Mechanism Underlying Conflicting Drug-Drug Interaction Between Aprepitant and Voriconazole via Cytochrome P450 3A4-Mediated Metabolism

Background

Voriconazole is an antifungal drug for which therapeutic monitoring is recommended to prevent side effects. Temporary administration of the antiemetic drug fosaprepitant remarkably decreases the plasma concentration of voriconazole from the therapeutic range. The ratio of the major metabolite voriconazole N-oxide to voriconazole exceeded that at any other time for a patient who started chemotherapy during voriconazole therapy. We attributed this unpredictable result to cytochrome P450 3A4 induced by aprepitant that was converted from fosaprepitant in vivo.

Methods

Concentrations of voriconazole and voriconazole N-oxide were measured using liquid chromatography-mass spectrometry/mass spectrometry in primary human hepatocytes after incubation with aprepitant. Aprepitant suppressed voriconazole N-oxide formation within 24 h, followed by a continuous increase. Levels of drug-metabolizing cytochrome P450 mRNA were measured using real-time PCR in primary human hepatocytes incubated with aprepitant.

Results

Cytochrome P450 3A4 and 2C9 mRNA levels increased ~4- and 2-fold, respectively, over time. Cytochrome P450 3A4 induction was confirmed using reporter assays. We also assessed L-755446, a major metabolite of aprepitant that lacks a triazole ring. Both compounds dose-dependently increased reporter activity; however, induction by L-755446 was stronger than that by aprepitant.

Conclusion

These results indicate that aprepitant initially inhibited voriconazole metabolism via its triazole ring and increased cytochrome P450 3A4 induction following L-755446 formation. The decrease in plasma voriconazole concentration 7 days after fosaprepitant administration was mainly attributed to cytochrome P450 3A4 induction by L-755446.

Effect of Aprepitant on Etoposide Pharmacokinetics in Patients with Testicular Cancer: A Pharmacokinetic Study to Determine the Absence of a Clinically Relevant Interaction

All patients treated with anticancer agents should receive the most effective anti-emetic regimen. Anti-emetic guidelines provide recommendations but do not take into account possible drug-drug interactions between anti-emetics and anticancer drugs. This study determines the clinical relevance of the potential drug-drug interaction of the neurokinin-1 receptor antagonist, aprepitant, on the pharmacokinetics of etoposide. Aprepitant is a moderate CYP3A4 inhibitor and may increase the systemic exposure of etoposide which is partly metabolized by cytochrome P450 enzyme 3A4 (CYP3A4). In this prospective observational study, the pharmacokinetics of etoposide with and without concomitant use of aprepitant was determined in 12 patients receiving first-line chemotherapy for testicular cancer. The geometric mean (95% confidence interval (CI)) area under the plasma concentration-time curve 0-24 hour (AUC0-24h ) of etoposide with aprepitant was 86.2 (79.7-93.2) mg/L*hour vs. 83.7 (75.8-92.4) mg/L*hour without aprepitant. Geometric mean ratios (90% CIs) of AUC0-24h and maximum plasma concentration (Cmax ) for etoposide with and without aprepitant were 1.03 (0.96-1.10) and 0.96 (0.89-1.03), respectively. This study confirms the absence of a clinically relevant interaction between etoposide and aprepitant. Both drugs can be safely combined without affecting etoposide exposure.

Drug-Drug Interactions Involving Dexamethasone in Clinical Practice: Myth or Reality?

Concomitant administration of multiple drugs frequently causes severe pharmacokinetic or pharmacodynamic drug-drug interactions (DDIs) resulting in the possibility of enhanced toxicity and/or treatment failure. The activity of cytochrome P450 (CYP) 3A4 and P-glycoprotein (P-gp), a drug efflux pump sharing localization and substrate affinities with CYP3A4, is a critical determinant of drug clearance, interindividual variability in drug disposition and clinical efficacy, and appears to be involved in the mechanism of numerous clinically relevant DDIs, including those involving dexamethasone. The recent increase in the use of high doses of dexamethasone during the COVID-19 pandemic have emphasized the need for better knowledge of the clinical significance of drug-drug interactions involving dexamethasone in the clinical setting. We therefore aimed to review the already published evidence for various DDIs involving dexamethasone in vitro in cell culture systems and in vivo in animal models and humans.

