The cost effectiveness of antiretroviral regimens for the treatment of HIV/AIDS

On the Use of Markov Models in Pharmacoeconomics: Pros and Cons and Implications for Policy Makers

We present an overview of the main methodological features and the goals of pharmacoeconomic models that are classified in three major categories: regression models, decision trees, and Markov models. In particular, we focus on Markov models and define a semi-Markov model on the cost utility of a vaccine for Dengue fever discussing the key components of the model and the interpretation of its results. Next, we identify some criticalities of the decision rule arising from a possible incorrect interpretation of the model outcomes. Specifically, we focus on the difference between median and mean ICER and on handling the willingness-to-pay thresholds. We also show that the life span of the model and an incorrect hypothesis specification can lead to very different outcomes. Finally, we analyse the limit of Markov model when a large number of states is considered and focus on the implementation of tools that can bypass the lack of memory condition of Markov models. We conclude that decision makers should interpret the results of these models with extreme caution before deciding to fund any health care policy and give some recommendations about the appropriate use of these models.

Implementation of HIV treatment as prevention strategy in 17 Canadian sites: immediate and sustained outcomes from a 35-month Quality Improvement Collaborative

BACKGROUND

Rapid scale-up of effective antiretroviral therapy (ART) is required to meet global targets to eliminate new HIV infections and AIDS-related deaths. Yet, gaps persist in all nations striving for these targets. In the intervention setting of British Columbia (BC), Canada, where ART is publicly funded, 73% of HIV-diagnosed were on ART in 2011, and only 49% were achieving viral suppression.

METHODS

An observational case descriptive study of HIV care sites in BC recruited to participate in a 35-month Breakthrough Series Quality Improvement Collaborative and sustainability network. Sites collected four quality indicators, qualitative change descriptions and implemented the chronic care model (CCM) and HIV care and treatment guidelines. Two reviewers assigned monthly implementation scores to evaluate site progress (January 2011-2012). All quality indicators were pooled and analysed using probability-based run chart rules.

RESULTS

Seventeen teams with a pooled median population of 2296 HIV patients joined the initiative. Comprehensive CCM implementation and evidence of improvement was achieved by 29% of sites (implementation score of 4.0 or higher on 5.0 scale). Evidence of sustained improvement was observed for patient engagement (88.8-90.4%), ART uptake among patients unequivocally in need (92.9-94.8%), and ART uptake (≥6 months) and achieving viral suppression (57.3-78.4%) (all p<0.05).

CONCLUSIONS

This study shows evidence of sustained improvements in HIV care processes and treatment outcomes for an estimated population of 2296 HIV patients in 17 BC sites. Overall success points to opportunities for other high-income countries seeking to improve HIV health outcomes.

Cost-Effectiveness of Dolutegravir in HIV-1 Treatment-Naive and Treatment-Experienced Patients in Canada

Introduction

The Antiretroviral Analysis by Monte Carlo Individual Simulation (ARAMIS) model was adapted to evaluate the cost-effectiveness of dolutegravir (DTG) in Canada in treatment-naive (TN) and treatment-experienced (TE) human immunodeficiency virus (HIV)-1 patients.

Methods

The ARAMIS-DTG model is a microsimulation model with a lifetime analytic time horizon and a monthly cycle length. Markov health states were defined by HIV health state (with or without opportunistic infection). DTG was compared to efavirenz (EFV), raltegravir (RAL), darunavir/ritonavir, rilpivirine (RPV), elvitegravir/cobicistat, atazanavir/ritonavir and lopinavir/ritonavir in TN patients and to RAL in TE patients. The initial cohort, the main efficacy data and safety data were derived from phase III clinical trials. Treatment algorithms were based on expert opinion. Costs normalized to the year 2013 included antiretroviral treatment cost, testing, adverse event, HIV and cardiovascular disease care and were derived from the literature.

Results

Dolutegravir was estimated to be the dominant strategy compared with all comparators in both TN and TE patients. Treatment with DTG was associated with additional quality-adjusted life-years that ranged from 0.17 (vs. RAL) to 0.47 (vs. EFV) in TN patients and was 0.60 in TE patients over a lifetime. Cost savings ranged from Can$1393 (vs. RPV) to Can$28,572 (vs. RAL) in TN patients and amounted to Can$3745 in TE patients. Sensitivity analyses demonstrated the robustness of the model.

Conclusions

Dolutegravir is a dominant strategy in the management of TN and TE patients when compared to recommended comparators. This is mainly related to the high efficacy and high barrier to resistance.

Funding

ViiV Healthcare.

