Effect of highly active antiretroviral therapy on tacrolimus pharmacokinetics in hepatitis C virus and HIV co-infected liver transplant recipients in the ANRS HC-08 study

Drug Interactions and Safe Prescription Writing for Liver Transplant Recipients

Immunosuppression optimization is central to graft function in liver transplant recipients. Post-transplantation patients develop new onset or worsening metabolic syndrome, are prone to atypical infections, and are at higher risk of developing cardiac and brain-related clinical events. In this context, liver transplant recipients are at risk of using multiple comedications alongside immunosuppressants. It is imperative for the transplant physician to understand the various drug-drug interactions that potentially reduce or promote toxicity of immunosuppression, as well as associated synergistic or antagonistic effects on extrahepatic organ systems. This comprehensive review discusses drug-drug interactions in liver transplant recipients and the impact and role of complementary and alternative medicines among individuals on immunosuppression.

Pharmacotherapeutic Interventions in People Living With HIV Undergoing Solid Organ Transplantation: A Scoping Review

The pharmacotherapeutic management of people living with HIV (PLWHIV) undergoing solid organ transplantation (SOT) is clinically challenging, mainly due to the frequent occurrence of complex drug-drug interactions. Although various strategies have been proposed to improve treatment outcomes in these patients, several uncertainties remain, and consensus practice guidelines are just beginning to emerge. The main objective of this scoping review was to map the extent of the literature on the pharmacotherapeutic interventions performed by healthcare professionals for PLWHIV undergoing SOT.

Methods

We searched Medline, Embase, and the Cochrane databases as well as gray literature for articles published between January 2010 and February 2020. Study selection was performed by at least 2 independent reviewers. Articles describing pharmacotherapeutic interventions in PLWHIV considered for or undergoing SOT were included in the study.

Results

Of the 12 599 references identified through our search strategy, 209 articles met the inclusion criteria. Results showed that the vast majority of reported pharmacotherapeutic interventions concerned the management of immunosuppressive and antimicrobial therapy, including antiretrovirals. Analysis of the data demonstrated that for several aspects of the pharmacotherapeutic management of PLWHIV undergoing SOT, there were differing practices, such as the choice of immunosuppressive induction and maintenance therapy. Other important aspects of patient management, such as patient counseling, were rarely reported.

Conclusions

Our results constitute an extensive overview of current practices in the pharmacotherapeutic management of SOT in PLWHIV and identify knowledge gaps that should be addressed to help improve patient care in this specific population.

Nirmatrelvir/ritonavir Use With Tacrolimus in Lung Transplant Recipients: A Single-center Case Series

BACKGROUND

Limited data and guidelines exist for using nirmatrelvir/ritonavir in solid organ transplant recipients stabilized on tacrolimus for the treatment of mild-to-moderate coronavirus disease. Concern exists regarding the impact of utilizing a 5-d course of nirmatrelvir/ritonavir with calcineurin inhibitors because of significant drug-drug interactions between ritonavir, a potent cytochrome P450 3A inhibitor, and other cytochrome P450 3A substrates, such as tacrolimus.

METHODS

We report the successful use of nirmatrelvir/ritonavir in 12 outpatient lung transplant recipients with confirmed severe acute respiratory syndrome coronavirus 2 infection stabilized on tacrolimus immunosuppression. All patients stopped tacrolimus and started nirmatrelvir/ritonavir 10 to 14 h after the last dose of tacrolimus. Tacrolimus was withheld and then reinitiated at a modified dose 48 h following the completion of nirmatrelvir/ritonavir therapy. Tacrolimus trough levels were checked during nirmatrelvir/ritonavir therapy and tacrolimus reinitiation.

RESULTS

Ten (10/12) patients were able to resume their original tacrolimus dose within 4 d of completing nirmatrelvir/ritonavir therapy and maintain therapeutic levels of tacrolimus. No patients experienced tacrolimus toxicity or acute rejection during the 30-d postcompletion of nirmatrelvir/ritonavir therapy.

CONCLUSIONS

In this cohort of lung transplant recipients on tacrolimus, we demonstrated that nirmatrelvir/ritonavir can be safely used with close monitoring of tacrolimus levels and appropriate dose adjustments of tacrolimus. Further confirmatory studies are needed to determine the appropriate use of therapeutic drug monitoring and tacrolimus dose following completion of nirmatrelvir/ritonavir in the solid organ transplant population.

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.

Predictors of tacrolimus pharmacokinetic variability: current evidences and future perspectives

INTRODUCTION

In kidney transplantation, tacrolimus (TAC) is at the cornerstone of current immunosuppressive strategies. Though because of its narrow therapeutic index, it is critical to ensure that TAC levels are maintained within this sharp window through reactive adjustments. This would allow maximizing efficiency while limiting drug-associated toxicity. However, TAC high intra- and inter-patient pharmacokinetic (PK) variability makes it more laborious to accurately predict the appropriate dosage required for a given patient.

AREAS COVERED

This review summarizes the state-of-the-art knowledge regarding drug interactions, demographic and pharmacogenetics factors as predictors of TAC PK. We provide a scoring index for each association to grade its relevance and we present practical recommendations, when possible for clinical practice.

EXPERT OPINION

The management of TAC concentration in transplanted kidney patients is as critical as it is challenging. Recommendations based on rigorous scientific evidences are lacking as knowledge of potential predictors remains limited outside of DDIs. Awareness of these limitations should pave the way for studies looking at demographic and pharmacogenetic factors as well as gut microbiota composition in order to promote tailored treatment plans. Therapeutic approaches considering patients' clinical singularities may help allowing to maintain appropriate concentration of TAC.