Overestimation of the effect of (fos)aprepitant on intravenous dexamethasone pharmacokinetics requires adaptation of the guidelines for children with chemotherapy-induced nausea and vomiting

Purpose

Chemotherapy-induced nausea and vomiting (CINV) are common side effects in pediatric oncology treatment. Besides 5-HT₃-antagonists, both dexamethasone and aprepitant are cornerstone drugs in controlling these side effects. Based on results of adult studies, the dexamethasone dose is reduced by 50% when combined with aprepitant, because of a drug-drug interaction, even though data on the interaction in children is lacking. The current study was developed to investigate the effect of aprepitant on dexamethasone clearance (CL) in children, in order to assess if dexamethasone dose reduction for concomitant use of aprepitant is appropriate in the current antiemetic regimen.

Methods

In total, 65 children (0.6–17.9 years), receiving intravenous or oral antiemetic therapy (dexamethasone ± aprepitant) as standard of care, were included. 305 dexamethasone plasma concentrations were determined using LC–MS/MS. An integrated dexamethasone and aprepitant pharmacokinetic model was developed using non-linear mixed effects modelling in order to investigate the effect of aprepitant administration on dexamethasone CL.

Results

In this population, dexamethasone CL in patients with concomitant administration of aprepitant was reduced by approximately 30% of the uninhibited CL (23.3 L/h (95% confidence interval 20.4–26.0)). This result is not consistent with the results of adult studies (50% reduction). This difference was not age dependent, but might be related to the route of administration of dexamethasone. Future studies are needed to assess the difference in oral/intravenous dexamethasone.

Conclusion

When dexamethasone is given intravenously as a component of triple therapy to prevent CINV in children, we advise to reduce the dexamethasone dose by 30% instead of 50%.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00520-022-07423-6.

Development and validation of a combined liquid chromatography tandem-mass spectrometry assay for the quantification of aprepitant and dexamethasone in human plasma to support pharmacokinetic studies in pediatric patients

A pharmacokinetic study was set up to investigate the pharmacokinetics of the anti-emetic agents aprepitant and dexamethasone and the drug-drug interaction between these drugs in children. In order to quantify aprepitant and dexamethasone, a liquid chromatography-tandem mass spectrometry assay was developed and validated for the simultaneous analysis of aprepitant and dexamethasone. Protein precipitation with acetonitrile-methanol (1:1, v/v) was used to extract the analytes from plasma. The assay was based on reversed-phase chromatography coupled with tandem mass spectrometry detection operating in the positive ion mode. The assay was validated based on the guidelines on bioanalytical methods by the US Food and Drug Administration and European Medicines Agency. The calibration model was linear and a weighting factor of 1/concentration² was used over the range of 0.1-50 ng/mL for aprepitant and 1-500 ng/mL for dexamethasone. Intra-assay and inter-assay bias were within ±20% for all analytes at the lower limit of quantification and within ±15% at remaining concentrations. Dilution integrity tests showed that samples exceeding the upper limit of quantification can be diluted 100 times in control matrix. Stability experiments showed that the compounds are stable in the biomatrix for 25 h at room temperatures and 89 days at -20 °C. This assay is considered suitable for pharmacokinetic studies and will be used to study the drug-drug interaction between aprepitant and dexamethasone in pediatric patients.

