Practical guidelines to interpret plasma concentrations of antiretroviral drugs

Mannosylated PAMAM G2 dendrimers mediated rate programmed delivery of efavirenz target HIV viral latency at reservoirs

In this current research, we conceptualized a novel nanotechnology-enabled synthesis approach of targeting HIV-harboring tissues via second-generation (G2) polyamidoamine (PAMAM) mannosylated (MPG2) dendrimers for programmed delivery of anti-HIV drugs efavirenz (EFV) and ritonavir (RTV). Briefly, here mannose served purpose of ligand in this EFV and RTV-loaded PAMAM G2 dendrimers, synthesized by divergent techniques, denoted as MPG2ER. The developed nanocarriers were characterized by different analytical tools FTIR, NMR, zeta potential, particle size, and surface morphology. The results of confocal microscopy showed substantial alterations in the morphology of H9 cells, favored by relatively higher drug uptake through the MPG2ER. Interestingly, the drug uptake study and cytotoxicity assay of MPG2ER demonstrated that it showed no significant toxicity up to 12.5 µM. A typical flow cytometry histogram also revealed that MPG2ER efficiently internalized both drugs, with an increase in drug uptake of up to 81.2 %. It also enhanced the plasma pharmacokinetics of EFV, with Cmax7.68 μg/ml, AUC of 149.19 (μg/ml) * hr, and MRT of 26.87 hrs. Subsequently, tissue pharmacokinetics further evidence that MPG2ER accumulated more in distant Human immunodeficiency virus (HIV) reservoir tissues, such as the lymph nodes and spleen, but without exhibiting significant toxicity. Abovementioned compelling evidences strongly favored translational roles of MPG2 as a potential therapeutic strategy in the clinical eradication of HIV from viral reservoir tissue.

Is Routine Therapeutic Drug Monitoring of Anti-Retroviral Agents Warranted in Children Living with HIV?

OBJECTIVE

The utility of routine therapeutic drug monitoring (TDM) in children living with HIV has not been extensively studied. The purpose of this study was to assess this strategy.

METHODS

This was a single-center, prospective observational study of routine TDM for protease inhibitors (PIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs), and integrase strand transfer inhibitors (INSTIs) in children living with HIV who were receiving antiretroviral therapy (ART) between February and December 2014. Outcome measures included the proportion of serum antiretroviral (ARV) medication concentrations in the therapeutic range (target values extrapolated from adult data) and the effect of serum concentrations on virologic control, medication adherence, and toxicity.

RESULTS

Forty-eight children with a median age of 13 years (interquartile range, 3–18) were included. Median viral load (VL) and CD4% were <40 copies/mL (range, <40–124) and 37.4% (range, 8.4–47.9), respectively. Adherence was considered excellent in 95.8% of patients. Of the 50 serum trough concentrations (PI n = 19 [38%]; NNRTI n = 27 [54%]; INSTI n = 4 [8%]), 66% (n = 33) were in the therapeutic range, 12% (n = 6) were subtherapeutic, and 22% (n = 11) were supratherapeutic. There was no statistically significant correlation between serum ARV concentrations and patient demographics, VL, CD4%, or adherence. No clinically significant adverse events were noted. One dose adjustment was made for a subtherapeutic serum raltegravir concentration, likely attributable to interaction with ritonavir.

CONCLUSIONS

This study does not support routine TDM in healthy children living with HIV who are well controlled on antiretroviral medication regimens. A more targeted strategy, such as when adherence is questioned or when there are suspected drug interactions, may be more appropriate.

Improvement in Bioavailability and Pharmacokinetic Characteristics of Efavirenz with Booster Dose of Ritonavir in PEGylated PAMAM G4 Dendrimers

Efavirenz (EFV) with a booster dose of ritonavir (RTV) (EFV-RTV) inhibits the metabolism of EFV and improves its bioavailability. However, inadequate organ perfusion with surface permeability glycoprotein (P-gp) efflux sustains the viable HIV. Hence, the present investigations were aimed to evaluate the pharmacokinetics and tissue distribution efficiency of EFV by encapsulating it into PEGyalated PAMAM (polyamidoamine) G4 dendrimers with a booster dose of RTV (PPG4ER). The entrapment efficiency of PEGylated PAMAM G4 dendrimers was found to be 94% and 92.12% for EFV and RTV respectively with a zeta potential of 0.277 mV. The pharmacokinetics and tissue distribution behavior of EFV within PPG4ER was determined by developing and validating a simple, sensitive, and reliable bioanalytical method of RP-HPLC. The developed bioanalytical method was very sensitive with a quantification limit of 18.5 ng/ml and 139.2 ng/ml for EFV and RTV, respectively. The comparative noncompartmental pharmacokinetic parameters of EFV were determined by administrating a single intraperitoneal dose of EFV, EFV-RTV, and PPG4ER to Wistar rats. The PPG4ER produced prolonged release of EFV with a mean residential time (MRT) of 24 h with C_max 7.68 µg/ml in plasma against EFV-RTV with MRT 11 h and C_max 3.633 µg/ml. The PPG4ER was also detected in viral reservoir tissues (lymph node and spleen) for 3-4 days, whereas free EFV and EFV-RTV were cleared within 72 h. The pharmacokinetic data including C_max, t_1/2, AUC_tot, and MRT were significantly improved in PPG4ER as compared with single EFV and EFV-RTV. This reveals that the PPG4ER has great potential to target the virus harbors tissues and improve bioavailability.

Untimed Efavirenz Drug Levels After Switching From Brand to Generic Formulations: A Short Communication

BACKGROUND

In British Columbia, antiretrovirals are distributed at no cost to patients via a publicly funded program, using generic formulations if available. A generic efavirenz-emtricitabine-tenofovir DF (EFV-FTC-TDF) combination pill became available in April 2018. The authors compared EFV untimed drug levels in subjects switching from brand to generic EFV-FTC-TDF.

METHODS

Archived plasma HIV viral load samples were identified for consenting participants who switched from brand to generic EFV-FTC-TDF; 3 preswitch and 2-3 postswitch samples, collected ≥1 month apart were assessed for each subject. "Untimed" EFV concentrations with unknown dosing and collection time were assessed using a validated liquid chromatography-tandem mass spectrometry method. Participants' mean, minimum, and maximum EFV levels were compared using the Wilcoxon signed rank test. Participants with EFV levels in the range associated with lower risks of virologic failure and central nervous system toxicity (1000-4000 ng/mL), preswitch and postswitch, were enumerated.