Comparison of the effect of direct-acting antiviral with and without ribavirin on cyclosporine and tacrolimus clearance values: results from the ANRS CO23 CUPILT cohort

PURPOSE

Direct-acting antiviral agents have demonstrated their efficacy in treating HCV recurrence after liver transplantation and particularly the sofosbuvir/daclatasvir combination. Pharmacokinetic data on both calcineurin inhibitors and direct-acting antiviral exposure in liver transplant recipients remain sparse.

METHODS

Patients were enrolled from the ANRS CO23 CUPILT cohort. All patients treated with sofosbuvir/daclatasvir with or without ribavirin were included in this study when blood samples were available to estimate the clearance of immunosuppressive therapy before direct-acting antiviral initiation and during follow-up. Apparent tacrolimus and cyclosporine clearances were estimated from trough concentrations measured using validated quality control assays.

RESULTS

Sixty-seven mainly male patients (79%) were included, with a mean age of 57 years and mean MELD score of 8.2; 50 were on tacrolimus, 17 on cyclosporine. Ribavirin was combined with sofosbuvir/daclatasvir in 52% of patients. Cyclosporine clearance remained unchanged as well as tacrolimus clearance under the ribavirin-free regimen. Tacrolimus clearance increased 4 weeks after direct-acting antivirals and ribavirin initiation versus baseline (geometric mean ratio 1.81; 90% CI 1.30-2.52). Patients under ribavirin had a significantly higher fibrosis stage (> 2) (p = 0.02) and lower haemoglobin during direct-acting antiviral treatment (p = 0.02) which impacted tacrolimus measurements. Direct-acting antiviral exposure was within the expected range.

CONCLUSION

Our study demonstrated that liver transplant patients with a recurrence of hepatitis C who are initiating ribavirin combined with a sofosbuvir-daclatasvir direct-acting antiviral regimen may be at risk of lower tacrolimus concentrations because of probable ribavirin-induced anaemia and higher fibrosis score, although there are no effects on cyclosporine levels.

TRIAL REGISTRATION

NCT01944527.

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.

Combination Drug Products for HIV-A Word of Caution for the Transplant Clinician

Modern-day treatment regimens for human immunodeficiency virus (HIV) are not only highly effective, but are now more often available as convenient fixed-dose combination products. Furthermore, as medication adherence is of utmost importance in this setting, national guidelines endorse the use of such products. Transplant providers of HIV-infected patients will undoubtedly encounter these products, some of which contain medications known to drastically alter the metabolism of certain immunosuppressants. Herein, we describe an instance of drug interaction-induced calcineurin inhibitor (CNI) nephrotoxicity in a renal transplant recipient being started on a cobicistat-containing combination product for HIV. CNI toxicity, in turn, was resolved with the aid of phenytoin as an inducer of drug metabolism. This case underscores the importance of familiarity with newer combination products on the market and constant communication with HIV-positive transplant recipients and their providers.

Liver transplantation for hepatitis C virus in the era of direct-acting antiviral agents

PURPOSE OF REVIEW

Liver transplantation is widely used to treat HIV patients with an end-stage liver disease, mainly decompensated cirrhosis and hepatocellular carcinoma. The results are good especially in non-hepatitis C virus (HCV)-coinfected patients. In HIV-HCV-coinfected patients, 5-year post-liver transplantation survival is around 50-55%, negatively impacted by HCV recurrence. The results of PEG-IFN/RBV are poor in terms of efficacy and safety. In patients with genotype 1 infection, triple therapy (boceprevir or telaprevir) has increased sustained virological response (SVR) rate, but drug-drug interactions (DDIs) with immunosuppressive agents and high rates of adverse events lead to forsake these combinations. Herein, we provide new data and practical management regarding HIV-HCV liver transplantation patients using new direct-acting antiviral agents (DAA).

RECENT FINDINGS

The second-generation DAA have good safety profile. In patients who are candidates for liver transplantation or are already recipients, the optimal therapeutic option is to combine the new DAA. Efficacy results have dramatically improved with greater than 90% of SVR rate in many studies enrolling HCV-monoinfected liver transplant recipients. Some concerns persist in terms of DDI.

SUMMARY

Even sparse, data regarding efficacy and safety of these regimens in HCV-HIV-coinfected liver transplantation will radically change the prognosis of this peculiar population.

Drug interactions and antiretroviral drug monitoring

Owing to the improved longevity afforded by combination antiretroviral therapy (cART), HIV-infected individuals are developing several non-AIDS-related comorbid conditions. Consequently, medical management of the HIV-infected population is increasingly complex, with a growing list of potential drug-drug interactions (DDIs). This article reviews some of the most relevant and emerging potential interactions between antiretroviral medications and other agents. The most common DDIs are those involving protease inhibitors or non-nucleoside reverse transcriptase inhibitors, which alter the cytochrome P450 enzyme system and/or drug transporters such as p-glycoprotein. Of note are the new agents for the treatment of chronic hepatitis C virus infection. These new classes of drugs and others drugs that are increasingly used in this patient population represent a significant challenge with regard to achieving the goals of effective HIV suppression and minimization of drug-related toxicities. Awareness of DDIs and a multidisciplinary approach are imperative in reaching these goals.

Antiretroviral blood levels in HIV/HCV-coinfected patients with cirrhosis after liver transplant: a report of three cases

Since the introduction of combined antiretroviral therapy, human immunodeficiency virus (HIV) infection is no longer a contraindication for solid organ transplantation. In HIV/hepatitis C virus (HCV)-coinfected patients undergoing liver transplantation, HCV-related cirrhosis, drug-drug interactions, and calcineurin inhibitors-related toxicity affect clinical outcomes. Therapeutic drug monitoring can be useful to assess antiretroviral over- or underexposure in this cohort. We report the clinical characteristics along with antiretroviral trough levels of maraviroc, darunavir, and etravirine in 3 HIV/HCV-coinfected liver transplant recipients who developed post-transplant liver cirrhosis.