Pharmacokinetics of Dexamethasone when Administered with Fosaprepitant for Chemotherapy-Induced Nausea and Vomiting and Differences in Dose-Dependent Antiemetic Effects

BACKGROUND

Fosaprepitant, an NK1 receptor antagonist, inhibits and induces cytochrome P450 3A4 (CYP3A4) as its substrate. Contrarily dexamethasone is metabolized by CYP3A4. Therefore, in combination therapy wherein both agents interact with each other, it is recommended that the dexamethasone dose be reduced in the first two days. Thus far, there are only a few studies on the optimum dose of dexamethasone after day 3. Thus, we aimed to determine the pharmacokinetics of dexamethasone on day3 when administered together with fosaprepitant and investigate the dose-dependent differences in its antiemetic effect in patients with cancer.

METHODS

Twelve patients with esophageal, stomach, or lung cancer received primary highly emetogenic chemotherapy (HEC). We intravenously administered 9.9 mg and 6.6 mg of dexamethasone on days 1 and 2, respectively, and 6.6 mg or 13.2 mg on day 3 together with the administration of 150 mg fosaprepitant and 0.75 mg palonosetron. We assessed the pharmacokinetics of dexamethasone on day 3 by dose and examined the dose-dependent antiemetic effect.

RESULTS

No differences were observed in the time-to-maximum concentration and blood half-life of dexamethasone between patient groups that received dexamethasone at doses of 6.6 mg and 13.2 mg. In contrast, the area under the blood concentration-time curve and the maximum concentration of dexamethasone correlated with its dose. Moreover, the blood dexamethasone concentration on day 3 increased by twofold after the administration of a higher dose than after a lower dose. The severity of nausea in the delayed phase significantly decreased in a dose-dependent manner.

CONCLUSION

Administration of a higher dexamethasone dose on day 3 improved the antiemetic effect of the combined regimen in patients with cancer who underwent HEC.<br />.

Neurokinin-1 receptor antagonists: review of their role for the prevention of chemotherapy-induced nausea and vomiting in adults

Introduction: The addition of neurokinin-1 receptor antagonists (NK₁RAs) to standard prophylaxis of 5-hydroxytryptamine-3 RA (5-HT₃RA) plus dexamethasone more effectively prevents chemotherapy-induced nausea and vomiting (CINV) associated with highly and moderately emetogenic chemotherapy. Areas covered: This review presents the evidence base for the use of oral and intravenous (IV) NK₁RAs, focusing on the pharmacologic and clinical properties as a class, and highlighting differences between agents. A PubMed literature search was conducted from 2000 to 2018. Expert opinion: Adherence to international antiemetic guidelines remains a clinical challenge. Strategies to simplify antiemetic regimens and facilitate their administration may improve compliance and treatment outcomes. The use of fixed-combination antiemetics offers clinical utility, in combining an NK₁RA with a 5-HT₃RA in a single oral dose. The use of long-lasting NK₁RAs and administering CINV prophylaxis closer to the time of chemotherapy may also assist with guideline and treatment compliance, diminishing the need for home-based administration, and potentially reducing resource utilization. The availability of IV and oral formulations of NK₁RAs and NK₁RA-5-HT₃RA fixed combinations offers further utility, particularly for those patients unsuited for oral administration. However, safety considerations with respect to injection site toxicity and hypersensitivity reactions of the new NK₁RA IV formulations deserve close attention.

Intravenous fosaprepitant for the prevention of chemotherapy-induced vomiting in children: A double-blind, placebo-controlled, phase III randomized trial

BACKGROUND

Fosaprepitant is a neurokinin-1 receptor antagonist, approved for the prevention of chemotherapy-induced nausea and vomiting. The data on the use of fosaprepitant in children are limited and therefore we conducted a phase III randomized controlled trial.

PROCEDURE

Children aged 1-12 years scheduled to receive moderately or highly emetogenic chemotherapy were randomly assigned to arm-A (fosaprepitant) or arm-B (placebo). Children recruited to arm-A received intravenous ondansetron plus dexamethasone followed by fosaprepitant infusion. Children recruited to arm-B received the same drugs as those given to children in arm-A, except that fosaprepitant was substituted with a placebo. Ondansetron and dexamethasone were continued for 48 hours after completion of chemotherapy. The primary end point of the study was to determine the proportion of patients who achieved a complete response (CR), defined as no vomiting, no retching, and no use of rescue medication, during the 24-120 hours (delayed phase) after administration of the last dose of chemotherapy. Secondary end points were the proportion of patients who achieved a CR during the acute phase (0-24 hours) and overall after administration of the last dose of chemotherapy.

