Factors Influencing the Magnitude and Clinical Significance of Drug Interactions Between Azole Antifungals and Select Immunosuppressants

Effects of clotrimazole troches on tacrolimus dosing in heart transplant recipients

BACKGROUND

Tacrolimus is a cornerstone of immunosuppression after transplantation but is highly susceptible to changes from interacting variables and has a narrow therapeutic index. Clotrimazole troches are commonly used as a non-systemic antifungal to prevent oral candidiasis. Studies suggest that clotrimazole troches, though minimally absorbed systemically, may affect tacrolimus concentrations by inhibition of metabolic enzyme activity in the intestines. However, the magnitude of the impact of clotrimazole on tacrolimus dosing requirements to maintain goal levels is not well described.

METHODS

To assess this, tacrolimus dose adjustments and trough concentrations were retrospectively examined in 95 heart transplant recipients before and after the discontinuation of clotrimazole.

RESULTS

The median percent tacrolimus dose change was an increase of 66.7% (IQR 28.6%, 100%) after clotrimazole discontinuation, and the median trough concentration percent change from baseline to the first trough after clotrimazole discontinuation (in the absence of a dose change) was -42.5% (IQR -52.3%, -30.9%). Five cases of allograft rejection were observed.

CONCLUSION

In conclusion, clotrimazole troches exert a meaningful interaction with tacrolimus that requires close monitoring and dose adjustment. The data from this single-center study provide novel information that could guide providers on the degree of tacrolimus dose adjustment needed when discontinuing clotrimazole prophylaxis after heart transplantation.

Safety and efficacy of chronic suppressive azole therapy for endemic fungal infections in solid organ transplant recipients

BACKGROUND

Although the research is limited, treatment guidelines recommend lifelong suppressive azole therapy for disseminated endemic fungal infection (EFI) after solid organ transplantation (SOT). Suppressive azole therapy may prevent EFI recurrence at the risk of hepatotoxicity and drug interactions. We present real-world safety and effectiveness data of chronic suppressive azole therapy for EFI in SOT recipients over a 10-year period at a single comprehensive transplant center.

METHODS

A retrospective analysis was conducted of SOT recipients diagnosed with EFI from January 1, 2005, to May 1, 2015. Chronic suppressive azole therapy was defined as treatment for more than 12 months after diagnosis. Effectiveness of suppression was defined as preventing EFI reactivation. Safety endpoints included adverse reactions and drug interactions.

RESULTS

Over a 10-year period, 28 SOT recipients were diagnosed with EFI: 16 histoplasmosis, 9 blastomycosis, and 3 coccidioidomycosis. Eighteen (64%) patients were treated with chronic suppressive azole therapy for a median length of 36 months (range 15-90). One patient had an adverse drug interaction requiring azole discontinuation. There were no episodes of azole-related hepatotoxicity, toxicity from antirejection medication, or EFI reactivation.

CONCLUSIONS

Chronic suppressive azole therapy was safe and effective in preventing reactivation of EFI in SOT recipients.

Posaconazole-Induced Pseudohyperaldosteronism

A woman in her late 60s with disseminated histoplasmosis was treated with posaconazole because first-line therapies were not tolerated. She subsequently presented with decompensated heart failure, hypertension, and hypokalemia. Laboratory tests revealed low renin and aldosterone levels. A potential mechanism is inhibition of the enzyme 11β-hydroxysteroid dehydrogenase 2, with resultant apparent mineralocorticoid excess.

Micafungin Breakthrough Fungemia in Patients with Hematological Disorders

Limited data are available on micafungin breakthrough fungemia (MBF), fungemia that develops on administration of micafungin, in patients with hematological disorders. We reviewed medical and microbiological records of patients with hematological disorders who developed MBF between January 2008 and June 2015. A total of 39 patients with MBF were identified, and Candida (30 strains) and non-Candida (9 strains) fungal species were recognized as causative strains. Among 35 stored strains, Candida parapsilosis (14 strains), Trichosporon asahii (7 strains), Candida glabrata (5 strains), and other fungal species (9 strains) were identified by sequencing. Neutropenia was identified as an independent predictor of non-Candida fungemia (P = 0.023). T. asahii was the most common causative strain (7/19) during neutropenia. The 14-day crude mortality rate of patients treated with early micafungin change (EMC) to other antifungal agents was lower than that of the patients not treated with EMC (14% versus 43%, P = 0.044). Most of the stored causative Candida strains were susceptible (80%) or showed wild-type susceptibility (72%) to micafungin. The MICs of voriconazole for T. asahii were low (range, 0.015 to 0.12 μg/ml), whereas the MICs of amphotericin B for T. asahii were high (range, 2 to 4 μg/ml). MBF caused by non-Candida fungus should be considered, especially in patients with neutropenia. EMC could improve early mortality. Based on epidemiology and drug susceptibility profiling, empirical voriconazole-containing therapy might be suitable for treating MBF during neutropenia to cover for T. asahii.