Lack of drug interaction between cyclosporine and telaprevir in a liver transplant recipient

Telaprevir is a novel NS3A/4A protease inhibitor approved in combination with ribavirin and peg-interferon alfa for the treatment of genotype-1 chronic hepatitis C. This drug is also known to be a potent cytochrome P450 3A and drug efflux protein ATP-binding cassette B1 (also called P-glycoprotein) inhibitor, and could therefore interact with immunosuppressive drugs. For this reason, a decrease in cyclosporine (CsA) dosage has been proposed when combining this drug with telaprevir. We report herein the case of an unpredictable lack of interaction between CsA and telaprevir in a liver transplant recipient. The decrease in CsA dosage, conducted as recommended in the literature, did not result in stable CsA concentrations but decreased them. However, the decrease in CsA exposure could have been unseen without the measurement of CsA concentrations 2 h after the administration (C2 ) of the drug, because it mainly resulted from the decrease in CsA peak. The mechanism leading to this lack of drug interaction in this patient has not been fully elucidated yet, but is likely to affect the absorption phase. Therapeutic drug monitoring using only CsA trough concentrations could be falsely reassuring, and the addition of the measurement of the C2 may add useful information to adapt CsA dosage in patients co-treated with telaprevir.

Clinical practice guideline for the management of chronic kidney disease in patients infected with HIV: 2014 update by the HIV Medicine Association of the Infectious Diseases Society of America

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. IDSA 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.

Best single time point correlations with AUC for cyclosporine and tacrolimus in HIV-infected kidney and liver transplant recipients

BACKGROUND

Interactions between antiretrovirals (ARVs) and transplant immunosuppressant agents (IS) among HIV-infected transplant recipients may lead to lack of efficacy or toxicity. In transplant recipients not infected with HIV, tacrolimus (TAC) trough levels (C0) or cyclosporine (CsA) drawn at C0 or 2 hours after dosing (C2) correlate with drug exposure (area under the curve [AUC]/dose) and outcomes. Because of ARV-IS interactions in HIV-infected individuals, and the high rate of rejection in these subjects, this study investigated the correlations between IS concentrations and exposure to determine the best method to monitor immunosuppressant levels.

METHODS

This study prospectively studied 50 HIV-infected transplant recipients undergoing kidney or liver transplantation evaluating the pharmacokinetics of the IS in 150 studies over time after transplantation (weeks 2 to 4, 12, 28, 52, and 104). IS levels were measured with liquid chromatography-tandem mass spectrometry and AUC calculated using WinNonlin 9.0. Correlation analyses were run on SAS 9.2.

RESULTS

CsA concentration at C4 correlated better with AUC than C0 or C2, and over time TAC concentration correlated better at C0 or C2.

CONCLUSIONS

It is suggested that C0 is acceptable for TAC monitoring, but poor predictability will occur at C0 with CsA. The low correlation of C0 with CsA AUC could be responsible for the higher rejection rates on CsA that has been reported in these subjects.

Pharmacokinetic interaction between the hepatitis C virus protease inhibitor boceprevir and cyclosporine and tacrolimus in healthy volunteers

The hepatitis C virus protease inhibitor boceprevir is a strong inhibitor of cytochrome P450 3A4 and 3A5 (CYP3A4/5). Cyclosporine and tacrolimus are calcineurin inhibitor immunosuppressants used to prevent organ rejection after liver transplantation; both are substrates of CYP3A4. This two-part pharmacokinetic interaction study evaluated boceprevir with cyclosporine (part 1) and tacrolimus (part 2). In part 1, 10 subjects received single-dose cyclosporine (100 mg) on day 1, single-dose boceprevir (800 mg) on day 3, and concomitant cyclosporine/boceprevir on day 4. After washout, subjects received boceprevir (800 mg three times a day) for 7 days plus single-dose cyclosporine (100 mg) on day 6. In part 2A, 12 subjects received single-dose tacrolimus (0.5 mg). After washout, they received boceprevir (800 mg three times a day) for 11 days plus single-dose tacrolimus (0.5 mg) on day 6. In part 2B, 10 subjects received single-dose boceprevir (800 mg) and 24 hours later received boceprevir (800 mg) plus tacrolimus (0.5 mg). Coadministration of boceprevir with cyclosporine/tacrolimus was well tolerated. Concomitant boceprevir increased the area under the concentration-time curve from time 0 to infinity after single dosing (AUC(inf) ) and maximum observed plasma (or blood) concentration (C(max) ) of cyclosporine with geometric mean ratios (GMRs) (90% confidence interval [CI]) of 2.7 (2.4-3.1) and 2.0 (1.7-2.4), respectively. Concomitant boceprevir increased the AUC(inf) and C(max) of tacrolimus with GMRs (90% CI) of 17 (14-21) and 9.9 (8.0-12), respectively. Neither cyclosporine nor tacrolimus coadministration had a meaningful effect on boceprevir pharmacokinetics.

CONCLUSION

Dose adjustments of cyclosporine should be anticipated when administered with boceprevir, guided by close monitoring of cyclosporine blood concentrations and frequent assessments of renal function and cyclosporine-related side effects. Administration of boceprevir plus tacrolimus requires significant dose reduction and prolongation of the dosing interval for tacrolimus, with close monitoring of tacrolimus blood concentrations and frequent assessments of renal function and tacrolimus-related side effects.

