Refill Compliance Research Articles

Discontinuation, persistence and adherence to subcutaneous biologics delivered via a homecare route to Scottish adults with rheumatic diseases: a retrospective study

ObjectivesTo understand patterns of subcutaneous (SC) biologics use over time in adults with inflammatory rheumatic musculoskeletal diseases receiving a homecare delivery service.DesignRetrospective cohort.SettingPatients in secondary care receiving SC biologics in...

The causal effect of opioid substitution treatment on HAART medication refill adherence.

People who inject drugs (PWID) account for roughly 13% of the prevalent HIV/AIDS population outside of sub-Saharan Africa, and access to opioid substitution treatment (OST) is limited in many settings globally. OST likely facilitates access to HAART, yet sparse evidence is available to support this hypothesis. Our objective was to determine the causal impact of OST exposure on HAART adherence among HIV-positive PWID in a Canadian setting. We executed a retrospective cohort study using linked population-level data for British Columbia, Canada (January 1996-March 2010). We considered HIV-positive PWID after meeting HAART initiation criteria. A marginal structural model was estimated on a monthly timescale using inverse probability of treatment weights. The primary outcome was 95% HAART adherence, according to pharmacy refill compliance. Exposure to OST was defined as 95% of OST receipt, and we controlled for a range of fixed and time-varying covariates. Our study included 1852 (63.3%) HIV-positive PWID with a median follow-up of 5.5 years; 34% were female and 39% had previously accessed OST. The baseline covariate-adjusted odds of HAART adherence following OST exposure was 1.96 (95% confidence interval: 1.72-2.24), although the adjusted odds estimated within the marginal structural model was 1.68 (1.48-1.92). Findings were robust to sensitivity analyses on model specification. In a setting characterized by universal healthcare and widespread access to both office-based OST and HAART, OST substantially increased the odds of HAART adherence. This underlines the need to address barriers to OST globally to reduce the disease burden of both opioid dependence and HIV/AIDS.

Abstract 164: Adherence to Oral Antiplatelet (OAP) Therapy among ACS Patients Undergoing Percutaneous Coronary Intervention (PCI)

Background: The benefit of oral antiplatelet therapy following PCI is well established. Dual antiplatelet therapy is guideline recommended treatment for one year following a PCI. Objective: To examine discontinuation and adherence rates of oral anti-platelet therapy of patients with acute coronary syndrome (ACS) in the year following a PCI. Methods: From the HealthCore Integrated Research Environment, patients ≥18 years old and hospitalized for ACS (inpatient hospitalization with a primary diagnosis for acute myocardial infarction or unstable angina) during 8/1/09-6/30/13 (index hospitalization) were identified and followed up to 12 months. Patients with an OAP prescription fill within 6 months prior to the index hospitalization, those with a fill for ticagrelor at any time during the study period, those simultaneously starting clopidogrel and prasugrel following the index hospitalization, and those who had a coronary artery bypass graft during index hospitalization were excluded. OAP prescription utilization patterns were examined drug class (clopidogrel or prasugrel) as a whole and by branded versus generic clopidogrel. Medication adherence to OAP therapy was assessed as discontinuation (a period of >45 days not covered by supply of OAP therapy) and the proportion of days covered (PDC; calculated as total day supply during the follow-up divided by days from first fill to end of follow-up). Results: Of 38,626 ACS patients identified, 20,753 were revascularized with PCI during the index hospitalization, and 17,237 (83.1%) went on to fill an OAP prescription (12,714 with clopidogrel as first OAP treatment; 4,523 with prasugrel). On average, patients filled OAP medication 6.7 days following index hospitalization discharge (71% filled on discharge date). The study also found that 20% of patients discontinued OAP therapy during follow-up and 86% of follow-up days were covered by an OAP therapy supply on average. Other medication classes within the same patients had higher discontinuation rates and lower PDC: anti-hypertensive (27% discontinuation; 82% PDC), anti-diabetics (27%; 83%) statins (27%; 82%), and beta-blockers (37%; 72%). Discontinuation rates were considerably lower in patients taking generic clopidogrel versus those filling branded drug (11% for generic vs. 37% for branded) and PDC was higher for generic clopidogrel (90% PDC vs. 75% for branded). Conclusions: Adherence to OAP therapy compares favorably to adherence rates of other cardiovascular/metabolic medications taken by the same patients. Lower out of pocket costs were also associated with better refill compliance. The above findings present healthcare providers with an opportunity to further improve on medication adherence post-PCI in ACS patients by reducing the economic burden on patients.