RESULTS

EFV levels were assessed in 297 preswitch and 249 postswitch samples from 99 participants, having exposure to brand and generic EFV for a median of 103 (Q1-Q3: 87-116) and 10.3 (Q1-Q3: 8.9-11.7) months, respectively. The final brand sample was collected at a median of 98 days preswitch; the first generic sample was collected at a median of 133 days postswitch. No significant differences were observed in participant mean EFV levels before (median 1968 ng/mL; Q1-Q3: 1534-2878 ng/mL) and after (median 1987 ng/mL; Q1-Q3: 1521-2834 ng/mL) switch (P = 0.85). Eighty participants had mean EFV levels within the 1000-4000 ng/mL range on the brand drug, of which 74 remained within this range postswitch.

CONCLUSIONS

There were no statistically significant differences between untimed EFV levels in patients switching from the brand to generic EFV combination pill. Given the long elimination half-life of EFV, untimed drug levels may be a convenient way to estimate product bioequivalence.

The association between cigarette smoking and efavirenz plasma concentration using the population pharmacokinetic approach

AIMS

Efavirenz is still widely used as the preferred first-line antiretroviral agent in middle- and low-income countries, including Malaysia. The efavirenz population pharmacokinetic profile among HIV-positive smokers is still unknown. We aimed to assess the association of smoking with efavirenz and the differences in HIV clinical outcomes.

METHODS

A total of 154 stable HIV-positive patients on efavirenz in northern Malaysia were recruited with a sparse sampling for this multicentre prospective cohort study. The association between smoking and efavirenz pharmacokinetic parameters was determined using the nonlinear mixed-effect model. A mixture model of clearance was adopted to describe the metaboliser status because genetic data are unavailable. The effect of smoking on HIV clinical markers (CD4, CD4/CD8 ratio and viral blips) for at least 2 years after the antiretroviral initiation was also investigated.

RESULTS

Our data were best fitted with a 1-compartment mixture model with first-order absorption without lag time. Smoking significantly associated with higher clearance (β = 1.39; 95% confidence interval: 1.07 to 1.91), while weight affected both clearance and volume. From the mixture model, 20% of patients were in the slow clearance group, which mimic the genotype distribution of slow metaboliser. An efavirenz dose reduction is not recommended for smokers ≥60 kg with normal metabolism rate. Smoking significantly associated with slower normalisation of CD4 and CD4/CD8 ratio.

CONCLUSIONS

HIV-positive smokers presented with significantly higher efavirenz clearance and unfavourable clinical outcomes. Close monitoring of adherence and clinical response among smokers is warranted.

Recent progress of antiviral therapy for coronavirus disease 2019

The coronavirus disease 2019 (COVID-19) pandemic has become a global public health crisis, for which antiviral treatments are considered mainstream therapeutic approaches. With the development of this pandemic, the number of clinical studies on antiviral therapy, including remdesivir, chloroquine and hydroxychloroquine, lopinavir/ritonavir, ribavirin, arbidol, interferon, favipiravir, oseltamivir, nitazoxanide, nelfinavir, and camostat mesylate, has been increasing. However, the efficacy of these antiviral drugs for COVID-19 remains controversial. In this review, we summarize the recent progress and findings on antiviral therapies, aiming to provide clinical support for the management of COVID-19. In addition, we analyze the causes of controversy in antiviral drug research and discuss the quality of current studies on antiviral treatments. High-quality randomized clinical trials are required to demonstrate the efficacy and safety of antiviral drugs for the treatment of COVID-19.

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.

Immunologic and Virologic Outcomes of Obese and Nonobese Incarcerated Adults on Antiretroviral Therapy for HIV Infection

Background:

Obesity is common among patients with HIV. The objective of this study was to characterize response to antiretroviral therapy (ART) in a cohort of obese incarcerated adults compared to a nonobese cohort.

Methods:

A retrospective matched cohort study was conducted in an HIV telemedicine clinic. Patients with body mass index (BMI) >30 kg/m² who received the same ART with >95% adherence for at least 6 months were matched to nonobese patients by age, gender, ART, CD4 count, and viral load at baseline.

Results:

Twenty pairs were included, with an average BMI of 24 kg/m² in the nonobese cohort and 35 kg/m² in the obese cohort. No difference was observed in the proportion of patients who achieved virologic suppression or the change in CD4 count from baseline to 6 to 12 months.

Conclusion:

This study revealed no differences in immunologic recovery or virologic suppression between obese and nonobese patients in an adult correctional population.

Viral and antiretroviral dynamics in HIV mother-to-child transmission fluids (VADICT) – Protocol and data analysis plan for a cohort study

Background: Pregnancy and polymorphisms in drug disposition genes alter the clearance of key antiretrovirals used as part of regimens for prevention of mother-to-child transmission of HIV (PMTCT). The clinical significance of these in women initiating therapy late in pregnancy has not been investigated. The primary objective of the Viral and Antiretroviral Dynamics in HIV Mother-To-Child Transmission Fluids (VADICT) study is to investigate viral and antiretroviral dynamics in matrices associated with mother-to-child transmission (MTCT) (plasma, genital fluid and breastmilk) in women (stratified by CYP2B6 genotypes) who initiate antiretroviral therapy (ART) before or early in pregnancy versus late in pregnancy or early postpartum. Methods: A cohort of HIV-1 infected women who initiated ART containing 600 mg efavirenz before or early in pregnancy (n = 120), during the third trimester (n = 60), or early postpartum (n = 60) will be studied.  Eligible patients will be recruited from four hospitals in Benue State, North Central Nigeria and followed until the end of breastfeeding. Procedures at follow up visits will include sample collection for drug quantification and HIV-1 RNA and DNA in plasma, genital fluid and breastmilk; adherence monitoring; and newborn and infant assessment. Using newborn exposure to maternal efavirenz at birth for validation, prenatal pharmacogenetics of efavirenz will be explored using physiologically-based pharmacokinetic modelling. Three integrated methods will be used to monitor patterns and correlates of adherence across pregnancy and the breastfeeding period. A population pharmacokinetic-pharmacodynamic model will be developed to describe the observed data and simulate what to expect in women initiating ART containing 400 mg efavirenz (recently approved for non-pregnant adults) late in pregnancy or early postpartum. Discussion: This study will help in understanding residual MTCT in women receiving ART and reasons for the rise in MTCT risk during the breastfeeding period. Trial registration: ClinicalTrials.gov: NCT03284645 (15/09/2017)

Pharmacogenetics of artemether-lumefantrine influence on nevirapine disposition: Clinically significant drug-drug interaction?

AIMS

In this study the influence of first-line antimalarial drug artemether-lumefantrine on the pharmacokinetics of the antiretroviral drug nevirapine was investigated in the context of selected single nucleotide polymorphisms (SNPs) in a cohort of adult HIV-infected Nigerian patients.