Drug-drug interactions between antiretroviral and immunosuppressive agents in HIV-infected patients after solid organ transplantation: a review

Since the introduction of combination antiretroviral therapy (cART) resulting in the prolonged survival of HIV-infected patients, HIV infection is no longer considered to be a contraindication for solid organ transplantation (SOT). The combined management of antiretroviral and immunosuppressive therapy proved to be extremely challenging, as witnessed by high rates of allograft rejection and drug toxicity, but the profound drug-drug interactions between immunosuppressants and cART, especially protease inhibitors (PIs) also play an important role. Caution and frequent drug level monitoring of calcineurin inhibitors, such as tacrolimus are necessary when PIs are (re)introduced or withdrawn in HIV-infected recipients. Furthermore, the pharmacokinetics of glucocorticoids and mTOR inhibitors are seriously affected by PIs. With the introduction of integrase inhibitors, CCR5-antagonists and fusion inhibitors which cause significantly less pharmacokinetic interactions, have minor overlapping toxicity, and offer the advantage of pharmacodynamic synergy, it is time to revaluate what may be considered the optimal antiretroviral regimen in SOT recipients. In this review we provide a brief overview of the recent success of SOT in the HIV population, and an update on the pharmacokinetic and pharmacodynamic interactions between currently available cART and immunosuppressants in HIV-infected patients, who underwent SOT.

Practical management of boceprevir and immunosuppressive therapy in liver transplant recipients with hepatitis C virus recurrence

Hepatitis C virus (HCV) recurrence is the most important complication in HCV liver transplant patients. Boceprevir with pegylated interferon and ribavirin (PegIFN/RBV) enabled improvement in sustained virological response rates of patients with genotype 1 HCV. Boceprevir interacts with immunosuppressive therapy (IT) by inhibiting the cytochrome P450 3A enzyme. Our aim was to study interactions and assess the safety of boceprevir in the context of HCV recurrence. Boceprevir (800 mg three times a day) initiated after a 4-week lead-in phase was associated with cyclosporine (three patients), tacrolimus (two patients), and everolimus (one patient) in five liver transplant patients with genotype 1 HCV infection who experienced HCV recurrence. The mean follow-up period after HCV therapy was 14.8 ± 3.1 weeks. Estimated oral clearances of IT decreased on average by 50%, requiring reduced dosing regimens. Anemia occurred in all patients, with a mean fall in hemoglobin levels between baseline and week 12 of 3.12 ± 2.27 g/dl. All patients required administration of β-erythropoietin (n = 5), three needed ribavirin dose reduction, and one needed a blood transfusion. A virological response was observed in all patients (mean HCV viral load [HVL] decrease at week 12, 6.64 ± 0.35 log(10) IU/ml). These preliminary results in liver transplant patients with HCV recurrence demonstrate the feasibility and safety of coadministration of boceprevir and IT.

Review and management of drug interactions with boceprevir and telaprevir

Boceprevir (BOC) and telaprevir (TPV), when added to pegylated interferon and ribavirin for the treatment of chronic hepatitis C virus (HCV) infection, increase the rates of sustained virologic response in treatment-naïve persons to approximately 70%. Though these agents represent an important advance in the treatment of chronic HCV, they present new treatment challenges to the hepatology community. BOC and TPV are both substrates and inhibitors of the hepatic enzyme, cytochrome P450 3A, and the drug transporter, P-glycoprotein, which predisposes these agents to many drug interactions. Identification and appropriate management of potential drug interactions with TPV and BOC is critical for optimizing therapeutic outcomes during hepatitis C treatment. This review highlights the pharmacologic characteristics and drug-interaction potential of BOC and TPV and provides guidance on the management of drug interactions with these agents.

Hepatitis C virus treatment pre- and post-liver transplantation

Liver disease caused by the hepatitis C virus is the main indication for liver transplantation in Western countries. However, HCV re-infection post-transplantation is constant and recent data confirm that it significantly impairs patient and graft survival. Chronic HCV infection develops in 75-90% of patients, and 5-30% ultimately progress to cirrhosis within 5 years. Because of the impact of HCV recurrence on graft and patient survival, several treatment strategies have been evaluated. Antiviral therapy could be administered before transplantation to suppress viral replication and reduce the risk of recurrence. However, this approach is applicable in around 50% of patients and tolerance is poor, particularly in patients with decompensated cirrhosis. Pre-emptive therapy in the early post-transplant period is limited by the high rate of side effects. Frequently, antiviral therapy is initiated when HCV recurs to obtain viral eradication and/or reduce disease progression. Treatment of established graft lesions with Pegylated Interferon (PEG-IFN) and Ribavirin (RBV) combination therapy results in a sustained virological response (SVR) in around 30% of patients. The new classes of potent and direct antiviral agents (DAA) will certainly improve the results of pre- and post-transplant antiviral therapy. However, at the present time, no data are available on the use of these drugs in patients with decompensated cirrhosis or post-transplant hepatitis.

Effect of telaprevir on the pharmacokinetics of cyclosporine and tacrolimus

The hepatitis C virus protease inhibitor telaprevir is an inhibitor of the enzyme cytochrome P450 3A, responsible for the metabolism of both cyclosporine and tacrolimus. This Phase I, open-label, nonrandomized, single-sequence study assessed the effect of telaprevir coadministration on the pharmacokinetics of a single dose of either cyclosporine or tacrolimus in two separate panels of 10 healthy volunteers each. In Part A, cyclosporine was administered alone as a single 100-mg oral dose, followed by a minimum 8-day washout period, and subsequent coadministration of a single 10-mg oral dose of cyclosporine with either a single dose of telaprevir (750 mg) or with steady-state telaprevir (750 mg every 8 hours [q8h]). In Part B, tacrolimus was administered alone as a single 2-mg oral dose, followed by a minimum 14-day washout period, and subsequent coadministration of a single 0.5-mg dose of tacrolimus with steady-state telaprevir (750 mg q8h). Coadministration with steady-state telaprevir increased cyclosporine dose-normalized (DN) exposure (DN_AUC(0-∞)) by approximately 4.6-fold and increased tacrolimus DN_AUC(0-∞) by approximately 70-fold. Coadministration with telaprevir increased the terminal elimination half-life (t(½)) of cyclosporine from a mean (standard deviation [SD]) of 12 (1.67) hours to 42.1 (11.3) hours and t(½) of tacrolimus from a mean (SD) of 40.7 (5.85) hours to 196 (159) hours.

