The Advantages of Therapeutic Drug Monitoring in Patients Receiving Antiretroviral Treatment and Experiencing Medication-Related Problems

Building clinical pharmacology laboratory capacity in low- and middle-income countries: Experience from Uganda

Background

Research and clinical use of clinical pharmacology laboratories are limited in low- and middle-income countries. We describe our experience in building and sustaining laboratory capacity for clinical pharmacology at the Infectious Diseases Institute, Kampala, Uganda.

Intervention

Existing laboratory infrastructure was repurposed, and new equipment was acquired. Laboratory personnel were hired and trained to optimise, validate, and develop in-house methods for testing antiretroviral, anti-tuberculosis and other drugs, including 10 high-performance liquid chromatography methods and four mass spectrometry methods. We reviewed all research collaborations and projects for which samples were assayed in the laboratory from January 2006 to November 2020. We assessed laboratory staff mentorship from collaborative relationships and the contribution of research projects towards human resource development, assay development, and equipment and maintenance costs. We further assessed the quality of testing and use of the laboratory for research and clinical care.

Lessons learnt

Fourteen years post inception, the clinical pharmacology laboratory had contributed significantly to the overall research output at the institute by supporting 26 pharmacokinetic studies. The laboratory has actively participated in an international external quality assurance programme for the last four years. For clinical care, a therapeutic drug monitoring service is accessible to patients living with HIV at the Adult Infectious Diseases clinic in Kampala, Uganda.

Recommendations

Driven primarily by research projects, clinical pharmacology laboratory capacity was successfully established in Uganda, resulting in sustained research output and clinical support. Strategies implemented in building capacity for this laboratory may guide similar processes in other low- and middle-income countries.

Short-cycle therapy in HIV-infected adults: rilpivirine combination 4 days on/3 days off therapy

BACKGROUND

Short-cycle therapy (SCT) is the administration of ART for 4 or 5 consecutive days a week, followed by 3 or 2 days off therapy. Its benefits include improving patient satisfaction and reducing ART toxicity and costs.

METHODS

In this observational study we included HIV-infected adults with a three-drug ART containing rilpivirine, a history of long-term virological suppression and no evidence of resistance to previous drug regimens. Patients switched to a SCT of 4 days on/3 days off and were followed for 48 weeks with regular check-ups. The primary outcome was virological suppression; secondary outcomes were changes in CD4+ cells and rilpivirine plasma concentration, the occurrence of adverse events and resistance in the case of failure, and patient satisfaction.

RESULTS

At week 48 no virological failure was observed, with a virological suppression rate of 30/30 (100%). Three patients switched back to continuous therapy for other reasons, with an overall success rate of SCT of 30/33 (90.9%, 95% CI = 81.24% to 100%). The CD4+ mean value increased by +64 cells/mm3 (95% CI = -59 to +187 cells/mm3; P = 0.052). No adverse events were observed and the mean total score in the satisfaction questionnaire was 57.7/60 (96.22%). Rilpivirine plasma concentration was below the efficacy threshold in 71.3% of the samples, suggesting that the patients' characteristics, more than the drug's pharmacokinetics, played a role in maintaining virological suppression.

CONCLUSIONS

SCT with rilpivirine-containing regimens could be an effective alternative to continuous therapy in selected HIV-infected patients with previous long-term virological suppression.

Pharmacological data of a successful 4-days-a-week regimen in HIV antiretroviral therapy (ANRS 162-4D trial)

INTRODUCTION

Few data are available on plasma concentrations of antiretroviral therapy (ARV) during intermittent treatment.

OBJECTIVE

To compare plasma concentrations in OFF vs ON treatment periods at several time points during treatment.