METHODS

This was a two-period, single sequence crossover study. In stage 1, 150 HIV-infected patients receiving nevirapine-based antiretroviral regimens were enrolled and genotyped for seven SNPs. Sparse pharmacokinetic sampling was conducted to identify SNPs independently associated with nevirapine plasma concentration. Patients were categorized as poor, intermediate and extensive metabolizers based on the numbers of alleles of significantly associated SNPs. Intensive sampling was conducted in selected patients from each group. In stage 2, patients received standard artemether-lumefantrine treatment with nevirapine, and intensive pharmacokinetic sampling was conducted on day 3.

RESULTS

No clinically significant changes were observed in key nevirapine pharmacokinetic parameters, the 90% confidence interval for the measured changes falling completely within the 0.80-1.25 no-effect boundaries. However, the number of patients with trough plasma nevirapine concentration below the 3400 ng ml^-1 minimum effective concentration increased from 10% without artemether-lumefantrine (all extensive metabolizers) to 21% with artemether-lumefantrine (14% extensive, 4% intermediate, and 3% poor metabolizers).

CONCLUSIONS

This approach highlights additional increase in the already existing risk of suboptimal trough plasma concentration, especially in extensive metabolizers when nevirapine is co-administered with artemether-lumefantrine.

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.

K. HK, Ramachandran G, Shet A. Sub-therapeutic nevirapine concentration during antiretroviral treatment initiation among children living with HIV: Implications for therapeutic drug monitoring

Nevirapine, a component of antiretroviral therapy (ART) in resource-limited settings, known for auto-induction of metabolism, is initiated at half therapeutic dose until day 14 (‘lead-in period’), and subsequently escalated to full dose. However, studies have shown that this dosing strategy based on adult studies may not be appropriate in children, given that younger children have higher drug clearance rates. In this prospective cohort study, we studied trough plasma nevirapine levels by high performance liquid chromatography (HPLC) at days 7, 14 (lead-in period) and 28 (full dose period) after ART initiation amongst HIV-1 infected children initiating nevirapine-based ART in southern India. Among the 20 children (50% male, median age 9 years) included in the study, sub-therapeutic trough plasma nevirapine concentration (<4μg/ml) was seen in 65% (13/20) of children during the lead-in period within two weeks of ART initiation and among 10% of children at 4 weeks during full-dose nevirapine. Adherence was documented as ≥95% in all children by both caregiver self-report and pill count. Median nevirapine concentrations achieved at week 1 was 4.8 μg/ml, significantly lower than 8 μg/ml, the concentration achieved at week 4 (p = 0.034). Virological failure at one year of ART was observed in six children, and was not associated with median nevirapine concentration achieved during week 1, 2 or 4. We conclude that the dose escalation strategy currently practiced among young children living with HIV-1 resulted in significant subtherapeutic nevirapine concentration (≤4μg/ml) during the lead-in period. We call for a closer look at pediatric-focused dosing strategies for nevirapine initiation in young children. Further studies to establish age-appropriate threshold nevirapine concentration are warranted in young children to corroborate the role of therapeutic drug monitoring in predicting virological outcome.

Pharmacogenetics of nevirapine excretion into breast milk and infants' exposure through breast milk versus postexposure prophylaxis

AIM

The influence of genetic factors on nevirapine (NVP) breast milk pharmacokinetics and breastfed infants' exposure were investigated.

PATIENTS & METHODS

Associations between nine SNPs in NVP disposition genes in mothers and its plasma and breast milk concentrations were explored in nursing mother-infant pairs.

RESULTS

NVP pharmacokinetics in maternal plasma, breast milk and infant exposure indices were influenced by CYP2B6 516G>T and 983T>C. The median (range) milk-to-plasma area under the curve (AUC0-12) ratio was 0.95 (0.56-1.5). Calculated as percentages of pediatric treatment, infant postexposure prophylaxis and maternal weight-adjusted doses, the maximum exposure indices were 3.64% (1.99-9.88), 26.0% (9.93-79.1) and 13.8% (5.77-27.7), respectively. Infant plasma concentration as a result of exposure through breast milk (n = 93), pre-exposure prophylaxis (n = 10) and both (n = 27) were 660 (104-3090), 1020 (401-3325) and 2720 ng/ml (1360-7290), respectively.

CONCLUSION

The clinical significance of the observed differences between routes of infants' exposure warrants further investigation.

No Need for Lopinavir Dose Adjustment during Pregnancy: a Population Pharmacokinetic and Exposure-Response Analysis in Pregnant and Nonpregnant HIV-Infected Subjects

Lopinavir-ritonavir is frequently prescribed to HIV-1-infected women during pregnancy. Decreased lopinavir exposure has been reported during pregnancy, but the clinical significance of this reduction is uncertain. This analysis aimed to evaluate the need for lopinavir dose adjustment during pregnancy. We conducted a population pharmacokinetic analysis of lopinavir and ritonavir concentrations collected from 84 pregnant and 595 nonpregnant treatment-naive and -experienced HIV-1-infected subjects enrolled in six clinical studies. Lopinavir-ritonavir doses in the studies ranged between 400/100 and 600/150 mg twice daily. In addition, linear mixed-effect analysis was used to compare the area under the concentration-time curve from 0 to 12 h (AUC0-12) and concentration prior to dosing (Cpredose) in pregnant women and nonpregnant subjects. The relationship between lopinavir exposure and virologic suppression in pregnant women and nonpregnant subjects was evaluated. Population pharmacokinetic analysis estimated 17% higher lopinavir clearance in pregnant women than in nonpregnant subjects. Lopinavir clearance values postpartum were 26.4% and 37.1% lower than in nonpregnant subjects and pregnant women, respectively. As the tablet formulation was estimated to be 20% more bioavailable than the capsule formulation, no statistically significant differences between lopinavir exposure in pregnant women receiving the tablet formulation and nonpregnant subjects receiving the capsule formulation were identified. In the range of lopinavir AUC0-12 or Cpredose values observed in the third trimester, there was no correlation between lopinavir exposure and viral load or proportion of subjects with virologic suppression. Similar efficacy was observed between pregnant women and nonpregnant subjects receiving lopinavir-ritonavir at 400/100 mg twice daily. The pharmacokinetic and pharmacodynamic results support the use of a lopinavir-ritonavir 400/100-mg twice-daily dose during pregnancy.

Fundament and Prerequisites for the Application of an Antifungal TDM Service

Therapeutic drug monitoring (TDM) involves the measurement of plasma or serum drug concentration to adapt dosages to achieve predefined target concentrations that are associated with optimal clinical response while minimizing the chance of encountering toxicity. Many papers in the field of antifungal drugs have focused on the evidence that supports the use of TDM thereby emphasizing the breakpoints or target concentrations in general literature. This review focuses on the process of TDM to inform health care workers on the fundaments and prerequisites that safeguard the good application of TDM. Knowledge on the complete process of TDM including pharmacokinetics (and relevant covariates), pharmacodynamic aspects, trials that are necessary to provide us with evidence, translation of knowledge to other populations and pathogens, and implications for the pre-analytical, analytical, and post-analytical phases (the process of TDM) are discussed in relevant detail. For each individual step, recommendations are made for the readers. We believe this will be a valuable resource and to be of added value to the many papers that focus on relations between exposure and efficacy or toxicity. It will help to achieve greater benefit of TDM.