RESULTS

One-hundred-sixty-three patients were analyzed (81 in the fosaprepitant arm and 82 in the placebo arm). CR rates were significantly higher in the fosaprepitant arm compared to those in the placebo arm during the acute phase (86% vs 60%, P < 0.001), delayed phase (79% vs 51%, P < 0.001), and overall phase (70% vs 41%, P < 0.001). Three (4%) patients in the fosaprepitant arm and sixteen (20%) in the placebo arm required rescue anti-emetics (P = 0.0017).

CONCLUSION

Addition of fosaprepitant to ondansetron and dexamethasone improved chemotherapy-induced vomiting control in children treated with moderately or highly emetogenic chemotherapy.

Drug review: Fosaprepitant

Chemotherapy-induced nausea and vomiting (CINV) is a significant contributor to the treatment morbidity experienced by patients with cancer. With effective prophylactic anti-emetics given prior to administration of moderately or highly emetogenic chemotherapy (MEC or HEC) it is expected that 70-80% of patients will have no CINV. Fosaprepitant is an intravenous prodrug of aprepitant that acts as an anti-emetic by blocking the neurokinin (NK-1) receptor. Fosaprepitant in combination with dexamethasone and 5-HT3 antagonist like ondansetron has been shown to be effective in preventing CINV in patients receiving MEC or HEC. The current review discusses the pharmacology and clinical indications for the use of fosaprepitant. The evidence for the effectiveness of fosaprepitant in the prevention of CINV and the commonly observed adverse events with its administration is discussed in this review.

Pharmacokinetic Interactions of Rolapitant With Cytochrome P450 3A Substrates in Healthy Subjects

Rolapitant (Varubi) is a neurokinin-1 receptor antagonist approved for the prevention of chemotherapy-induced nausea and vomiting. Rolapitant is primarily metabolized by the cytochrome P450 3A4 (CYP3A4) enzyme. Unlike other neurokinin-1 receptor antagonists, rolapitant is neither an inhibitor nor an inducer of CYP3A4 in vitro. The objective of this analysis was to examine the pharmacokinetics of rolapitant in healthy subjects and assess drug-drug interactions between rolapitant and midazolam (a CYP3A substrate), ketoconazole (a CYP3A inhibitor), or rifampin (a CYP3A4 inducer). Three phase 1, open-label, drug-drug interaction studies were conducted to examine the pharmacokinetic interactions of orally administered rolapitant with midazolam, rolapitant with ketoconazole, and rolapitant with rifampin. The pharmacokinetic profiles of midazolam and 1-hydroxy midazolam metabolites were essentially unchanged when coadministered with rolapitant, indicating the lack of a clinically relevant inhibition or induction of CYP3A by rolapitant. Coadministration of ketoconazole with rolapitant had no effects on rolapitant maximum concentration and resulted in an approximately 20% increase in the area under the concentration-time curve of rolapitant, suggesting that strong CYP3A inhibitors have minimal inhibitory effects on rolapitant exposure. Repeated administrations of rifampin appeared to reduce rolapitant exposure, resulting in a 33% decrease in maximum concentration and 87% decrease in area under the concentration-time curve from time zero to infinity. Coadministration of rolapitant did not affect the exposure of midazolam. Rifampin coadministration resulted in lower concentrations of rolapitant, and ketoconazole coadministration had no or minimal effects on rolapitant exposure. Rolapitant was safe and well tolerated when coadministered with ketoconazole, rifampin, or midazolam. No new safety signals were reported compared with previous studies of rolapitant.

