxadiazole-2-(3H)thiones 4a-e, which on treatment with hydrazine hydrate yields 4-amino-5-(2-aroyl aryloxy)methyl-1,2,4-triazole-3-(2H)thiones 5a-e. Condensation of 5a-e with alpha-halocarbonyl compound results in 3-(2-aroylaryloxy)methyl-6-phenyl-1,2,4-triazolo[3,4-b][1,3,4] thiadiazine 6a-e analogues. The compounds 4a-e, 5a-e and 6a-e were tested against variety of fungal and bacterial strains in comparison to fluconazole and chloramphenicol, respectively.

Voriconazole-induced retinoid-like photosensitivity in children

Voriconazole is a new triazole antifungal agent with activity against a wide range of systemic fungal pathogens, including Aspergillus spp. Photosensitivity is a rarely reported side effect of voriconazole, hypothesized to be a result of retinoid-like effects. We report two children with chronic granulomatous disease to whom voriconazole was administered for chronic invasive aspergillosis. Severe photosensitivity occurred in both patients, one of whom had striking photodamage at the 5-month follow-up.