Pharmacogenetics of pregnancy-induced changes in efavirenz pharmacokinetics

Pregnancy-induced physiological changes alter many drugs' pharmacokinetics. We investigated pregnancy-induced changes in efavirenz pharmacokinetics in 25 pregnant and 19 different postpartum women stratified from 211 HIV-positive women in whom a preliminary pharmacogenetic study had been undertaken. Despite significant changes in CL/F during pregnancy (42.6% increase; P = 0.023), median (range) Cmin was 1,000 ng/mL (429-5,190) with no significant change in Cmax (P = 0.072). However, when stratified for CYP2B6 516G>T (rs3745274) genotype, efavirenz AUC0-24 , Cmax and Cmin were 50.6% (P = 0.0013), 17.2% (P = 0.14), and 61.6% (P = 0.0027) lower during pregnancy (n = 8) compared with postpartum (n = 6) in 516G homozygotes, with values of 25,900 ng.h/mL (21,700-32,600), 2,640 ng/mL (1,260-3,490), and 592 ng/mL (429-917), respectively, and CL/F was 100% higher (P = 0.0013). No changes were apparent in CYP2B6 516 heterozygotes (14 pregnant vs. 7 postpartum). The clinical implications of these findings warrant further investigation.

Determination of total and unbound concentrations of lopinavir in plasma using liquid chromatography-tandem mass spectrometry and ultrafiltration methods

Lopinavir is an HIV protease inhibitor with high protein binding (98-99%) in human plasma. This study was designed to develop an ultrafiltration method to measure the unbound concentrations of lopinavir overcoming the non-specific binding issue. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the determination of total concentrations of lopinavir in plasma was developed and validated, and an adaptation was also optimized and validated for the determination of unbound concentrations. The chromatographic separation was performed with a C18 column (100 mm × 2.1mm i.d., 5 μm particle size) using a mobile phase containing deionized water with formic acid, and acetonitrile, with gradient elution at a flow-rate of 350 μL min(-1). Identification of the compounds was performed by multiple reaction monitoring, using electrospray ionization in positive ion mode. The method was validated over a clinical range of 0.01-1 μg/mL for human plasma ultrafiltrate and 0.1-15 μg/mL in human plasma. The inter and intra-assay accuracies and precisions were between 0.23% and 11.37% for total lopinavir concentrations, and between 3.50% and 13.30% for plasma ultrafiltrate (unbound concentration). The ultrafiltration method described allows an accurate separation of the unbound fraction of lopinavir, circumscribing the loss of drug by nonspecific binding (NSB), and the validated LC-MS/MS methodology proposed is suitable for the determination of total and unbound concentrations of lopinavir in clinical practice.

Are lopinavir and efavirenz serum concentrations in HIV-infected children in the therapeutic range in clinical practice?

BACKGROUND

In antiretroviral treatment the role of therapeutic drug monitoring via measurement of serum levels remains unclear, especially in children.

AIM

To quantify exposure to LPV and EFV in children receiving therapy in a routine clinical setting in order to identify risk factors associated with inadequate drug exposure.

METHOD

A prospective study was conducted in a routine clinical setting in Tygerberg Children's Hospital, South Africa. A total of 53 random serum levels were analyzed. Serum concentrations were determined by an established high-performance liquid chromatography method.

RESULTS

Of 53 HIV-infected children treated with lopinavir (n = 29, median age 1·83 y) or efavirenz (n = 24, median age 9·3 years), 12 showed serum levels outside the therapeutic range (efavirenz) or below Cmin (lopinavir). Low bodyweight, rifampicin co-treatment, and significant comorbidity were potential risk factors for inadequate drug exposure.

CONCLUSION

These findings, together with previous studies, indicate that therapeutic drug monitoring can improve the management of antiretroviral therapy in children at risk.

Population pharmacokinetics of nevirapine in Thai HIV-infected patients

BACKGROUND

Nevirapine-based antiretroviral therapy is widely used as a first-line treatment for HIV-infected patients in resource-limited settings. Nevirapine plasma concentration has been shown to be associated with virological response and treatment failure. Therefore, identifying sources of the variability of nevirapine pharmacokinetics is important for dose optimization. The purpose of the current study was to determine the population mean pharmacokinetic parameters and identify factors that influence pharmacokinetic parameters of nevirapine in Thai HIV-infected patients.

METHODS

The model was developed by a non-linear mixed-effects modelling approach using NONMEM. Model validation was performed using bootstrap analysis and external validation. Additionally, nevirapine plasma concentrations of 200 mg twice daily (NVPBID) and 400 mg once daily (NVPOD) were simulated using the final model to investigate the impact of the covariates and different dosage regimens on nevirapine steady state concentrations.

RESULTS

The apparent clearance (CL/F) of nevirapine estimated from this population was 2.51 l/h which is lower than the values previously reported in other populations. The concomitant use of rifampicin increased CL/F by 20%. Simulated nevirapine plasma concentrations from NVPBID were superior to the NVPOD regimen.

CONCLUSIONS

This population-based pharmacokinetic model can be used for optimizing nevirapine dosage regimens for individual patients to improve efficacy and safety of nevirapine therapy in this population.

Pharmacokinetic drug interactions between drugs of abuse and antiretroviral medications: implications and management for clinical practice

Substance abuse and HIV/AIDS are two of the most serious, yet treatable diseases worldwide. Global access to HIV treatment continues to expand. In settings where both active illicit drug use and HIV treatment are concurrent, potentional problematic pharmacokinetic drug interactions may arise and complicate therapy. Clinical case series and carefully controlled pharmacokinetic interaction studies have been conducted between only a few drugs of abuse and approved antiretroviral therapies. Important pharmacokinetic drug interactions have been described for benzodiazepines, 3,4-methylenedioxymethamphetamine, methadone and buprenorphine; however, most have not been studied and few well-controlled studies have been conducted to adequately address the clinical implications of these interactions. The metabolism of drugs of abuse, description of the known interactions, and clinical implications and management of these interactions are reviewed. Certain interactions between drugs of abuse and antiretroviral therapies are known and others are likely based upon shared metabolic pathways. These may result in important clinical consequences. To optimize care, clinicians must be alert, knowledgeable about known and possible interactions and equipped to clinically manage the medical consequences. Moreover, there is considerable need for carefully controlled studies in this important and emerging area.