Posaconazole Tablets in Real-Life Lung Transplantation: Impact on Exposure, Drug-Drug Interactions, and Drug Management in Lung Transplant Patients, Including Those with Cystic Fibrosis

Appropriate exposure to posaconazole (PSZ) has been limited until the recent approval of the delayed-release oral tablet formulation. Our goal was to determine the exposure obtained by using the standard dose of 300 mg once a day in lung transplant (LT) patients, including patients with cystic fibrosis (CF). PSZ trough concentrations (C0) were determined using a liquid chromatography-tandem mass spectrometry assay. Indicative thresholds of interest were <0.7 mg/liter for prophylaxis and 1 to 3 mg/liter for cure. The tacrolimus (TRL) and everolimus (ERL) C0 measured during PSZ exposure were also collected. The interaction with proton-pump inhibitors (PPI) was evaluated. We recorded the results for 21 CF patients with LT (CFLT patients), 11 non-CF patients with LT (NCFLT patients), and 27 nontransplant (NT) patients in pneumology departments. The weights of the NCFLT, CFLT, and NT patients were 59.2 ± 8.4, 48.8 ± 8.4, and 63.7 ± 16.6 kg, respectively (P = 0.001* [asterisk means that statistical test is significant]), and the PSZ C0 exposures for these patients were 1.9 ± 1.5, 1.1 ± 0.8, and 2.4 ± 1.8 mg/liter, respectively (P < 0.00001*). More than 60% of the concentrations were in the therapeutic range. In CFLT patients, the administration of one 300-mg PSZ tablet quickly achieved an exposure similar to that achieved with the PSZ oral suspension formulation (OSF) administered 3 or 4 times a day for several months. The TRL C0/dose ratio (C0/D) was 7.4 ± 4.4 mg/liter with PSZ tablets, whereas it was 4.6 ± 0.8 mg/liter with the PSZ oral solution (P = 0.034*). The ERL C0/D was similar with both formulations. PPI had no impact on the PSZ concentration (1.49 ± 1.07 mg/liter without PPI versus 1.33 ± 1.17 mg/liter with PPI; P = 0.4134*). Despite the high levels of exposure, PSZ remained well tolerated (one case of diarrhea and one case of fatigue were reported). PSZ tablet administration allows satisfactory exposure, even in CFLT patients, with a dosage lower than that of the PSZ OSF. This once-a-day formulation was not impacted by PPI, which are extensively used in CF patients.

[Posaconazole as primary prevention of fungal infection in intensive immunosuppressive therapy for severe aplastic anemia]

Objective: To Evaluate the efficacy and safety of posaconazole as primary prevention of invasive fungal disease (IFD) in patients with severe aplastic anemia (SAA) treated with anti-thymus/lymphocyte immunoglobulin (ATG/ALG) combined with cyclosporine intensive immunosuppressive therapy (IST). Methods: A retrospective analysis of clinical data of 58 SAA patients who received IST of anti-thymocyte immunoglobulin combining cyclosporine and antifungal prophylaxis during April 2013 to May 2017 in Peking Union Medical College Hospital was performed. The patients were divided into posaconazole prophylaxis group and the control group (itraconazole or fluconazole). The disease characteristics, IFD prevention effect and adverse drug reaction, curative effect and prognosis of the two groups were compared. Results: Posaconazole was used to prevent fungal infection in 20 patients. The other 38 patients were used as the control group. Retrospective analysis showed comparable characteristics (gender, age, disease severity, etiology, interval between the onset of disease to treatment, ATG/ALG type) of both groups. The incidence of IFD were 0 and 15.8% in posaconazole prophylaxis group and the control group, respectively (P=0.084). In the control group, there were 6 cases diagnosed as IFD. Of them, 2 were confirmed, 2 suspected and 2 not identified. Five of the 6 cases were pulmonary infection, 1 bloodstream infections. Of the 6 IFD cases, 5 were very severe aplastic anemia (VSAA). There was no obvious adverse reaction in posaconazole prophylaxis group. Conclusion: Posaconazole is safe and effective for primary prevention of fungal infection of SAA patients receiving IST, especially for the VSAA.

Real-world challenges and unmet needs in the diagnosis and treatment of suspected invasive pulmonary aspergillosis in patients with haematological diseases: An illustrative case study

Recent years have seen important advances in the diagnosis of invasive pulmonary aspergillosis (IPA), complemented by the introduction of new therapies. Despite this, IPA remains a major cause of infection-related mortality in patients with haematological diseases. There are two main reasons for this. First, diagnosis of IPA remains a challenge, since risk factors and the clinical, radiological and mycological presentations vary not only by fungal disease stage, but also by patient group (eg neutropenic vs non-neutropenic patients). Diagnosis is particularly challenging in patients receiving mould-active prophylactic or empirical treatment, which reduces the sensitivity of all diagnostic tests for IPA. Second, treatment of IPA is complex due to unpredictable pharmacokinetic profiles of antifungal agents, small therapeutic window in terms of exposure and adverse events, and multiple drug-drug interactions through the CYP450 system. Here we report a case of a 23-year-old male with severe aplastic anaemia and subpleural nodules. Diagnostic tests for IPA obtained during ongoing mould-active empirical treatment were negative. Intravenous voriconazole was stopped after visual disturbances and hallucinations. The patient then had an anaphylactic reaction to liposomal amphotericin B and was switched to intravenous posaconazole, which had to be discontinued due to a significant increase in transaminase levels. He was treated with oral isavuconazole with reduced dosage, triggered by increasing transaminases under the standard dosage. Even under reduced dosage, blood concentrations of isavuconazole were high and treatment was successful. The case illustrates real-world challenges and unmet needs in the diagnosis and treatment of IPA in patients with haematological diseases.

Drug-drug interactions between triazole antifungal agents used to treat invasive aspergillosis and immunosuppressants metabolized by cytochrome P450 3A4

Patients undergoing treatment with immunosuppressant drugs following solid organ or hematopoietic stem cell transplantation are at particular risk for development of serious infections such as invasive aspergillosis. Four triazole antifungal drugs, voriconazole, posaconazole, itraconazole, and isavuconazole, are approved to treat invasive aspergillosis either as first- or second-line therapy. All of these agents are inhibitors of cytochrome P450 3A4, which plays a key role in metabolizing immunosuppressant drugs such as cyclosporine, tacrolimus, and sirolimus. Thus, co-administration of a triazole antifungal drug with these immunosuppressant drugs can potentially increase plasma concentrations of the immunosuppressant drugs, thereby resulting in toxicity, or upon discontinuation, inadvertently decrease the respective concentrations with increased risk of rejection or graft-versus-host disease. In this article, we review the evidence for the extent of inhibition of cytochrome P450 3A4 by each of these triazole antifungal drugs and assess their effects on cyclosporine, tacrolimus, and sirolimus. We also consider other factors affecting interactions of these two classes of drugs. Finally, we examine recommendations and strategies to evaluate and address those potential drug-drug interactions in these patients.