METHODS

During a successful 48-week multicenter study (ANRS 162-4D trial) of 4 days with treatment (ON) followed by 3 days without treatment (OFF) in adults treated by two nucleoside analogues and a third agent belonging to a boosted protease-inhibitor (PI, darunavir [DRV], atazanavir [ATV], lopinavir [LPV]) or a non-nucleoside-reverse-transcriptase inhibitor (NNRTI, efavirenz [EFV], etravirine [ETR], rilpivirine [RPV]) conducted in 100 patients (96% success), we determined the plasma concentrations of ARV. Blood samples were collected for analysis at inclusion (W0, 7/7 strategy for all patients), W16 and W40 (ON) and at W4, W8, W12, W24, W32 and W48 (OFF).

RESULTS

A total of 866 samples was analysed. Plasma concentrations were not statistically lower after 4 days (ON) vs 7/7 days of treatment except for RPV (-30 ng/mL at 4/7, P = 0.003). Significant lower plasma concentrations were observed for OFF vs ON except for ETR (n = 5, P = 0.062). Overall, 87.1% of ON concentrations (ATV 92.1%, DRV 51.1%, LPV 62.5%, EFV 94.4%, ETR 100% and RPV 94.9%) and 21.8% of OFF concentrations (ATV 1.4%, DRV 0.0%, LPV 0.0%, EFV 16.0%, ETR 92.6% and RPV 39.0%) were above the theoretical limit of efficacy of the molecule. In the OFF period, 85.8% of PI concentrations were under the limit of quantification, while 98.0% of NNRTI concentrations were quantifiable.

CONCLUSION

Despite low/undetectable PI/NNRTI plasma concentrations in the OFF period, patients maintained an undetectable viral load. The mechanistic explanation should be investigated.

Benefits and Limits of Antiretroviral Drug Monitoring in Routine Practice

BACKGROUND

HIV infection is a chronic disease for which therapeutic adherence and tolerance require particular attention.

OBJECTIVE

This study aimed to assess whether and when therapeutic drug monitoring (TDM) could be associated with a benefit in routine practice.

METHODS

All HIV-infected patients who underwent at least one TDM at the University Hospital of Dijon (France) between 1st January 2009 and 31st December 2012 were retrospectively included. Compliance with the recommendations, the results (antiretroviral concentrations), any subsequent therapeutic modifications, and the virological results at 4-8 months were analysed each time TDM was performed. TDM was defined as "practically relevant" when low or high antiretroviral concentrations led to a change in therapy.

RESULTS

Of the 571 patients who followed-up, 43.4% underwent TDM. TDM complying with recommendations (120 patients) was associated with a higher proportion of antiretroviral concentrations outside the therapeutic range (p=0.03). Antiretroviral treatment was modified after TDM in 22.6% of patients. Protease inhibitors, non-nucleoside reverse transcriptase inhibitors and raltegravir were more significantly modified when the measured concentration was outside the therapeutic range (p=0.008, p=0.05 and p=0.02, respectively). Overall, 11.7% of TDM was considered "practically relevant", though there was no significant correlation between subsequent changes in antiretroviral treatment and undetectable final HIV viral load.

CONCLUSION

TDM may be a useful tool in the management of HIV infection in specific situations, but the overall benefit seems moderate in routine practice. TDM cannot be systematic and/or a decision tool per se, but should be included in a comprehensive approach in certain clinical situations.

Individualized Protease Inhibitor Monotherapy: The Role of Pharmacokinetics and Pharmacogenetics in an Aged and Heavily Treated HIV-Infected Patient

Antiretroviral therapy has changed the history of HIV infection from a lethal disease to a chronic infection, with the emergence of long-term adverse effects. Herein we present a case of a heavily treated HIV-infected man in whom antiretroviral toxicity had been observed. The lopinavir/ritonavir plasma concentrations at standard doses were significantly above the recommended levels. Pharmacogenetic analysis revealed a polymorphism in the DRD3 gene associated with a decrease in the rate of drug metabolism. Additionally, the patient's low body mass index could have contributed to a greater degree of patient exposure to the drug. After the withdrawal of tenofovir disoproxil and the establishment of individualized protease inhibitor monotherapy at reduced doses, a decrease in the intensity of adverse events was observed, while the clinical outcomes were maintained. The pharmacokinetic-pharmacogenetic analysis was shown to be a tool of huge interest for the management and durability of antiretroviral therapy.