A review of pharmacological interactions between HIV or hepatitis C virus medications and opioid agonist therapy: implications and management for clinical practice

Global access to opioid agonist therapy and HIV/hepatitis C virus (HCV) treatment is expanding but when used concurrently, problematic pharmacokinetic and pharmacodynamic interactions may occur. Articles published from 1966 to 2012 in Medline were reviewed using the following keywords: HIV, AIDS, HIV therapy, HCV, HCV therapy, antiretroviral therapy, highly active antiretroviral therapy, drug interactions, methadone and buprenorphine. In addition, a review of abstracts from national and international meetings and conference proceedings was conducted; selected reports were reviewed as well. The metabolism of both opioid and antiretroviral therapies, description of their known interactions and clinical implications and management of these interactions were reviewed. Important pharmacokinetic and pharmacodynamic drug interactions affecting either methadone or HIV medications have been demonstrated within each class of antiretroviral agents. Drug interactions between methadone, buprenorphine and HIV medications are known and may have important clinical consequences. Clinicians must be alert to these interactions and have a basic knowledge regarding their management.

Protein binding of lopinavir and ritonavir during 4 phases of pregnancy: implications for treatment guidelines

OBJECTIVE

To investigate the intraindividual pharmacokinetics (PKs) of total (protein bound plus unbound) and unbound lopinavir/ritonavir (LPV/RTV) and to assess whether the pediatric formulation (100 mg/25 mg) can overcome any pregnancy-associated changes.

DESIGN

Prospective longitudinal PK study.

METHODS

HIV-infected pregnant antiretroviral therapy-naive and experienced women receiving LPV/RTV 400 mg/100 mg tablets twice daily. Intensive PK evaluations were performed at 20-24 weeks (PK1), 30 weeks (PK2) followed by empiric dose increase using the pediatric formulation (100 mg/25 mg twice daily), 32 weeks (PK3), and 8 weeks postpartum (PK4).

RESULTS

Twelve women completed prespecified PK evaluations. Median (range) age was 28 (18-35) years and baseline BMI was 32 (19-41) kg/m. During pregnancy, total area under the time concentration (AUC0-12h) for LPV was significantly lower than postpartum (PK1, PK2, or PK3 vs. PK4, P = 0.005). Protein-unbound LPV AUC0-12h remained unchanged during pregnancy [PK1: 1.6 (1.3-1.9) vs. PK2: 1.6 (1.3-1.9) μg·h/mL, P = 0.4] despite a 25% dose increase [PK2 vs. PK3: 1.8 (1.3-2.1) μg·h/mL, P = 0.5]. Protein-unbound LPV predose concentrations (C12h) did not significantly change despite dose increase [PK2: 0.10 (0.08-0.15) vs. PK3: 0.12 (0.10-0.15) μg/mL, P = 0.09]. Albumin and LPV AUC0-12h fraction unbound were correlated (rs = 0.3, P = 0.03).

CONCLUSIONS

Total LPV exposure was significantly decreased throughout pregnancy despite the increased dose. However, the exposure of unbound LPV did not change significantly regardless of trimester or dose. Predose concentrations of unbound LPV were not affected by the additional dose and were 70-fold greater than the minimum efficacy concentration. These findings suggest dose adjustments may not be necessary in all HIV-infected pregnant women.

Free and total plasma levels of lopinavir during pregnancy, at delivery and postpartum: implications for dosage adjustments in pregnant women

BACKGROUND

Physiological changes associated with pregnancy may alter antiretroviral plasma concentrations and might jeopardize prevention of mother-to-child HIV transmission. Lopinavir is one of the protease inhibitors more frequently prescribed during pregnancy in Europe. We described the free and total pharmacokinetics of lopinavir in HIV-infected pregnant and non-pregnant women, and evaluated whether significant alterations in its disposition and protein binding warrant systematic dosage adjustment.

METHODS

Plasma samples were collected at first, second and third trimester of pregnancy, at delivery, in umbilical cord and postpartum. Lopinavir free and total plasma concentrations were measured by HPLC-MS/MS. Bayesian calculations were used to extrapolate total concentrations to trough (Cmin).

RESULTS

A total of 42 HIV-positive pregnant women and 37 non-pregnant women on lopinavir/ritonavir were included in the study. Compared to postpartum and control values, total lopinavir Cmin was decreased moderately (31-39%) during pregnancy, and free Cmin minimally, showing significant alteration only at delivery (-35%). However, total and free Cmin remained in all patients above the target concentrations for wild-type virus of 1,000 ng/ml, and above the unbound IC50(WT) of 0.64-0.77 ng/ml of lopinavir, respectively. Lopinavir free fractions remained higher during pregnancy compared to postpartum and controls, and were influenced by α-1-acid-glycoprotein and albumin decrease. Free cord-to-mother ratio (0.43) was 2.7-fold higher than total cord-to-mother ratio (0.16), suggesting higher fetal exposure.

CONCLUSIONS

The moderate decrease of total lopinavir concentrations during pregnancy is not associated with proportional decrease in free concentrations. Both reach a nadir at delivery, albeit not to an extent that would put treatment-naive women at risk of insufficient exposure to the free, pharmacologically active concentrations of lopinavir. No dosage adjustment is therefore needed during pregnancy as it is unlikely to further enhance treatment efficacy but could potentially increase the risk of maternal and fetal toxicity. Nonetheless, in case of viral resistance in treatment-experienced pregnant women, loss of virological control or questionable adherence, it is justified to consider lopinavir dosage adjustment based on total plasma concentration measurement.

[New strategies in the optimisation of lopinavir/ritonavir doses in human immunodeficiency virus-infected patients]

Lopinavir/ritonavir (LPV/r) has demonstrated virological and immunological efficacy in the combined antiretroviral treatment (cART), in both naïve and experienced patients. Furthermore, LPV/r showed a high barrier to the development of resistance. Although generally well tolerated, adverse gastrointestinal side effects and metabolic disorders are frequent. The different tools used to optimise the cART with this drug combination in the daily clinical practice, emphasising the therapeutic drug monitoring (TDM) of LPV/r and the genetic analysis of the main enzymes responsible for the metabolism and transport, are reviewed. The relationship between phenotype and genotype, established through TDM, could be useful for the physician to improve the clinical management of the HIV infection, due to the possibility of individualising the dose with this drug. Monotherapy is also reviewed as a new strategy used in the simplification of the treatment with this drug, which could increase safety and reduce costs.