Sirolimus and mirabegron interaction in a hematopoietic cell transplant patient

PURPOSE

Hematopoietic cell transplant patients are exposed to numerous classes of medications. Transplant practitioners must vigilantly monitor for drug interactions especially involving immunosuppressants. We report a hematopoietic cell transplant patient receiving sirolimus who developed supratherapeutic serum concentrations after initiating mirabegron.

SUMMARY

A 31-year-old, 98 kg female received a second umbilical cord blood transplant four years after the first transplant for relapsed acute myeloid leukemia. Mycophenolate mofetil and sirolimus were utilized for graft versus host disease prophylaxis. The patient was receiving sirolimus 2 mg daily and the serum concentration on day 26 post-transplant (day + 26) was within therapeutic range (6.7 μg/L, goal range 3-12 μg/L). Her post-transplant course was complicated by BK viruria-associated cystitis for which she was started on mirabegron. Six days after starting the new medication (day + 33), the sirolimus serum concentration increased to 19.2 μg/L. Thus mirabegron was discontinued and sirolimus was held. Sirolimus was restarted once the serum concentration was within goal and subsequently stabilized with a combination of 1 mg and 2 mg daily for a total weekly dose of 10 mg. The proposed mechanisms of interaction include: (1) sirolimus inhibition of organic anion transporting polypeptide leading to increased mirabegron in the intestinal lumen; (2) mirabegron inhibition of P-glycoprotein leading to increased absorption of sirolimus and; (3) increased sirolimus absorption leading to increased sirolimus serum concentrations.

CONCLUSION

To our knowledge, this is the first report of a potential drug interaction between sirolimus and mirabegron. Transplant specialists should be aware of this potential interaction when considering the concurrent use of these medications.

Immunosuppression in pediatric liver transplant recipients: Unique aspects

Pediatric liver transplantation has experienced improved outcomes over the last 50 years. This can be attributed in part to establishing optimal use of immunosuppressive agents to achieve a balance between minimizing the risks of allograft rejection and infection. The management of immunosuppression in children is generally more complex and can be challenging when compared with the use of these agents in adult liver transplant patients. Physiologic differences in children alter the pharmacokinetics of immunosuppressive agents, which affects absorption, distribution, metabolism, and drug excretion. Children also have a longer expected period of exposure to immunosuppression, which can impact growth, risk of infection (bacterial, viral, and fungal), carcinogenesis, and likelihood of nonadherence. This review discusses immunosuppressive options for pediatric liver transplant recipients and the unique issues that must be addressed when managing this population. Further advances in the field of tolerance and accommodation are needed to relieve the acute and cumulative burden of chronic immunosuppression in children. Liver Transplantation 23 244-256 2017 AASLD.

Inhibition of 11β-hydroxysteroid dehydrogenase 2 by the fungicides itraconazole and posaconazole

Impaired 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2)-dependent cortisol inactivation can lead to electrolyte dysbalance, hypertension and cardiometabolic disease. Furthermore, placental 11β-HSD2 essentially protects the fetus from high maternal glucocorticoid levels, and its impaired function has been associated with altered fetal growth and a higher risk for cardio-metabolic diseases in later life. Despite its important role, 11β-HSD2 is not included in current off-target screening approaches. To identify potential 11β-HSD inhibitors among approved drugs, a pharmacophore model was used for virtual screening, followed by biological assessment of selected hits. This led to the identification of several azole fungicides as 11β-HSD inhibitors, showing a significant structure-activity relationship between azole scaffold size, 11β-HSD enzyme selectivity and inhibitory potency. A hydrophobic linker connecting the azole ring to the other, more polar end of the molecule was observed to be favorable for 11β-HSD2 inhibition and selectivity over 11β-HSD1. The most potent 11β-HSD2 inhibition, using cell lysates expressing recombinant human 11β-HSD2, was obtained for itraconazole (IC₅₀ 139±14nM), its active metabolite hydroxyitraconazole (IC₅₀ 223±31nM) and posaconazole (IC₅₀ 460±98nM). Interestingly, experiments with mouse and rat kidney homogenates showed considerably lower inhibitory activity of these compounds towards 11β-HSD2, indicating important species-specific differences. Thus, 11β-HSD2 inhibition by these compounds is likely to be overlooked in preclinical rodent studies. Inhibition of placental 11β-HSD2 by these compounds, in addition to the known inhibition of cytochrome P450 enzymes and P-glycoprotein efflux transport, might contribute to elevated local cortisol levels, thereby affecting fetal programming.

Acute Kidney Injury from Excessive Potentiation of Calcium-channel Blocker via Synergistic CYP3A4 Inhibition by Clarithromycin Plus Voriconazole

CYP3A4-inhibitors can potentiate the hypotensive effect of calcium-channel blockers. However, insufficient attention to such drug interactions may result in serious adverse reactions. A 71-year-old hypertensive man prescribed nifedipine was hospitalized for infectious endophthalmitis. Antimicrobial therapy with voriconazole lowered the blood pressure, and then clarithromycin further lowered it through the excessively elevated nifedipine concentration, leading to ischemic acute kidney injury. After the discontinuation of clarithromycin and voriconazole, the blood pressure and renal function were recovered. The combination of CYP3A4-inhibitors such as clarithromycin plus voriconazole can synergistically potentiate calcium-channel blockers. Co-prescription of multiple CYP3A4-inhibitors with calcium-channel blockers increases the risk of hypotension and acute kidney injury.

