Effect of Oral Posaconazole on the Pharmacokinetics of Cyclosporine and Tacrolimus

Clinical Trial Data-Driven Risk Assessment of Drug-Drug Interactions: A Rapid and Accurate Decision-Making Tool

BACKGROUND

In clinical practice, the vast array of potential drug combinations necessitates swift and accurate assessments of pharmacokinetic drug-drug interactions (DDIs), along with recommendations for adjustments. Current methodologies for clinical DDI evaluations primarily rely on basic extrapolations from clinical trial data. However, these methods are limited in accuracy owing to their lack of a comprehensive consideration of various critical factors, including the inhibitory potency, dosage, and type of the inhibitor, as well as the metabolic fraction and intestinal availability of the substrate.

OBJECTIVE

This study aims to propose an efficient and accurate clinical pharmacokinetic-mediated DDI assessment tool, which comprehensively considers the effects of inhibitory potency and dosage of inhibitors, intestinal availability and fraction metabolized of substrates on DDI outcomes.

METHODS

This study focuses on DDIs caused by cytochrome P450 3A4 enzyme inhibition, utilizing extensive clinical trial data to establish a methodology to calculate the metabolic fraction and intestinal availability for substrates, as well as the concentration and inhibitory potency for inhibitors ( K i ork inact / K I ). These parameters were then used to predict the outcomes of DDIs involving 33 substrates and 20 inhibitors. We also defined the risk index for substrates and the potency index for inhibitors to establish a clinical DDI risk scale. The training set for parameter calculation consisted of 73 clinical trials. The validation set comprised 89 clinical DDI trials involving 53 drugs. which was used to evaluate the reliability of in vivo values of K i andk inact / K I , the accuracy of DDI predictions, and the false-negative rate of risk scale.

RESULTS

First, the reliability of the in vivo K i andk inact / K I values calculated in this study was assessed using a basic static model. Compared with values obtained from other methods, this study values showed a lower geometric mean fold error and root mean square error. Additionally, incorporating these values into the physiologically based pharmacokinetic-DDI model facilitated a good fitting of the C-t curves when the substrate's metabolic enzymes are inhibited. Second, area under the curve ratio predictions of studied drugs were within a 1.5 × margin of error in 81% of cases compared with clinical observations in the validation set. Last, the clinical DDI risk scale developed in this study predicted the actual risks in the validation set with only a 5.6% incidence of serious false negatives.

CONCLUSIONS

This study offers a rapid and accurate approach for assessing the risk of pharmacokinetic-mediated DDIs in clinical practice, providing a foundation for rational combination drug use and dosage adjustments.

Evaluation of Published Population Pharmacokinetic Models to Inform Tacrolimus Therapy in Adult Lung Transplant Recipients

BACKGROUND

The applicability of currently available tacrolimus population pharmacokinetic models in guiding dosing for lung transplant recipients is unclear. In this study, the predictive performance of relevant tacrolimus population pharmacokinetic models was evaluated for adult lung transplant recipients.

METHODS

Data from 43 lung transplant recipients (1021 tacrolimus concentrations) administered an immediate-release oral formulation of tacrolimus were used to evaluate the predictive performance of 17 published population pharmacokinetic models for tacrolimus. Data were collected from immediately after transplantation up to 90 days after transplantation. Model performance was evaluated using (1) prediction-based assessments (bias and imprecision) of individual predicted tacrolimus concentrations at the fourth dosing based on 1 to 3 previous dosings and (2) simulation-based assessment (prediction-corrected visual predictive check; pcVPC). Both assessments were stratified based on concomitant azole antifungal use. Model performance was clinically acceptable if the bias was within ±20%, imprecision was ≤20%, and the 95% confidence interval of bias crossed zero.

RESULTS

In the presence of concomitant antifungal therapy, no model showed acceptable performance in predicting tacrolimus concentrations at the fourth dosing (n = 33), and pcVPC plots displayed poor model fit to the data set. However, this fit slightly improved in the absence of azole antifungal use, where 4 models showed acceptable performance in predicting tacrolimus concentrations at the fourth dosing (n = 33).

CONCLUSIONS

Although none of the evaluated models were appropriate in guiding tacrolimus dosing in lung transplant recipients receiving concomitant azole antifungal therapy, 4 of these models displayed potential applicability in guiding dosing in recipients not receiving concomitant azole antifungal therapy. However, further model refinement is required before the widespread implementation of such models in clinical practice.

Assessing the Impact of Posaconazole Cessation on Tacrolimus Serum Concentrations and Incident Cardiac Allograft Rejection: Take Caution

Invasive aspergillosis (IA) is a rare and often fatal complication of immunosuppression following orthotopic heart transplant. Prophylaxis plays a crucial role in preventing the emergence of this opportunistic infection. The azole class of medications are the bellwether agents utilized in this patient population. Unfortunately, given their impact on the Cytochrome P450 enzyme system, significant fluctuations in serum tacrolimus concentrations occur when initiating and stopping azole therapy, increasing the risk for prolonged periods of sub-optimal immunosuppression. While there are recommended dosing adjustments for these transition periods based on small data sets primarily with fluconazole, there is no published literature on recommended dosing adjustments for posaconazole. Given our institution utilizes posaconazole as the primary therapeutic for aspergillosis prophylaxis, we aimed to explore and report our local data to better guide dosing decisions during these transition periods.