Electronic supplementary material

The online version of this article (doi:10.1007/s40121-015-0071-0) contains supplementary material, which is available to authorized users.

A methodological review of models used to estimate the cost effectiveness of antiretroviral regimens for the treatment of HIV infection

The aim of this article was to perform a detailed methodological review of models used to estimate the cost effectiveness of drug treatment regimens for HIV infection in Europe and North America and assess the relationship between the different modeling approaches or key structural assumptions and the results. Electronic searches in three databases (MEDLINE, EMBASE, and the Cochrane Library) identified the cost-effectiveness models. Modeling approaches and structural assumptions were abstracted for all models. For three case studies of multiple analyses that compared the cost effectiveness of two drug regimens using the same clinical data inputs, differences in results were compared with differences in modeling approaches and structural assumptions. Forty-one model publications were reviewed. Recent models included Monte Carlo simulations, Markov models, or discrete-event simulation models, all including multiple lines of therapy and capturing the long-expected duration of efficacy of highly active antiretroviral therapy. In the three case studies, assumptions about the duration of efficacy after the trial time period, whether differences between the two regimens persist after the trial time period, the sequence of regimens after initial regimen failure, and the cost and utility assigned to adverse events, but not the modeling approach, were the most important factors in explaining differences in the results. As the models and treatment pathways get more complex, models should be validated using clinical trial data and local observational databases. The results of sensitivity analyses testing the impact of the structural assumptions that might change the results as identified in this review should also be presented in modeling papers.

Counting the cost of not costing HIV health facilities accurately: pay now, or pay more later

The HIV pandemic continues to be one of our greatest contemporary public health threats. Policy makers in many middle- and low-income countries are in the process of scaling up HIV prevention, treatment and care services in the context of a reduction in international HIV funding due to the global economic downturn. In order to scale up services that are sustainable in the long term, policy makers and implementers need to have access to robust and contemporary strategic information, including financial information on expenditure and cost, in order to be able to plan, implement, monitor and evaluate HIV services. A major problem in middle- and low-income countries continues to be a lack of basic information on the use of services, their cost, outcome and impact, while those few costing studies that have been performed were often not done in a standardized fashion. Some researchers handle this by transposing information from one country to another, developing mathematical or statistical models that rest on assumptions or information that may not be applicable, or using top-down costing methods that only provide global financial costs rather than using bottom-up ingredients-based costing. While these methods provide answers in the short term, countries should develop systematic data collection systems to store, transfer and produce robust and contemporary strategic financial information for stakeholders at local, sub-national and national levels. National aggregated information should act as the main source of financial data for international donors, agencies or other organizations involved with the global HIV response. This paper describes the financial information required by policy makers and other stakeholders to enable them to make evidence-informed decisions and reviews the quantity and quality of the financial information available, as indicated by cost studies published between 1981 and 2008. Among the lessons learned from reviewing these studies, a need was identified for providing countries with practical guidance to produce reliable and standardized costing data to monitor performance, as countries want to improve programmes and services, and have to demonstrate an efficient use of resources. Finally, the issues raised in this paper relate to the provision of all areas of healthcare in countries and it is going to be increasingly important to leverage the lessons learned from the HIV experience and use resources more effectively and efficiently to improve health systems in general.

Modeling the cost-effectiveness of health programs: HIV testing and early treatment in the USA

The recent results from the NIH HIV Prevention Trials Network (HPTN) 052 trial, confirmed the relationship between plasma viral load and degree of infectivity of people living with HIV (PLHIV); when PLHIV are treated with antiretroviral therapy (ART), their infectivity is significantly reduced. This reiterates the importance of 'treatment for prevention', as well as the therapeutic function of ART. This and other studies raise a number of important questions, including when to start ART. Given the substantial number of PLHIV that are unaware that they are infected, should policy-makers set-up specific programs to identify these PLHIV and get them into treatment early? Long et al. tried to answer this question by modeling the cost-effectiveness of an expanded screening and treatment program in the USA but how good was their model, how can modeling exercises assist policy-makers in answering these difficult questions and what are some of the broader implications?