Evaluation of the Interaction of Intravenous and Oral Voriconazole with Oral Cyclosporine in Iranian HSCT Patients

OBJECTIVE

Voriconazole as a triazole antifungal agent is widely used for prophylaxis or treatment of fungal infections in allogeneic hematopoietic stem cell transplantation (HSCT). It can increase blood concentrations of other medications including cyclosporine A (CsA) which are substrates for cytochrome P450 3A4. The aim of this study was to evaluate comparatively the interaction between oral/intravenous (IV) voriconazole and oral CsA.

METHODS

Twenty-nine recipients of allogeneic HSCT who had been already on a steady dose of CsA and were started on oral or IV voriconazole were evaluated in a prospective cohort study. Blood concentration of CsA was determined before and 5-8 days after voriconazole initiation. Plasma concentration of voriconazole was measured in steady state. The changes in blood concentration of CsA after administration of voriconazole were evaluated.

FINDINGS

The concentration/dose (C/D) ratio of CsA increased significantly (P < 0.001) after voriconazole initiation in both routes of administration (8.40%-174.10% increase in C/D ratio). The C/D ratio alteration of CsA did not differ significantly between oral and IV voriconazole group (P = 0.405). There was a significant correlation in all patients between plasma concentration of voriconazole and percentage of CsA C/D ratio increment (P = 0.046).

CONCLUSION

There was a significant intrapatient variability in the magnitude of CsA blood concentration increment after voriconazole initiation. We also demonstrated that magnitude of drug interaction did not differ in IV and oral voriconazole administration. Furthermore, we found that the magnitude of drug interaction was correlated with plasma concentration of voriconazole.

An update on the safety and interactions of antifungal drugs in stem cell transplant recipients

INTRODUCTION

Invasive fungal diseases (IFDs) are a major cause of morbidity and mortality in patients undergoing allogeneic hematopoietic stem cell transplant (HSCT). Improvement in the management of IFDs have been achieved with the availability of new effective and safe antifungal drugs, however, many of these newer treatments have some limitations in their variable toxicity and unique predisposition for pharmacokinetic drug-drug interactions. Areas covered: This article is an update of a previous review published in this journal evaluating the safety profile of the antifungal drugs. Interesting new features include the availability of the new drug isavuconazole and the new tablet and intravenous formulations of posaconazole. Different dosages and new ways of administration of liposomal Amphotericin B (L-AmB) and echinocandins may be considered in the HSCT practice. Expert opinion: Nephrotoxicity continues to be a clinically relevant and frequent side effect of L-AmB which may cause a reduced clearance of other renally eliminated drugs frequently used in HSCT patients. Echinocandins are favorable therapeutic options in view of their low toxicity and uncommon drug-drug interactions. Important limitations of triazoles are represented by hepatic toxicity and certain side effects particularly after prolonged treatments. The new triazole isavuconazole and the new tablet formulation of posaconazole will be probably increasingly used in the HSCT setting not only due to their efficacy but in particular for their interesting toxicity profile and pharmacokinetic characteristics. The knowledge of these pharmacological findings is crucial in the daily care of allogeneic HSCT patients.

Trypanosoma brucei CYP51: Essentiality and Targeting Therapy in an Experimental Model

Trypanosoma brucei gambiense is the main causative agent of Human African Trypanosomiasis (HAT), also known as sleeping sickness. Because of limited alternatives and treatment toxicities, new therapeutic options are urgently needed for patients with HAT. Sterol 14alpha-demethylase (CYP51) is a potential drug target but its essentiality has not been determined in T. brucei. We used a tetracycline-inducible RNAi system to assess the essentiality of CYP51 in T. brucei bloodstream form (BSF) cells and we evaluated the effect of posaconazole, a well-tolerated triazole drug, within a panel of virulent strains in vitro and in a murine model. Expression of CYP51 in several T. brucei cell lines was demonstrated by western blot and its essentiality was demonstrated by RNA interference (CYP51RNAi) in vitro. Following reduction of TbCYP51 expression by RNAi, cell growth was reduced and eventually stopped compared to WT or non-induced cells, showing the requirement of CYP51 in T. brucei. These phenotypes were rescued by addition of ergosterol. Additionally, CYP51RNAi induction caused morphological defects with multiflagellated cells (p<0.05), suggesting cytokinesis dysfunction. The survival of CYP51RNAi Doxycycline-treated mice (p = 0.053) and of CYP51RNAi 5-day pre-induced Doxycycline-treated mice (p = 0.008) were improved compared to WT showing a CYP51 RNAi effect on trypanosomal virulence in mice. The posaconazole concentrations that inhibited parasite growth by 50% (IC50) were 8.5, 2.7, 1.6 and 0.12 μM for T. b. brucei 427 90-13, T. b. brucei Antat 1.1, T. b. gambiense Feo (Feo/ITMAP/1893) and T. b. gambiense Biyamina (MHOM/SD/82), respectively. During infection with these last three virulent strains, posaconazole-eflornithine and nifurtimox-eflornithine combinations showed similar improvement in mice survival (p≤0.001). Our results provide support for a CYP51 targeting based treatment in HAT. Thus posaconazole used in combination may represent a therapeutic alternative for trypanosomiasis.

Antifungal Prophylaxis in Immunocompromised Patients

Invasive fungal infections (IFIs) represent significant complications in patients with hematological malignancies. Chemoprevention of IFIs may be important in this setting, but most antifungal drugs have demonstrated poor efficacy, particularly in the prevention of invasive aspergillosis. Antifungal prophylaxis in hematological patients is currently regarded as the gold standard in situations with a high risk of infection, such as acute leukemia, myelodysplastic syndromes, and autologous or allogeneic hematopoietic stem cell transplantation. Over the years, various scientific societies have established a series of recommendations for antifungal prophylaxis based on prospective studies performed with different drugs. However, the prescription of each agent must be personalized, adapting its administration to the characteristics of individual patients and taking into account possible interactions with concomitant medication.