Low-dose fluconazole as a useful and safe prophylactic option in patients receiving allogeneic hematopoietic stem cell transplantation

BACKGROUND

Invasive fungal infections (IFIs) represent a potentially fatal complication in patients who undergo allogeneic hematopoietic stem cell transplantation (HSCT) if the initiation of therapy is delayed. Some guidelines recommend antifungal prophylaxis or preemptive therapy for these patients depending on the risk of IFIs following allogeneic HSCT. This retrospective study aimed to identify the group of patients who safely undergo allogeneic HSCT with low-dose fluconazole (FLCZ) prophylaxis (100 mg/day).

METHODS

We retrospectively reviewed 107 patients who underwent their first allogeneic HSCT at Nagoya City University Hospital from January 1, 2010, to December 31, 2019. We analyzed the efficacy of low-dose FLCZ prophylaxis and investigated the relationship between major risk factors and antifungal prophylaxis failure (APF) within 100 days post-transplant.

RESULTS

Of the 107 patients, 70 received low-dose FLCZ prophylaxis, showing a cumulative incidence of APF of 37.1% and a proven/probable IFI rate of 4.3%. There were no fungal infection-related deaths, including Aspergillus infections, in the FLCZ prophylaxis group. In a multivariable analysis, cord blood transplantation (CBT) (subdistribution hazard ratio (SHR), 3.55; 95% confidence interval (CI), 1.44-8.77; p = 0.006) and abnormal findings on lung CT before transplantation (SHR, 2.24; 95% CI, 1.02-4.92; p = 0.044) were independent risk factors for APF in the FLCZ prophylaxis group.

CONCLUSION

Low-dose FLCZ prophylaxis is a useful and safe option for patients receiving allogeneic HSCT, except in those undergoing CBT or having any fungal risk features including history of fungal infections, positive fungal markers, and abnormal findings on lung CT before transplantation.

Impact of posaconazole and diltiazem on pharmacokinetics of encorafenib, a BRAF V600 kinase inhibitor for melanoma and colorectal cancer with BRAF mutations

Encorafenib is a potent and selective ATP competitive inhibitor of BRAF V600-mutant kinase approved for patients with BRAF-mutant melanoma and colorectal cancer. Encorafenib is mainly metabolized by cytochrome P450 (CYP) 3A4 in vitro and may be susceptible to drug-drug interactions when co-administered with CYP3A inhibitors or inducers. The primary objective was to assess the impact of the strong CYP3A inhibitor posaconazole (part 1) and the moderate CYP3A and P-gp inhibitor diltiazem (part 2) on encorafenib pharmacokinetics in healthy volunteers following a single 50-mg dose. A total of 32 participants were enrolled (16 each in parts 1 and 2). The area under the curve extrapolated to infinity (AUCinf ) and maximum plasma concentration (Cmax ) geometric mean for encorafenib increased by 183% and 68.4%, respectively, when co-administered with posaconazole. Apparent encorafenib clearance decreased from 26.0 to 9.2 L/h when coadministered with posaconazole, and plasma terminal half-life (t½ ) of encorafenib increased from 4.3 to 7.3 h. The AUCinf and Cmax geometric mean for encorafenib increased by 83.0% and 44.7%, respectively, when co-administered with diltiazem. Similarly, the apparent encorafenib clearance decreased from 29.0 to 16.0 L/h when co-administered with diltiazem, and plasma t½ of encorafenib increased from 6.6 to 7.9 h. There were no deaths, serious adverse events (AEs), or patient discontinuations due to AEs in parts 1 or 2. The most frequently reported treatment-related AEs were erythema (n = 14; 88%) and headache (n = 11; 69%) in part 1 and headache (n = 7; 44%) in part 2. The results of this study indicate that co-administration of encorafenib with strong or moderate CYP3A4 inhibitors should be avoided.

Part 2: Mucormycosis: Focus on Therapy

INTRODUCTION

Mucormycosis (MCR) a rare but life-threatening infection occurs primarily in immunocompromised hosts. Mortality rates with invasive MCR are high (>30-50%), up to 90% with disseminated disease, but lower (10-30%) with localized cutaneous disease. Due to the rarity of MCR, randomized, controlled therapeutic trials are lacking. Lipid formulations of amphotericin B (LFAB) are the mainstay of therapy but oral triazoles (posaconazole and isavuconazole) may be effective as step-down therapy or in MCR cases refractory to or intolerant of LFAB. Early surgical debridement or excision play important adjunctive roles in localized invasive disease. Control of hyperglycemia in diabetic patients, correction of neutropenia and reduction of immunosuppressive therapy is critical for optimal survival.

AREAS COVERED

The authors discuss various therapeutic options for mucormycosis. A literature search of mucormycosis therapies was performed via PubMed (up to December 2022), using the key words: invasive fungal infections; mold; mucormycosis; Mucorales; amphotericin B; isavuconazole; posaconazole.

EXPERT OPINION

Randomized, controlled therapeutic trials are lacking. Lipid formulations of amphotericin B (LFAB) are the mainstay of therapy but oral triazoles (posaconazole and isavuconazole) may be effective as step-down therapy, in MCR cases refractory to or intolerant of LFAB. We encourage early surgical debridement or excision as adjunctive measures.