CONCLUSION

In this study, telaprevir increased the blood concentrations of both cyclosporine and tacrolimus significantly, which could lead to serious or life-threatening adverse events. Telaprevir has not been studied in organ transplant patients; its use in these patients is not recommended because the required studies have not been completed to understand appropriate dose adjustments needed for safe coadministration of telaprevir with cyclosporine or tacrolimus, and regulatory approval has not been obtained.

Liver transplant outcomes in HIV-infected patients: a systematic review and meta-analysis with synthetic cohort

OBJECTIVES

The relative success of liver transplantation in those with HIV compared to HIV-uninfected individuals remains a point of intense debate. We aimed to evaluate the effectiveness of liver transplantation in HIV-hepatitis co-infected patients using a meta-analysis and individual patient data meta-analysis as a synthetic cohort.

METHODS

We searched MEDLINE via PubMed, EMBASE, Cochrane CENTRAL, AIDSLINE (inception to 2010), AMED, CINAHL, TOXNET, Development and Reproductive Toxicology, Hazardous Substances Databank, Psych-info and relevant conferences. We included cohort studies and individual case-reports evaluating survival of co-infected transplant patients. We abstracted data on cohort and case demographics and outcomes. We pooled cohorts using a random-effects analysis and created a synthetic cohort of cases using individual patient data. We confirmed this with the pooled cohort analysis.

RESULTS

We included 15 cohort studies and 49 case series with individual patient data. At 12 months, 84.4% [95% confidence interval (CI) 81.1-87.8%] of patients had survived. Within the HIV-infected population evaluated, HIV-hepatitis B virus (HBV) co-infection was associated with optimal survival. In an adjusted model, individuals positive for HBV were 8.28 (95% CI 2.26-30.33) times more likely to survive when compared to those without HBV. Further, individuals with an undetectable HIV viral load at the time of transplantation were 2.89 (95% CI 1.41-5.91) times more likely to survive when compared to those with detectable HIV viremia. Hepatitis C virus was not a predictor of patient survival when adjusted for by other key predictors [0.54 (95% CI 0.17-1.80)].

Liver transplantation in HCV/HIV positive patients

Since the introduction of highly active antiretroviral therapy (HAART) in 1996 for human immunodeficiency virus (HIV)-infected patients, the incidence of liver diseases secondary to co-infection with hepatitis C has increased. Although data on the outcome of liver transplantation in HIV-infected recipients is limited, the overall results to date seem to be comparable to that in non-HIV-infected recipients. Liver transplant centers are now accepting HIV-infected individuals as organ recipients. Post-transplantation HIV replication is controlled by HAART. Hepatitis C re-infection of the liver graft, however, remains an important problem because cirrhotic changes of the liver graft may be more rapid in HIV-infected recipients. Interactions between the HAART components and immunosuppressive drugs influence drug metabolism and therefore meticulous monitoring of drug blood level concentrations is required. The risk of opportunistic infection in HIV-positive transplant patients seems to be similar to that in HIV-negative transplant recipients.

Recipient-based approach to tailoring immunosuppression in liver transplantation

Improvements in the field of transplant immunosuppression (IS) have led to significant advances in long-term survival of liver transplant recipients. Despite this progress, survival rates vary depending on recipient, donor and/or perioperative factors. Tailoring IS based on recipient factors is of growing interest among health care providers involved in the care of organ transplant recipients. To date there is no consensus document addressing individualized IS therapy for liver transplant recipients. This review will discuss the information available on the effect of the various IS drugs on recipient-based factors such as age, ethnicity, and liver disease etiology.

Daily dosing of tacrolimus in patients treated with HIV-1 therapy containing a ritonavir-boosted protease inhibitor or raltegravir

OBJECTIVES

The number of HIV-infected patients receiving orthotopic liver transplantation (OLTX) is increasing. One major challenge is the severe drug-drug interactions between immunosuppressive drugs such as tacrolimus and ritonavir-boosted HIV-1 protease inhibitors (PIs). The introduction of raltegravir, which is not metabolized by the cytochrome system, may allow concomitant treatment without dose adaptation.

PATIENTS AND METHODS

We conducted a retrospective analysis of HIV-1-infected patients receiving tacrolimus concomitantly with different HIV therapies, including 12 h pharmacokinetic assessment of drug levels.

RESULTS

Three OLTX patients received a ritonavir-boosted PI therapy when tacrolimus was added at very low doses of 0.06, 0.03 and 0.08 mg daily. Median tacrolimus blood levels were 6.6, 3.0 and 7.9 ng/mL over a follow-up period of 8, 22 and 33 months, respectively. In two other patients (one after OLTX and one with Crohn's disease), a raltegravir-based HIV therapy was started while patients received 1 or 2 mg of tacrolimus twice daily. No tacrolimus dose adjustment was necessary and drug levels remained unchanged.

CONCLUSIONS

Decreasing the dose of tacrolimus to 0.03-0.08 mg daily in patients with concomitant boosted PI therapy resulted in stable tacrolimus blood levels without alteration of PI drug levels. Concomitant use of raltegravir and tacrolimus revealed no clinically relevant drug interaction.

