Once-a-day treatment: the consequences of poor adherence may be more serious

Although once-a-day treatment regimes can be expected to make adherence easier to handle, if a person does miss doses, the clinical consequences are more serious than if a person misses doses from a twice-a-day regime. Tracy Glass reported these findings from the Swiss HIV Cohort at the Fifth International Conference on HIV Treatment Adherence in Miami on Monday.

Much effort has been taken in recent years to make antiretroviral therapy more tolerable and easier to take, in particular the development of once-daily therapy. Treatment regimes involving fewer doses are generally easier for people to adhere to.

Patients starting HIV therapy for the first time in Switzerland were recruited to the study between 2003 and 2009. Adherence was measured by self-report of missed doses over the last month. The investigators assessed the association of missed doses with viral rebound and death.

A total of 2410 individuals were recruited to the study and were followed for a median of 2.7 years.

At approximately one-third (30%) of interviews, patients reported missing one or more dose of their antiretroviral therapy. Viral load rebounded to detectable levels in 8% of patients, and 3% of individuals died.

For patients taking once-daily treatment, missing any doses increased the risk of viral load rebounding. The risk increased with the number of doses missed (one dose missed, hazard ratio (HR) = 5.46; 95% CI, 1.69 to 17.67; two missed doses, HR = 6.87; 95% CI, 1.07 to 44.01; three or more missed doses, HR = 9.26; 95% CI, 2.26 to 37.99).

Moreover, patients taking their HIV treatment once a day who reported missing three or more doses had a significantly increased risk of death (HR = 2.90; 95% CI, 1.09 to 7.72).

On the other hand, missed doses did not have such serious consequences for patients taking twice-daily therapy. No statistically significant relationship was found between missed doses and either an increased risk of viral load, or an increased risk of death.

However during questions and answers, an audience member requested further information on the once-a-day regimes being taken. He suggested that it was possible that doctors were prescribing drugs which are optimally taken twice a day, but which are sometimes prescribed as once-a-day to people who request a simpler regimen. The problem is that these particular drugs are not active in the body for long enough to allow for lapses in adherence.

While the researcher could not clarify the nature of these regimes, she did confirm that the data were also analysed to see if the risk of these events varied according to whether the treatment regime featured a non nucleoside reverse transcriptase inhibitor, boosted protease inhibitor or unboosted protease inhibitor. No variation was found.

Concluding, Tracy Glass said she believed that missed doses on a twice-a-day regimen do not lead to clinical consequences as serious as those created by missed doses on a once-a-day regimen. She cautioned that once-a-day regimens are not necessarily best for all patients.