Diagnosis and Treatment of Fungal Infections in Lung Transplant Recipients

Fungal infections are a significant source of morbidity in the lung transplant population via direct allograft damage and predisposing patients to the development of chronic lung allograft dysfunction. Prompt diagnosis and treatment are imperative to limit allograft damage. This review article discusses incidence, risk factors, and symptoms with a specific focus on diagnostic and treatment strategies in the lung transplant population for fungal infections caused by Aspergillus, Candida, Coccidioides, Histoplasma, Blastomyces, Scedosporium/Lomentospora, Fusarium, and Pneumocystis jirovecii. Evidence for the use of newer triazole and inhaled antifungals to treat isolated pulmonary fungal infections in lung transplant recipients is also discussed.

Invasive aspergillosis in liver transplant recipients

BACKGROUND

Liver transplantation is increasing worldwide with underlying pathologies dominated by metabolic and alcoholic diseases in developed countries.

METHODS

We provide a narrative review of invasive aspergillosis (IA) in liver transplant (LT) recipients. We searched PubMed and Google Scholar for references without language and time restrictions.

RESULTS

The incidence of IA in LT recipients is low (1.8%), while mortality is high (∼50%). It occurs mainly early (<3 months) after LT. Some risk factors have been identified before (corticosteroid, renal, and liver failure), during (massive transfusion and duration of surgical procedure), and after transplantation (intensive care unit stay, re-transplantation, re-operation). Diagnosis can be difficult and therefore requires full radiological and clinicobiological collaboration. Accurate identification of Aspergillus species is recommended due to the cryptic species, and susceptibility testing is crucial given the increasing resistance of Aspergillus fumigatus to azoles. It is recommended to reduce the dose of tacrolimus (50%) and to closely monitor the trough level when introducing voriconazole, isavuconazole, and posaconazole. Surgery should be discussed on a case-by-case basis. Antifungal prophylaxis is recommended in high-risk patients. Environmental preventative measures should be implemented to prevent outbreaks of nosocomial aspergillosis in LT recipient units.

CONCLUSION

IA remains a very serious disease in LT patients and should be promptly sought and, if possible, prevented by clinicians when risk factors are identified.

Adaptation of a population pharmacokinetic model to inform tacrolimus therapy in heart transplant recipients

AIM

Existing tacrolimus population pharmacokinetic models are unsuitable for guiding tacrolimus dosing in heart transplant recipients. This study aimed to develop and evaluate a population pharmacokinetic model for tacrolimus in heart transplant recipients that considers the tacrolimus-azole antifungal interaction.

METHODS

Data from heart transplant recipients (n = 87) administered the oral immediate-release formulation of tacrolimus (Prograf®) were collected. Routine drug monitoring data, principally trough concentrations, were used for model building (n = 1099). A published tacrolimus model was used to inform the estimation of Ka , V2 /F, Q/F and V3 /F. The effect of concomitant azole antifungal use on tacrolimus CL/F was quantified. Fat-free mass was implemented as a covariate on CL/F, V2 /F, V3 /F and Q/F on an allometry scale. Subsequently, stepwise covariate modelling was performed. Significant covariates influencing tacrolimus CL/F were included in the final model. Robustness of the final model was confirmed using prediction-corrected visual predictive check (pcVPC). The final model was externally evaluated for prediction of tacrolimus concentrations of the fourth dosing occasion (n = 87) from one to three prior dosing occasions.

RESULTS

Concomitant azole antifungal therapy reduced tacrolimus CL/F by 80%. Haematocrit (∆OFV = -44, P < .001) was included in the final model. The pcVPC of the final model displayed good model adequacy. One recent drug concentration is sufficient for the model to guide tacrolimus dosing.

CONCLUSION

A population pharmacokinetic model that adequately describes tacrolimus pharmacokinetics in heart transplant recipients, considering the tacrolimus-azole antifungal interaction was developed. Prospective evaluation is required to assess its clinical utility to improve patient outcomes.

Adverse Events Associated with Universal versus Targeted Antifungal Prophylaxis among Lung Transplant Recipients-A Nationwide Cohort Study 2010-2019

Background: Invasive fungal infections in lung transplant (LTX) recipients cause substantial morbidity, but the best strategy for prevention has not yet been determined. We evaluated adherence to and rates of adverse events of universal versus targeted prophylaxis. Methods: All LTX recipients in the Danish National LTX Centre (2010−2019) were included. Before July 2016, universal voriconazole prophylaxis was used. After July 2016, only high-risk patients received targeted prophylaxis with posaconazole and inhaled amphotericin B. Proportions of triazole discontinuation, side-effects, off-target calcineurin-inhibitor (CNI) levels, and acute rejection were compared between the two periods. Results: Universal and targeted prophylaxis was initiated in 183/193 and 6/102 patients, respectively. Only 37% completed > 9 of the intended 12 weeks of voriconazole; 72% of discontinuations were due to hepatotoxicity. In the universal vs. targeted prophylaxis period, 89% vs. 72% (p < 0.001) patients had low CNI episodes, and 37% vs. 1% (p < 0.001) of these were associated with discontinuation of triazole; 40% vs. 14% (p < 0.001) had acute rejection; and 23% vs. 3% (p < 0.001) had acute rejection associated with low CNI episodes. Conclusions: Universal voriconazole prophylaxis was associated with high rates of discontinuation, mainly caused by hepatotoxicity. In comparison to the targeted posaconazole period, more patients had low CNI levels and acute rejection in the universal voriconazole period.

Effect of posaconazole on the concentration of intravenous and oral cyclosporine in patients undergoing hematopoietic stem cell transplantation

PURPOSE

This study aimed to investigate the interactions between posaconazole (POS) and intravenously/orally administered cyclosporine A (CsA) in allogeneic hematopoietic stem cell transplant (HSCT) recipients.

