Voriconazole and fluconazole increase the exposure to oral diazepam

Interaction and potential mechanisms between atorvastatin and voriconazole, agents used to treat dyslipidemia and fungal infections

Purpose: Voriconazole (VOR) is combined with atorvastatin (ATO) to treat fungal infections in patients with dyslipidemia in clinical practice. However, the pharmacokinetic interactions and potential mechanisms between them are unknown. Therefore, this study aimed to investigate the pharmacokinetic interactions and potential mechanisms between ATO and VOR. Patients and methods: We collected plasma samples from three patients using ATO and VOR. Rats were administered either VOR or normal saline for 6 days, followed by a single dose of 2 mg/kg ATO, and then plasma samples were collected at different time points. The incubation models of human liver microsomes or HepG2 cells were constructed in vitro. A high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) system was developed to determine the concentration of ATO, 2-hydroxy-ATO, 4-hydroxy-ATO, and VOR. Results: In patients, VOR significantly reduced the metabolism of ATO and slowed the formation of 2-hydroxy- and 4-hydroxy-ATO. In rats pretreated with orally administered VOR for 6 days or normal saline given a single dose of 2 mg/kg ATO administered orally on Day 6, the t1/2 of ATO was significantly prolonged from 3.61 to 6.43 h, and the area under the concentration-time curve (AUC0-24h) values of ATO increased from 53.86 to 176.84 h μg.L-1. However, the pharmacokinetic parameters of VOR (20 mg/kg) with or without pretreatment with ATO (2 mg/kg) only slightly changed. In vitro studies indicated that VOR inhibited the metabolism of ATO and testosterone, and the IC50 values were 45.94 and 49.81 μM. However, no significant change in transporter behaviors of ATO was observed when VOR or transporter inhibitors were co-administered. Conclusion: Our study demonstrated that VOR has significant interactions with ATO, probably due to VOR's inhibition of the CYP3A4-mediated metabolism of ATO. Based on the clinical cases and potential interactions, the basic data obtained in our study are expected to help adjust the dose of ATO and promote the design of rational dosage regimens for pharmacotherapy for fungal infections in patients with dyslipidemia.

Effects of voriconazole and fluconazole on the pharmacokinetics of almonertinib in rats by UPLC-MS/MS

Almonertinib was included in the first-line treatment of non-small cell lung cancer with EGFR T790M mutations by the Chinese Society of Clinical Oncology in 2021. Considering that immunocompromised lung cancer patients are prone to opportunistic fungal infections, and most triazole antifungal drugs are moderate or strong inhibitors of CYP3A4, this study was conducted to develop and validate an accurate and rapid ultra-performance liquid chromatography tandem mass spectrometry method for quantifying almonertinib in plasma and for investigating the pharmacokinetic changes of almonertinib caused by voriconazole and fluconazole in rats. After liquid-liquid extraction with tert-butyl methyl ether, an XSelect HSS T3 column (2.1 × 100 mm, 2.5 μm, Waters) was used for the chromatographic separation of almonertinib and sorafenib-D₃ (internal standard). The analytes were detected using an AB Sciex Triple Quad 5,500 mass spectrometer in the positive ionization mode. The method exhibited great linearity (0.5-200 ng/ml, r > 0.997) and stability under the established experimental conditions. All validation experiments were in accordance with the guidelines, and the results were all within the acceptable limits. This method was successfully applied to the researches of pharmacokinetics and drug interactions for almonertinib in rats. Voriconazole and fluconazole significantly altered the pharmacokinetic profiles of almonertinib and increased the systemic exposure of almonertinib in rats to different degrees, but further human trials should be conducted to validate the results.

Pharmacokinetic Drug-drug Interaction of Antibiotics Used in Sepsis Care in China

BACKGROUND

Many antibiotics have a high potential for interactions with drugs, as a perpetrator and/or victim, in critically ill patients, and particularly in sepsis patients.

METHODS

The aim of this review is to summarize the pharmacokinetic drug-drug interaction (DDI) of 45 antibiotics commonly used in sepsis care in China. Literature search was conducted to obtain human pharmacokinetics/ dispositions of the antibiotics, their interactions with drug-metabolizing enzymes or transporters, and their associated clinical drug interactions. Potential DDI is indicated by a DDI index ≥ 0.1 for inhibition or a treatedcell/ untreated-cell ratio of enzyme activity being ≥ 2 for induction.

