Plasma drug level validates self-reported adherence but predicts limited specificity for nonadherence to antiretroviral therapy

Pharmacokinetics of nevirapine, stavudine and lamivudine in Indian HIV-infected children receiving generic fixed dose combinations

OBJECTIVE

To determine the trough and two hour plasma levels of nevirapine, stavudine, and lamivudine when administered in fixed dose combinations (FDC).

DESIGN

Cross sectional.

SETTING

Tertiary care hospital in Northern India.

PARTICIPANTS

79 HIV-infected children receiving antiretroviral therapy with FDCs for more than month.

INTERVENTION

Two-point sampling (0 and 2 hours after the morning dose).

OUTCOME MEASURES

Plasma concentrations of all three drugs were simultaneously assayed by liquid chromatography/mass spectroscopy.

RESULTS

Majority (77%) of children were receiving fixed dose combination of stavudine, lamivudine, nevirapine in the ratio of 6:30:50 mg. The median (IQR) trough and 2-hour plasma levels (µg/mL) of nevirapine, stavudine and lamivudine were 5.2 (4.0, 6.3) and 7.9 (6.0, 9.7); 0.1 (0.06, 0.16) and 1.1 (0.59, 1.6); 0.1 (0.02, 0.2) and 2.5 (1.4, 3.1), respectively. Very few children had sub-therapeutic plasma drug levels of stavudine (2.5%), lamivudine (7.6%) and nevirapine (10%). Inadequate viral suppression at 6 months follow up was significantly associated with initial high viral load, low CD4 percentage at the time of enrolment in study, and lower doses of lamivudine and stavudine.

CONCLUSIONS

The currently available generic pediatric fixed dose antiretroviral combinations in India provide adequate drug exposure in majority of children.

Adherence in the treatment of patients with extensively drug-resistant tuberculosis and HIV in South Africa: a prospective cohort study

OBJECTIVE

Extensively drug-resistant tuberculosis (XDR-TB)/HIV coinfection is difficult to treat with frequent adverse drug reactions and associated with high mortality. Adherence to antiretroviral therapy (ARV) and second-line TB medications may reduce mortality, prevent amplification of drug resistance, and improve outcomes.

METHODS

Prospective cohort study of XDR-TB patients on treatment in KwaZulu-Natal, South Africa. Adherence to ARV and TB medications was assessed separately at baseline and monthly. Knowledge, attitudes, and beliefs were assessed at baseline. Optimal adherence was defined as self-report of taking all pills in the previous 7 days; missing any pills was defined as suboptimal adherence. Primary outcome was optimal adherence 6 months after initiation of XDR-TB treatment to TB medications, ARV, and both ("dual adherence").

RESULTS

One hundred four XDR-TB patients (79.8% HIV coinfected, 84.3% on ARV at enrollment) were enrolled and followed monthly (median 8 visits; interquartile range: 4-12). Six-month optimal adherence was higher for ARV (88.2%) than TB medications (67.7%) (P < 0.001). Low educational attainment, male gender, and year of enrollment were independently associated with dual suboptimal adherence. At baseline, participants indicated that XDR-TB was curable (76.0%), HIV and TB were linked (81.7%), and ARV improves TB outcomes (72.1%). Baseline knowledge, attitudes, and beliefs did not predict subsequent adherence.

CONCLUSIONS

Medication adherence was significantly higher for ARV than for TB medications in this cohort. Short-course treatment regimens for drug-resistant TB with lower pill burden may increase adherence and improve outcomes in XDR-TB/HIV. Programmatic support for dual adherence is critical in the treatment of drug-resistant TB and HIV.

Pharmacy refill adherence outperforms self-reported methods in predicting HIV therapy outcome in resource-limited settings

Background

Optimal adherence to antiretroviral therapy is critical to prevent HIV drug resistance (HIVDR) epidemic. The objective of the study was to investigate the best performing adherence assessment method for predicting virological failure in resource-limited settings (RLS).

Method

This study was a single-centre prospective cohort, enrolling 220 HIV-infected adult patients attending an HIV/AIDS Care and Treatment Centre in Dar es Salaam, Tanzania, in 2010. Pharmacy refill, self-report (via visual analog scale [VAS] and the Swiss HIV Cohort study-adherence questionnaire), pill count, and appointment keeping adherence measurements were taken.

Univariate logistic regression (LR) was done to explore a cut-off that gives a better trade-off between sensitivity and specificity, and a higher area under the curve (AUC) based on receiver operating characteristic curve in predicting virological failure. Additionally, the adherence models were evaluated by fitting multivariate LR with stepwise functions, decision trees, and random forests models, assessing 10-fold multiple cross validation (MCV). Patient factors associated with virological failure were determined using LR.

Results

Viral load measurements at baseline and one year after recruitment were available for 162 patients, of whom 55 (34%) had detectable viral load and 17 (10.5%) had immunological failure at one year after recruitment. The optimal cut-off points significantly predictive of virological failure were 95%, 80%, 95% and 90% for VAS, appointment keeping, pharmacy refill, and pill count adherence respectively. The AUC for these methods ranged from 0.52 to 0.61, with pharmacy refill giving the best performance at AUC 0.61.

Multivariate logistic regression with boost stepwise MCV had higher AUC (0.64) compared to all univariate adherence models, except pharmacy refill adherence univariate model, which was comparable to the multivariate model (AUC = 0.64). Decision trees and random forests models were inferior to boost stepwise model.

Pharmacy refill adherence (<95%) emerged as the best method for predicting virological failure. Other significant predictors in multivariate LR were having a baseline CD4 T lymphocytes count < 200 cells/μl, being unable to recall the diagnosis date, and a higher weight.

Conclusion

Pharmacy refill has the potential to predict virological failure and to identify patients to be considered for viral load monitoring and HIVDR testing in RLS.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2458-14-1035) contains supplementary material, which is available to authorized users.