One-pill regimen improves adherence and reduces hospitalisation in insured US patients

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People taking a single-pill daily drug regimen do appear to have better adherence than people taking more pills a day, according to a study of a large database of patients in the USA presented this week at the Tenth International Congress on Drug Therapy in HIV Infection (HIV10) in Glasgow.

This improved adherence also translated into better health, according to the study, which was sponsored by Gilead, one of the manufacturers of the once-a-day tenofovir/FTC-efavirenz pill Atripla. Patients taking one pill a day had fewer hospitalisations, even when other factors were controlled for.

Judith Meyers of the health consultancy RTI Health Solutions told the conference that the study investigated 7073 patients on the Life Links claims database, a group of patients insured by a commercial insurer, who were diagnosed with HIV between June 2006 and December 2008 and received a complete antiretroviral therapy (cART) regimen for at least 90 days. This was defined as regimens of at least three drugs and therefore excluded 1829 patients who were on what was described as incomplete ART, which included protease inhibitor monotherapy and dual therapy.

Glossary

multivariate analysis

An extension of multivariable analysis that is used to model two or more outcomes at the same time.

boosting agent

Booster drugs are used to ‘boost’ the effects of protease inhibitors and some other antiretrovirals. Adding a small dose of a booster drug to an antiretroviral makes the liver break down the primary drug more slowly, which means that it stays in the body for longer times or at higher levels. Without the boosting agent, the prescribed dose of the primary drug would be ineffective.

exclusion criteria

Defines who cannot take part in a research study. Eligibility criteria may include disease type and stage, other medical conditions, previous treatment history, age, and gender. For example, many trials exclude women who are pregnant, to avoid any possible danger to a baby, or people who are taking a drug that might interact with the treatment being studied.

monotherapy

Taking a drug on its own, rather than in combination with other drugs.

protease inhibitor (PI)

Family of antiretrovirals which target the protease enzyme. Includes amprenavir, indinavir, lopinavir, ritonavir, saquinavir, nelfinavir, and atazanavir.

Adherence was calculated by dividing the number of days covered by refilled prescriptions by the total days people were on treatment.

It was found that a third of patients (2365) were on one pill a day, six per cent (411) on two a day (this would most likely be efavirenz plus one of the two-NRTI combination pills) and the remainder (4297) on three or more, which included all the patients on protease inhibitors.

Not surprisingly a higher proportion of patients on one pill (42%) were on their first cART regimen compared with 25% on two drugs and 20% on three or more.

Of the patients on three or more pills, a third were on NNRTI-based regimens and two-thirds on PI-based ones. Only 50% of these were on boosted PIs.

Only a minority of patients achieved better than 95% adherence, but more of them on a one-pill regimen did so: 47% on one pill, 41% on two and 34% on three or more. This pattern persisted at lower adherence rates: for instance 72%, 68% and 62% achieved more than 90% adherence on one, two and three pills respectively.

A multiple regression analysis, controlling for factors like drink/drug use, length of treatment, gender etc. found that patients on one pill were 61% more likely to take more than 95% of doses than patients taking three or more pills a day. In contrast patients with drug or alcohol abuse were 40% less likely.

Adherence clearly translated into better health, with patients 40% less likely to be admitted to hospital over the study period if they achieved over 95% adherence. In contrast patients with drink/drugs problems were nearly three times as likely to be admitted to hospital (192% higher), patients with psychological illness 40% more likely, and women 30% more likely.

In univariate analysis (not controlling for confounders) taking a one-pill regimen was directly associated with 20% fewer hospitalisations, and in multivariate analysis this correlation was slightly strengthened, with 24% fewer hospitalisations. This was strongly statistically significant (p = 0.003). In absolute terms, and controlling for all other variables, the hospitalisation rate was 7.7% in patients taking one pill versus 9.9% in patients taking two or more.

The limitation of this study, Meyers said, was that there was no way of telling why patients had been selected for their particular regimen, and the difference in hospitalisations could have been due to patients who were less sick being selected for a one-pill regimen.

Conversely, it was pointed out that as there is only one current one-pill-a-day regimen (Atripla) this was essentially a study comparing the performance of that particular combination of drugs against other regimens rather than one pill versus more, and the results could have been due to the intrinsically greater efficacy of tenofovir/FTC/efavirenz.

The study was also of patients who have private health insurance; it may not be possible to generalise the results to the significant proportion of poorer and unemployed patients in the USA who rely on public health resources.

References

Meyers J et al. Adherence to antiretroviral treatment regimens and correlation with risk of hospitalization among commercially insured patients in the US. Tenth International Congress on Drug Therapy in HIV Infection, Glasgow, abstract O113, 2010.