Access to antiretroviral therapy among HIV/AIDS patients in khon kaen province, Thailand

This study attempted to identify the factors associated with the access to antiretroviral therapy (ARV) among HIV/AIDS patients in Khon Kaen Province, Thailand. We collected medical and sociodemographic data from the medical charts of adult patients living in the province who received medical services at two public hospitals in the province. The study period was from December 1, 2001 to February 28, 2002. Total 593 outpatients were included in the analysis. One hundred and forty-six patients (24.6%) received ARV. A logistic regression analysis was conducted to identify the factors associated with the use of ARV. Patients who were covered by the Civil Servant Medical Benefit Scheme were significantly more likely to receive ARV than those who were covered by the Universal Coverage Scheme (UC), a publicly-funded medical insurance (OR = 12.43; 95% CI = 6.03-25.62). The results of this study indicated that there were inequalities in access to and use of ARV among HIV/AIDS patients by health insurance status. The current government announced that they would include ARV in the benefits package of UC. It would be important to monitor how this policy will improve the access to ARV among HIV/AIDS patients.

Determinants of health care costs of HIV-positive patients in the Canary Islands, Spain

The aims of this study were to estimate medical expenditures on human immunodeficiency virus (HIV) treatment and to identify significant associated variables. We performed a retrospective multi-centre study in the Canary Islands using a sample of 569 patients recruited at outpatient visits. The study examined demographic and clinical variables, health-related quality of life (HRQOL), and health care resources. Clinical data was obtained from medical records and patient interviews. Several empirical models for identifying the relationship between health care costs and independent variables were developed. The greatest expense came from pharmaceutical expenditure (82.1% of direct costs), while hospital costs only represented 4.6% of total expenditure. The data showed a statistically significant association between health care costs and the CD4 count of the previous year. HRQOL was also a significant variable. Therefore, CD4 cell count can be used to predict health care costs in patients. Policymakers could use this information to help guide their decisions in allocating limited health care resources to HIV treatments.

Cost effectiveness of darunavir/ritonavir in highly treatment-experienced, HIV-1-infected adults in the USA

INTRODUCTION

Darunavir is a new protease inhibitor (PI) that is co-administered with low-dose ritonavir and has demonstrated substantial efficacy in clinical trials of highly treatment-experienced patients when combined with an optimized background regimen (with or without enfuvirtide). This study estimates the cost effectiveness of darunavir with ritonavir (DRV/r) in this population over 5-year and lifetime time horizons in the USA.

METHODS

A Markov model was used to follow a treatment-experienced HIV-1 cohort through six health states, based on CD4 cell count: greater than 500, 351-500, 201-350, 101-200, 51-100 and 0-50 cells/mm³, and death. The magnitude of the CD4 cell count increase and duration of increasing and stable periods were derived from week 48 DRV/r clinical trial results (POWER 1 and 2). The treatment pathway assumed one regimen switch following treatment failure on the initial regimen. The use of antiretroviral drugs was based on usage in DRV/r clinical trials. US daily wholesale acquisition costs were calculated using the recommended daily doses. For each CD4 cell count range, utility values, HIV-1-related mortality rates and costs for medical resources (other than antiretroviral drug costs) were obtained from published literature. Non-HIV-1-related mortality rates were calculated by applying a relative risk value to the US general population age and gender-specific mortality rates. Costs and outcomes were discounted at 3% per year. One-way and probabilistic sensitivity analyses and variability analysis were performed.

RESULTS

In a 5-year analysis, patients receiving DRV/r experienced 3.80 quality-adjusted life-years (QALYs) and incurred total medical costs of US$217,288, while those receiving control PIs experienced 3.60 QALYs and incurred costs of US$218,962. DRV/r was both more effective and less costly than control PIs. For the lifetime analysis, the QALYs and lifetime medical costs with DRV/r were 10.03 and US$565,358, compared with 8.76 and US$527,287 with control PIs. The incremental cost-effectiveness ratio for DRV/r compared with control PIs was US$30,046. One-way sensitivity analyses for both time horizons indicated that the results were most sensitive to changes in the rate of CD4 cell count change during stable and declining periods (lifetime only), duration of stable period (5-year only) and HIV-1-related mortality rates. The results of the variability analysis were most sensitive to the model time horizon. Nevertheless, for all ranges and scenarios tested in these analyses, the incremental cost per QALY gained remained below US$50,000. The probabilistic sensitivity analysis showed that there was a 0.921 and 0.950 probability of a cost-effectiveness ratio below US$50,000 per QALY for the 5-year and lifetime time horizon, respectively.

CONCLUSIONS

DRV/r is predicted to be cost effective compared with control PI in highly treatment-experienced patients and is predicted to yield an average of 0.20 additional QALYs per treatment-experienced patient over 5 years and 1.27 additional QALYs over a lifetime in this population.

