Fewer pills means better adherence, says Spanish study

Michael Carter
Published: 23 July 2004

Switching from a protease inhibitor-based HAART regimen to an efavirenz-based regimen led to a significant improvement in the level of adherence in a Spanish cohort of patients, according to a poster presentation to the Fifteenth International AIDS Conference in Bangkok last week. Although investigators identified several baseline characteristics in their cohort associated with poor adherence, the only factor which investigators could identify as associated with the observed improvement in adherence was the lower pill burden of the efavirenz regimen.

For six months investigators followed 754 patients who were recruited to a multi-centre prospective study, the objectives of which were to assess changes in rates of adherence and changes in risk factors for non-adherence to HAART in patients who switched from a protease inhibitor-based HAART regimen to an efavirenz-based one.

In total 49.9% of patients switched to efavirenz to simplify their treatment regimen, and 51.1% changed to efavirenz because of their previous protease inhibitor regimen either caused side-effects or failed to control viral load.

Adherence was assessed using a self-completed questionnaire at baseline, and then at twelve and 24 weeks. The investigators identified several risk factors at baseline for poor adherence. These were age under 40 years, female sex, a low level of education attainment, a low income, lack of social support, alcoholism, and drug abuse.

Just over a third of patients (33.5%) were assessed as being adherent throughout the study period, 15.4% were always non-adherent, 15.4% had worsening adherence, and 36.3% had improving adherence. The overall improvement in adherence, 21.5%, was highly statistically significant (p = 0.0001).

There was no change in the odds ratios for any of the variables associated with poor adherence other than lower pill burden. The investigators conclude “switch to a lower pill burden regimen containing efavirenz, significantly improved adherence in patients previously treated with [protease inhibitor] based therapies.”


Knobel H et al. Impact of simplification to a lower pill burden HAART in adherence and risk factors for non-adherence. XV International AIDS Conference, Bangkok, poster presentation, abstract WePeB5773, 2004.

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