METHODS

We included 118 allogeneic HSCT patients who received CsA and POS simultaneously between January 2017 and June 2020 in this study. The ratio of CsA blood concentration (ng/mL) to dosage (mg/day) (C/D) before and after POS initiation was compared.

RESULTS

After the initiation of POS, the level of CsA increased 1 to 2 times in 66% (78/118) of patients compared to those without POS. However, the CsA C/D ratio increased by more than threefold in 6% (7/118) of patients after POS initiation, with an increase of more than fourfold in two patients. The median C/D ratio of CsA increased from 0.89 to 1.23 (P < 0.001) and 0.78 to 1.22 (P < 0.001) after POS initiation when CsA was administered intravenously and orally, respectively. In patients who received POS at the time of transition from intravenous to oral CsA, the value increased from 1.01 to 1.38 (P = 0.001). The route of administration had no significant effect on the change in the CsA C/D ratio (P = 0.615). Additionally, we observed the time required for the C/D ratio to reach a plateau after POS initiation was similar on days 13, 8, and 15 under various scenarios.

CONCLUSION

POS treatment increased blood CsA levels. A large variability was found in the fold-change in the CsA C/D ratio. Therefore, CsA doses should be adjusted by closely monitoring the blood levels of CsA after POS initiation.

Fungal Infections in Lung Transplantation

Purpose of Review

We aim to understand the most common fungal infections associated with the post-lung transplant period, how to diagnose, treat, and prevent them based on the current guidelines published and our center’s experience.

Recent Findings

Different fungi inhabit specific locations. Diagnosis of invasive fungal infections (IFIs) depends on symptoms, radiologic changes, and a positive microbiological or pathology data. There are several molecular tests that have been used for diagnosis. Exposure to fungal prophylaxis can predispose lung transplant recipients to these emerging molds. Understanding and managing medication interactions and drug monitoring are essential in successfully treating IFIs.

Summary

With the increasing rate of lung transplantations being performed, and the challenges posed by the immunosuppressive regimen, understanding the risk and managing the treatment of fungal infections are imperative to the success of a lung transplant recipient. There are many ongoing clinical trials being conducted in hopes of developing novel antifungals.

Effects of CYP2C9*3 and *13 alleles on the pharmacokinetics and pharmacodynamics of glipizide in healthy Korean subjects

Glipizide is a second-generation sulfonylurea antidiabetic drug. It is principally metabolized to inactive metabolites by genetically polymorphic CYP2C9 enzyme. In this study, we investigated the effects of CYP2C9*3 and *13 variant alleles on the pharmacokinetics and pharmacodynamics of glipizide. Twenty-four healthy Korean volunteers (11 subjects with CYP2C9*1/*1, 8 subjects with CYP2C9*1/*3, and 5 subjects with CYP2C9*1/*13) were recruited for this study. They were administered a single oral dose of glipizide 5 mg. The plasma concentration of glipizide was quantified for pharmacokinetic analysis and plasma glucose and insulin concentrations were measured as pharmacodynamic parameters. The results represented that CYP2C9*3 and *13 alleles significantly affected the pharmacokinetics of glipizide. In subjects with CYP2C9*1/*3 and CYP2C9*1/*13 genotypes, the mean AUC_0-∞ were increased by 44.8% and 58.2%, respectively (both P < 0.001), compared to those of subjects with CYP2C9*1/*1 genotype, while effects of glipizide on plasma glucose and insulin levels were not significantly different between CYP2C9 genotype groups. In conclusion, individuals carrying the defective CYP2C9*3 and CYP2C9*13 alleles have markedly elevated plasma concentrations of glipizide compared with CYP2C9*1/*1 wild-type.

Evaluating posaconazole, its pharmacology, efficacy and safety for the prophylaxis and treatment of fungal infections

INTRODUCTION

Invasive fungal diseases (IFDs) are a significant cause of morbidity and mortality among immunocompromised patients. Safe and effective antifungal medications used for prophylaxis and treatment are pivotal in their management. Posaconazole is a promising triazole antifungal agent.

AREAS COVERED

The authors discuss the pharmacological properties of posaconazole, including pharmacokinetics/pharmacodynamics, safety and tolerability profile, together with efficacy data for prophylaxis and treatment as well as its use in special populations based on current literature.

EXPERT OPINION

Posaconazole has a favorable safety and tolerability profile; however, caution is advised when co-administered with agents that are CYP3A4 inhibitors, because their concentration may significantly increase, and their levels should be closely monitored. It has an extended spectrum of activity against yeasts and filamentous fungi. It is successfully used as prophylaxis for patients with acute myeloid leukemia (AML)/myelodysplastic syndrome (MDS) and post-hematopoietic cell transplantation (HCT) with graft-versus-host disease (GVHD). It is the first line treatment for oropharyngeal candidiasis and is also used as a salvage treatment for refractory IFDs. Currently available formulations include the oral suspension, delayed-release tablets and solution for intravenous infusion, all with different PK/PD properties and indications. Its use in children and adolescents is currently being examined in Phase-II clinical trials.

Evaluation of published population pharmacokinetic models to inform tacrolimus dosing in adult heart transplant recipients

BACKGROUND AND AIM

Identification of the most appropriate population pharmacokinetic model-based Bayesian estimation is required prior to its implementation in routine clinical practice to inform tacrolimus dosing decisions. This study aimed to determine the predictive performances of relevant population pharmacokinetic models of tacrolimus developed from various solid organ transplant recipient populations in adult heart transplant recipients, stratified based on concomitant azole antifungal use. Concomitant azole antifungal therapy alters tacrolimus pharmacokinetics substantially, necessitating dose adjustments.