Development, Verification, and Prediction of Osimertinib Drug-Drug Interactions Using PBPK Modeling Approach to Inform Drug Label

Osimertinib is a potent, highly selective, irreversible inhibitor of epidermal growth factor receptor (EGFR) and T790M resistance mutation. In vitro metabolism data suggested osimertinib is a substrate of cytochrome P450 (CYP)3A4/5, a weak inducer of CYP3A, and an inhibitor of breast cancer resistance protein (BCRP). A combination of in vitro data, clinical pharmacokinetic data, and drug-drug interaction (DDI) data of osimertinib in oncology patients were used to develop the physiologically based pharmacokinetic (PBPK) model and verify the DDI data of osimertinib. The model predicted the observed monotherapy concentration profile of osimertinib within 1.1-fold, and showed good predictability (within 1.7-fold) to the observed peak plasma concentration (Cmax ) and area under the curve (AUC) DDI ratio changes, when co-administered with rifampicin, itraconazole, and simvastatin, but not with rosuvastatin. Based on observed clinical data and PBPK simulations, the recommended dose of osimertinib when dosed with strong CYP3A inducers is 160 mg once daily. PBPK modeling suggested no dose adjustment with moderate and weak CYP3A inducers.

Aprepitant and fosaprepitant drug interactions: a systematic review

AIMS

Aprepitant and fosaprepitant, commonly used for the prevention of chemotherapy-induced nausea and vomiting, alter cytochrome P450 activity. This systematic review evaluates clinically significant pharmacokinetic drug interactions with aprepitant and fosaprepitant and describes adverse events ascribed to drug interactions with aprepitant or fosaprepitant.

METHODS

We systematically reviewed the literature to September 11, 2016, to identify articles evaluating drug interactions involving aprepitant/fosaprepitant. The clinical significance of each reported pharmacokinetic drug interaction was evaluated based on the United States Food and Drug Administration guidance document on conducting drug interaction studies. The probability of an adverse event reported in case reports being due to a drug interaction with aprepitant/fosaprepitant was determined using the Drug Interaction Probability Scale.

RESULTS

A total of 4377 publications were identified. Of these, 64 met inclusion eligibility criteria: 34 described pharmacokinetic drug interactions and 30 described adverse events ascribed to a drug interaction. Clinically significant pharmacokinetic interactions between aprepitant/fosaprepitant and bosutinib PO, cabazitaxel IV, cyclophosphamide IV, dexamethasone PO, methylprednisolone IV, midazolam PO/IV, oxycodone PO and tolbutamide PO were identified, as were adverse events resulting from an interaction between aprepitant/fosaprepitant and alcohol, anthracyclines, ifosfamide, oxycodone, quetiapine, selective serotonin reuptake inhibitors/serotonin-norepinephrine reuptake inhibitors and warfarin.

CONCLUSIONS

The potential for a drug interaction with aprepitant and fosaprepitant should be considered when selecting antiemetic therapy.

Fosaprepitant Dimeglumine: A Review in the Prevention of Nausea and Vomiting Associated with Chemotherapy

Intravenous fosaprepitant dimeglumine (Emend(®) for injection, IVEmend(®); henceforth referred to as fosaprepitant) is a prodrug of and is rapidly converted to the antiemetic aprepitant, and is approved in several countries worldwide (as part of an antiemetic regimen) for the prevention of nausea and vomiting associated with highly and moderately emetogenic chemotherapy (HEC and MEC). This narrative review discusses the pharmacological properties of intravenous fosaprepitant and its clinical efficacy and tolerability in the prevention of nausea and vomiting associated with HEC and MEC. In large, randomized phase III clinical trials, a single intravenous dose of fosaprepitant 150 mg was an effective and generally well tolerated addition to an antiemetic regimen that included dexamethasone and a serotonin 5-HT3 receptor antagonist in adult cancer patients undergoing treatment with HEC or MEC. It was also noninferior to an oral aprepitant-based regimen in adult cancer patients undergoing HEC treatment. The tolerability profile of a fosaprepitant-based regimen was typical of that in patients receiving emetogenic chemotherapy, and adverse events were generally consistent with those observed with an aprepitant-based regimen. Fosaprepitant provides a useful addition to antiemetic therapy regimens.