Liver transplantation in HIV-positive patients

Death from end-stage liver disease (ESLD) because of chronic hepatitis B and C has become an increasing problem in human immunodeficiency virus (HIV)-infected patients in the last years. This is mainly because of the dramatic decrease of HIV-related morbidity and mortality since the introduction of highly active antiretroviral therapy (HAART). Although the data on the outcome of liver transplantation in HIV-infected recipients with ESLD is limited, overall results seem comparable to non-HIV-infected recipients. Therefore, liver transplant centres around the world are increasingly accepting HIV-infected individuals as organ recipients. Post-transplantation control of HIV replication is achieved by continuing HAART. As in non-HIV-infected patients, hepatitis B virus recurrence is efficiently prevented by hepatitis B immunoglobulin and antiviral therapy. Re-infection of the allograft with hepatitis C virus, however, remains an important problem, and progress to allograft cirrhosis may even be more rapid than in HIV-negative patients. Interactions in drug metabolism between the HAART components and the immunosuppressive drugs are difficult to predict and require close monitoring of drug levels and dose adjustments. The complexity in this setting makes close cooperation between transplant surgeons, hepatologists, HIV-clinicians and pharmacologists mandatory. As experience on liver transplantation in HIV-infected individuals is still limited, to date results from large prospective trials addressing key issues are needed.

Preservation of immune function and anti-hepatitis C virus (HCV) immune responses after liver transplantation in HIV-HCV coinfected patients (ANRS-HC08 "THEVIC" trial)

BACKGROUND/AIMS

Liver transplantation (LT) in immune-suppressed human immunodeficiency virus (HIV) and hepatitis C virus (HCV) coinfected patients is feasible but raises questions regarding the severity of HCV recurrence on the liver graft and preservation of immune function. We investigated whether LT is deleterious to the immune system.

METHODS

Fourteen HIV-HCV coinfected patients (HIV viral load [VL] <50 copies/ml; median CD4 count of 276/mm(3) pretransplantation) were grafted for HCV-cirrhosis and followed over 2 years. Nine patients received anti-HCV therapy post-transplantation. HCV and HIV VLs and degree of acute and chronic hepatitis were monitored. Peripheral blood T-cell phenotypes and interferon-gamma (IFN-gamma) immune responses against opportunistic pathogens, HCV, and HIV-1 p24 were evaluated.

RESULTS

Median HCV VLs, CD4 counts, T-cell subsets, and IFN-gamma-producing T-cell frequencies against opportunistic pathogens and HIV-1 p24 did not change over time. HCV-specific T cells were observed ex vivo in two patients pretransplantation and in two others post-transplantation. HCV-specific in vitro amplification enabled the detection of HCV-specific IFN-gamma-producing responses in three further patients post-transplantation. Anti-HCV responses were observed independently of anti-HCV therapy and were undetectable in patients with severe hepatitis or liver fibrosis.

CONCLUSIONS

These results demonstrate that LT in HIV-HCV coinfected patients is not deleterious to the immune system and does not alter immune responses directed against HCV, HIV, or opportunistic pathogens.

Drug interactions in transplant patients: what everyone should know

PURPOSE OF REVIEW

Adverse events due to drug-drug interactions remain a challenge in the postsurgical care of transplant recipients. A combination of potent and selective immunosuppressive drugs, which have a narrow therapeutic index, with medications for the treatment of comorbidities such as dyslipidemia, infection, psychiatric conditions, and hypertension, can lead to life-threatening drug-drug interactions.

RECENT FINDINGS

There are a number of important drug-drug interactions which are important for physicians to consider. It is critical to understand the pharmacodynamics and pharmacokinetics of drug-drug interactions, their potential impact on patient care, and the management strategies.

SUMMARY

Close therapeutic drug monitoring and evaluation of drug-specific side effects continue to be an important key to minimize adverse events due to drug-drug interactions.

Immunotherapy in elderly transplant recipients: a guide to clinically significant drug interactions

Currently, >50% of candidates for solid organ transplantation in Europe and the US are aged >50 years while approximately 15% of potential recipients are aged >or=65 years. Elderly transplant candidates are characterized by specific co-morbidity profiles that compromise graft and patient outcome after transplantation. The presence of coronary artery or peripheral vascular disease, cerebrovascular disease, history of malignancy, chronic obstructive lung disease or diabetes mellitus further increases the early post-transplant mortality risk in elderly recipients, with infections and cardiovascular complications as the leading causes of death. Not only are elderly patients more prone to developing drug-related adverse effects, but they are also more susceptible to pharmacokinetic and pharmacodynamic drug interactions because of polypharmacy. The majority of currently used immunosuppressant drugs in organ transplantation are metabolized by cytochrome P450 (CYP) or uridine diphosphate-glucuronosyltransferases and are substrates of the multidrug resistance (MDR)-1 transporter P-glycoprotein, the MDR-associated protein 2 or the canalicular multispecific organic anion transporter, which predisposes these immunosuppressant compounds to specific interactions with commonly prescribed drugs. In addition, important drug interactions between immunosuppressant drugs have been identified and require attention when choosing an appropriate immunosuppressant drug regimen for the frail elderly organ recipient. An age-related 34% decrease in total body clearance of the calcineurin inhibitor ciclosporin was observed in elderly renal recipients (aged >65 years) compared with younger patients, while older recipients also had 44% higher intracellular lymphocyte ciclosporin concentrations. Similarly, using a Bayesian approach, an inverse relationship was noted between sirolimus clearance and age in stable kidney recipients. Ciclosporin and tacrolimus have distinct pharmacokinetics, but both are metabolized by intestinal and hepatic CYP3A4/3A5 and transported across the cell membrane by P-glycoprotein. The most common drug interactions with ciclosporin are therefore also observed with tacrolimus, but the two drugs do not interact identically when administered with CYP3A inhibitors or inducers. The strongest effects on calcineurin-inhibitor disposition are observed with azole antifungals, macrolide antibacterials, rifampicin, calcium channel antagonists, grapefruit juice, St John's wort and protease inhibitors. Drug interactions with mycophenolic acids occur mainly through inhibition of their enterohepatic recirculation, either by interference with the intestinal flora (antibacterials) or by limiting drug absorption (resins and binders). Rifampicin causes a reduction in mycophenolic acid exposure probably through induction of uridine diphosphate-glucuronosyltransferases. Proliferation signal inhibitors (PSIs) such as sirolimus and everolimus are substrates of CYP3A4 and P-glycoprotein and have a macrolide structure very similar to tacrolimus, which explains why common drug interactions with PSIs are comparable to those with calcineurin inhibitors. Ciclosporin, in contrast to tacrolimus, inhibits the enterohepatic recirculation of mycophenolic acids, resulting in significantly lower concentrations and hence risk of underexposure. Therefore, when switching from tacrolimus to ciclosporin and vice versa or when reducing or withdrawing ciclosporin, this interaction needs to be taken into account. The combination of ciclosporin with PSIs requires dose reductions of both drugs because of a synergistic interaction that causes nephrotoxicity when left uncorrected. Conversely, when switching between calcineurin inhibitors, intensified monitoring of PSI concentrations is mandatory. Increasing age is associated with structural and functional changes in body compartments and tissues that alter absorptive capacity, volume of distribution, hepatic metabolic function and renal function and ultimately drug disposition. While these age-related changes are well-known, few specific effects of the latter on immunosuppressant drug metabolism have been reported. Therefore, more clinical data from elderly organ recipients are urgently required.