RESULTS

The literature-mined information on human pharmacokinetics of the identified antibiotics and their potential drug interactions is summarized.

CONCLUSION

Antibiotic-perpetrated drug interactions, involving P450 enzyme inhibition, have been reported for four lipophilic antibacterials (ciprofloxacin, erythromycin, trimethoprim, and trimethoprim-sulfamethoxazole) and three antifungals (fluconazole, itraconazole, and voriconazole). In addition, seven hydrophilic antibacterials (ceftriaxone, cefamandole, piperacillin, penicillin G, amikacin, metronidazole, and linezolid) inhibit drug transporters in vitro. Despite no clinical PK drug interactions with the transporters, caution is advised in the use of these antibacterials. Eight hydrophilic antibiotics (all β-lactams; meropenem, cefotaxime, cefazolin, piperacillin, ticarcillin, penicillin G, ampicillin, and flucloxacillin), are potential victims of drug interactions due to transporter inhibition. Rifampin is reported to perpetrate drug interactions by inducing CYP3A or inhibiting OATP1B; it is also reported to be a victim of drug interactions, due to the dual inhibition of CYP3A4 and OATP1B by indinavir. In addition, three antifungals (caspofungin, itraconazole, and voriconazole) are reported to be victims of drug interactions because of P450 enzyme induction. Reports for other antibiotics acting as victims in drug interactions are scarce.

Drug-drug interactions in the treatment for alcohol use disorders: A comprehensive review

Drug interactions are one of the most common causes of side effects in polypharmacy. Alcoholics are a category of patients at high risk of pharmacological interactions, due to the presence of comorbidities, the concomitant intake of several medications and the pharmacokinetic and pharmacodynamic interferences of ethanol. However, the data available on this issue are limited. These reasons often frighten clinicians when prescribing appropriate pharmacological therapies for alcohol use disorder (AUD), where less than 15% of patients receive an appropriate treatment in the most severe forms. The data available in literature regarding the relevant drug-drug interactions of the medications currently approved in United States and in some European countries for the treatment of AUD (benzodiazepines, acamprosate, baclofen, disulfiram, nalmefene, naltrexone and sodium oxybate) are reviewed here. The class of benzodiazepines and disulfiram are involved in numerous pharmacological interactions, while they are not conspicuous for acamprosate. The other drugs are relatively safe for pharmacological interactions, excluding the opioid withdrawal syndrome caused by the combination of nalmefene or naltrexone with an opiate medication. The information obtained is designed to help clinicians in understanding and managing the pharmacological interactions in AUDs, especially in patients under multi-drug treatment, in order to reduce the risk of a negative interaction and to improve the treatment outcomes.

Development of a simple and sensitive HPLC-MS/MS method for determination of diazepam in human plasma and its application to a bioequivalence study

We developed a simple, sensitive, and effective ultra-performance liquid chromatography/tandem mass spectrometry (HPLC-MS/MS) method with an electrospray ionization (ESI) interface in multiple reaction monitoring (MRM) and positive ion modes to determine diazepam concentrations in human plasma using voriconazole as an internal standard (IS). Diazepam and IS were detected at transition 285.2→193.1 and 350.2→127.1, respectively. After liquid-liquid extraction (LLE) using 1.2 ml of ethyl acetate:n-hexane (80:20, v/v), diazepam and IS were eluted on a Phenomenex Cadenza CD-C18 column (150 × 3.0 mm, 3 µm) with an isocratic mobile phase (10 mM ammonium acetate in water:methanol [5:95, v/v]) at a flow rate of 0.4 mL/min. The peak retention time was 2.32 min for diazepam and 2.01 min for IS, respectively. The lower limit of quantitation (LLOQ) was 0.5 ng/mL (S/N > 10) using 50 µL of plasma, and no interferences were observed in chromatograms. Our analytical method was fully validated and successfully applied to a bioequivalence study of two formulations of diazepam in healthy Korean volunteers.