METHODS

Population pharmacokinetic models of tacrolimus were selected (n = 17) for evaluation from a recent systematic review. The models were transcribed and implemented in NONMEM version 7.4.3. Data from 85 heart transplant recipients (2387 tacrolimus concentrations) administered the oral immediate-release formulation of tacrolimus (Prograf) were obtained up to 391 days post-transplant. The performance of each model was evaluated using: (i) prediction-based assessment (bias and imprecision) of the individual predicted tacrolimus concentration of the fourth dosing occasion (MAXEVAL = 0, FOCE-I) from 1-3 prior dosing occasions; and (ii) simulation-based assessment (prediction-corrected visual predictive check). Both assessments were stratified based on concomitant azole antifungal use.

RESULTS

Regardless of the number of prior dosing occasions (1-3) and concomitant azole antifungal use, all models demonstrated unacceptable individual predicted tacrolimus concentration of the fourth dosing occasion (n = 152). The prediction-corrected visual predictive check graphics indicated that these models inadequately predicted observed tacrolimus concentrations.

CONCLUSION

All models evaluated were unable to adequately describe tacrolimus pharmacokinetics in adult heart transplant recipients included in this study. Further work is required to describe tacrolimus pharmacokinetics for our heart transplant recipient cohort.

A novel highly bio-available itraconazole formulation (SUBA®-Itraconazole) for anti-fungal prophylaxis in lung transplant recipients

BACKGROUND

Antifungal prophylaxis remains a mainstay of lung transplantation, given invasive fungal infection is a common and serious complication after lung transplantation. Choice of systemic agent to prevent invasive fungal infection varies between centers and funding of agents remains challenging. Our center has recently changed from posaconazole to a highly bioavailable formulation of itraconazole (SUBA®-itraconazole) at substantially reduced cost, but safety and toxicity require further assessment. A retrospective study of lung transplant patients receiving systemic antifungal prophylaxis from December 2016 through December 2019 following change from posaconazole to itraconazole as standard practice. 150 patients with lung transplants were managed in this time period, with 88 (59%) receiving at least 1 mold-active triazole during the study period. 48 (58%) of these patients received SUBA®-itraconazole; 68 (82%) received posaconazole and 10 (12%) received voriconazole. The average cost per patient during the study period was significantly lower on SUBA®-itraconazole (mean $1548/patient/6 month course) than posaconazole (mean $16 921.35/patient/6 month course). Target trough concentrations for prophylaxis of itraconazole > 0.5 mg/L and posaconazole > 0.7 mg/L were achieved on empiric dosing in 49% and 68% respectively. Overall trough itraconazole (0.50 vs 1.12 mg/L, P < .001) and posaconazole (1.37 vs 2.10 mg/L P < .001) concentrations were significantly lower in patients with cystic fibrosis. Calcineurin inhibitor dose changes on introduction or cessation were similar for SUBA®-itraconazole and posaconazole. Breakthrough invasive fungal infection and toxicity were rare. SUBA®-itraconazole is well-tolerated, associated with rare breakthrough invasive fungal infection, and lower cost. Prospective studies following general introduction are required to determine long-term safety, tolerability, and efficacy.

Drug Interactions between Antimicrobial and Immunosuppressive Agents in Solid Organ Transplant Recipients

The number of allogeneic solid organ and bone marrow transplants is increasing all over the world. To prevent transplant rejection and treat acute rejection of transplant, immunosuppressant drugs are used. The outcomes of solid organ transplants have dramatically improved over last 30 years, due to availability of multiple immunosuppressive agents, with varied mechanisms of action. The use of intense immunosuppression makes the individual having undergone solid organ transplant at the risk of several serious infections, which may prove fatal. To prevent and treat these infections (when they occur), patients are often given antimicrobial prophylaxis and therapy. The use of antimicrobials can interfere with the metabolism of the immunosuppressants, and may put the patient at risk of developing severe adverse effects due to unwanted increase or decrease in the serum levels of immunosuppressive agents. Knowledge of these interactions is essential for successful management of solid organ transplant patients. We therefore decided to review the literature and present the interactions that commonly occur between these two life-saving groups of drugs.

How to cite this article: Bhagat V, Pandit RA, Ambapurkar S, Sengar M, Kulkarni AP. Drug Interactions between Antimicrobial and Immunosuppressive Agents in Solid Organ Transplant Recipients. Indian J Crit Care Med 2021;25(1):67–76.

Initial tacrolimus weight-based dosing strategy in allogeneic hematopoietic stem-cell transplantation

Tacrolimus is a mainstay medication for graft-versus-host disease (GVHD) prophylaxis in combination with other immunosuppressive agents. Achieving therapeutic tacrolimus levels is vital in preventing acute GVHD (aGVHD), while supratherapeutic levels may increase risk of toxicity and relapse. We performed a single center retrospective chart review including all adult patients post-allogeneic hematopoietic stem-cell transplantation who received initial tacrolimus continuous intravenous infusion for GVHD prophylaxis between June 1, 2017 and December 31, 2019. The primary outcome was the percent of patients with an initial therapeutic tacrolimus level, defined as 5-12 ng/mL, after empiric weight-based dosing at 0.02 mg/kg/day. Secondary outcomes included evidence of tacrolimus toxicity within seven days of initiation, incidence of aGVHD by day 100, and relapse after six months. An initial therapeutic level was achieved in 47% of patients with a median initial level of 12.4 ng/mL. Fifty-two percent of patients had supratherapeutic levels. No significant nephrotoxicity, hepatotoxicity, or neurotoxicity occurred within a week of starting tacrolimus or at neutrophil engraftment. Grade II-IV aGVHD by day 100 was observed in 22% of patients, and relapse after six months was found in 16% of patients. These results have led to consideration of an empiric 20% dose reduction to 0.016 mg/kg/day or an expanded initial tacrolimus target of 5-15 ng/mL as there was low aGVHD incidence and no increased risk of toxicity.