Analyzing contraception refill compliance in college students and pharmacist's role in the provision of contraception

Analyzing contraception refill compliance in college students and pharmacist's role in the provision of contraception

Heart failure in patients treated with bisphosphonates

The aim of this study was to investigate the occurrence of heart failure in patients treated with bisphosphonates. In this nationwide retrospective cohort study from Denmark, all users of bisphosphonates and raloxifene between 1996 and 2006 (n = 102 342) were included in the 'exposed' group and three age- and gender-matched subjects (n = 307.026) from the general population comprised the control group. The risk of heart failure was estimated by Cox proportional hazard analyses. The mean follow-up times were 2.8, 5.5 and 4.9 years for alendronate-, etidronate- and raloxifene-treated patients, respectively. The absolute risk of heart failure was 4.4% in the exposed group and 3.7% in the control group (P < 0.01). The relative risk (RR) of heart failure was significantly increased in users of bisphophonates: crude RR 1.71 [95% confidence interval (CI) 1.63-1.79]; adjusted hazard ratio (HR) 1.41 (95% CI 1.34-1.48). By comparison, raloxifene, which is used for the same indication but has a different mechanism of action, was not associated with an increased risk of heart failure: adjusted HR 1.07 (95% CI 0.76-1.50). When the two most commonly used bisphosphonates, alendronate and etidronate, were analysed separately, significant trends in the risk of heart failure were observed across refill compliance strata. The risk of heart failure increased significantly with increasing refill compliance for etidronate (P for trend < 0.01), whereas it decreased for alendronate (P for trend < 0.01). Bisphosphonate users were at increased risk of heart failure compared to age- and gender-matched control subjects. However, users of alendronate showed a dose-dependent reduction in this risk, suggesting that alendronate may reduce the risk of heart failure.

AB1355 Observed dosing and refill compliance in bio-naÏve and bio-experienced psoriatic arthritis patients treated with golimumab

BackgroundGolimumab is a once-monthly, subcutaneously-administered, anti-TNF agent indicated for treatment of active psoriatic arthritis (PsA). Real-world dosing and refill compliance patterns of golimumab use in PsA patients have not been...

AB1356 Observed dosing and refill compliance in bio-naÏve and bio-experienced rheumatoid arthritis patients treated with golimumab

BackgroundLittle information on dosing, and refill compliance in golimumab-treated patients with rheumatoid arthritis has been published.ObjectivesThis study reports golimumab (GLM) dosing and refill compliance observed in rheumatoid arthritis (RA) patients.MethodsThis...

AB1354 Observed dosing and refill compliance in bio-naÏve and bio-experienced ankylosing spondylitis patients treated with golimumab

BackgroundGolimumab is a once-monthly, subcutaneously-administered, anti-TNF agent indicated for treatment of patients with ankylosing spondylitis (AS). Real-world dosing and refill compliance patterns of golimumab use in AS patients have not...

Heart failure in patients treated with bisphosphonates

Objectives The aim of this study was to investigate the occurrence of heart failure in patients treated with bisphosphonates. Design In this nationwide retrospective cohort study from Denmark, all users of bisphosphonates and raloxifene between 1996 and 2006 (n = 102 342) were included in the ‘exposed’ group and three age- and gender-matched subjects (n = 307.026) from the general population comprised the control group. The risk of heart failure was estimated by Cox proportional hazard analyses. Results The mean follow-up times were 2.8, 5.5 and 4.9 years for alendronate-, etidronate- and raloxifene-treated patients, respectively. The absolute risk of heart failure was 4.4% in the exposed group and 3.7% in the control group (P < 0.01). The relative risk (RR) of heart failure was significantly increased in users of bisphophonates: crude RR 1.71 [95% confidence interval (CI) 1.63–1.79]; adjusted hazard ratio (HR) 1.41 (95% CI 1.34–1.48). By comparison, raloxifene, which is used for the same indication but has a different mechanism of action, was not associated with an increased risk of heart failure: adjusted HR 1.07 (95% CI 0.76–1.50). When the two most commonly used bisphosphonates, alendronate and etidronate, were analysed separately, significant trends in the risk of heart failure were observed across refill compliance strata. The risk of heart failure increased significantly with increasing refill compliance for etidronate (P for trend <0.01), whereas it decreased for alendronate (P for trend <0.01). Conclusions Bisphosphonate users were at increased risk of heart failure compared to age- and gender-matched control subjects. However, users of alendronate showed a dose-dependent reduction in this risk, suggesting that alendronate may reduce the risk of heart failure.