Notable Drug-Drug Interaction Between Etizolam and Itraconazole in Poor Metabolizers of Cytochrome P450 2C19

In this study, impact of a polymorphism of CYP2C19 on drug-drug interaction (DDI) was examined for etizolam. The effect of itraconazole (a strong CYP3A inhibitor) on the pharmacokinetics of etizolam (a substrate of CYP2C19 and CYP3A) was assessed in both extensive metabolizers (EMs) and poor metabolizers (PMs) of CYP2C19. Sixteen participants (8 EMs and 8 PMs) received a single oral dose of etizolam (0.25 mg) on day 1. The participants ingested itraconazole (200 mg twice a day) on days 2-5. On day 5, participants received an oral dose of etizolam (0.25 mg) again. Before coadministration of itraconazole (day 1), the area under the time-plasma concentration curve from time zero to infinity (AUC_∞ ) of etizolam was higher in PMs than in EMs (2.65-fold, P < .01). Coadministration of itraconazole increased the AUC_∞ of etizolam 1.66-fold and 2.34-fold in EMs and PMs, respectively (day 5). Consequently, AUC_∞ was 6.18-fold higher in PMs with itraconazole than that in EMs without itraconazole. The increase by itraconazole was larger in PMs (P < .01). In heterozygous EMs (hEMs), AUC_∞ was simulated to be 2.56-fold higher with itraconazole than that in EMs without itraconazole. We found that in vitro measurements of fraction metabolized (f_m ) using the liver microsome prepared from PM donors would be helpful to predict polymorphism-dependent DDIs. These results suggest that the PMs and hEMs of a polymorphic CYP would be at higher risk of DDIs relative to EMs for drugs metabolized by both polymorphic and nonpolymorphic CYPs such as etizolam.

A Model for Predicting the Interindividual Variability of Drug-Drug Interactions

Pharmacokinetic drug-drug interactions are frequently characterized and quantified by an AUC ratio (Rauc). The typical value of the AUC ratio in case of cytochrome-mediated interactions may be predicted by several approaches, based on in vitro or in vivo data. Prediction of the interindividual variability of Rauc would help to anticipate more completely the consequences of a drug-drug interaction. We propose and evaluate a simple approach for predicting the standard deviation (sd) of Ln(Rauc), a metric close to the interindividual coefficient of variation of Rauc. First, a model was derived to link sd(Ln Rauc) with the substrate fraction metabolized by each cytochrome and the potency of the interactors, in case of induction or inhibition. Second, the parameters involved in these equations were estimated by a Bayesian hierarchical model, using the data from 56 interaction studies retrieved from the literature. Third, the model was evaluated by several metrics based on the fold prediction error (PE) of sd(Ln Rauc). The median PE was 0.998 (the ideal value is 1) and the interquartile range was 0.96-1.03. The PE was in the acceptable interval (0.5 to 2) in 52 cases out of 56. Fourth, a surface plot of sd(Ln Rauc) as a function of the characteristics of the substrate and the interactor has been built. The minimal value of sd(Ln Rauc) was about 0.08 (obtained for Rauc = 1) while the maximal value, 0.7, was obtained for interactions involving highly metabolized substrates with strong interactors.

Voriconazole more likely than posaconazole increases plasma exposure to sublingual buprenorphine causing a risk of a clinically important interaction

PURPOSE

This study aimed to determine possible effects of voriconazole and posaconazole on the pharmacokinetics and pharmacological effects of sublingual buprenorphine.

METHODS

We used a randomized, placebo-controlled crossover study design with 12 healthy male volunteers. Subjects were given a dose of 0.4 mg (0.6 mg during placebo phase) sublingual buprenorphine after a 5-day oral pretreatment with either (i) placebo, (ii) voriconazole 400 mg twice daily on the first day and 200 mg twice daily thereafter or (iii) posaconazole 400 mg twice daily. Plasma and urine concentrations of buprenorphine and its primary active metabolite norbuprenorphine were monitored over 18 h and pharmacological effects were measured.

