Active injecting drug users must be provided with adherence support when they start HIV therapy

Michael Carter
Published: 20 June 2012

Chances of achieving an undetectable viral load are equally poor for patients who inject heroin, cocaine, or a combination of these two drugs, Canadian researchers report in Drug and Alcohol Dependence. Between 56 and 58% of people who injected these drugs had an undetectable viral load one year after starting HIV therapy, compared to 89% of individuals who were not active injecting drug users.

However, when considered as a time-dependent variable, injection of these drugs was not associated with poorer virological outcomes. The investigators believe that this is because injecting habits are not constant, with people switching between drugs and between injecting and not injecting. Factors associated with a greater chance of viral suppression were baseline viral load, methadone therapy and, most strongly of all, high levels of adherence to HIV therapy.

The investigators therefore stress the importance of providing adherence support to people with a history of injecting drug use who are starting HIV therapy.

It is well recognised that active injecting drug use is associated with poorer responses to HIV therapy. However, the impact of specific patterns of injecting on the chances of virological suppression is poorly understood.

Therefore, investigators from Vancouver designed a longitudinal study involving 267 people with a history of drug use who started HIV therapy for the first time between 1996 and 2008.

These participants were interviewed at baseline and then every six months. They were asked if they had injected heroin, cocaine, or a combination of these drugs in the previous six months. Those who answered yes were classified as active injecting drug users and their chances of achieving viral suppression (below 500 copies/ml) was compared to individuals who did not report recent injecting. Information was also gathered on the participants’ demographic characteristics, baseline viral load and CD4 cell count, use of methadone therapy, type of HIV therapy taken and adherence to this treatment.

The rate of viral suppression twelve months after starting therapy was 56% for cocaine injectors, 58% for those who injected heroin and 56% for participants who injected both drugs.

“The effects of various drugs (e.g. heroin vs cocaine) on HIV-1 RNA viral suppression did not differ greatly when baseline drug use was considered,” write the authors.

In contrast, 89% of patient who did not report current injecting behaviour achieved virological suppression. The difference in outcome between those who injected drugs and those who did not was significant (p < 0.01).

However, when considered longitudinally as a time-dependent variable, the only injecting pattern associated with a significantly lower chance of viral suppression was combining cocaine and heroin (HR = 0.67, 95% CI, 0.47-0.97; p < 0.05). This association ceased to be significant after controlling for factors such as CD4 cell count, viral load and the year therapy was started.

Further statistical analysis showed that none of the drug use patterns were associated with suppression of viral load.

Nevertheless, the investigators found that several factors were associated with a better chance of achieving viral suppression. These included methadone use (AHR = 1.33, 95% CI, 1.01-1.76), therapy with a protease inhibitor (AHR = 1.35, 95% CI, 1.03-1.77), the year treatment was initiated (AHR = 1.10, 95% CI, 1.05-1.15) and, most strongly of all, adherence to therapy of at least 95% (AHR = 4.00, 95% CI, 2.91-5.49).

“Suppression of HIV-1 RNA was most strongly predicted by baseline clinical characteristics, use of methadone, and adherence to ART,” emphasise the researchers.

They conclude: “Active injecting at the time of ART initiation is associated with lower plasma HIV-1 RNA suppression rates…when considered longitudinally as time-updated behaviors, there was little association between patterns of drug injecting and plasma HIV-1 RNA suppression rates.” The authors believe these findings show “adherence interventions should be applied at the time of ART initiation for active drug injectors”.

Reference

Kerr T et al. Patterns of heroin and cocaine injection and plasma HIV-1 RNA suppression among a long-term cohort of injection drug users. Drug and Alcohol Dependence 124: 108-12, 2012.