Rolapitant for the treatment of chemotherapy-induced nausea and vomiting: a review of the clinical evidence

Chemotherapy-induced nausea and vomiting (CINV), both acute and delayed, has a dramatic effect on the well-being and quality of life of patients with cancer. Improved understanding of the mechanisms involved in CINV has led to the development of agents targeting the 5-HT3 receptor as well as the NK-1 receptor. Antiemetic prophylaxis given to patients receiving highly emetogenic chemotherapy combines agents blocking the 5-HT3 and NK-1 receptors along with corticosteroids given regularly and repeatedly. Rolapitant is a long-acting NK-1 receptor antagonist with proven efficacy in controlling CINV as part of the prophylaxis regimen. This review will detail the clinical efficacy and safety of rolapitant in the treatment of patients with cancer receiving highly or moderately emetogenic chemotherapy.

Drug interactions with aprepitant or fosaprepitant: Review of literature and implications for clinical practice

Purpose Aprepitant and its parenteral formulation fosaprepitant are widely used for the prevention of chemotherapy-induced nausea and vomiting. Aprepitant exerts modest inhibitory effect on CYP3A4 and modest inductive effect on CYP2C9 substrates such as some antineoplastics and multiple other medications. This article is aimed to provide pharmacists and other healthcare professionals with an updated summary of drug-drug interactions of aprepitant/fosaprepitant and implications for clinical practice. Method We reviewed publications reporting drug-drug interactions between aprepitant/fosaprepitant and other medications. Results Coadministration of aprepitant with antineoplastics or opiods may result in significant elevations in the serum levels of the agents metabolized via CYP3A4, with the best documentation for cyclophosphamide, ifosfamide, erlotinib and oxycodone. These alterations did not translate into adverse outcomes and/or necessitate dosing adjustments. The levels of warfarin were significantly decreased by aprepitant requiring prolonged monitoring after discontinuation of aprepitant. Among direct oral anticoagulants, a theoretical interaction between aprepitant and rivaroxaban or apixaban exists. Interactions between aprepitant and quetiapine or diltiazem or sirolimus required dose reductions to avoid adverse outcomes. The intravenous route had a weaker inhibitory effect on CYP3A4 than the oral pathway. Conclusion The evidence on drug interactions of aprepitant with other medications is limited, and the impact on therapeutic outcomes remains to be determined. The intravenous regimen may be a preferred option. As utilization of aprepitant is expanding, practitioners and patients need to be educated about the potential for drug interactions and a need for careful monitoring of patients concurrently receiving aprepitant and CYP2C9 or CYP3A4 substrates, especially those with a narrow therapeutic window.

The effects of intravenous fosaprepitant and ondansetron for the prevention of postoperative nausea and vomiting in neurosurgery patients: a prospective, randomized, double-blinded study

The incidence of postoperative nausea and vomiting (PONV) is 30–50% after surgery. PONV occurs frequently, especially after craniotomy. In this study, we investigated the preventive effects on PONV in a randomized study by comparing patients who had been administered fosaprepitant, a neurokinin-1 (NK1) receptor antagonist, or ondansetron intravenously. Sixty-four patients undergoing craniotomy were randomly allocated to receive fosaprepitant 150 mg i.v. (NK1 group, n = 32) or ondansetron 4 mg i.v. (ONS group, n = 32) before anesthesia. The incidence of vomiting was significantly less in the NK1 group, where 2 of 32 (6%) patients experienced vomiting compared to 16 of 32 (50%) patients in the ONS group during the first 24 and 48 hours following surgery. Additionally, the incidence of complete response (no vomiting and no rescue antiemetic use) was significantly higher in the NK1 group than in the ONS group, and was 66% versus 41%, respectively, during the first 24 hours, and 63% versus 38%, respectively, during the first 48 hours. In patients undergoing craniotomy, fosaprepitant is more effective than ondansetron in increasing the rate of complete response and decreasing the incidence of vomiting at 24 and 48 hours postoperatively.