Cost-effectiveness of tipranavir versus comparator protease inhibitor regimens in HIV infected patients previously exposed to antiretroviral therapy in the Netherlands

Background

This study compares the costs and effects of a regimen with ritonavir-boosted tipranavir (TPV/r) to a physician-selected genotypically-defined standard-of-care comparator protease inhibitor regimen boosted with ritonavir (CPI/r) in HIV infected patients that were previously exposed to antiretroviral therapy in the Netherlands.

Methods

We compared the projected lifetime costs and effects of two theoretical groups of 1000 patients, one receiving a standard of care regimen with TPV/r as a component and the other receiving a standard of care regimen with CPI/r. A 3-stage Markov model was formulated to represent three different consecutive HAART regimens. The model uses 12 health states based on viral load and CD4+ count to simulate disease progression. The transition probabilities for the Markov model were derived from a United States cohort of treatment experienced HIV patients. Furthermore, the study design was based on 48-week data from the RESIST-2 clinical trial and local Dutch costing data. Cost and health effects were discounted at 4% and 1.5% respectively according to the Dutch guideline. The analysis was conducted from the Dutch healthcare perspective using 2006 unit cost prices.

Results

Our model projects an accumulated discounted cost to the Dutch healthcare system per patient receiving the TPV/r regimen of €167,200 compared to €145,400 for the CPI/r regimen. This results in an incremental cost of €21,800 per patient. The accumulated discounted effect is 7.43 life years or 6.31 quality adjusted life years (QALYs) per patient receiving TPV/r, compared to 6.91 life years or 5.80 QALYs per patient receiving CPI/r. This translates into an incremental effect of TPV/r over CPI/r of 0.52 life years gained (LYG) or 0.51 QALYs gained. The corresponding incremental cost effectiveness ratios (iCERs) are €41,600 per LYG and €42,500 per QALY.

Conclusion

We estimated the iCER for TPV/r compared to CPI/r at approximately €40,000 in treatment experienced HIV-1 infected patients in the Netherlands. This ratio may well be in range of what is acceptable and warrants reimbursement for new drug treatments in the Netherlands, in particular in therapeutic areas as end-stage oncology and HIV and other last-resort health-care interventions.

Pathogenesis of HIV in the gastrointestinal tract

Gut-associated lymphoid tissue (GALT) is an important site for early HIV replication and severe CD4+ T-cell depletion. Initiation of highly active antiretroviral therapy leads to incomplete suppression of viral replication and substantially delayed and only partial restoration of CD4+ T cells in GALT compared with peripheral blood. Persistent viral replication in GALT leads to replenishment and maintenance of viral reservoirs. Increased levels of inflammation, immune activation, and decreased levels of mucosal repair and regeneration contribute to enteropathy. Assessment of gut mucosal immune system will provide better insights into the efficacy of highly active antiretroviral therapy in immune restoration and suppression of viral reservoirs.

Clinical care of the HIV-infected drug user

HIV/AIDS and chemical dependency, the latter often intertwined with mental illness, are complex, overlapping spheres that adversely influence each other and the overall clinical outcomes of the affected individual. Each disorder individually impact tens of millions of people adversely, with explosive epidemics described worldwide. This article addresses the adverse consequences of HIV/AIDS, drug injection, the secondary comorbidities of both, and the impact of immunosuppression on presentation of disease as well as approaches to managing the HIV-infected drug user.

Cost-Efficacy Comparison among Three Antiretroviral Regimens in??HIV-1 Infected, Treatment-Experienced Patients

BACKGROUND AND OBJECTIVE

In the face of increasing antiretroviral (ARV) treatment options and costs, payers are progressively challenged with prioritising resources. The cost effectiveness of the ARV agent enfuvirtide has been shown to be comparable to that of other available HIV treatment strategies, based on Markov modeling. However, an evaluation of enfuvirtide treatment costs that considers the impact of virological and immunological responses to therapy may provide a more clinically meaningful perspective for primary HIV healthcare providers. The aim of this study was to assess the cost per unit change in efficacy (HIV RNA decreases and CD4 count increases) of three different ARV regimens for triple class-experienced HIV-1 infected patients using actual drug costs and data from randomised, controlled clinical trials.

STUDY DESIGN

The analysis included three steps. First, re-analysis of 48-week clinical trial data (T-20 vs Optimized Regimen Only [TORO]) to allow for a more direct comparison of enfuvirtide versus other commonly used ARV agents. All patients included in the re-analysis received a common optimised background (COB) regimen of three drugs: two nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs) and a ritonavir-boosted protease inhibitor (PI), lopinavir. HIV RNA levels and CD4 count changes were determined for three patient groups according to the treatment received - group 1: COB + enfuvirtide; group 2: COB + PI; group 3: COB + NRTI + PI. The second step of the analysis involved calculating the annualised regimen costs ($US wholesaler acquisition cost) for each patient group. In the third step, cost-efficacy ratios were calculated and compared between groups: (a) the annualised regimen cost ($US)/change in viral load from baseline, and (b) the annualised regimen cost ($US)/change in CD4+ cell count from baseline.