Association between refill compliance to oral bisphosphonate treatment, incident fractures, and health care costs—an analysis using national health databases

The study estimates the cost of poor and suboptimal refill compliance by estimating fracture costs and assessing the association between refill compliance with oral bisphosphonates and incident fractures using Danish health registers. Patients with poor and suboptimal refill compliance had more major osteoporotic fractures, and the direct costs related to hospital care, primary care, and pharmaceutical treatment for these excess fractures reached almost 14 M DKK (2.5 M USD) for the study population which compares to a national annual excess cost of around 17 M DKK (3.1 M USD) using 2011 prescription prevalence. Adherence to oral anti-osteoporosis treatment has been shown in several studies to be relatively low and the potential impact on fracture burden is high. The aim of the study was to assess the association between refill compliance and all-cause health care costs. A national dataset was extracted with all treatment-naive patients who began oral bisphosphonate (BP) treatment for osteoporosis in Denmark between 1997 and 2006 (N = 54,876, 87 % women). Patients who survived for at least 2 years (N = 47,176) were divided into groups based on Medication Possession Ratio (MPR). Logistic regressions were used to derive difference in the probability of incident fractures between the three MPR groups. Fracture costs (related to medication use, primary care practice, specialists, and hospitals) were derived by comparing cost 12 months before and after fracture. For alendronate, the adjusted risk of major osteoporotic fractures was significantly reduced (OR 0.768; 0.686-0.859), including fractures of the hip (0.718; 0.609-0.846) and humerus (0.54; 0.431-0.677) with MPR ≥ 0.8. The risk reduction was lower with etidronate. Over 2 years, a total of 171 hip fractures and 53 other major osteoporotic fractures were attributed to suboptimal or poor refill compliance, with an excess cost of 13.7 M DKK (2.5 M USD). Poor refill compliance is not unusual in patients on oral bisphosphonates, and we demonstrate that this is accompanied by excess major osteoporotic fractures and health care costs at the societal level.

Anti-osteoporotic therapy in Denmark—predictors and demographics of poor refill compliance and poor persistence

In this study of 100,949 new users of oral bisphosphonates age ≥ 35 years, "early quitters" were found to differ from others with poor refill compliance in terms of socioeconomic, demographic, and treatment-related characteristics. New risk factors for poor compliance and persistence were identified. Poor compliance with anti-osteoporotic therapy is an on-going worldwide challenge. In this study, we hypothesized that "early quitters" differ in socioeconomics, demographics, co-medications, and comorbid conditions from other patients with low compliance. The study was a register-based nationwide cohort study of anti-osteoporotic therapy comprising 100,949 men and women. Statistical analysis including backward stepwise logistic regression analysis was used to explain causes of treatment failure and Kaplan-Meier survival analysis to estimate persistence of treatment. It was noted that 56.6 % of the patients were persistent and compliant, 4.7 % of the patients were persistent but "low compliant" while 38.7 % of the patients were "early quitters". "Early quitters" were found to differ in socioeconomics from "low compliant" patients. Differences concerning increased risk of "early quitters" were associated with high household income, subjects' age 71.9-79 years, living in the countryside or village, prior treatment with analgesics and anti-parkinson drugs, and dementia. Differences concerning decreased risk of "early quitters" were associated with male, living in an apartment, children living at home, living close to a university hospital, anti-osteoporotic therapy other than alendronate, number of drugs especially above three, pulmonary disease, collagen disease. The results suggest a need for improved support for patients to facilitate the interpretation of the disease and the perception of the benefits and risks of treatment-to reduce the risk of "early quitters". We were able to identify new risk groups that may be candidates for targeted actions.