The Double-Edged Sword of Immunosuppressive Therapy in Kidney Transplantation: A Rare Case Report of Pulmonary Mucormycosis Post-Transplant and Literature Review

Immunosuppressive therapy is improving the graft survival of kidney transplant recipients and increasing the potential risk of infection. Pulmonary mucormycosis is a rare post-operative infection complication characterized with rapid deterioration and high mortality. In this case, a 33-year-old patient underwent a kidney transplantation with regular immunosuppressive therapy. Soon, 38 days post-transplant, pulmonary patchy shadows can be seen in the radiological examination and rounded into a large cavity formation with splenic rupture 25 days later. The diagnosis of mucormycosis was confirmed by lung biopsy and spleen histopathology. This case is a reminder that early diagnosis is imperative, meanwhile, rational antifungal therapy, timely elimination of immunosuppressants, and alternatively, abandoning the graft should be prudently assessed in the treatment of mucormycosis.

Optimal oral cyclosporin dosing with concomitant posaconazole post allogeneic stem cell transplantation

Cyclosporin is an immunosuppressive agent in allogeneic hematopoietic stem cell transplantation and its metabolism is strongly affected by concomitant drugs, including posaconazole which is now extensively used as anti-fungal prophylaxis post-allograft. We undertook a retrospective audit of 29 patients undergoing their first allograft who were receiving posaconazole at the time of transition from intravenous to oral cyclosporin. This group had a median initial oral cyclosporin dose of 2.58 mg/kg bd (range 1.75-3.95) and high incidence of cyclosporin-related toxicity was noted, requiring significant dose reductions such that by day 60 the media dose was 1.60 mg/kg bd (range 0.86-3.33). We subsequently amended our dosing protocol and analyzed a further 20 patients specifying an initial oral cyclosporin dose of 2.25 mg/kg bd and found this had little impact on toxicity or requirement for dose reductions. Starting doses of no greater than 2 mg/kg bd appear optimal to prevent toxicity in allograft recipients receiving concomitant posaconazole.

Clinical Pharmacokinetics and Dose Recommendations for Posaconazole in Infants and Children

Objectives

The objectives of this study were to investigate the population pharmacokinetics of posaconazole in immunocompromised children, evaluate the influence of patient characteristics on posaconazole exposure and perform simulations to recommend optimal starting doses.

Methods

Posaconazole plasma concentrations from paediatric patients undergoing therapeutic drug monitoring were extracted from a tertiary paediatric hospital database. These were merged with covariates collected from electronic sources and case-note reviews. An allometrically scaled population-pharmacokinetic model was developed to investigate the effect of tablet and suspension relative bioavailability, nonlinear bioavailability of suspension, followed by a step-wise covariate model building exercise to identify other important sources of variability.

Results

A total of 338 posaconazole plasma concentrations samples were taken from 117 children aged 5 months to 18 years. A one-compartment model was used, with tablet apparent clearance standardised to a 70-kg individual of 15 L/h. Suspension was found to have decreasing bioavailability with increasing dose; the estimated suspension dose to yield half the tablet bioavailability was 99 mg/m². Diarrhoea and proton pump inhibitors were also associated with reduced suspension bioavailability.

Conclusions

In the largest population-pharmacokinetic study to date in children, we have found similar covariate effects to those seen in adults, but low bioavailability of suspension in patients with diarrhoea or those taking concurrent proton pump inhibitors, which may in particular limit the use of posaconazole in these patients.

Electronic supplementary material

The online version of this article (10.1007/s40262-018-0658-1) contains supplementary material, which is available to authorized users.

Case Report: Paracoccidioidomycosis in Solid Organ Transplantation: Disseminated Disease in a Liver Recipient and Literature Review

Paracoccidioidomycosis (PCM) is an endemic systemic mycosis that is of great importance in Latin America. Its occurrence in solid organ transplantation (SOT) is rare, but with high mortality rate. In this report, we describe a case of PCM in a liver transplant recipient 19 months after transplantation. The patient presented with multiple skin abscesses, arthritis, osteolytic lesions, and pulmonary and adrenal involvement. Despite the presence of disseminated disease and the patient's immunosuppressed condition, the patient responded well to prolonged antifungal treatment with no sequelae, thus suggesting that early diagnosis and correct treatment may lead to favorable outcomes in SOT recipients with PCM.