Four-days-a-week antiretroviral maintenance therapy in virologically controlled HIV-1-infected adults: the ANRS 162-4D trial

Background

Intermittent treatment could improve the convenience, tolerability and cost of ART, as well as patients' quality of life. We conducted a 48 week multicentre study of a 4-days-a-week antiretroviral regimen in adults with controlled HIV-1-RNA plasma viral load (VL).

Methods

Eligible patients were adults with VL < 50 copies/mL for at least 1 year on triple therapy with a ritonavir-boosted PI (PI/r) or an NNRTI. The study protocol consisted of the same regimen taken on four consecutive days per week followed by a 3 day drug interruption. The primary outcome was the proportion of participants remaining in the strategy with VL < 50 copies/mL up to week 48. The study was designed to show an observed success rate of > 90%, with a power of 87% and a 5% type 1 error. The study was registered with ClinicalTrials.gov (NCT02157311) and EudraCT (2014-000146-29).

Results

One hundred patients (82 men), median age 47 years (IQR 40-53), were included. They had been receiving ART for a median of 5.1 (IQR 2.9-9.3) years and had a median CD4 cell count of 665 (IQR 543-829) cells/mm3. The ongoing regimen included PI/r in 29 cases and NNRTI in 71 cases. At 48 weeks, 96% of participants (95% CI 90%-98%) had no failure while remaining on the 4-days-a-week regimen. Virological failure occurred in three participants, who all resumed daily treatment and became resuppressed. One participant stopped the strategy. No severe treatment-related events occurred.

Conclusions

Antiretroviral maintenance therapy 4 days a week was effective for 48 weeks in 96% of patients, leading to potential reduction of long-term toxicities, high adherence to the antiretroviral regimen and drug cost saving.

Comparison of Population Pharmacokinetics Based on Steady-State Assumption Versus Electronically Monitored Adherence to Lopinavir, Atazanavir, Efavirenz, and Etravirine: A Retrospective Study

BACKGROUND

Population pharmacokinetic (PopPK) analyses often rely on steady state and full adherence to prescribed dosage regimen assumptions from data gathered during therapeutic drug monitoring (TDM). Nonadherence is common in chronic diseases such as HIV. This study evaluates the impact of adherence measurement by electronic monitoring on PopPK parameter estimation and individual concentration profile predictions, and also the influence of adherence issues on the clinical interpretation of a concentration measurement.

METHODS

Published PopPK models for lopinavir, atazanavir, efavirenz, and etravirine were applied to estimate PK parameters and individual concentrations in 140 HIV patients taking part in a medication adherence program using 2 dosing data sets. The first set included the last dose reported by the patient with steady-state and full adherence assumptions; the second set used detailed electronic dosing history. PopPK parameter estimates and individual predictions were compared between the 2 dosing entries.

RESULTS

Clearance estimates and likewise predicted concentrations did not markedly differ between the 2 dosing histories. However, certain patterns of nonadherence such as sparse missed doses or consecutive missed doses lead to suboptimal drug exposure. The interpretation based on self-reported information would have concluded on a wrongly appropriate individual exposure.

CONCLUSIONS

PopPK analysis assuming steady state with full adherence produced similar results to those based on detailed electronic dosing history reconciled with patients' allegations. Self-reported last dose intake appeared reliable for concentration predictions and therapeutic drug monitoring interpretation for most patients followed at the medication adherence program. Yet, clinicians should be aware that concentration predictions based on self-reported last dose intake might be overestimated in case of undetected patterns of nonadherence, increasing the risk of forthcoming therapeutic failure.