Adherence in HIV‐positive patients treated with single‐tablet regimens and multi‐pill regimens: findings from the COMPACT study

The use of Combination AntiRetroviral Therapy (cART) has decreased the morbidity and mortality of patients infected with HIV. However, adherence to cART remains crucial to prevent virological failure and disease progression. The aim of this study was to assess adherence to treatment among patients treated with Single Tablet Regimen (STR) or with multi-pill regimens based on Protease Inhibitors (PI), Non-Nucleoside Reverse-Transcriptase Inhibitors (NNRTI), or raltegravir (RAL). An observational retrospective cohort analysis based on administrative and clinical databases was conducted at the National Institute for Infectious Diseases (Rome, Italy). HIV-positive patients treated with a cART between Jan 1st, 2008–Dec 31st, 2010 were included. Patients were followed-up for one year since the first prescription during the inclusion period or up to death or switch of at least one drug of the regimen. Adherence and selective non-adherence (days without backbone or 3rd drug) were calculated using pharmacy refill compliance [1]. cART regimens were classified based on number of daily pills (STR vs multi-pill regimen) and on type of third drug. Viral Load (VL) and CD4 cell counts at the end of the follow-up were evaluated. A total of 1,604 patients were analyzed, 70.0% male, age 45.0±8.7, 14.3% newly treated. Patients on STR were 159 (9.9%), PI 878 (54.7%), NNRTI 523 (32.6%), RAL 44 (2.7%). Presence of at least one AIDS-defining conditions (according to Centers for Disease Control classification) was 30% in the STR group, 34% PI, 26% NNRTI, 34% RAL (p=n.s.). Adherence was 80.4±14.7% for STR, 71.8±21.8% PI, 77.1±20.3% NNRTI, 74.0±22.4% RAL. Selective non-adherence was 5.5% (18 days) PI, 2.8% (8 days) NNRTI, 12.5% (43 days) RAL (Figure 1). At the end of the follow-up, VL/CD4 values were available among 709 patients (44%); CD4 count >500 cell/mm3 was observed among 61% of patients on STR, 44% PI, 48% NNRTI, 42% RAL and VL < 50 copies/ml was observed among 96% of patients on STR, 78% PI, 88% NNRTI, 87% RAL. Interruptions in cART refill remain a relevant problem across all cART regimens. Patients on STR displayed a higher adherence rate compared to multi-pill regimes (PI, NNRTI, and RAL), primarily due to lack of selective non-adherence. Patients on STR experienced also higher rates of VL < 50 and CD4 > 500. The use of an STR regimen appears an effective therapeutic option to avoid selective non-adherence and, consequently, to prevent virological failure and disease progression.Figure 1Non-adherence to cART regimens.

Performance of Compliance and Persistence Measures in Predicting Clinical and Economic Outcomes Using Administrative Data from German Sickness Funds

To compare the performance of various compliance and persistence measures in predicting schizophrenia-related hospitalization rates and inpatient costs. Retrospective, nonrandomized cohort study. Prescription claims databases from three German sickness funds (public health insurance programs). A total of 1484 patients who were hospitalized in 2003 for a schizophrenia-related episode and subsequently received long-term antipsychotic pharmacotherapy. Data on age, sex, schizophrenia, prescription drugs, hospitalizations, and inpatient expenditures were collected for each patient from the three German sickness funds. Refill compliance measures based on single-interval availability and multiple-interval availability, as well as refill persistence, were calculated for each patient over 1year. Ten measurement variables were compared with respect to their performance in predicting disease-related hospitalization and inpatient expenditure, using multivariate logistic regression and gamma regression, respectively. C-statistics were calculated to determine each measure's predictive performance. Likelihood ratio tests showed that inclusion of compliance and persistence measures significantly improved (p<0.05) outcomes prediction in 6 of 10 hospitalization models and in 3 of 10 inpatient cost models compared with a baseline model that included only age, sex, and disease severity covariates. Refill compliance as a continuous variable of drug persistence, including transfer of oversupplies into subsequent periods, performed best in predicting hospitalization (C=0.669). Availability ratios, capped at 100%, were superior to default availability ratios in predicting hospitalization. Allowing for cross-period carryover improved the discriminatory performance of the persistence models. Refill persistence measures appear sufficiently flexible to account for hospitalizations common in schizophrenia and other psychiatric diseases. A continuous refill persistence measure should be used to assess compliance in psychiatric conditions when working with administrative data.