Improved oral bioavailability of lopinavir in melt-extruded tablet formulation reduces impact of third trimester on lopinavir plasma concentrations

Lopinavir exposure was reduced during the third trimester in pregnant women receiving standard dosing of the soft-gel capsule (SGC; 400/100 mg twice daily [b.i.d.]). Pharmacokinetic data on the lopinavir tablet in pregnancy are limited. On the basis of the tablet's improved bioavailability, standard dosing (400/100 mg b.i.d.) may provide adequate lopinavir exposure in pregnancy without a need for dose adjustment. Here we compared the total and unbound lopinavir pharmacokinetics throughout pregnancy in the second and third trimesters in HIV-infected women receiving standard dosing of the lopinavir SGC or tablet. Postpartum sampling was also performed in patients continuing therapy postdelivery. Blood samples were collected at 0 to 12 h postdosing, and lopinavir concentrations were determined by high-pressure liquid chromatography-tandem mass spectrometry. Nineteen patients were included: 8 received the SGC (cohort 1) and 11 received the tablet (cohort 2). Total lopinavir exposures in the third trimester were lower than those in the second trimester (35 and 28% for cohorts 1 and 2, respectively) and postpartum (35% for cohort 2). In the third trimester, the area under the concentration-time curve (AUC) from 0 to 12 h (AUC(0-12)) and maximum concentration were ∼15% and 25% higher, respectively, for the lopinavir tablet than the SGC. One SGC patient had lopinavir concentrations of <1,000 ng/ml; all patients on the tablet had concentrations of >1,000 ng/ml. In cohort 2, the percentage of the AUC that was unbound was higher (nonsignificantly) in the second (1.28%) and third (1.18%) trimesters than postpartum (1.01%). Seventeen of 19 patients had an undetectable viral load at delivery. There were no HIV transmissions. Although lopinavir (tablet) exposures were reduced during the third trimester, the higher total and unbound concentrations achieved in women receiving the tablet than in women receiving the SGC suggest that the tablet's improved oral bioavailability may partly compensate for the reduction in lopinavir exposure during the later stages of pregnancy.

Antiretroviral drug interactions: overview of interactions involving new and investigational agents and the role of therapeutic drug monitoring for management

Antiretrovirals are prone to drug-drug and drug-food interactions that can result in subtherapeutic or supratherapeutic concentrations. Interactions between antiretrovirals and medications for other diseases are common due to shared metabolism through cytochrome P450 (CYP450) and uridine diphosphate glucuronosyltransferase (UGT) enzymes and transport by membrane proteins (e.g., p-glycoprotein, organic anion-transporting polypeptide). The clinical significance of antiretroviral drug interactions is reviewed, with a focus on new and investigational agents. An overview of the mechanistic basis for drug interactions and the effect of individual antiretrovirals on CYP450 and UGT isoforms are provided. Interactions between antiretrovirals and medications for other co-morbidities are summarized. The role of therapeutic drug monitoring in the detection and management of antiretroviral drug interactions is also briefly discussed.

The role of therapeutic drug monitoring in the management of patients with human immunodeficiency virus infection

Therapeutic drug monitoring (TDM) is a well-established method to optimize dosing regimens in individual patients for drugs that are characterized by a narrow therapeutic range and large interindividual pharmacokinetic variability. For some antiretroviral drugs, mainly nonnucleoside reverse transcriptase inhibitors and protease inhibitors, TDM has been proposed as a means to improve the response in human immunodeficiency virus-infected patients. In contrast, nucleoside reverse transcriptase inhibitors do not show a predictable plasma concentration-response (toxicity, efficacy) relationship, and intracellular analyses are expensive. Therefore, TDM is generally not recommended for this class of drugs. TDM has been successfully applied in the clinical practice for certain antiretroviral drugs, but there are ongoing research efforts on the use and refinement of TDM for human immunodeficiency virus treatment, and convincing data from randomized trials are still needed. The best pharmacokinetic measures of drug exposure such as trough and peak concentrations or concentration ratios have not been unambiguously established.

Bioanalytical issues in patient-friendly sampling methods for therapeutic drug monitoring: focus on antiretroviral drugs

Therapeutic drug monitoring is a way to pharmacokinetically guide drug therapy to assure a certain exposure to a drug when this exposure is related to treatment effectiveness or toxicity. Routinely, drug concentrations are measured in plasma obtained by venipuncture. However, venous sampling is difficult in some populations, such as neonates and patients suffering from phlebitis, and there may be logistical challenges, for example when nonhospital-based sampling is warranted (e.g., resource-limited settings). A proper bioanalytical method is crucial for measurements of drug level matrices suitable for patient-friendly drug monitoring. Special attention must be paid to bioanalytical methods in these patient-friendly matrices, since specific matrix-associated issues may have important implications. In this review, we will discuss these issues and give an overview of published bioanalytical methods with a focus on patient-friendly drug monitoring of antiretroviral drugs, where dried blood spots, hair and saliva have been the most important matrices for patient-friendly therapeutic drug monitoring. Furthermore, we will point out considerations for proper assay development and validation.

A less sensitive detector does not necessarily result in a less sensitive method: fast quantification of 13 antiretroviral analytes in plasma with liquid chromatography coupled with tandem mass spectrometry

BACKGROUND

We previously developed a method for the simultaneous determination of the human immunodeficiency protease inhibitors: amprenavir, atazanavir, darunavir, indinavir, lopinavir, nelfinavir, ritonavir, saquinavir and tipranavir, the active nelfinavir metabolite M8 the non-nucleoside reverse transcriptase inhibitors efavirenz, nevirapine and etravirine and the internal standards dibenzepine, (13)C(6)-efavirenz, D5-saquinavir and D6-indinavir in plasma using liquid chromatography coupled with tandem mass spectrometry with a Sciex API3000 triple quadrupole mass spectrometer and an analytical run time of only 10 min. We report the transfer of this method from the API3000 to a supposedly less sensitive Sciex API365 mass spectrometer.

METHODS

We describe the steps that were undertaken to optimize the sensitivity and validation of the method that we transferred.

RESULTS AND CONCLUSIONS

We showed that transfer of a method to a putative less sensitive detector did not necessarily result in a less sensitive assay, and this method can be applied in laboratories where older mass spectrometers are available. Ultimately, the performance of the method was validated. Accuracy and precision was within 87%-110% and <13%, respectively. No notable loss in selectivity was observed.

The role of therapeutic drug monitoring in pediatric HIV/AIDS

International guidelines do not recommend therapeutic drug monitoring (TDM) of HIV-infected children as a routine measurement as part of medical management. There are, however, several clinical scenarios in which TDM may be indicated. Underdosing may be one of the major risks, especially in younger children. No randomized controlled clinical trials have been conducted to assess the added value of TDM in HIV-infected children, making recommendations for TDM in children with HIV/AIDS merely based on expert opinion. There is a need for more descriptive studies on the usefulness of TDM in HIV-infected children to convince pediatricians worldwide to let more children benefit from TDM.

Pharmacokinetic interactions between ritonavir and quinine in healthy volunteers following concurrent administration

AIMS

To evaluate the pharmacokinetic interactions between ritonavir and quinine in healthy volunteers.