RESULTS

One hundred and fifty-seven patients were included in this previously unplanned secondary analysis (group 1: 79 patients; group 2: 42 patients; group 3: 36 patients). HIV RNA and CD4 count changes from baseline to week 48 were -1.80, -0.89 and -0.61 log(10) copies/mL (p < 0.001 for enfuvirtide vs each non-enfuvirtide group) and +102, +57 and +52 cells/mm(3) (p < 0.05 for enfuvirtide versus each non-enfuvirtide subgroup) for groups 1, 2 and 3, respectively. The annualised costs of the combination therapies were $US 35,624, $US 27,549 and $US 30,624; and the costs per 0.50 log(10) copies/mL HIV RNA decrease were $US 9,872, $US 15,542 and $US 24,907 (p < 0.05 for enfuvirtide vs each non-enfuvirtide subgroup) for groups 1, 2 and 3, respectively. The costs per 25 cells/mm(3) CD4 count increase were $US 8,722, $US 12,127 and $US 14,636 for subgroups 1, 2 and 3, respectively. Similar patterns in regimen cost per unit change were achieved after adjusting for baseline prognostic variables. The incremental cost-efficacy ratios for group 1 versus the combination of groups 2 and 3 were $US 3,124 for HIV RNA reduction and $US 3,239 for CD4 count increase.

CONCLUSION

Enfuvirtide-containing regimens are associated with higher cost as well as improved virological and immunological outcomes when compared with alternative four- and five-drug regimens. When costs and outcomes are considered jointly, an enfuvirtide-based regimen is more cost efficacious than alternative regimens in this patient population.

Neuropsychiatric disorders in HIV infection: impact of diagnosis on economic costs of care

BACKGROUND

HAART is associated with a growing prevalence of HIV-associated neuropsychiatric disorders (NPD) despite improved overall survival.

OBJECTIVE

To investigate the added direct costs of medical care for patients with and without NPD.

METHODS

Nine dimensions of patient-specific costs [as costs per patient per month (CPM)] were followed prospectively between 1997 and 2003 in a community-based HIV/AIDS clinic for HIV-1-seropositive patients with a diagnosis of NPD (n = 188) and without (n = 153). Patients with NPD were stratified into subgroups of cognitive impairment (CI), peripheral neuropathies (PN), or other neuropsychiatric disorders (OND).

RESULTS

Compared with the non-NPD group ($916), patients in the NPD group showed an increased mean CPM during the 12-month intervals immediately preceding and subsequently following NPD diagnosis [$1371 (P < 0.001) and 1463 US dollars (P < 0.001), respectively], but not at 18 months prior to diagnosis (1061 US dollars; P > 0.05). Intragroup comparisons between 12 month post-diagnosis and 18 month pre-diagnosis showed a mean CPM increased of 67% (1613 US dollars; P < 0.001) with CI, 31% (1490 US dollars; P < 0.01) with PN, and 33% (1362 US dollars; P < 0.01) with OND. Increased numbers of clinic and physician visits, non-antiretroviral drugs and home care accounted for the higher mean CPM (P < 0.05) both pre-and post-diagnosis within the NPD group.

CONCLUSIONS

Neuropsychiatric disorders in patients with HIV/AIDS increase medical costs both before and after diagnosis, primarily owing to the management of the neuropsychiatric illness. Cost analyses offer useful measures of evolving patient needs, and provide a basis for allocation of healthcare resources.

Viral suppression and immune restoration in the gastrointestinal mucosa of human immunodeficiency virus type 1-infected patients initiating therapy during primary or chronic infection