2016 Infectious Diseases Society of America (IDSA) Clinical Practice Guideline for the Treatment of Coccidioidomycosis

It is important to realize that guidelines cannot always account for individual variation among patients. They are not intended to supplant physician judgment with respect to particular patients or special clinical situations. Infectious Diseases Society of America considers adherence to these guidelines to be voluntary, with the ultimate determination regarding their application to be made by the physician in the light of each patient's individual circumstances.Coccidioidomycosis, also known as San Joaquin Valley fever, is a systemic infection endemic to parts of the southwestern United States and elsewhere in the Western Hemisphere. Residence in and recent travel to these areas are critical elements for the accurate recognition of patients who develop this infection. In this practice guideline, we have organized our recommendations to address actionable questions concerning the entire spectrum of clinical syndromes. These can range from initial pulmonary infection, which eventually resolves whether or not antifungal therapy is administered, to a variety of pulmonary and extrapulmonary complications. Additional recommendations address management of coccidioidomycosis occurring for special at-risk populations. Finally, preemptive management strategies are outlined in certain at-risk populations and after unintentional laboratory exposure.

Salvage Treatment of Mucormycosis Post-Liver Transplant With Posaconazole During Sirolimus Maintenance Immunosuppression

We describe the first successful case of posaconazole salvage therapy for mucormycosis with concomitant sirolimus (SRL) maintenance immunosuppression following liver transplantation, despite black box drug interaction following intolerance to first-line tacrolimus and amphotericin due to nephrotoxicity and neurotoxicity. This case describes a 55-year-old female who developed rhinocerebral mucormycosis 108 days after liver transplantation. After 3 months of posaconazole therapy, the patient remains free of disease at 3 years posttransplant. This case report illustrates successful resolution of mucormycosis without SRL toxicity to resolve nephrotoxicity of long-term amphotericin on top of already nephrotoxic immunosuppression. With higher bioavailability of recently FDA-approved posaconazole delayed release tablets, this azole may be a therapeutic option for transplant patients who need to remain on CYP3A4-metabolized immunosuppressive agents.

Rifampin-sirolimus-voriconazole interaction in a hematopoietic cell transplant recipient

Purpose Patients undergoing hematopoietic cell transplantation are treated with multiple medications, potentially complicated by drug-drug interactions. Drug interactions with sirolimus, voriconazole, and rifampin are particularly difficult because of the complex and simultaneous enzyme inhibition and induction mechanisms. We report a hematopoietic cell transplantation patient receiving sirolimus and voriconazole who was given rifampin while being treated for presumed methicillin-resistant Staphylococcus aureus meningitis. Summary A 31 year-old female received a nonmyeloablative allogeneic umbilical cord hematopoietic cell transplantation for myelodysplastic syndrome transformed to acute myeloid leukemia (AML). Her graft versus host disease and antifungal prophylaxis included sirolimus and voriconazole, respectively. Therapeutic drug monitoring prior to admission revealed a stable outpatient sirolimus regimen of 0.4 mg orally daily (trough goal 3-12 mcg/L). She was admitted to the inpatient hematopoietic cell transplantation service and diagnosed with methicillin-resistant Staphylococcus aureus bacteremia and presumed bacterial meningitis 217 days after transplant. Intravenous rifampin and vancomycin were initiated and voriconazole was changed to micafungin. Sirolimus trough concentrations were undetectable two days after starting rifampin. Therapeutic sirolimus concentrations were achieved four days later, at a sirolimus dose of 16-18 mg orally daily. Rifampin was discontinued after nine days and the sirolimus dose was adjusted accordingly, maintaining therapeutic levels throughout follow-up. The patient suffered a flare of chronic skin graft versus host disease requiring etanercept, high-dose systemic steroids, and topical steroids. Conclusion To the best of our knowledge, this is the first report describing the management of sirolimus during the transition from voriconazole inhibition to rifampin induction. Clinicians should be aware of potential drug-drug interactions.

Effects of CYP3A5 polymorphism on the pharmacokinetics of a once-daily modified-release tacrolimus formulation and acute kidney injury in hematopoietic stem cell transplantation

Background

Tacrolimus is metabolized by cytochrome P450 (CYP) 3A4 and 3A5. We investigated the influence of CYP3A5 polymorphism and concurrent use of azole antifungal agents (AZ) on the pharmacokinetics of a once-daily modified-release tacrolimus formulation (Tac-QD) in patients after hematopoietic stem cell transplantation (HSCT).

Design and methods

Twenty-four patients receiving allogeneic HSCT were enrolled. Genotyping for CYP3A5*3 was done by a PCR-restriction fragment length polymorphism method. Trough blood concentrations (C₀) of tacrolimus were measured by chemiluminescence magnetic microparticle immunoassay. Continuous infusion of tacrolimus was administered from the day before transplantation and was switched to Tac-QD after adequate oral intake.

Results

Thirteen patients had a CYP3A5*3/*3 genotype, and 11 patients had a CYP3A5*1/*1 or *1/*3 genotype. No significant difference was observed in daily dosages and the C₀ of tacrolimus between the two genotype groups without AZ. However, in patients who were co-administered AZ, the C₀ values of tacrolimus were higher in patients with the CYP3A5*3/*3 allele than with the CYP3A5*1 allele (P = 0.034), although daily doses of Tac-QD in patients with CYP3A5*3/*3 were significantly lower than those with the CYP3A5*1 allele (P = 0.041). The cumulative incidence of acute kidney injury was higher in patients with the CYP3A5*3/*3 than with the CYP3A5*1 allele when AZ was co-administered. The decrement for daily dosage of Tac-QD was significantly greater in patients expressing the CYP3A5*3/*3 than the CYP3A5*1 allele.