Enfuvirtide: a safe and effective antiretroviral agent for human immunodeficiency virus-infected patients shortly after liver transplantation

The aim of this study was to evaluate the impact of an enfuvirtide-based antiretroviral (ARV) regimen on the management of immunosuppression and follow-up in hepatitis C virus (HCV)/hepatitis B virus (HBV)/human immunodeficiency virus (HIV)-coinfected liver transplant patients in comparison with a lopinavir/ritonavir-based ARV regimen. Tacrolimus and cyclosporine trough concentrations were determined at a steady state during 3 periods: after liver transplantation without ARV treatment (period 1), at the time of ARV reintroduction (period 2), and 2 to 3 months after liver transplantation (period 3). The findings for 22 HIV-coinfected patients were compared (18 with HCV and 4 with HBV); 11 patients were treated with enfuvirtide and were matched with 11 lopinavir/ritonavir-exposed patients. During period 1, tacrolimus and cyclosporine A doses were 8 and 600 mg/day, respectively, and the trough concentrations were within the therapeutic range in both groups. In period 2, the addition of lopinavir/ritonavir to the immunosuppressant regimen enabled a reduction in the dose of immunosuppressants required to maintain trough concentrations within the therapeutic range (to 0.3 mg/day for tacrolimus and 75 mg/day for cyclosporine). Immunosuppressant doses were not modified by the reintroduction of enfuvirtide, there being no change in the mean trough concentrations over the 3 periods. CD4 cell counts remained at about 200 cells/mm3. The HIV RNA viral load remained undetectable. Both groups displayed signs of mild cytolysis and cholestasis due to the recurrence of HCV, whereas no renal insufficiency was observed. Enfuvirtide is an attractive alternative to standard ARV therapy, facilitating the management of drug-drug interactions shortly after liver transplantation. Moreover, the lack of liver toxicity renders this drug valuable in the event of a severe HCV recurrence.

Differential dose adjustments of immunosuppressants after resuming boosted versus unboosted HIV-protease inhibitors postliver transplant

Pharmacokinetic (PK) interactions between protease inhibitors (PI(s)) and immunosuppressive agents (IS) are critical elements in the management of HIV-infected patients who undergo liver transplantation (LT(x)). The primary objective of this study was to evaluate the decreases in IS dosages necessary to maintain an appropriate therapeutic window (TW) after initiating PI-based antiretroviral therapy regimens post-LT(x). Single-center, PK cross-sectional study of consecutive HIV-infected adult patients who underwent LT(x) was done. Blood trough concentrations (C(t)) of IS were obtained using a commercial MEIA test; plasma C(t) of PI(s) were measured using HPLC. Twelve consecutive HIV-infected adult patients (11 males, 1 female) were enrolled. More rapid increases in IS plasma C(t) were observed 48 h after initiating ritonavir (RTV)-boosted PI therapy post-LT(x) than when using unboosted PI(s). Seven patients developed acute renal failure. The median fold decrease in IS dosages required to regain IS concentrations that were in the TW was 7.5 (range 6-14) after resuming boosted PI(s) and 2.9 (range 2-4) after unboosted PI(s). The overall median time necessary to reach IS TW after dose adjustment was 3.5 days (range 0-15). Unboosted PI(s) exhibited lesser PK interactions with IS than did RTV-boosted PI(s) and were thus more amenable to use in the post-LT(x) setting.