RESULTS

Compared to placebo, voriconazole increased the mean area under the plasma concentration-time curve (AUC_0-∞) of buprenorphine 1.80-fold (90 % confidence interval 1.45-2.24; P < 0.001), its peak concentration (C_max) 1.37-fold (P < 0.013) and half-life (t _½ ) 1.37-fold (P < 0.001). Posaconazole increased the AUC0_0-∞ of buprenorphine 1.25-fold (P < 0.001). Most of the plasma norbuprenorphine concentrations were below the limit of quantification (0.05 ng/ml). Voriconazole, unlike posaconazole, increased the urinary excretion of norbuprenorphine 1.58-fold (90 % confidence interval 1.18-2.12; P < 0.001) but there was no quantifiable parent buprenorphine in urine. Plasma buprenorphine concentrations correlated with the pharmacological effects, but the effects did not differ significantly between the phases.

CONCLUSIONS

Voriconazole, and to a minor extent posaconazole, increase plasma exposure to sublingual buprenorphine, probably via inhibition of cytochrome P450 3 A and/or P-glycoprotein. Care should be exercised in the combined use of buprenorphine with triazole antimycotics, particularly with voriconazole, because their interaction can be of clinical importance.

Consensus guidelines for optimising antifungal drug delivery and monitoring to avoid toxicity and improve outcomes in patients with haematological malignancy, 2014

Antifungal agents may be associated with significant toxicity or drug interactions leading to sub-therapeutic antifungal drug concentrations and poorer clinical outcomes for patients with haematological malignancy. These risks may be minimised by clinical assessment, laboratory monitoring, avoidance of particular drug combinations and dose modification. Specific measures, such as the optimal timing of oral drug administration in relation to meals, use of pre-hydration and electrolyte supplementation may also be required. Therapeutic drug monitoring (TDM) of antifungal agents is warranted, especially where non-compliance, non-linear pharmacokinetics, inadequate absorption, a narrow therapeutic window, suspected drug interaction or unexpected toxicity are encountered. Recommended indications for voriconazole and posaconazole TDM in the clinical management of haematology patients are provided. With emerging knowledge regarding the impact of pharmacogenomics upon metabolism of azole agents (particularly voriconazole), potential applications of pharmacogenomic evaluation to clinical practice are proposed.

Voriconazole pharmacokinetics and exposure-response relationships: assessing the links between exposure, efficacy and toxicity

The triazole antifungal voriconazole (VCZ) exhibits broad-spectrum antifungal activity and is the first-line treatment for invasive aspergillosis. Highly variable, non-linear pharmacokinetics, metabolism via the polymorphic drug-metabolising enzyme CYP2C19, and a range of serious adverse events (AEs) including hepatotoxicity and neurotoxicity complicate the clinical utility of VCZ. As interest in optimising VCZ treatment has increased, a growing number of studies have examined the relationships between VCZ exposure and efficacy in the treatment and prevention of invasive fungal infections, as well as associations with VCZ-related AEs. This review provides a critical analysis of VCZ pharmacokinetics and exposure-response (E-R) relationships, assessing the links between VCZ exposure, efficacy and toxicity. Low VCZ exposure has frequently been associated with a higher incidence of treatment failure; fewer studies have addressed E-R relationships with prophylactic VCZ. VCZ-related neurotoxicity appears common at high VCZ concentrations and can be minimised by maintaining concentrations below the recommended upper concentration thresholds; hepatotoxicity appears to be associated with increased VCZ exposure but is also prevalent at low concentrations. Further research should aim to inform and optimise the narrow therapeutic range of VCZ as well as develop interventions to individualise VCZ dosing to achieve maximal efficacy with minimal toxicity.

Current and future therapies for invasive aspergillosis

Invasive fungal infections have increase worldwide and represent a threat for immunocompromised patients including HIV-infected, recipients of solid organ and stem cell transplants, and patients receiving immunosuppressive therapies. High mortality rates and difficulties in early diagnosis characterize pulmonary fungal infections. Invasive pulmonary aspergillosis has been reviewed focussing on therapeutic management. Although new compounds have become available in the past years (i.e., amphotericin B lipid formulations, last-generation azoles, and echinocandines), new diagnostic tools and careful therapeutic management are mandatory to assure an early appropriate targeted treatment that represents the key factor for a successful conservative approach in respiratory fungal infections.