Metabolic considerations of drugs in the treatment of allergic diseases

INTRODUCTION

The clinical management of allergic diseases involves a number of drugs, most of which are extensively metabolized. This review aims to analyze the metabolism and the clinical implications of altered metabolism for these drugs.

AREAS COVERED

The authors present an overview of current knowledge of the metabolism of: antihistamine drugs, glucocorticoids, inhaled β-2 bronchodilators, anticholinergics and other drugs used in allergic diseases, such as cromoglycate, omalizumab, montelukast and epinephrine. Polymorphic drug metabolism is relevant for chlorpheniramine, loratadine and montelukast. Inhibition of drug metabolism is relevant for loratadine, methylprednisolone, fluticasone, mometasone, triamcinolone or prednisolone. Polymorphic pre-systemic metabolism may be relevant to budesonide, fluticasone, beclomethasone, mometasone or salmeterol. The authors also discuss the current information on gene variations according to the 1,000 genomes catalog and other databases. Finally, the authors review the clinical implications of these variations with a particular regard to drugs used in the management of allergic diseases.

EXPERT OPINION

Most drugs used in allergic diseases are extensively metabolized. Drug interaction or adverse reactions related to altered metabolism are relevant issues that should be considered in the management of allergic diseases. However, much additional research is required before defining pharmacogenomic biomarkers for the management of drugs used in allergic diseases.

Influence of chronic hepatitis C infection on cytochrome P450 3A4 activity using midazolam as an in vivo probe substrate

PURPOSE

Inflammation-related changes in pharmacokinetics have been described for a number of disease-states including cancer, infection, and autoimmune disorders. This study examined the impact of chronic hepatitis C infection (CHC) on the pharmacokinetics of the cytochrome P450 3A probe midazolam in patients without significant liver disease who were either treatment naïve or prior interferon null-responders.

METHODS

Data were pooled from three studies which compared the pharmacokinetics of oral midazolam in healthy volunteers (n = 107) and in treatment-naive patients (n = 35) and interferon-null responders (n = 24) with CHC but without significant liver disease. Oral midazolam was administered as a single 2 mg oral dose, followed by frequent pharmacokinetic sampling and determination of the pharmacokinetics of midazolam and its α-hydroxy metabolite. CYP3A activity was determined by the metabolic ratio (MR) of the AUC metabolite/AUC parent and compared across groups as the mean effect ratio (test/reference).

RESULTS

The midazolam MR was lower in treatment-naïve patients with CHC than in health volunteers with a mean effect ratio of 0.63 [90 % confidence interval (CI) 0.56-0.72]. The effect was more pronounced in null-responders, who demonstrated a mean MR effect ratio of 0.46 (90 % CI 0.39-0.53) compared to volunteers. The mean area under the concentration-time curve (AUCinf) for midazolam in healthy volunteers, naïve patients, and null-responders was 32.3 [coefficient of variation (CV%) 41], 36.5 (CV% 33.5), and 55.3 (CV% 36.9) ng.h/mL, respectively.

CONCLUSIONS

The results of this study demonstrate a reduction in CYP3A4 activity between healthy volunteers and patients with CHC, with interferon null-responders demonstrating the most substantial difference. These results may have implications for the pharmacotherapy of patients infected with CHC.

Effect of netupitant, a highly selective NK₁ receptor antagonist, on the pharmacokinetics of midazolam, erythromycin, and dexamethasone

PURPOSE

Netupitant is a new highly selective neurokinin-1 receptor antagonist being studied for the prevention of nausea and vomiting in patients undergoing chemotherapy. In vitro studies suggest that netupitant inhibits the cytochrome P-450 isoenzyme 3A4 (CYP3A4). Because netupitant may be used with a variety of drugs, which may be substrates of CYP3A4, two studies were designed to establish the potential risk for drug-drug interaction with three different CYP3A4 substrates: midazolam, erythromycin, and dexamethasone.