PSY39 Dosing and Refill Compliance in Ankylosing Spondylitis Patients Treated With Golimumab

PSY39 Dosing and Refill Compliance in Ankylosing Spondylitis Patients Treated With Golimumab

PMS42 Observed Dosing and Refill Compliance in Psoriatic Arthritis Patients Treated with Golimumab

PMS42 Observed Dosing and Refill Compliance in Psoriatic Arthritis Patients Treated with Golimumab

Are long-term bisphosphonate users a reality? Dose years for current bisphosphonate users assessed using the danish national prescription database

The prevalence of long-term bisphosphonate use may be low due to low refill compliance and gaps in treatment. An analysis of the prescription history of 58,674 bisphosphonate users in Denmark found that only 2.8% had received ten dose years of treatment or above. This study aims to describe the demographics of present bisphosphonate (BP) users, to determine the prevalence of long-term BP use, and to establish if long-term use (a 10-year history of osteoporosis treatment) translated to ten dose years of bisphosphonate prescriptions filled, given the propensity for treatment gaps and low refill compliance with bisphosphonates. The study population was all persons aged 35 and above, who had filled at least one prescription for an oral bisphosphonate in the year 2008. Past use of osteoporosis medications (bisphosphonates, raloxifene, strontium ranelate, or PTH analogs) for the period January 1, 1995 to December 31, 2007 was retrieved from the Danish National Prescription Database for descriptive analysis. Of the 58,674 BP users, 46% were above the age of 75, and 13% were men. Though 5.9% had at least a 10-year history of treatment, only half (2.8%) had received more than ten dose years of a BP. For any osteoporosis drug, 3.0% had received ten dose years or more, while 23.2% had received between 5 and 10years of treatment. Long-term users with ten dose years or more of a BP are rare due to periods of low compliance and gaps, with a discrepancy between the length of treatment and doses taken. The study also highlights the great number of patients who have used BP for more than five dose years and should be advised on length of treatment, a decision process that will be difficult due to the paucity of long-term safety and efficacy data.

Levodopa dosage determines adherence to long-acting dopamine agonists in Parkinson's disease

ObjectiveTo test whether adherence to non-ergot, once-daily dopamine agonist (ODDA) therapy depends upon concomitant levodopa daily dose in Parkinson's disease (PD). MethodsConsecutive levodopa-treated PD patients on ODDA therapy were invited to participate in the study. ODDA adherence was measured using subjective (Morisky–Green test, MGT) and objective (electronic monitoring of refill compliance, IANUS) methods. A combination of MGT and IANUS was used to define full (100%) adherence to ODDA therapy. Logistic regression methods were used to investigate the impact of levodopa daily dose on ODDA adherence after adjusting for relevant covariates. ResultsThirty-nine patients (19 men, 20 women; age, 70.2±8.9years) were enrolled in the study. Twelve (31%) participants admitted to suboptimal ODDA compliance. Only 18 (46%) were estimated to be fully compliant. As expected, adherence was inversely related to levodopa daily dose. For every 100mg increase in levodopa dose, the risk to failure to adhere increased 1.86 times (95% CI, 1.21–3.74; p=0.0020). The covariate “total daily number of drugs” (not total daily number of pills) was also associated with worse adherence (p=0.0061). In contrast, patients who were initially treated with a dopamine agonist showed better ODDA adherence than those who were initially treated with levodopa (p=0.012). Levodopa doses greater than 600mg/day were associated with suboptimal compliance. ConclusionsIn levodopa-treated PD patients, adherence to ODDA therapy is suboptimal and strongly associated with the levodopa daily dose and the total number of drugs used to treat patients' medical conditions.

Generic switch after ramipril patent expiry is not associated with decreased pharmacy refill compliance

For treatment success in chronic diseases such as hypertension, adequate adherence to long-term pharmacotherapy is a prerequisite. The purpose of this study was to evaluate whether switching from brand name ramipril to a generic product after patent expiry may negatively affect patients' refill compliance. Claims data for ambulatory prescriptions within the statutory health insurance system were evaluated. Patients were included if they had filled a ramipril prescription (index) for either brand name or generic ramipril products between September 2003 and June 2004. Patients had to be continuously treated with ramipril for at least 12 months before and after the index date. Patients with a change from brand name to generic product or vice versa during follow-up after the index date were excluded from the analyses, as were patients who could not be unequivocally allocated to characteristics of covariates. Refill compliance was analysed by calculating the medication possession ratio (MPR), assuming that patients were prescribed one unit dose per day (MPR(UD)). In total, 142,690 and 79,191 patients were classified as brand name or generic therapy, respectively. Median MPR(UD) values were 0.95 and 0.96 (P < 0.001). In a logistic regression model adjusting for covariates, the probability for noncompliance (MPR(UD) < 0.8) was marginally lower in the generic compared with the brand name group (odds ratio 0.926, 99% confidence interval 0.901-0.951, P < 0.001). These results suggest that refill compliance is not negatively affected by a physician-induced switch from brand name to generic ramipril products after patent expiry.