Conclusions

CYP3A5 genotyping may be useful for safe and effective immunosuppressive therapy with Tac-QD in HSCT patients in whom the use of AZ is anticipated.

Electronic supplementary material

The online version of this article (doi:10.1007/s00280-016-3060-4) contains supplementary material, which is available to authorized users.

Combination effects of azole fungicides in male rats in a broad dose range

Two 28-day feeding studies were performed in male rats to investigate combination effects of azole fungicides in a broad dose range. Following separate administration of cyproconazole, epoxiconazole, prochloraz, propiconazole, and tebuconazole at five dose levels, the first three compounds were selected to be administered in two different mixtures at three dose levels including very low doses. Here we present the data obtained by clinical observations, pathology, histopathology, clinical chemistry and haematology. The liver was the common main target organ of all compounds and their mixtures. In addition, epoxiconazole exhibited an effect on the adrenals. Furthermore, food consumption and efficiency and body weight (gain) were affected. Adverse effects of the combinations were observed at dose levels at which the individual substances caused similar effects. No evidence of adverse effects was found at dose levels below the previously established NOAELs. Our findings indicate that the concept of dose additivity appears sufficiently protective for risk assessment of the fungicides examined. Besides toxicological testing, tissue residues of the azole compounds in liver, testis and kidney were determined revealing remarkable differences following administration of the single substances and of the mixtures.

A case of treatment with voriconazole for chronic progressive pulmonary aspergillosis in a patient receiving tacrolimus for dermatomyositis-associated interstitial lung disease

We report a successful treatment with voriconazole (VRCZ) for chronic progressive pulmonary aspergillosis (CPPA) in a patient with dermatomyositis-associated interstitial lung disease (DM-ILD) treated with tacrolimus. A 73-year-old man with DM-ILD, treated with tacrolimus and prednisolone, complained of productive cough and his chest X-ray showed infiltration in the left upper lung field. We diagnosed CPPA and added VRCZ. Although we reduced the dose of tacrolimus for drug interaction, serum VRCZ level increased after the treatment. The patient was found to have cytochrome P450 (CYP) 2C19 *2/*2, a genetic polymorphism in poor metabolizers of VRCZ. We adjusted the doses of both drugs and treated him successfully. We recommend performing individual therapeutic drug monitoring (TDM) in CYP-mediated drug interactions and considering the effect of CYP polymorphisms.

Duration of Prophylaxis against Fungal Infection in Kidney Transplant Recipients

Objective—

To compare the efficacy of 2 strategies that use nystatin to prevent thrush and Candida esophagitis in kidney transplant recipients.

Methods—

A retrospective chart review was conducted of adult kidney transplant recipients at our center, where the protocol for prophylaxis against fungal infection was changed in March 2013. Before the protocol change, kidney transplant recipients received nystatin for 1 month (before group) and after the change they received nystatin for the duration of admission (after group). The primary outcome measure was the incidence of thrush and Candida esophagitis within 3 months after transplant. Analyses were conducted on all kidney transplant recipients (intention to treat) and on only those kidney transplant recipients who received at least 1 dose of nystatin (modified intention to treat). Additional data collected included the duration of nystatin and immunosuppression regimens. The Student t test and Fisher exact test were used to calculate P values for continuous and categorical data.

Results—

A total of 84 kidney transplant recipients, 42 in each cohort, were included in the analysis. The groups did not differ significantly at baseline. Nystatin was administered for a mean of 29 days in the before group and 5.74 days in the after group. Overall, 3 kidney transplant recipients (4%), all from the after group, experienced an episode of thrush and no patients experienced Candida esophagitis. Two recipients who experienced thrush did not receive any nystatin.

Conclusions—

Limiting the administration of nystatin to the duration of admission after transplant may be sufficient for prophylaxis of fungal infections in kidney transplant recipients.

Role of New Antifungal Agents in the Treatment of Invasive Fungal Infections in Transplant Recipients: Isavuconazole and New Posaconazole Formulations

Invasive fungal infections are a major cause of morbidity and mortality among solid organ transplant (SOT) and hematopoietic stem cell transplant (HSCT) recipients. Transplant patients are at risk for such invasive fungal infections. The most common invasive fungal infections are invasive candidiasis in the SOT and invasive aspergillosis in the HSCT. In this article, we will discuss the epidemiology of invasive fungal infections in the transplant recipients and susceptibility patterns of the fungi associated with these infections. Additionally, the pharmacology and clinical efficacy of the new antifungal, isavuconazole, and the new posaconazole formulations will be reviewed. Isavuconazole is a new extended-spectrum triazole that was recently approved for the treatment of invasive aspergillosis and mucormycosis. Advantages of this triazole include the availability of a water-soluble intravenous formulation, excellent bioavailability of the oral formulation, and predictable pharmacokinetics in adults. Posaconazole, a broad-spectrum triazole antifungal agent, is approved for the prevention of invasive aspergillosis and candidiasis in addition to the treatment of oropharyngeal candidiasis. Posaconazole oral suspension solution has shown some limitations in the setting of fasting state absorption, elevated gastrointestinal pH, and increased motility. The newly approved delayed-release oral tablet and intravenous solution formulations provide additional treatment options by reducing interpatient variability and providing flexibility in these set of critically ill patients. This review will detail these most recent studies.

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.