METHODS

Ten healthy volunteers were each given 600-mg single oral doses of quinine alone, ritonavir alone (200 mg every 12 h for 9 days), and quinine in combination with ritonavir, in a three-period pharmacokinetic nonrandomized sequential design study. Quinine was co-administered with the 15th dose of ritonavir. Blood samples collected at predetermined time intervals were analysed for ritonavir, quinine and its major metabolite, 3-hydroxyquinine, using a validated high-performance liquid chromatography method.

RESULTS

Concurrent ritonavir administration resulted in about fourfold increases in both the C(max) and AUC(T)[C(max) 2.79 +/- 0.22 vs. 10.72 +/- 0.32 mg l(-1), 95% confidence interval (CI) 7.81, 8.04; AUC 50.06 +/- 2.52 vs. 220.47 +/- 6.68 mg h(-1) l(-1), 95% CI 166.3, 175.3], a significant increase (P < 0.01) in the elimination half-life (11.15 +/- 0.80 vs. 13.37 +/- 0.33 h, 95% CI 1.64, 2.77) and about a 4.5-fold decrease in CL/F (12.01 +/- 0.61 vs. 2.71 +/- 0.09 l h(-1)) of quinine. Also, with ritonavir, there was a pronounced reduction of AUC(metabolite)/AUC(unchanged drug) ratio of quinine (1.35 +/- 0.10 vs. 0.13 +/- 0.02) along with a marked decrease in C(max) (1.80 +/- 0.12 vs. 0.96 +/- 0.09 mg l(-1)) and AUC(0-48h) (62.80 +/- 6.30 vs. 25.61 +/- 2.44 mg h(-1) l(-1)) of the metabolite. Similarly, quinine caused modest but significant increases (P < 0.01) in the C(max), AUC and elimination T((1/2)) of ritonavir.

CONCLUSIONS

Downward dosage adjustment of quinine appears necessary when concurrently administered with ritonavir.

Pharmacokinetic interactions between buprenorphine/naloxone and once-daily lopinavir/ritonavir

BACKGROUND

This study was conducted to examine the pharmacokinetic interactions between buprenorphine/naloxone (BUP/NLX) and lopinavir/ritonavir (LPV/r) in HIV-seronegative subjects chronically maintained on BUP/NLX.

METHODS

This study was an open labeled pharmacokinetic study in twelve HIV-seronegative subjects stabilized on at least 3 weeks of BUP/NLX therapy. Subjects sequentially underwent baseline and steady-state pharmacokinetic evaluation of once-daily LPV/r (800/200 mg).

RESULTS

Compared to baseline values, BUP AUC0-24h (46.8 vs. 46.2 ng*hr/mL) and Cmax (6.54 vs. 5.88 ng/mL) did not differ significantly after achieving steady-state LPV/r. Similar analyses of norBUP, the primary metabolite of BUP, demonstrated no significant difference in norBUP AUC0-24 hours (73.7 vs. 52.7 ng x h/mL); however, Cmax (5.29 vs. 3.11 ng/mL) levels were statistically different (P < 0.05) after LPV/r administration. Naloxone concentrations were similarly unchanged for AUC0-24 hours (0.421 vs. 0.374 ng x hr/mL) and Cmax (0.186 vs. 0.186 ng/mL). Using standardized measures, no objective opioid withdrawal was observed. The AUC0-24 hours and Cmin of LPV in this study did not significantly differ from historical controls (159.6 vs. 171.3 microg x hr/mL) and (2.3 vs. 1.3 microg/mL).

CONCLUSIONS

The addition of LPV/r to stabilized patients receiving BUP/NLX did not affect buprenorphine pharmacokinetics but did increase the clearance of norbuprenorphine. Pharmacodynamic responses indicate that the altered norbuprenorphine clearance did not lead to opioid withdrawal. Buprenorphine/naloxone and LPV/r can be safely coadministered without need for dosage modification.

LC-APCI mass spectrometric method development and validation for the determination of atovaquone in human plasma

A newly developed LC-APCI mass spectrometric method is described for human plasma determination of atovaquone using lapachol internal standard. A single-step protein precipitation technique for plasma extraction of atovaquone achieving mean recovery of 94.17% (CV 8%) without compromising sensitivity (limit of quantitation 50.3 ng/mL) or linearity (50.3 ng/mL-23924.6 ng/mL) is delineated in this paper. Heated nebulizer in negative multiple reaction monitoring mode was employed with transitions m/z 365.2 --> m/z 337.1 and m/z 240.9 --> m/z 185.7 for atovaquone and lapachol respectively in this liquid chromatographic-tandem mass spectrometric method. Excellent chromatographic separation on a Synergi 4 micro Polar-RP 80A (150 x 2.0 mm) column, using 100 microL of plasma extraction volume along with 10 microL of injection load, completing analysis run-time within 2.5 min, highlights this simple yet unique bioanalytical method. The developed method can be successfully applied to pharmacokinetic studies on atovaquone suspension administered in healthy volunteers or HIV-infected patients. Moreover full method validation results not published before are presented and discussed in detail for the first time in this article.

Dose adjustment of the non-nucleoside reverse transcriptase inhibitors during concurrent rifampicin-containing tuberculosis therapy: one size does not fit all

IMPORTANCE OF THE FIELD

HIV/tuberculosis (TB) co-infection is common and associated with high mortality. Simultaneous highly active antiretroviral therapy during TB treatment is associated with substantial survival benefit but drug-drug interactions complicate NNRTI dosing.

AREAS COVERED IN THIS REVIEW

We reviewed the impact of rifampicin-containing TB therapy on the NNRTIs pharmacokinetics and clinical outcome. PubMed database was searched from 1966 to July 2009 using the terms efavirenz, rifampicin, nevirapine, pharmacokinetics, pharmacogenetics, HIV, TB, CYP2B6, CYP3A4 and metabolism. References from identified articles and abstracts from meetings were also reviewed.

WHAT THE READER WILL GAIN

A comprehensive review of the literature on this subject including pharmacokinetic and clinical studies. Most studies were small, observational or underpowered to detect the true effect of rifampicin on NNRTI-based therapy. None of the studies were controlled for genetic factors and there were limited data on children.

TAKE HOME MESSAGE

There were insufficient data to make definitive recommendations about dose adjustment of the NNRTIs during rifampin-containing therapy. Current data suggest that the standard dose of efavirenz or nevirapine is adequate in most HIV/TB co-infected adults. However, more research is needed in pediatric populations as well as to define role of drug-gene interactions.

Effects of concurrent administration of nevirapine on the disposition of quinine in healthy volunteers

Objectives

Nevirapine and quinine are likely to be administered concurrently in the treatment of patients with HIV and malaria. Both drugs are metabolised to a significant extent by cytochrome P450 (CYP)3A4 and nevirapine is also an inducer of this enzyme. This study therefore evaluated the effect of nevirapine on the pharmacokinetics of quinine.