Impact of genetic polymorphism on drug-drug interactions mediated by cytochromes: a general approach

Currently, quantitative prediction of the impact of genetic polymorphism and drug-drug interactions mediated by cytochromes, based on in vivo data, is made by two separate methods and restricted to a single cytochrome. We propose a unified approach for describing the combined impact of drug-drug interactions and genetic polymorphism on drug exposure. It relies on in vivo data and uses the following three characteristic parameters: one for the victim drug, one for the interacting drug, and another for the genotype. These parameters are known for a wide range of drugs and genotypes. The metrics of interest are the ratio of victim drug area under the curve (AUC) in patients with genetic variants taking both drugs, to the AUC in patients with either variant or wild-type genotype taking the victim drug alone. The approach was evaluated by external validation, comparing predicted and observed AUC ratios found in the literature. Data were found for 22 substrates, 30 interacting drugs, and 38 substrate-interacting drug couples. The mean prediction error of AUC ratios was 0.02, and the mean prediction absolute error was 0.38 and 1.34, respectively. The model may be used to predict the variations in exposure resulting from a number of drug-drug-genotype combinations. The proposed approach will help (1) to identify comedications and population at risk, (2) to adapt dosing regimens, and (3) to prioritize the clinical pharmacokinetic studies to be done.

In vivo quantitative prediction of the effect of gene polymorphisms and drug interactions on drug exposure for CYP2C19 substrates

We present a unified quantitative approach to predict the in vivo alteration in drug exposure caused by either cytochrome P450 (CYP) gene polymorphisms or CYP-mediated drug-drug interactions (DDI). An application to drugs metabolized by CYP2C19 is presented. The metrics used is the ratio of altered drug area under the curve (AUC) to the AUC in extensive metabolizers with no mutation or no interaction. Data from 42 pharmacokinetic studies performed in CYP2C19 genetic subgroups and 18 DDI studies were used to estimate model parameters and predicted AUC ratios by using Bayesian approach. Pharmacogenetic information was used to estimate a parameter of the model which was then used to predict DDI. The method adequately predicted the AUC ratios published in the literature, with mean errors of -0.15 and -0.62 and mean absolute errors of 0.62 and 1.05 for genotype and DDI data, respectively. The approach provides quantitative prediction of the effect of five genotype variants and 10 inhibitors on the exposure to 25 CYP2C19 substrates, including a number of unobserved cases. A quantitative approach for predicting the effect of gene polymorphisms and drug interactions on drug exposure has been successfully applied for CYP2C19 substrates. This study shows that pharmacogenetic information can be used to predict DDI. This may have important implications for the development of personalized medicine and drug development.

Importance of multi-p450 inhibition in drug-drug interactions: evaluation of incidence, inhibition magnitude, and prediction from in vitro data

Drugs that are mainly cleared by a single enzyme are considered more sensitive to drug-drug interactions (DDIs) than drugs cleared by multiple pathways. However, whether this is true when a drug cleared by multiple pathways is coadministered with an inhibitor of multiple P450 enzymes (multi-P450 inhibition) is not known. Mathematically, simultaneous equipotent inhibition of two elimination pathways that each contribute half of the drug clearance is equal to equipotent inhibition of a single pathway that clears the drug. However, simultaneous strong or moderate inhibition of two pathways by a single inhibitor is perceived as an unlikely scenario. The aim of this study was (i) to identify P450 inhibitors currently in clinical use that can inhibit more than one clearance pathway of an object drug in vivo and (ii) to evaluate the magnitude and predictability of DDIs caused by these multi-P450 inhibitors. Multi-P450 inhibitors were identified using the Metabolism and Transport Drug Interaction Database. A total of 38 multi-P450 inhibitors, defined as inhibitors that increased the AUC or decreased the clearance of probes of two or more P450s, were identified. Seventeen (45%) multi-P450 inhibitors were strong inhibitors of at least one P450, and an additional 12 (32%) were moderate inhibitors of one or more P450s. Only one inhibitor (fluvoxamine) was a strong inhibitor of more than one enzyme. Fifteen of the multi-P450 inhibitors also inhibit drug transporters in vivo, but such data are lacking on many of the inhibitors. Inhibition of multiple P450 enzymes by a single inhibitor resulted in significant (>2-fold) clinical DDIs with drugs that are cleared by multiple pathways such as imipramine and diazepam, while strong P450 inhibitors resulted in only weak DDIs with these object drugs. The magnitude of the DDIs between multi-P450 inhibitors and diazepam, imipramine, and omeprazole could be predicted using in vitro data with similar accuracy as probe substrate studies with the same inhibitors. The results of this study suggest that inhibition of multiple clearance pathways in vivo is clinically relevant, and the risk of DDIs with object drugs may be best evaluated in studies using multi-P450 inhibitors.