Automated high throughput analysis of antiretroviral drugs in dried blood spots

For therapeutic drug monitoring in remote settings, dried blood spots (DBS) are particularly advantageous, as blood sample collection and handling is uncomplicated. The aim of this study was to develop and validate an automated extraction method for the analysis of nevirapine, efavirenz and lopinavir in DBS samples. Automated extraction was performed with methanol : water (70 : 30 v/v), using a DBS-MS 500 autosampler coupled to a liquid chromatography tandem mass spectrometry system. The autosampler used digital images of each DBS to position the extraction head, sprayed 10 μl of internal standard onto each DBS and extracted a 4-mm disc (Ø) from the centre of each spot by unilateral flow using 25-μl extraction solvent. The analytes were baseline separated on a pentafluorophenyl column and analysed by using electrospray ionization with multiple reaction monitoring in positive polarity mode for nevirapine and lopinavir and in negative mode for efavirenz. The method was linear between 10 and 10 000 ng/ml for all analytes. Automated sample extraction resulted in consistent recoveries (nevirapine: 70 ± 6%, efavirenz: 63 ± 11% and lopinavir: 60 ± 10%) and matrix effects between different donors and concentration levels. Intra-day and inter-day accuracy and precision deviations were ≤15%. Manual and automated extractions of DBS samples collected within the framework of an adherence assessment study in rural Tanzania showed good agreements with deviations of less than 10%. Our study highlights that therapeutic drug monitoring samples obtained in the resource-constrained setting of rural Africa can be reliably determined by automated extraction of DBS. Overall, automatization improved method sensitivity and facilitates analysis of large sample numbers. Copyright © 2017 John Wiley & Sons, Ltd.

A single untimed plasma drug concentration measurement during low-level HIV viremia predicts virologic failure

Suboptimal untimed plasma drug levels (UDL) have been associated with lower rates of virologic suppression and the emergence of drug resistance. Our aim was to evaluate whether UDL among patients with low-level viremia (LLV) while receiving highly active antiretroviral therapy (HAART) can predict subsequent virologic failure (plasma viral load ≥1000 copies/mL) and emergence of resistance. The first documented LLV episode of 328 consenting patients was analysed in terms of drug levels, viral load and resistance, which were monitored while patients were on a consistent HAART regimen. UDL of protease inhibitors (PIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs), were categorized as 'therapeutic' or 'subtherapeutic' based on predefined target trough concentrations. Drug resistance genotype was assessed using the Stanford algorithm. Time to virologic failure was evaluated by Kaplan-Meier analysis and Cox proportional hazards regression. We found 78 of 328 patients (24%) with subtherapeutic drug levels at time of first detectable LLV, while 19% harboured drug-resistant virus. Both subtherapeutic UDL and drug resistance independently increased the risk of subsequent virologic failure (p <0.001 and p 0.04, respectively). In a multivariable model, variables associated with LLV and virologic failure included subtherapeutic UDL, elevated plasma viral load, and drug resistance. Patients with subtherapeutic UDL accumulated further drug resistance faster during follow-up (p 0.03). Together, resistance and UDL variables can explain a higher proportion of virologic failure than either measure alone. Our results support further prospective evaluation of UDL in the management of low-level viremia.

Therapeutic drug monitoring to individualize the dosing of pazopanib: a pharmacokinetic feasibility study

BACKGROUND

Patients treated with the standard dose of pazopanib show a large interpatient variability in drug exposure defined as the area under the plasma concentration-time curve (AUC0-24h). The primary objective of this study was to evaluate the feasibility of pharmacokinetics (PK)-guided individualized dosing to reduce the interpatient variability in pazopanib exposure.

METHODS

Thirteen patients were treated with pazopanib for 3 consecutive periods of 2 weeks. During the first period, all patients received 800 mg of pazopanib once daily to reach steady-state exposure. During the second period, the patients either received a PK-guided individualized pazopanib dose or the registered fixed 800-mg dose. During the third period, these 2 dosing regimens were switched.

RESULTS

The interpatient variability in pazopanib AUC0-24h during fixed dosing (27.3 coefficient of variation) was not significantly different when compared with the variability in AUC0-24h during PK-guided dosing (24.8 coefficient of variation). The percentage of patients within the target window during PK-guided dosing (53.9%) was not significantly different from the percentage during fixed dosing (46.2%). Both Ctrough and C24 were significantly (P < 0.001) correlated to pazopanib AUC0-24h (R = 0.596 and R = 0.940, respectively). Pazopanib AUC0-24h decreased 17% over time.