Although the gut-associated lymphoid tissue (GALT) is an important early site for human immunodeficiency virus (HIV) replication and severe CD4+ T-cell depletion, our understanding is limited about the restoration of the gut mucosal immune system during highly active antiretroviral therapy (HAART). We evaluated the kinetics of viral suppression, CD4+ T-cell restoration, gene expression, and HIV-specific CD8+ T-cell responses in longitudinal gastrointestinal biopsy and peripheral blood samples from patients initiating HAART during primary HIV infection (PHI) or chronic HIV infection (CHI) using flow cytometry, real-time PCR, and DNA microarray analysis. Viral suppression was more effective in GALT of PHI patients than CHI patients during HAART. Mucosal CD4+ T-cell restoration was delayed compared to peripheral blood and independent of the time of HAART initiation. Immunophenotypic analysis showed that repopulating mucosal CD4+ T cells were predominantly of a memory phenotype and expressed CD11 alpha, alpha(E)beta 7, CCR5, and CXCR4. Incomplete suppression of viral replication in GALT during HAART correlated with increased HIV-specific CD8+ T-cell responses. DNA microarray analysis revealed that genes involved in inflammation and cell activation were up regulated in patients who did not replenish mucosal CD4+ T cells efficiently, while expression of genes involved in growth and repair was increased in patients with efficient mucosal CD4+ T-cell restoration. Our findings suggest that the discordance in CD4+ T-cell restoration between GALT and peripheral blood during therapy can be attributed to the incomplete viral suppression and increased immune activation and inflammation that may prevent restoration of CD4+ T cells and the gut microenvironment.

Pharmacokinetic drug interactions between opioid agonist therapy and antiretroviral medications: implications and management for clinical practice

BACKGROUND

Opioid dependence and HIV/AIDS are 2 of the most serious yet treatable diseases worldwide. Global access to opioid agonist therapy and HIV treatment is expanding but when concurrently used, problematic pharmacokinetic drug interactions can occur.

METHODS

We reviewed English, Spanish, French, and Italian language articles from 1966 to 2005 in Medline using the following keywords: HIV, AIDS, HIV therapy, antiretroviral therapy, HAART, drug interactions, methadone, and buprenorphine. Additionally, we reviewed abstracts from national and international meetings and conference proceedings. Selected references from these articles were reviewed as well.

RESULTS

Clinical case series and carefully controlled pharmacokinetic interaction studies have been conducted between methadone and most approved antiretroviral therapies. Important pharmacokinetic drug interactions have been demonstrated within each class of agents, affecting either methadone or antiretroviral agents. Few studies, however, have been conducted with buprenorphine. The metabolism of both therapies, description of the known interactions, and clinical implications and management of these interactions are reviewed.

CONCLUSIONS

Certain interactions between methadone and antiretroviral medications are known and may have important clinical consequences. To optimize care, clinicians must be alert to these interactions and have a basic knowledge regarding their management.

Costs of medical services for patients with HIV/AIDS in Khon Kaen, Thailand

OBJECTIVE

To estimate the savings and cost of providing highly active antiretroviral therapy (HAART) to adult patients with AIDS under Universal Coverage (UC) in Khon Kaen Province, Thailand.

DESIGN

Micro-costing of outpatient and inpatient services of two referral hospitals, and cost modelling.

SETTING

Khon Kaen Regional Hospital and Northeast Regional Infectious Hospital.

PATIENTS

Adult patients who resided in Khon Kaen and made outpatient visits at and/or those who were discharged from those hospitals from 1 December 2001 to 28 February 2002.

MAIN OUTCOME MEASURE

The average cost per outpatient visit and per inpatient day. Based on these figures, the savings and cost of providing HAART to adult patients with AIDS under UC at outpatient settings in this province were estimated.

RESULTS

The average cost per outpatient visit with and without antiretroviral drugs (ARV) was US$294.2 and US$26.1, respectively. The average cost per inpatient day with and without ARV drugs was US$368.1 and US$43.8, respectively. The net annual cost of HAART was estimated to be US$5 674 629. This is equivalent to 20.0% of the annual UC budget for adults in this province in 2002. Sensitivity analysis and projection to the year 2006 were conducted.

CONCLUSION

A large increase in the budget would be required to provide HAART to all adult patients with AIDS under UC. However, the sensitivity analysis showed it would be an affordable policy option if low-cost antiretroviral drugs were successfully introduced. This type of analysis would be useful to assess the financial implications of providing HAART in public health systems worldwide.