Azole interactions with multidrug therapy in pediatric oncology

Patients with cancer receive multidrug therapy. Antineoplastic agents and supportive care drugs are often administered together, leading to potential drug-drug interactions. These interactions may have significant clinical implications in terms of toxicity or a decrease in the efficacy of the treatment administered. Here, we focus on the role of azoles and their main pharmacokinetic interactions with the principal classes of drugs used in pediatric oncology. The co-administration of azoles and antineoplastic agents, corticosteroids, immunosuppressants, antacids, antiemetics, antiepileptic drugs and analgesics was investigated, and a practical guide on the management of these drugs when administered together is provided.

Effects of the moderate CYP3A4 inhibitor, fluconazole, on the pharmacokinetics of fesoterodine in healthy subjects

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Available data suggest that fesoterodine dosage should not exceed 4 mg once daily when taken concomitantly with potent CYP3A4 inhibitors, such as ketoconazole. Currently, no information is available on whether dose adjustment is necessary when fesoterodine is administered with a moderate CYP3A4 inhibitor.

WHAT THIS STUDY ADDS

This study shows that adjustment of fesoterodine dose is not warranted when co-administered with a moderate CYP3A4 inhibitor.

AIMS

To assess the effects of fluconazole, a moderate CYP3A4 inhibitor, on the pharmacokinetics (PK) and safety/tolerability of fesoterodine.

METHODS

In this open-label, randomized, two-way crossover study, 28 healthy subjects (18-55 years) received single doses of fesoterodine 8 mg alone or with fluconazole 200 mg. PK endpoints, including the area under the plasma concentration-time curve from 0 to infinity (AUC(0,∞)), maximum plasma concentration (C(max) ), time to C(max) (t(max) ), and half-life (t(1/2) ), were assessed for 5-hydroxymethyl tolterodine (5-HMT), the active moiety of fesoterodine.

RESULTS

Concomitant administration of fesoterodine with fluconazole increased AUC(0,∞) and C(max) of 5-HMT by approximately 27% and 19%, respectively, with corresponding 90% confidence intervals of (18%, 36%) and (11%, 28%). There was no apparent effect of fluconazole on 5-HMT t(max) or t(½) . Fesoterodine was generally well tolerated regardless of fluconazole co-administration, with no reports of death, serious adverse events (AEs) or severe AEs. Following co-administration of fesoterodine with fluconazole, 13 subjects (48%) experienced a total of 40 AEs; following administration of fesoterodine alone, six subjects (22%) experienced a total of 19 AEs. The majority of AEs were of mild intensity. There were no clinically significant changes in laboratory or physical examination parameters.

CONCLUSION

Fesoterodine 8 mg single dose was well tolerated when administered alone or with fluconazole. Based on the observed increase in 5-HMT exposures being within the inherent variability of 5-HMT pharmacokinetics, adjustment of fesoterodine dose is not warranted when co-administered with a moderate CYP3A4 inhibitor provided they are not also inhibitors of transporters.

Fluconazole but not the CYP3A4 inhibitor, itraconazole, increases zafirlukast plasma concentrations

PURPOSE

Zafirlukast is a substrate of cytochrome P450 2C9 (CYP2C9) and cytochrome P450 3A4 (CYP3A4) in vitro, but the role of these enzymes in its metabolism in vivo is unknown. To investigate the contribution of CYP2C9 and CYP3A4 to zafirlukast metabolism, we studied the effects of fluconazole and itraconazole on its pharmacokinetics (PK).

METHODS

In a randomized crossover study, 12 healthy volunteers ingested fluconazole 200 mg (first dose 400 mg) once daily, itraconazole 100 mg (first dose 200 mg) twice daily, or placebo twice daily for 5 days, and on day 3, 20 mg zafirlukast. Plasma concentrations of zafirlukast and the antimycotics were measured up to 72 h.