METHODS

Both trials were three-period crossover studies performed in healthy subjects. In the first study, 20 subjects received netupitant and either midazolam or erythromycin. In the second study, 25 subjects received netupitant and dexamethasone. Serial blood samples were collected over the course of the two studies and pharmacokinetic parameters were determined for all analytes.

RESULTS

Netupitant, by inhibiting the CYP3A4, increased the C max and AUCinf of midazolam by 40 and 144 %, respectively, and the C max and AUCinf of erythromycin by 30 %. Netupitant was shown to increase the exposure to dexamethasone in a dose-dependent manner with the mean increase in AUC and C max by 72 and 11 %, respectively, on day 1 and by 138 and 75 %, respectively, on day 4 when co-administered with 300 mg of netupitant.

CONCLUSIONS

The results of these studies suggest that netupitant is a moderate inhibitor of CYP3A4 and therefore, co-administration with drugs that are substrates of CYP3A4 may require dose adjustments. Treatments were well tolerated in both studies.

Safety of neurokinin-1 receptor antagonists

INTRODUCTION

The substance P (SP)/neurokinin (NK)-1 receptor system is involved in many pathological processes. NK-1 receptor antagonists have many promising therapeutic indications. However, the only NK-1 receptor antagonist used in clinical practice is the drug aprepitant and its intravenously administered prodrug, fosaprepitant. In general, NK-1 receptor antagonists are safe and well tolerated.

AREAS COVERED

A search was carried out in Medline using the following terms: adverse events, aprepitant, casopitant, clinical trials, CP-122,721, ezlopitant, fosaprepitant, NK-1 receptor antagonists, randomized, safety, side effects, tolerability and vofopitant.

EXPERT OPINION

Most clinical trials have focused on the antiemetic action of aprepitant in cancer patients treated with chemotherapy. However, the efficacy and safety of aprepitant have not been fully tested in other diseases in which the SP/NK-1 receptor system is involved (e.g., cancer, HIV, alcoholism); thus, clinical trials are required. The use of NK-1 receptor antagonists in oncology therapy is quite promising, but to date pharmacological therapy has not exploited the many possible therapies offered by such antagonists.

Efficacy and safety of single-dose fosaprepitant in the prevention of chemotherapy-induced nausea and vomiting in patients receiving high-dose cisplatin: a multicentre, randomised, double-blind, placebo-controlled phase 3 trial

Background

We evaluated the efficacy and safety of single-dose fosaprepitant in combination with intravenous granisetron and dexamethasone.

Patients and methods

Patients receiving chemotherapy including cisplatin (≥70 mg/m²) were eligible. A total of 347 patients (21% had received cisplatin with vomiting) were enrolled in this trial to receive the fosaprepitant regimen (fosaprepitant 150 mg, intravenous, on day 1 in combination with granisetron, 40 μg/kg, intravenous, on day 1 and dexamethasone, intravenous, on days 1–3) or the control regimen (placebo plus intravenous granisetron and dexamethasone). The primary end point was the percentage of patients who had a complete response (no emesis and no rescue therapy) over the entire treatment course (0–120 h).

Results

The percentage of patients with a complete response was significantly higher in the fosaprepitant group than in the control group (64% versus 47%, P = 0.0015). The fosaprepitant regimen was more effective than the control regimen in both the acute (0–24 h postchemotherapy) phase (94% versus 81%, P = 0.0006) and the delayed (24–120 h postchemotherapy) phase (65% versus 49%, P = 0.0025).

Conclusions

Single-dose fosaprepitant used in combination with granisetron and dexamethasone was well-tolerated and effective in preventing chemotherapy-induced nausea and vomiting in patients receiving highly emetogenic cancer chemotherapy, including high-dose cisplatin.