Lopinavir/ritonavir: a review of its use in the management of HIV infection

Lopinavir is a novel protease inhibitor (PI) developed from ritonavir. Coadministration with low-dose ritonavir significantly improves the pharmacokinetic properties and hence the activity of lopinavir against HIV-1 protease. Coformulated lopinavir/ritonavir was developed for ease of administration and to ensure both drugs are taken together, as part of combination therapy with other antiretroviral agents. Coformulated lopinavir/ritonavir-based regimens provide adequate and durable suppression of viral load and sustained improvements in CD4+ cell counts, as demonstrated in randomised trials in antiretroviral therapy-naive and -experienced adults and children. To date, development of primary resistance to lopinavir/ritonavir has not been observed in 470 antiretroviral therapy-naive patients treated for >48 weeks. The lopinavir/ritonavir-based regimen was more effective than nelfinavir in antiretroviral therapy-naive HIV-1-infected patients in a phase III trial. The coformulation is also effective as 'salvage' therapy, as shown by low cross-resistance rates in patients who failed to respond to treatment with other PIs in phase II trials. Coformulated lopinavir/ritonavir was well tolerated in both antiretroviral therapy-naive and -experienced HIV-1-infected adults and children with low rates of study drug-related treatment discontinuations. The most common adverse event in adults associated with lopinavir/ritonavir was diarrhoea, followed by other gastrointestinal disturbances, asthenia, headache and skin rash. The incidence of moderate-to-severe adverse events in children was low, skin rash being the most common. Changes in body fat composition occurred with equal frequency in lopinavir/ritonavir- and nelfinavir-treated naive patients, through week 60 in a phase III study. Although laboratory abnormalities occurred with similar frequency in both treatment groups, triglycerides grade 3/4 elevations were significantly more frequent with lopinavir/ritonavir. Total cholesterol and triglycerides grade 3/4 elevations appear to occur more frequently in PI-experienced than in PI-naive lopinavir/ritonavir-treated patients. A number of clinically important drug interactions have been reported with lopinavir/ritonavir necessitating dosage adjustments of lopinavir/ritonavir and/or the interacting drugs, and several other drugs are contraindicated in patients receiving the coformulation.

CONCLUSION

Coformulated lopinavir/ritonavir is a novel PI that, in combination with other antiretroviral agents, suppresses plasma viral load and enhances immunological status in therapy-naive and -experienced patients with HIV-1 infection. Lopinavir/ritonavir appears more effective than nelfinavir in 'naive' patients and is also suitable for 'salvage' therapy, because of its high barrier to development of resistance. Given its clinical efficacy, a tolerability profile in keeping with this class of drugs, favourable resistance profile and easy-to-adhere-to administration regimen, coformulated lopinavir/ritonavir should be regarded as a first-line option when including a PI in the management of HIV-1 infection.

OVERVIEW OF PHARMACODYNAMIC PROPERTIES

Lopinavir/ritonavir is a coformulation of two structurally related protease inhibitor (PI) antiretroviral agents. Lopinavir is a highly potent and selective inhibitor of the HIV type 1 (HIV-1) protease, an essential enzyme for production of mature, infective virus. It acts by arresting maturation of HIV-1 thereby blocking its infectivity. Thus, the main antiviral action of lopinavir is to prevent subsequent infections of susceptible cells; it has no effect on cells with already integrated viral DNA. Lopinavir has an approximate, equals 10-fold higher in vitro activity against both wild-type and mutant HIV-1 proteases than ritonavir; however, its in vivo activity is greatly attenuated by a high first-pass hepatic metabolism. The low-dose ritonavir coadministered with lopinavir inhibits metabolic inactivation of lopinavir and acts only as its pharmacokinetic enhancer. Therefore, the antiretroviral activity of roviral activity of coformulated lopinavir/ritonavir 400/100mg twice daily is derived solely from lopinavir plasma concentrations. Combining lopinavir with low-dose ritonavir produces lopinavir concentrations far exceeding those needed to suppress 50% of in vitro and in vivo viral replication in CD4+ cells and monocyte/macrophages (main human reservoirs of HIV-1 infection). Thus far, no resistance to lopinavir has been detected in clinical trials in antiretroviral therapy-naive patients treated for up to 204 weeks and only 12% of HIV-1 strains from patients in whom prior treatment with multiple PIs have failed, have been observed to develop resistance to coformulated lopinavir/ritonavir. A strong negative correlation was found between the number of PI mutations at baseline and the viral response rates achieved with lopinavir/ritonavir-based regimens in PI-experienced patients, indicating that resistance to lopinavir increases with increasing number of PI mutations and that five PI mutations represent the clinically relevant genotypic breakpoint for lopinavir.