RESULTS

Fluconazole increased the total area under the plasma concentration-time curve (AUC) of zafirlukast 1.6-fold [95% confidence interval (CI) 1.3-2.0-fold, P < 0.001), and its peak plasma concentration 1.5-fold (95% CI 1.2-2.0-fold, P < 0.05). Fluconazole did not affect the time of peak plasma concentration or elimination half-life of zafirlukast. None of the zafirlukast PK variables differed significantly from the control in the itraconazole phase; e.g., the ratio to control of the total AUC of zafirlukast was 1.0 (95% CI 0.82-1.2) during the itraconazole phase.

CONCLUSIONS

Fluconazole, but not itraconazole, increases zafirlukast plasma concentrations, strongly suggesting that CYP2C9 but not CYP3A4 participates in zafirlukast metabolism in humans.

Enhancement of GABAergic activity: neuropharmacological effects of benzodiazepines and therapeutic use in anesthesiology

GABA is the major inhibitory neurotransmitter in the central nervous system (CNS). The type A GABA receptor (GABA(A)R) system is the primary pharmacological target for many drugs used in clinical anesthesia. The α1, β2, and γ2 subunit-containing GABA(A)Rs located in the various parts of CNS are thought to be involved in versatile effects caused by inhaled anesthetics and classic benzodiazepines (BZD), both of which are widely used in clinical anesthesiology. During the past decade, the emergence of tonic inhibitory conductance in extrasynaptic GABA(A)Rs has coincided with evidence showing that these receptors are highly sensitive to the sedatives and hypnotics used in anesthesia. Anesthetic enhancement of tonic GABAergic inhibition seems to be preferentially increased in regions shown to be important in controlling memory, awareness, and sleep. This review focuses on the physiology of the GABA(A)Rs and the pharmacological properties of clinically used BZDs. Although classic BZDs are widely used in anesthesiological practice, there is a constant need for new drugs with more favorable pharmacokinetic and pharmacodynamic effects and fewer side effects. New hypnotics are currently developed, and promising results for one of these, the GABA(A)R agonist remimazolam, have recently been published.

Effects of oral clotrimazole troches on the pharmacokinetics of oral and intravenous midazolam

AIMS

The aim of the study was to determine the effects of oral clotrimazole troches on the pharmacokinetics of oral and intravenous midazolam in the plasma.

METHODS

We conducted a randomized, open-label, four-way crossover study in 10 healthy volunteers. Each volunteer received oral midazolam 2 mg or intravenous midazolam 0.025 mg kg(-1) with and without oral clotrimazole troches 10 mg taken three times daily for 5 days. Each study period was separated by 14 days. Serial blood samples were collected up to 24 h after oral midazolam and 6 h after intravenous midazolam. Plasma concentrations for midazolam and its metabolite 1-hydroxymidazolam were measured and fitted to a noncompartmental model to estimate the pharmacokinetic parameters.

RESULTS

Ten healthy volunteers aged 21-26 years provided written informed consent and were enrolled into the study. Clotrimazole decreased the apparent oral clearance of midazolam from 57 +/- 13 l h(-1)[95% confidence interval 48, 66] to 36 +/- 9.8 l h(-1) (95% confidence interval 29, 43) (P= 0.003). These changes were accompanied by a decrease in the area under the concentration-time curve (mean difference 22 microg h(-1) l(-1), P= 0.001) and bioavailability (mean difference 0.21, P= NS). There were no significant differences in the systemic clearance of midazolam with or without clotrimazole troches.

CONCLUSIONS

Oral clotrimazole troches decreased the apparent oral clearance of midazolam; no significant differences in the systemic clearance of midazolam were found.

Azole antimycotics and drug interactions in the perioperative period

PURPOSE OF REVIEW

A beneficial effect of antifungal prophylaxis on the prevention of invasive fungal infections has increased the use of azole antimycotics in intensive care and during the perioperative period. At the same time more severe illnesses are treated and multiple drug therapies are employed. Thus, the potential for severe drug-drug interactions has increased. Previous studies have shown that azole antimycotics increase the risk of many clinically significant drug interactions with potentially hazardous consequences.