Isavuconazole

Objective: To review the pharmacology, chemistry, in vitro susceptibility, pharmacokinetics, clinical efficacy, safety, tolerability, dosage, and administration of isavuconazole, a triazole antifungal agent. Data Sources: Studies and reviews were identified through an English language MEDLINE search (1978 to March 2015) and from http://www.clinicaltrials.gov , Food and Drug Administration (FDA) briefing documents, program abstracts from international symposia, and the manufacturer’s Web site. Study Selection and Data Extraction: All published and unpublished trials, abstracts, in vitro and preclinical studies, and FDA briefing documents were reviewed. Data Synthesis: Isavuconazole has activity against a number of clinically important yeasts and molds, including Candida spp, Aspergillus spp, Cryptococcus neoformans, and Trichosporon spp and variable activity against the Mucorales. Isavuconazole, available for both oral and intravenous administration, is characterized by slow elimination allowing once-daily dosing, extensive tissue distribution, and high (>99%) protein binding. The most commonly reported adverse events, which are mild and limited in nature, include nausea, diarrhea, and elevated liver function tests. Its drug interaction potential appears to be similar to other azole antifungals but less than those observed with voriconazole. Comparative trials are under way or have been recently completed for the treatment of candidemia, invasive candidiasis and aspergillosis, and rare mold infections. Conclusions: Isavuconazole has a broad spectrum of activity and favorable pharmacokinetic properties, providing an advantage over other currently available broad-spectrum azole antifungals and a clinically useful alternative to voriconazole for the treatment of invasive aspergillosis. It may also prove useful for the treatment of candidemia and invasive mold infections; however, these indications await the results of clinical trials.

Invasive aspergillosis in liver transplant recipients: epidemiology, clinical characteristics, treatment, and outcomes in 116 cases

Invasive aspergillosis (IA) in liver transplant recipients is associated with grave outcomes. We reviewed 116 individual cases reported in the literature from 1985 to 2013. IA was diagnosed after a median of 25 days after transplantation and involved a single organ in 51% of the cases, whereas in the remaining cases, multiple sites were involved. The most common infecting Aspergillus species were Aspergillus fumigatus (73%), Aspergillus flavus (14%), and Aspergillus terreus (8%). Amphotericin B was the drug most frequently used, and it was followed by voriconazole and itraconazole. Combination regimens were used in 51% of the cases. The overall 1-year cumulative survival probability was 35% [95% confidence interval (CI) = 24.6%-49.6%]. Survival was significantly higher for patients reported from the year 2000 and thereafter (P < 0.001), for those diagnosed with IA more than 30 days after transplantation versus those diagnosed earlier (P = 0.019), and for patients without renal failure (P = 0.020). Additionally, the use of voriconazole was significantly associated with a higher probability of survival (P < 0.001). Cox regression analysis showed that subjects with the involvement of multiple sites had a 2.52 times higher risk of a negative outcome (95% CI = 1.08-5.87) than those with the involvement of a single site. Thus, IA causes life-threatening infections in liver transplant recipients. Predictors associated with poor outcomes may help clinicians to optimize the management of this infection.

Safety of voriconazole and sirolimus coadministration after allogeneic hematopoietic SCT

Antifungal prophylaxis with azoles is considered standard in allogeneic hematopoietic SCT (allo-HSCT). Although sirolimus is being used increasingly for the prevention of GVHD, it is a substrate of CYP3A4, which is inhibited by voriconazole, and concurrent administration can lead to significantly increased exposure to sirolimus. We identified 67 patients with hematologic malignancies who underwent allo-HSCT with sirolimus, tacrolimus and low-dose MTX and received concomitant voriconazole prophylaxis from April 2008 to June 2011. All patients underwent a non-myeloablative or reduced-intensity conditioned allo-HSCT. Patients received sirolimus and voriconazole concurrently for a median of 113 days. The median daily dose reduction of sirolimus at the start of coadministration was 90%. The median serum sirolimus trough levels before and at steady state of coadministration were 5.8 ng/mL (range: 0-47.6) and 6.1 ng/mL (range: 1-14.2) (P=0.45), respectively. One patient with an average sirolimus level of 6 ng/mL developed sirolimus-related thrombotic microangiopathy that resolved after sirolimus discontinuation. No sinusoidal obstructive syndrome was reported. Seventeen patients (25%) prematurely discontinued voriconazole because of the adverse events. Only two patients (3%) presented with possible invasive fungal infections at day 100. We demonstrate that sirolimus and voriconazole coadministration with an empiric 90% sirolimus dose reduction and close monitoring of sirolimus trough levels is safe and well tolerated.

Targeted versus universal antifungal prophylaxis among liver transplant recipients

Guidelines recommend targeted antifungal prophylaxis for liver transplant (LT) recipients based on tiers of risk, rather than universal prophylaxis. The feasibility and efficacy of tiered, targeted prophylaxis is not well established. We performed a retrospective study of LT recipients who received targeted prophylaxis (n = 145; voriconazole [VORI; 54%], fluconazole [8%], no antifungal [38%]) versus universal VORI prophylaxis (n = 237). Median durations of targeted and universal prophylaxis were 11 and 6 days, respectively (p < 0.0001). The incidence of invasive fungal infections (IFIs) in targeted and universal groups was 6.9% and 4.2% (p = 0.34). Overall, intra-abdominal candidiasis (73%) was the most common IFI. Posttransplant bile leaks (p = 0.001) and living donor transplants (p = 0.04) were independent risk factors for IFI. IFIs occurred in 6% of high-risk transplants who received prophylaxis and 4% of low-risk transplants who did not receive prophylaxis (p = 1.0). Mortality rates (100 days) were 10% (targeted) and 7% (universal) (p = 0.26); attributable mortality due to IFI was 10%. Compliance with prophylaxis recommendations was 97%. Prophylaxis was discontinued for toxicity in 2% of patients. Targeted antifungal prophylaxis in LT recipients was feasible and safe, effectively prevented IFIs and reduced the number of patients exposed to antifungals. Bile leaks and living donor transplants should be considered high-risk indications for prophylaxis.