OVERVIEW OF PHARMACOKINETIC PROPERTIES

The absolute bioavailability of lopinavir coformulated with ritonavir in humans has not yet been established. Multiple-dosage absorption pharmacokinetics of lopinavir/ritonavir 400/100mg twice daily (the mean peak [C(max)] and trough [C(trough)] plasma concentrations at steady-state and the 12-hour area under the plasma concentration-time curve [AUC(12)] of either drug) were stable in antiretroviral therapy-naive and single PI-experienced adult patients receiving therapy over a 24-week evaluation period. The C(trough) values of lopinavir, achieved with lopinavir/ritonavir 400/100mg twice daily, were median 84-fold higher than the protein binding-adjusted 50% effective concentration (EC(50)) of lopinavir against wild-type HIV-1 in antiretroviral therapy-naive HIV-1-infected patients in a phase II study. Bioavailability of lopinavir administered in either the capsule or the liquid lopinavir/ritonavir formulation can be increased substantially with concurrent ingestion of food with moderate-to-high fat content. At steady state, lopinavir is approximately 98-99% plasma protein bound and the percentage of its unbound (i.e. pharmacologically active) fraction is dependent on total drug plasma concentration. Both lopinavir and ritonavir penetrate poorly into the human genital tracts and the cerebrospinal fluid. Both agents undergo extensive and rapid first-pass metabolism by hepatic cytochrome P450 (CYP) 3A4 isoenzyme. However, ritonavir also potently inhibits this enzyme and acts as a pharmacokinetic enhancer of lopinavir. The elimination half-life and apparent oral clearance of lopinavir average approximately 4-6 hours and approximately 6-7 L/h, respectively, with lopinavir/ritonavir 400/100mg twice daily administration. Less than 3% and 20% of the lopinavir dose is excreted unchanged in the urine and faeces, respectively. Limited data show similar pharmacokinetics of lopinavir in children as in adults.

DRUG INTERACTIONS

Coformulated lopinavir/ritonavir has the potential to interact with wide variety of drugs via several mechanisms, mostly involving the CYP enzymes. Coadministration of lopinavir/ritonavir is contraindicated with certain drugs (i.e. flecainide, propafenone, astemizole, terfenadine, ergot derivatives, cisapride, pimozide, midazolam and triazolam) that are highly dependent on CYP3A or CYP2D6 for clearance and for which elevated plasma concentrations are associated with serious and/or life-threatening events. Coadministration with lopinavir/ritonavir is also not recommended for drugs or herbal products (i.e. rifampicin [rifampin] and St. John's wort [Hypericum perforatum]) that may substantially reduce lopinavir plasma concentrations, or drugs whose plasma concentrations elevated by the coformulation may lead to serious adverse reactions (i.e. simvastatin and lovastatin). However, a recent study in healthy volunteers suggests that adequate lopinavir concentrations may be achieved during rifampicin coadministration by increasing the twice-daily dosage of lopinavir/ritonavir in conjunction with therapeutic drug monitoring. The liquid (but not the capsule) formulation of lopinavir/ritonavir contains 42.4% ethanol (v/v) and should not be coadministered with drugs capable of producing disulfiram-like reactions (e.g. disulfiram, metronidazole). Coadministration with saquinavir or indinavir requires no dosage adjustment, whereas coadministration with amprenavir, nevirapine or efavirenz requires a dosage increase of the coformulation typically by 33%. As the oral bioavailability of both didanosine and lopinavir/ritonavir is significantly affected by concurrent food ingestion, didanosine should be administered 1 hour before or 2 hours after lopinavir/ritonavir has been taken with food. Interactions between lopinavir/ritonavir and other nucleoside reverse transcriptase inhibitors (NRTIs) are not expected. The coformulation is also likely to increase plasma concentrations of non-antiretroviral drugs metabolised through the CYP3A pathway. To reduce the risk of their toxicity when coadministered with lopinavir/ritonavir, the recommended actions include: (i) monitoring of the drug plasma concentration (antiarrhythmics and immunosuppressants) or the international normalised ratio (warfarin); (ii) the use of alternative treatment (atorvastatin) or birth control methods (ethinylestradiol); and (iii) dosage adjustment (clarithromycin [only in patients with renal failure], rifabutin, dihydropyridine calcium-channel blockers, atorvastatin, ketoconazole and itraconazole). (ABSTRACT TRUNCATED)

Highly active antiretroviral therapy: pharmacoeconomic issues in the management of HIV infection

The advent of highly active antiretroviral therapy (HAART), including protease inhibitors and/or non-nucleoside reverse transcriptase inhibitors, for the treatment of HIV infection has led to a dramatic decline of morbidity and mortality. The acquisition costs of HAART are substantial. However, these costs are partially offset by reduced inpatient care for opportunistic infections and other AIDS-related diseases. Furthermore, job productivity in patients infected with HIV is increased under HAART. In developed countries with a low unemployment rate, the discounted value of savings caused by increased productivity in earlier years exceeds the discounted value of later increases in costs resulting from morbidity. Therefore, HAART represents a very efficient treatment strategy that leads to overall cost savings when taking a societal perspective.