Clinical Pharmacokinetics of Second-Generation Triazoles for the Treatment of Invasive Aspergillosis and Candidiasis

Second-generation triazoles were developed in response to the quest for more efficacious and safer therapeutic options for the treatment of severe systemic aspergillosis and candidiasis. These agents include voriconazole, posaconazole, isavuconazole, and ravuconazole. The aim of this review was to present and compare the pharmacokinetic characteristics of second-generation triazoles for the treatment of invasive aspergillosis and candidiasis, emphasizing their clinical implications. The MEDLINE, Scopus, EBSCO, Google Scholar, and SCIndeks databases were searched using advanced search options, including the names of second-generation triazoles and pharmacokinetic terms as keywords. The intravenous administration of voriconazole, posaconazole, and isavuconazole results in stable pharmacokinetics of these drugs, with mostly predictable variations influenced by common and usually known factors in routine clinical settings. The high oral bioavailability of isavuconazole and, to some extent, voriconazole makes them suitable for intravenous-to-oral switch strategies. Except for intravenous voriconazole (due to the accumulation of the toxic vehicle hydroxypropyl betadex), dose reduction of second-generation triazoles is not needed in patients with renal failure; patients with hepatic insufficiency require dose reduction only in advanced disease stages. The introduction of therapeutic drug monitoring could aid attempts to optimize the blood concentrations of triazoles and other drugs that are known to or that possibly interact, thus increasing treatment efficacy and safety. There is a need for new studies that are designed to provide useful data on second-generation triazole pharmacokinetics, particularly in special circumstances such as central nervous system and ocular infections, infections in newborns and infants, and in subjects with genetic polymorphisms of metabolizing enzymes.

Interactions between anti-infective agents and immunosuppressants-Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These updated guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation provide an update on potential drug-drug interactions between anti-infectives and immunosuppressants, which are most notable with calcineurin and mTOR inhibitors. Drug-drug interactions may occur through pharmacokinetic mechanisms leading to altered drug concentrations of either the anti-infective or immunosuppressive drug, or by pharmacodynamic interactions increasing or decreasing the efficacy or toxicity of the medications. Many of the significant pharmacokinetic interactions occur through inhibition or induction of the cytochrome 3A4 system by anti-infective agents leading to increased or decreased immunosuppressive agent levels, respectively. The membrane transporter P-glycoprotein is also often involved in drug interactions. Since the last iteration of these guidelines, multiple new hepatitis C virus direct-acting antivirals have become available for use in SOT recipients. Of these agents, some are substrates of cytochrome and drug transporter systems, while others inhibit these systems and may affect immunosuppressive agents. Due to the high risk for drug-drug interactions in the solid organ transplant population, practitioners must be aware of potential interactions and be vigilant in monitoring and adjusting drug dosing when appropriate.

The impact of initiating posaconazole on tacrolimus pharmacokinetics in allogeneic stem cell transplantation

Background

Posaconazole reduces the risk of invasive Aspergillus in transplant patients, but significantly inhibits tacrolimus metabolism. One study demonstrated that a three-fold dose reduction of tacrolimus was required to obtain therapeutic concentrations when used with posaconazole. However, with empiric dose reduction, there is a risk of subtherapeutic tacrolimus levels and subsequent graft failure or graft-versus-host disease. Overall, the existing data on the impact of posaconazole on tacrolimus pharmacokinetics is limited.

Objective

The purpose of this study is to determine whether tacrolimus doses should be decreased upon initiation of posaconazole in patients receiving an allogeneic stem cell transplant.

Methods

This is a retrospective chart review at an academic medical center. All allogeneic stem cell transplant adults who received concomitant posaconazole and tacrolimus from February 2016 through December 2017 were included.

Results

Seventy-nine patients identified using an internal electronic database were analyzed. The median time to therapeutic tacrolimus concentration was significantly longer in patients who did not receive an empiric dose reduction (0% DR, 10d; 1–30% DR, 4d; 31–65% DR, 5d; >65% DR, 4d; p = 0.0395). The rate of supratherapeutic levels was highest amongst patients who did not receive an empiric DR, and was noted to be significant compared to the group that had 31–65% DR ( p < 0.001).

Conclusion

This study validates our current practice of instituting an empiric 50% dose reduction of oral tacrolimus to 0.03 mg/kg/day when used concomitantly with posaconazole to achieve therapeutic levels in allogeneic stem cell transplant patients.

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

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

Endemic Mycoses in Solid Organ Transplant Recipients

The endemic mycoses are a group of thermally dimorphic fungal pathogens occupying a specific geographic range. In North America, the chief endemic mycoses are histoplasmosis, coccidioidomycosis, and blastomycosis. Endemic fungi can cause serious infections in solid organ transplant recipients from primary infection, reactivation of latent disease, or donor-derived infection.

Analysis of Clinical Drug-Drug Interaction Data To Predict Magnitudes of Uncharacterized Interactions between Antiretroviral Drugs and Comedications

Despite their high potential for drug-drug interactions (DDI), clinical DDI studies of antiretroviral drugs (ARVs) are often lacking, because the full range of potential interactions cannot feasibly or pragmatically be studied, with some high-risk DDI studies also being ethically difficult to undertake. Thus, a robust method to screen and to predict the likelihood of DDIs is required. We developed a method to predict DDIs based on two parameters: the degree of metabolism by specific enzymes, such as CYP3A, and the strength of an inhibitor or inducer. These parameters were derived from existing studies utilizing paradigm substrates, inducers, and inhibitors of CYP3A to assess the predictive performance of this method by verifying predicted magnitudes of changes in drug exposure against clinical DDI studies involving ARVs. The derived parameters were consistent with the FDA classification of sensitive CYP3A substrates and the strength of CYP3A inhibitors and inducers. Characterized DDI magnitudes (n = 68) between ARVs and comedications were successfully quantified, meaning 53%, 85%, and 98% of the predictions were within 1.25-fold (0.80 to 1.25), 1.5-fold (0.66 to 1.48), and 2-fold (0.66 to 1.94) of the observed clinical data. In addition, the method identifies CYP3A substrates likely to be highly or, conversely, minimally impacted by CYP3A inhibitors or inducers, thus categorizing the magnitude of DDIs. The developed effective and robust method has the potential to support a more rational identification of dose adjustment to overcome DDIs, being particularly relevant in an HIV setting, given the treatment's complexity, high DDI risk, and limited guidance on the management of DDIs.