Antifungal prophylaxis in liver transplantation: a systematic review and network meta-analysis

Invasive fungal infections (IFIs) cause significant morbidity and mortality in liver transplant recipients, but the need and best agent for prophylaxis is uncertain. A comprehensive literature search was performed to identify randomized controlled trials comparing regimens for antifungal prophylaxis in liver transplant recipients. Direct comparisons were made between treatments using random-effects meta-analysis and a Bayesian network meta-analysis was performed for the primary end point of proven IFI. Fourteen studies met inclusion criteria, reporting comparisons of fluconazole, liposomal amphotericin B (L-AmB), itraconazole, micafungin and placebo. Overall, antifungal prophylaxis reduced the rate of proven IFI (odds ratio [OR] 0.37, confidence interval [CI] 0.19-0.72, p = 0.003), suspected or proven IFI (OR 0.40, CI 0.25-0.66, p = 0.0003) and mortality due to IFI (OR 0.32, CI 0.10-0.83, p = 0.02) when compared to placebo. All-cause mortality was not significantly affected. There was no difference in risk of adverse events requiring cessation of prophylaxis (OR 1.11, 95% CI 0.48-2.55, p = 0.81). In the network meta-analysis an equivalent reduction in the rate of IFI was seen with fluconazole (OR 0.21, CI 0.06-0.57) and L-AmB (OR 0.21, CI 0.05-0.71) compared with placebo. Routine prophylaxis with fluconazole or L-AmB reduces the incidence of IFI following liver transplantation, and the available evidence suggests that the two are equivalent in efficacy.

Dosing algorithm for concomitant administration of sirolimus, tacrolimus, and an azole after allogeneic hematopoietic stem cell transplantation

BACKGROUND

Allogeneic hematopoietic stem cell transplant patients are at risk of invasive fungal infections and prophylaxis with azole agents is common practice. The concomitant use of these agents with sirolimus and tacrolimus for the prevention of graft-versus-host disease may result in excessive immunosuppression or toxicity.

METHODS

This retrospective study identified hospitalized patients who underwent allogeneic hematopoietic stem cell transplantation between August 2009 and April 2011 at Rush University Medical Center. From this group, patients who underwent concomitant tacrolimus, sirolimus, and azole therapy were included for evaluation. The immunosuppression dosing in conjunction with azole use at discharge was analyzed to develop a dosing algorithm dependent on whether fluconazole, posaconazole, or voriconazole was used.

RESULTS

A total of 36 patients were screened for inclusion, of which 8 were excluded due to acute renal failure and/or hemolysis. The remaining patients were stratified by the azole they were concomitantly taking with tacrolimus and sirolimus. The fluconazole arm required the lowest magnitude of dose reductions, while voriconazole required the greatest.

CONCLUSION

Dose reductions of 50-75% for both sirolimus and tacrolimus, in combination with standard dosing of azole antifungal agents, were necessary to achieve therapeutic drug concentrations for immunosuppressants and potentially avoid toxicities.

Preventing invasive fungal disease in patients with haematological malignancies and the recipients of haematopoietic stem cell transplantation: practical aspects

Invasive fungal disease (IFD), predominantly aspergillosis, is associated with significant morbidity and mortality in immunocompromised patients, especially those with haematological malignancies and recipients of allogeneic haematopoietic stem cell transplantation. There has been a great deal of scientific debate as to the effectiveness of antifungal prophylaxis in preventing infection in different patient groups and in which patients it is an appropriate management option. Deciding on an appropriate prophylaxis regimen for IFD is challenging as the incidence varies among different patient groups, due to the varied nature of their underlying haematological disease, and in different regions and centres. Attempts have been made to define risk factors and include them in treatment protocols. Impaired immune status of the patient, especially neutropenia, is a key risk factor for IFD and can sometimes be related to specific polymorphisms of genes controlling innate immunity. Risk factors also vary according to the type of fungal pathogen. Consequently, prophylaxis needs to be tailored to individual patient groups. Furthermore, the choice of antifungal agent for prophylaxis depends on the potential for drug-drug interactions with the patients' concomitant medications. Additional challenges are optimal timing of antifungal prophylaxis, when to change from prophylaxis to antifungal treatment and how to prevent recurrence of IFD. This article considers the use of antifungal prophylaxis for patients at risk of IFD in daily clinical practice, with clinical profiles that may be distinct from those covered by guidelines, and aims to provide practical advice for treatment of these patient groups.

Drug-drug interactions with oral anti-HCV agents and idiosyncratic hepatotoxicity in the liver transplant setting

Studies of boceprevir and telaprevir based antiviral therapy in liver transplant (LT) recipients with hepatitis C genotype 1 infection have demonstrated dramatic increases in tacrolimus, cyclosporine, and mTOR inhibitor exposure. In addition to empiric dose reductions, daily monitoring of immunosuppressant blood levels is required when initiating as well as discontinuing the protease inhibitors to maximize patient safety. Although improved suppression of HCV replication is anticipated, 20 to 40% of treated subjects have required early treatment discontinuation due to various adverse events including anemia (100%), infection (30%), nephrotoxicity (20%) and rejection (5 to 10%). Simeprevir and faldaprevir will likely have improved efficacy and safety profiles but potential drug interactions with other OATP1B1 substrates and unconjugated hyperbilirubinemia are expected. In contrast, sofosbuvir and daclatasvir based antiviral therapy are not expected to lead to clinically significant drug-drug interactions in LT recipients but confirmatory studies are needed. Liver transplant recipients may also be at increased risk of developing drug induced liver injury (DILI). Establishing a diagnosis of DILI in the transplant setting is very difficult with the variable latency, laboratory features and histopathological manifestations of hepatotoxicity associated with a given drug, the need to exclude competing causes of allograft injury, and the lack of an objective and verifiable confirmatory test. Nonetheless, a heightened awareness of the possibility of DILI is warranted in light of the large number of medications used in LT recipients and the potential adverse impact that DILI may have on patient outcomes.