CONCLUSIONS

PK-guided dosing did not reduce the interpatient variability in pazopanib exposure. In this study, the intrapatient variability in pazopanib exposure was relatively large compared with interpatient variability. This makes it challenging to achieve a target exposure within a predefined window. The causes of intrapatient variability must first be better understood and controlled, before PK-guided dosing can reduce the interpatient variability.

A pharmacist’s role in the individualization of treatment of HIV patients

The pharmacological treatment of HIV is complex and varies considerably among patients, as does the response of patients to therapy, requiring treatment plans that are closely tailored to individual needs. Pharmacists can take an active role in individualizing care by employing their knowledge of pharmacokinetics and pharmacogenetics and by interacting directly with patients in counseling sessions. These strategies promote the following: maintenance of plasma concentrations of antiretroviral agents within therapeutic ranges, prediction of pharmacological response of patients with certain genetic characteristics, and clinical control of HIV through the correct use of antiretroviral treatments. Together, these strategies can be used to tailor antiretroviral therapy to individual patients, thus improving treatment efficacy and safety.

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.

Evaluation of an immunoassay for determination of plasma efavirenz concentrations in resource-limited settings

Introduction

Therapeutic drug monitoring (TDM) may improve antiretroviral efficacy through adjustment of individual drug administration. This could result in reduced toxicity, prevent drug resistance, and aid management of drug–drug interactions. However, most measurement methods are too costly to be implemented in resource-limited settings. This study evaluated a commercially available immunoassay for measurement of plasma efavirenz.

Methods

The immunoassay-based method was applied to measure efavirenz using a readily available Humastar 80 chemistry analyzer. We compared plasma efavirenz concentrations measured by the immunoassay with liquid chromatography tandem mass spectrometry (LC-MS/MS) (reference method) in 315 plasma samples collected from HIV patients on treatment. Concentrations were categorized as suboptimal<1 µg/ml, normal 1–4 µg/ml or high>4 µg/ml. Agreement between results of the methods was assessed via Bland-Altman plot and κ statistic values.

Results

The median Interquartile range (IQR) efavirenz concentration was 2.8 (1.9; 4.5) µg/ml measured by the LC–MS/MS method and 2.5 (1.8; 3.9) µg/ml by the immunoassay and the results were well correlated (ρ=0.94). The limits of agreement assessed by Bland–Altman plots were −2.54; 1.70 µg/ml. Although immunoassay underestimated high concentrations, it had good agreement for classification into low, normal or high concentrations (K=0.74).

Conclusions

The immunoassay is a feasible alternative to determine efavirenz in areas with limited resources. The assay provides a reasonable approximation of efavirenz concentration in the majority of samples with a tendency to underestimate high concentrations. Agreement between tests evaluated in this study was clinically satisfactory for identification of low, normal and high efavirenz concentrations.

EFV/FTC/TDF-associated hepatotoxicity: a case report and review

The fixed-dose combination efavirenz, emtricitabine, and tenofovir (EFV/FTC/TDF) is a first-line agent for the treatment of HIV. We report the case of a 40-year-old female with a history of HIV acquired through heterosexual contact who initiated EFV/FTC/TDF. Hepatitis B and C serologies were negative, CD4 cell count was 253 cells per cubic millimeter (15.8%), and HIV viral load was 67,373 copies per milliliter. Eight months later she developed transaminitis and severe right upper quadrant pain. Neither illicit drug abuse nor hepatotoxic medication such as acetaminophen was reported. After evaluation including negative acute viral hepatitis studies, EFV/FTC/TDF was discontinued; both her transaminitis and pain resolved. Hepatotoxicity is most often associated with efavirenz. Rarely, fulminant hepatic failure occurs. Efavirenz-related hepatotoxicity is thought to result from a cellular self-digestion process known as autophagy. This is the first report to our knowledge of EFV/FTC/TDF-related hepatotoxicity.