Methods

Quinine (600 mg single dose) was administered either alone or with the 17th dose of nevirapine (200 mg every 12 h for 12 days) to 14 healthy volunteers in a crossover fashion. Blood samples collected at predetermined time intervals were analysed for quinine and its major metabolite, 3-hydroxquinine, using a validated HPLC method.

Key findings

Administration of quinine plus nevirapine resulted in significant decreases (P &lt; 0.01) in the total area under the concentration–time curve (AUCT), maximum plasma concentration (Cmax) and terminal elimination half-life (T1/2β) of quinine compared with values with quinine dosing alone (AUC: 53.29 ± 4.01 vs 35.48 ± 2.01 h mg/l; Cmax: 2.83 ± 0.16 vs 1.81 ± 0.06 mg/l; T1/2β: 11.35 ± 0.72 vs 8.54 ± 0.76 h), while the oral plasma clearance markedly increased (11.32 ± 0.84 vs 16.97 ± 0.98 l/h). In the presence of nevirapine there was a pronounced increase in the ratio of AUC(metabolite)/AUC (unchanged drug) and highly significant increases in Cmax and AUC of the metabolite (P &lt; 0.01).

Conclusions

Nevirapine significantly alters the pharmacokinetics of quinine. An increase in the dose of quinine may be necessary when the drug is co-administered with nevirapine.

Therapeutic drug monitoring of antiretrovirals for people with HIV

BACKGROUND

Despite the efficacy of combination antiretroviral therapy (ART) and the improvement in prognosis of those living with HIV/AIDS, a large proportion of individuals on ART does not achieve or maintain adequate virological suppression. Several tools have been proposed to enhance ART outcomes, including therapeutic drug monitoring (TDM) of antiretrovirals (ARVs). The aim of ARV TDM is to identify elevated (potentially toxic) or low (potentially sub-therapeutic) ARV concentrations. ARV TDM may thus optimise efficacy and minimise toxicity of ART.

OBJECTIVES

To evaluate whether ARV TDM reduces mortality and morbidity of adult patients on ART. The primary outcome measures that have been assessed include death (all cause); occurrence of HIV-related events (death or AIDS-defining illness) and the proportion of patients achieving and maintaining an undetectable viral load, as defined by the authors.

SEARCH STRATEGY

We conducted a comprehensive search including both published and unpublished studies in all languages in MEDLINE, EMBASE and The Cochrane Library, between January 1980 and January 2008. Databases listing conference abstracts and reference lists of articles were searched. Additional data were sought from relevant authors; however, no additional data were provided.

SELECTION CRITERIA

Only randomized controlled trials conducted subsequent to the introduction of combination ART were included in this systematic review. Participants could be on either a protease inhibitor (PI)-based regimen or non-nucleoside reverse transcriptase (NNRTI)-based regimen and be either ARV-naive or -experienced.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed and extracted data for analysis. Meta-analysis was conducted where appropriate. Where study outcomes could not be combined, a narrative review was performed. Outcome measures for dichotomous data were reported as a relative risk with 95% confidence intervals. Stratified analyses were conducted by ARV regimen and treatment groups. Heterogeneity between studies was anticipated; therefore, random effects models were chosen to generate pooled effects. Differences in the findings were assessed by the chi square test for heterogeneity (p <0.1) that was quantified by the Higgins I(2) statistic.

MAIN RESULTS

Identified were 1408 records, and eight trials with a total of 1181 participants were included in the review. Trials were conducted in higher income earning countries between 2002 and 2007. Sample sizes ranged between 40 and 230. The methodological quality of the studies was judged to be generally good, although allocation concealment was reported in only three of the eight studies. A meta-analysis including three studies did not show any significant effect on virological suppression below 500 HIV-RNA copies/mL at one year (RR 1.28; [0.86, 1.92] chi(2) = 11.55 (P = 0.003), I(2) = 83%). Two trials including participants predominantly treated with unboosted PI-based regimens reported a 49% increased likelihood of achieving a HIV-RNA viral load below 500 copies/mL at 52 weeks (RR 1.49 [1.20, 1.83] chi(2) = 0.69 (P = 0.4), I(2) = 0%). Safety outcomes were reported in four studies and were similar between TDM and standard of care. Uptake of expert advice based on TDM results was good in two trials (>70%), but low (<35%) in the remaining three studies that reported uptake of the recommendations.

AUTHORS' CONCLUSIONS

Our review does not support routine use of ARV TDM in ARV-naive or -experienced patients on either boosted PI or NNRTI ART regimens. TDM in treatment-naive participants on a PI-based ART regimen, particularly if unboosted by ritonavir, may improve virological outcomes. Trials were underpowered with small sample sizes, short durations of follow-up and generally poor uptake of TDM recommendations. As these trials were conducted in higher income earning countries, results may not be generalisable to resource-limited countries where the burden of HIV is heaviest.

Effects of concurrent administration of nevirapine on the disposition of quinine in healthy volunteers

OBJECTIVES

Nevirapine and quinine are likely to be administered concurrently in the treatment of patients with HIV and malaria. Both drugs are metabolised to a significant extent by cytochrome P450 (CYP)3A4 and nevirapine is also an inducer of this enzyme. This study therefore evaluated the effect of nevirapine on the pharmacokinetics of quinine.

METHODS

Quinine (600 mg single dose) was administered either alone or with the 17th dose of nevirapine (200 mg every 12 h for 12 days) to 14 healthy volunteers in a crossover fashion. Blood samples collected at predetermined time intervals were analysed for quinine and its major metabolite, 3-hydroxquinine, using a validated HPLC method.

KEY FINDINGS

Administration of quinine plus nevirapine resulted in significant decreases (P < 0.01) in the total area under the concentration-time curve (AUC(T)), maximum plasma concentration (C(max)) and terminal elimination half-life (T((1/2)beta)) of quinine compared with values with quinine dosing alone (AUC: 53.29 +/- 4.01 vs 35.48 +/- 2.01 h mg/l; C(max): 2.83 +/- 0.16 vs 1.81 +/- 0.06 mg/l; T((1/2)beta): 11.35 +/- 0.72 vs 8.54 +/- 0.76 h), while the oral plasma clearance markedly increased (11.32 +/- 0.84 vs 16.97 +/- 0.98 l/h). In the presence of nevirapine there was a pronounced increase in the ratio of AUC(metabolite)/AUC (unchanged drug) and highly significant increases in C(max) and AUC of the metabolite (P < 0.01).

CONCLUSIONS

Nevirapine significantly alters the pharmacokinetics of quinine. An increase in the dose of quinine may be necessary when the drug is co-administered with nevirapine.