Safety and efficacy of raltegravir in HIV-infected transplant patients cotreated with immunosuppressive drugs

Solid organ transplantations (SOT) are performed successfully in selected HIV-infected patients. However, multiple and reciprocal drug-drug interactions are observed between antiretroviral (ARV) drugs and calcineurin inhibitors (CNIs) through CYP450 metabolization. Raltegravir (RAL), a novel HIV-1 integrase inhibitor, is not a substrate of CYP450 enzymes. We retrospectively reviewed the outcomes of 13 HIV-infected transplant patients treated by an RAL + two nucleosidic reverse transcriptase inhibitor (NRTI) regimen, in terms of tolerability, ARV efficacy (plasma viral load, CD4 cell count), drug interactions, RAL pharmacokinetics and transplant outcome. Thirteen patients with liver (n = 8) or kidney (n = 5) transplantation were included. RAL was initiated (400 mg BID) either at time of transplantation (n = 6), or after transplantation (n = 7). Median RAL trough concentration was 507 ng/mL (176-890), which is above the in vitro IC95 for wild type HIV-1 strains (15 ng/mL). Target trough levels of CNIs were promptly obtained with standard dosages of tacrolimus or cyclosporine. RAL tolerability was excellent. There was no episode of acute rejection. HIV infection remained controlled. After a median follow-up of 9 months (range: 6-14), all patients were alive with satisfactory graft function. The use of an RAL + two NRTI-based regimen is a good alternative in HIV-infected patients undergoing SOT.

Liver transplantation: an update 2009

PURPOSE OF REVIEW

In this review we focus on three challenging aspects of liver transplantation: living donor liver transplant, transplantation in HIV-positive recipients and down-staging of hepatocellular carcinoma for liver transplantation.

RECENT FINDINGS

The adult-to-adult living donor liver transplantation cohort study is providing valuable information on recipient and donor outcomes associated with living donor liver transplantation. The recipient outcomes with living donor liver transplantation are comparable to those with deceased donor liver transplantation for most diseases, but increased hepatocellular carcinoma recurrence has been reported with living donor liver transplantation. Donor morbidity is not infrequent and donor mortality remains a concern. Liver transplantation for HIV-positive recipients is associated with equivalent outcomes as HIV-negative recipients for selected recipients. Transplantation in coinfected recipients (HIV and HCV+) is associated with less favorable outcomes. Drug interaction between immunosuppression and highly active antiretroviral therapy is increasingly recognized and requires major modifications in dosing. Down-staging hepatocellular carcinoma to within transplant criteria is being used in some centers using loco-regional therapy. Waiting time after loco-regional therapy is currently the best predictor of recurrence. The role of newer chemotherapeutics is being tested as part of neoadjuvant therapy after resection or loco-regional therapy.

SUMMARY

Living donor liver transplantation is a viable strategy to increase transplantation and reduce death on the waiting list. Donor morbidity should be the subject of further efforts to minimize these risks. The increased recurrence risk with living donor liver transplantation for hepatocellular carcinoma warrants further study. Careful coordination between transplant professionals and HIV experts is necessary to monitor issues of posttransplant care of the HIV-infected recipient. The role of loco-regional therapies in down-staging patients with hepatocellular carcinoma is expanding.

Drug-drug interaction in a kidney transplant recipient receiving HIV salvage therapy and tacrolimus

Concomitant use of immunosuppressive agents and antiretroviral drugs may lead to complex drug-drug interactions. The calcineurin inhibitor tacrolimus is metabolized by cytochrome P-450 3A4 (encoded by the CYP3A4 gene) and is a substrate of P-glycoprotein (encoded by the ABCB1 gene). Both pathways can be inhibited by protease inhibitors (PIs). The reduction in first-pass and postabsorptive metabolism of tacrolimus by PIs can lead to extreme prolongation of the elimination half-life and significantly increase tacrolimus trough levels. In a patient with human immunodeficiency virus (HIV)-associated focal segmental glomerulosclerosis leading to kidney cadaveric transplantation, HIV salvage therapy was started with the new PI darunavir and boosted with ritonavir, another PI. The reduction in first-pass and postabsorptive metabolism of tacrolimus by PIs led to a dramatic increase in tacrolimus trough levels and extreme prolongation of the elimination half-life. Trough levels of tacrolimus levels were as high as 106.7 ng/mL. A decrease in tacrolimus dosage to a single dose of 0.5 mg/wk, corresponding to 3.5% of the usual dose, enabled maintenance of stable tacrolimus trough levels. Our case highlights that coadministration of a PI and tacrolimus is feasible through intense reduction in dose and prolongation of the dosing interval of the calcineurin inhibitor. Complex drug interactions may become more frequent because more HIV-infected patients are undergoing transplantation and newer HIV drugs are being used. Close monitoring and excellent adherence are mandatory to avoid the risk of harm for the graft and patient.

Drop in trough blood concentrations of tacrolimus after switching from nelfinavir to fosamprenavir in four HIV-infected liver transplant patients

Solid organ transplantation in HIV-infected individuals requires concomitant use of immunosuppressants and antiretrovirals that may cause significant drug interactions. Here we report on a peculiar pharmacokinetic interaction between tacrolimus and protease inhibitors (PIs) which occurred in four HIV-infected liver transplant patients who had to shift PI therapy from nelfnavir to fosamprenavir as a consequence of regulatory restrictions. After the switch, tacrolimus trough blood concentrations significantly dropped in all patients (mean ±sd 6.9 ±2.6 versus 3.2 ±2.0 ng/ml before and after the switch, respectively; P=0.01), so that a marked dosage increase was needed (0.29 ±0.14 versus 0.88 ±0.48 mg/day, 1–3 days before and 3 weeks after the switch, respectively; P=0.046) to attain the desired target (8.7 ±2.3 ng/ ml). Consistently, marked changes of the concentration/dose ratio of tacrolimus were observed in all cases (27.2 ±9.7 ng/ml per mg/kg/day versus 9.7 ±4.0 ng/ml per mg/kg/day before and after the switch, respectively; P<0.001). Our findings suggest that fosamprenavir may be less potent than nelfinavir in inhibiting tacrolimus clearance and support the need for higher tacrolimus dosage to avoid insufficient immunosuppression in HIV-infected liver transplant patients when switching from nelfinavir to fosamprenavir or even when directly starting antiretroviral therapy with fosamprenavir.