Risk of Arrest in Persons With Schizophrenia and Bipolar Disorder in a Florida Medicaid Program

To examine (1) arrest outcomes for adults with schizophrenia and bipolar disorder who were treated with first-generation antipsychotics (FGAs) or second-generation atypical antipsychotics (SGAs) and (2) the interaction between medication class and outpatient services in a Florida Medicaid program. In a secondary data analysis, Florida Medicaid data covering the period from July 1, 2002, to March 31, 2008, were used to identify persons diagnosed with schizophrenia, schizoaffective disorder, and bipolar disorder and to examine antipsychotic medication episodes lasting at least 60 days. There were 93,999 medication episodes in the population examined (N = 36,519). Medication episodes were coded as (1) SGA-aripiprazole, clozapine, olanzapine, paliperidone, quetiapine, risperidone, risperidone long-acting therapy, or ziprasidone; or (2) FGA-any other antipsychotic medication. Outpatient services were defined as the proportion of 30-day periods of each medication episode with at least 1 behavioral health visit. Survival analyses were used to analyze the data, and they were adjusted for the baseline propensity for receiving an SGA. Second-generation antipsychotic episodes were not associated with reduced arrests compared to FGA episodes; however, the interaction between outpatient services and SGA episodes was significant (hazard ratio [HR] = 0.68; 95% CI, 0.50-0.93; P = .02) such that an SGA episode with an outpatient visit during at least 80% of every 30-day period of the episode was associated with reduced arrests compared to SGA episodes with fewer outpatient services. There was no significant effect for concurrent FGA episodes and outpatient treatment (HR = 0.81; 95% CI, 0.60-1.10; P = .18). Substance use, poor refill compliance, and prior arrest increased risk of subsequent arrest. The interaction between outpatient visits and treatment with SGAs was significantly associated with reduced arrests. These findings indicate the importance of concurrent antipsychotic medications and outpatient services to affect arrest outcomes for adults with schizophrenia and bipolar disorder.

Adherence and plasma HIV RNA response to antiretroviral therapy among HIV-seropositive injection drug users in a Canadian setting

HIV-positive individuals who use injection drugs (IDU) may have lower rates of adherence to highly active antiretroviral therapy (ART). However, previous studies of factors associated with adherence to ART among IDU have been limited primarily to samples drawn from clinical settings and in areas with financial barriers to healthcare.We evaluated patterns of ART adherence and rates of plasma HIV RNA response among a Canadian cohort of community-recruited IDU. Using data from a community-recruited cohort of antiretroviral-naive HIV-infected IDU, we investigated ART adherence patterns based on prescription refill compliance and factors associated with time to plasma HIV-1 RNA suppression (<500 copies/mL) using Cox proportional hazards regression in a setting with universal health care, including free ART. Between 1996 and 2008, 267 antiretroviral-naive HIV-infected IDU initiated ART and had a median of 51 months (inter-quartile range: 17–95 months) of follow-up. Overall, 81 (30.3%) were ≥95% adherent during the first year of HAART and 187 (70.0%) achieved HIV RNA suppression at least once over the study period, for an incidence-density of 34.5 (95% confidence interval [CI]: 29.8–39.9) per 100 person-years. The Kaplan-Meier cumulative plasma HIV RNA suppression rates at 12 months after the initiation of ART were 80.8% (95% CI: 71.2–88.7) for adherent and 28.9% (95% CI: 22.8–36.1) for non-adherent participants. While several socio-demographic characteristics and drug-using behaviours were identified as barriers to successful treatment in unadjusted analyses, the factor most strongly associated with time to HIV RNA suppression in multivariate analysis was adherence to ART of at least 95% (adjusted hazard ratio [AHR] = 6.0, 95% CI: 4.2–8.6, p<0.001). These results demonstrate low rates of adherence to ART among a community-recruited cohort of IDU and reinforce the importance of adherence as the key determinant of successful virological response to antiretroviral therapy.