Consensus recommendations for use of long-acting antiretroviral medications in the treatment and prevention of HIV-1: Endorsed by the American Academy of HIV Medicine, American College of Clinical Pharmacy, Canadian HIV and Viral Hepatitis Pharmacists Network, European AIDS Clinical Society, and Society of Infectious Diseases Pharmacists

Five long-acting (LA) antiretrovirals (ARVs) are currently available in a limited number of countries worldwide for HIV-1 prevention or treatment-cabotegravir, rilpivirine, lenacapavir, ibalizumab, and dapivirine. Implementing use of LA ARVs into routine clinical practice requires significant changes to the current framework of HIV-1 prevention, treatment, and service provision. Given the novelty, complexity, and interdisciplinary requirements needed to safely and optimally utilize LA ARVs, consensus recommendations on the use of LA ARVs will assist clinicians in optimizing use of these agents. The purpose of these recommendations is to provide guidance for the clinical use of LA ARVs for HIV-1 treatment and prevention. In addition, future areas of research are also identified and discussed.

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.

Use of phenytoin for treatment of tacrolimus toxicity with superimposed sepsis

A 40-year-old woman with a history of chronic graft-versus-host-disease on immunosuppression with tacrolimus presented to the hospital with somnolence, confusion and muscle cramps over a few days. She was found to have hypertension, hyperglycaemia and acute kidney injury with an elevated blood tacrolimus level of greater than 120 ng/mL (reference range 5-15 ng/mL). Discontinuation of tacrolimus with concomitant administration of intravenous phenytoin led to the successful reduction of elevated tacrolimus concentrations and the resolution of her symptoms. Tacrolimus is metabolised by the cytochrome P (CYP) 450 3A enzyme system, and utilisation of CYP 3A inducers to accelerate its clearance may be used as a successful therapy to treat tacrolimus toxicity.

Clinical aspects of tacrolimus use in paediatric renal transplant recipients

The calcineurin inhibitor tacrolimus, cornerstone of most immunosuppressive regimens, is a drug with a narrow therapeutic window: underexposure can lead to allograft rejection and overexposure can result in an increased incidence of infections, toxicity and malignancies. Tacrolimus is metabolised in the liver and intestine by the cytochrome P450 3A (CYP3A) isoforms CYP3A4 and CYP3A5. This review focusses on the clinical aspects of tacrolimus pharmacodynamics, such as efficacy and toxicity. Factors affecting tacrolimus pharmacokinetics, including pharmacogenetics and the rationale for routine CYP3A5*1/*3 genotyping in prospective paediatric renal transplant recipients, are also reviewed. Therapeutic drug monitoring, including pre-dose concentrations and pharmacokinetic profiles with the available "reference values", are discussed. Factors contributing to high intra-patient variability in tacrolimus exposure and its impact on clinical outcome are also reviewed. Lastly, suggestions for future research and clinical perspectives are discussed.

Phenytoin and Rifampin Do Not Decrease Levels in Acute Tacrolimus Toxicity

Tacrolimus is used in bone marrow transplant patients to prevent graft-versus-host disease. There have been few case reports of tacrolimus toxicity (>30 ng/mL) in solid organ recipients as well as in nontransplant patients. Several case reports suggest phenytoin and rifampin decrease tacrolimus levels in toxicity, but does it actually make a difference? A 60-year-old man with acute myeloblastic leukemia after allogenic stem cell transplant with fever, diarrhea, and abdominal pain was transferred to the intensive care unit for persistent hypotension and acute hypoxic respiratory failure requiring intubation. The following day his tacrolimus level was 8.6 ng/mL and creatinine was 2.2 (baseline = 1.8). The patient inadvertently received 15 mg intravenous tacrolimus instead of his scheduled 0.5 mg intravenous. Four hours later, a random tacrolimus level was 36.4 ng/mL. Tacrolimus was discontinued; phenytoin 200 mg BID was started for 4 doses and rifampin was started for 2 doses at 600 mg. Sixteen hours postinjection, tacrolimus level decreased to 26.4 ng/mL and to 9 ng/mL after 64 hours. Creatinine improved to 1.1 after 30 hours. He was extubated 5 days later without any new neurological findings and his creatinine returned to baseline. Our patient received 30 times his daily dose resulting high tacrolimus levels. Assuming there was sufficient time for distribution, our patient’s half-life increased to 34.5 hours compared with the reported half-life of 12 hours. The possibilities for this increase include ineffective or harmful effects of the phenytoin/rifampin combination, change in metabolism kinetics at high levels, or other unidentified patient-specific factors. Further studies should be done to ensure that phenytoin and rifampin are safe to give in tacrolimus toxicity.