RECENT FINDINGS

A recent pharmacoepidemiological study has found a more than five-fold incidence ratio in the adjusted rate of sudden death from cardiac diseases among those patients who were given simultaneously inhibitors of cytochrome P450 (CYP) enzymes and their substrates. Although new triazole antifungals are well tolerated, they still cause significant inhibition of CYP enzymes.

SUMMARY

This review focuses on azole antimycotics and anesthetic drugs being used during the perioperative period and discusses the possible clinically significant drug-drug interactions. Azole antimycotics are amongst the strongest inhibitors of CYP-mediated drug metabolism. Anesthesiologists must be aware of the interaction potential of azole antimycotics to be able to adjust their perioperative strategies according to the patient's condition and concomitant medication.

Disposition of everolimus in mdr1a-/1b- mice and after a pre-treatment of lapatinib in Swiss mice

The aim of this study was to document the in vivo transport of everolimus (inhibitor of mTOR) by P-glycoprotein (P-gp), and to investigate the influence of lapatinib (inhibitor of P-gp) on everolimus disposition. Pharmacokinetics of everolimus (0.25mg/kg) has been investigated after oral administration in mdr1a-/1b- mice compared to the wild type. Also, everolimus pharmacokinetics was characterized after oral administration on Swiss mice either alone or after 2 days of pre-treatment of lapatinib (200mg/kg). The influence of lapatinib pre-treatment on intestinal P-gp expression was investigated by Western blot analysis. The non-compartimental analysis was performed using Winonlin professional version 4.1 software (Pharsight, Mountain View, CA). The areas under the plasma concentration-time curve (AUC) were compared using Bailer's method. A significant 1.3-fold increase of everolimus AUC observed in mdr1a-/1b- mice suggested that everolimus is transported in vivo by intestinal P-gp in mice. In addition, a 2.6-fold significant increase of everolimus AUC with lapatinib pre-treatment as compared with the everolimus alone group was noticed. The elimination half-life was comparable (t(1/2)=5.3h vs. t(1/2)=4h). A 38.5% significant decrease of P-gp expression was observed in duodenum segment in lapatinib pre-treated group as compared with control group. In conclusion, lapatinib enhanced everolimus absorption by decreasing intestinal P-gp expression. An inhibition of CYP 450 could not be excluded. These results confirm the necessity of a therapeutic monitoring of everolimus combined with an inhibitor of the P-gp and CYP 450 like lapatinib in a future anti-tumor treatment.

Comprehensive in vitro analysis of voriconazole inhibition of eight cytochrome P450 (CYP) enzymes: major effect on CYPs 2B6, 2C9, 2C19, and 3A

Voriconazole is an effective antifungal drug, but adverse drug-drug interactions associated with its use are of major clinical concern. To identify the mechanisms of these interactions, we tested the inhibitory potency of voriconazole with eight human cytochrome P450 (CYP) enzymes. Isoform-specific probes were incubated with human liver microsomes (HLMs) (or expressed CYPs) and cofactors in the absence and the presence of voriconazole. Preincubation experiments were performed to test mechanism-based inactivation. In pilot experiments, voriconazole showed inhibition of CYP2B6, CYP2C9, CYP2C19, and CYP3A (half-maximal [50%] inhibitory concentrations, <6 microM); its effect on CYP1A2, CYP2A6, CYP2C8, and CYP2D6 was marginal (<25% inhibition at 100 microM voriconazole). Further detailed experiments with HLMs showed that voriconazole is a potent competitive inhibitor of CYP2B6 (K(i) < 0.5), CYP2C9 (K(i) = 2.79 microM), and CYP2C19 (K(i) = 5.1 microM). The inhibition of CYP3A by voriconazole was explained by noncompetitive (K(i) = 2.97 microM) and competitive (K(i) = 0.66 microM) modes of inhibition. Prediction of the in vivo interaction of voriconazole from these in vitro data suggests that voriconazole would substantially increase the exposure of drugs metabolized by CYP2B6, CYP2C9, CYP2C19, and CYP3A. Clinicians should be aware of these interactions and monitor patients for adverse effects or failure of therapy.