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.

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.

Infection in Organ Transplantation

The prevention, diagnosis, and management of infectious disease in transplantation are major contributors to improved outcomes in organ transplantation. The risk of serious infections in organ recipients is determined by interactions between the patient's epidemiological exposures and net state of immune suppression. In organ recipients, there is a significant incidence of drug toxicity and a propensity for drug interactions with immunosuppressive agents used to maintain graft function. Thus, every effort must be made to establish specific microbiologic diagnoses to optimize therapy. A timeline can be created to develop a differential diagnosis of infection in transplantation based on common patterns of infectious exposures, immunosuppressive management, and antimicrobial prophylaxis. Application of quantitative molecular microbial assays and advanced antimicrobial therapies have advanced care. Pathogen-specific immunity, genetic polymorphisms in immune responses, and dynamic interactions between the microbiome and the risk of infection are beginning to be explored. The role of infection in the stimulation of alloimmune responses awaits further definition. Major hurdles include the shifting worldwide epidemiology of infections, increasing antimicrobial resistance, suboptimal assays for the microbiologic screening of organ donors, and virus-associated malignancies. Transplant infectious disease remains a key to the clinical and scientific investigation of organ transplantation.

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Posaconazole, systemic antifungal marketed in France since 2006, is indicated as second line in curative treatment of invasive fungal infections (IFI) (aspergillosis. . . ) and prophylaxis of IFI in patients receiving chemotherapy or hematopoietic stem cell transplantation. The analysis of the literature indicates a concentration-efficacy relationship, but to date, no study has been able to show a concentration-toxicity correlation due to its favourable safety profile and the difficulty to obtain high concentrations. In curative, maintenance of trough plasma concentrations between 0.5 and 1.5 mg/L seems to be associate with an efficacy. In prophylaxis, a threshold of 0.5 mg/L corresponds to a minimal exposure. However this target is not yet well defined. Saturation of absorption above the 800 mg oral dose limits the adjustment of concentrations. As such, the Therapeutic Drug Monitoring of posaconazole can be recommended.

Pharmacologic and clinical evaluation of posaconazole

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. There is evidence of efficacy in the treatment and prevention of rarer, more difficult-to-treat fungal infections. Posaconazole oral suspension solution has shown limitations with respect to fasting state absorption, elevated gastrointestinal pH and increased motility. The newly approved delayed-release oral tablet and intravenous solution formulations provide an attractive treatment option by reducing interpatient variability and providing flexibility in critically ill patients. On the basis of clinical experience and further clinical studies, posaconazole was found to be a valuable pharmaceutical agent for the treatment of life-threatening fungal infections. This review will examine the development history of posaconazole and highlight the most recent advances.

Posaconazole: An Update of Its Clinical Use

Posaconazole (PCZ) is a relatively new addition to the azole antifungals. It has fungicidal activities against Aspergillus fumigatus, Blastomyces dermatitidis, selected Candida species, Crytopcoccus neoformans, and Trichosporon. PCZ also has fungistatic activities against Candida, Coccidioides, selected Fusarium spp., Histoplasma, Scedosporium and Zygomycetes. In addition, combining the drug with caspofungin or amphotericin B results in a synergistic interaction against A. fumigatus, C. glabrata and C. neoformans. The absorption of PCZ suspension is enhanced when given with food, nutritional supplements, and carbonated beverages. Oral administration of PCZ in divided doses also increases its bioavailability. PCZ has a large volume of distribution and is highly protein bound (>95%). The main elimination route of PCZ is fecal. PCZ is an inhibitor of the CYP3A4 enzyme; therefore, monitoring for drug-drug interactions is warranted with other CYP3A4 substrates/inhibitors/inducers. The most common adverse effects include headache, fatigue, nausea, vomiting and elevated hepatic enzymes. PCZ, with its unique antifungal activities, expands the azole class of antifungal agents. Because of its limit in formulation, PCZ oral suspension is recommended in immunocompromised patients with functional gastrointestinaltracts who fail conventional antifungal therapies or who are suspected to have a breakthrough fungal infection. However, a delayed-release tablet formulation and intravenous (IV) injection became available in 2014, expanding the use of PCZ in other patient populations, including individuals who are unable to take oral formulations.

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.

Therapeutic drug monitoring for triazoles: A needs assessment review and recommendations from a Canadian perspective

Invasive fungal infections cause significant morbidity and mortality in patients with concomitant underlying immunosuppressive diseases. The recent addition of new triazoles to the antifungal armamentarium has allowed for extended-spectrum activity and flexibility of administration. Over the years, clinical use has raised concerns about the degree of drug exposure following standard approved drug dosing, questioning the need for therapeutic drug monitoring (TDM). Accordingly, the present guidelines focus on TDM of triazole antifungal agents. A review of the rationale for triazole TDM, the targeted patient populations and available laboratory methods, as well as practical recommendations based on current evidence from an extended literature review are provided in the present document.