Using known drug interactions to manage supratherapeutic calcineurin inhibitor concentrations

OBJECTIVES

To summarize the available body of evidence guiding the management of supratherapeutic concentrations of calcineurin inhibitors (CNI) using cytochrome P450 (CYP450) enzyme inducers.

METHODS

A nondate restricted literature search within MEDLINE, Embase, and Scopus was performed using the terms "cyclosporine," "tacrolimus," "calcineurin inhibitor," "toxicity," "pharmacokinetics," "carbamazepine," "rifampin," "phenytoin," and "phenobarbital." Additional references were identified from a review of all included citations. All English-language reports that describe the management of supratherapeutic CNI concentrations with interventions targeting metabolic induction using CYP450 enzyme inducers were evaluated.

RESULTS

A total of 10 publications were identified in which a CYP450 enzyme inducer was utilized intentionally to enhance CNI clearance in the setting of supratherapeutic concentrations; 7 case reports describe the use of phenytoin and 3 case reports describe the use of phenobarbital. Patient demographics, dosing strategies employed, and reported efficacy across this series of publications are heterogeneous; however, both agents appear to be well-tolerated when used in this setting.

CONCLUSIONS

There is a paucity of published data on the use of CYP450 enzyme inducers for the management of supratherapeutic CNI concentrations. While routine use of this approach cannot be recommended, thorough risk-benefit analyses should be performed in the management of each such clinical scenario.

Optimising the use of medicines to reduce acute kidney injury in children and babies

The majority of medications in children are administered in an unlicensed or off-label manner. Paediatricians are obliged to prescribe using the limited evidence available. The 2007 EU regulation on the use of paediatric drugs means pharmaceutical companies are now obliged to (and receive incentives for) contributing to paediatric drug data and carrying out paediatric clinical trials. This is important, as the efficacy and adverse effect profiles of medicines vary across childhood. Additionally, there are significant age-related changes in the pharmacodynamic and pharmacokinetic activity of many drugs. This may be related to physiological (differential expressions of cytochrome P450 enzymes or variable glomerular filtration rates at different ages for example) and psychological (increasing autonomy and risk perception in teenage years) changes. Increasing numbers of children are surviving life-threatening childhood conditions due to medical advances. This means there is an increasing population who are at risk of the consequences of the long-term, early exposure to nephrotoxic agents. The kidney is an organ that is particularly vulnerable to damage as a consequence of drugs. Drug-induced acute kidney injury (AKI) episodes in children and babies are principally due to non-steroidal anti-inflammatory drugs, antibiotics or chemotherapeutic agents. The renal tubules are vulnerable to injury because of their concentrating ability and high-energy hypoxic environment. This review focuses on drug-induced AKI and the methods to minimise its effect, including general management plus the role of child-specific pharmacokinetic data, the use of pharmacogenomics and early detection of AKI using urinary biomarkers and electronic triggers.

Red blood cell exchange as an approach for treating a case of severe tacrolimus overexposure

Immunosuppressive medication dosing errors are not unfrequent and may present a number of challenges to transplant clinicians. Tacrolimus (TAC) is a widely used immunosuppressant with a narrow therapeutic index and potential severe side effects, including neurotoxicity and kidney injury. We herein report a case of 60-year-old woman who underwent deceased-donor liver transplantation at our center and due to inadvertent TAC overexposure was admitted to the Intensive Care Unit because of severe neurologic impairment, kidney injury and arterial hypotension. This case was challenging because TAC is largely bound to erythrocytes, has a high molecular weight, is highly lipophilic, has a high distribution volume and cannot be removed by hemodialysis or plasmapheresis. Based on these considerations, we decided to replace TAC-saturated erythrocytes with blood-bank red cells with the aim to accelerate its clearance. The treatment was effective in decreasing TAC whole blood trough levels within the therapeutic ranges with a significant improvement of the patient's clinical status. Red-blood cell exchange is a potentially safe and effective means of managing severe and symptomatic TAC toxicity.