A Guide to Primary Care of People with HIV/AIDS - Canadian Public ...

A Guide to Primary Care of People with HIV/AIDS
Chapter 7: Adherence to HIV Therapies
Chapter 7:
Adherence to HIV Therapies
Laura W. Cheever, MD, ScM
OVERVIEW
ASSESSMENT
INTERVENTIONS
KEY POINTS
SUGGESTED RESOURCES
REFERENCES
CASES
OVERVIEW
What is meant by medication adherence?
Medication adherence means a patient takes
the prescribed dose of prescribed medications
on the prescribed schedule, following prescribed
dietary instructions. Patient adherence to medical
appointments and to behaviors that minimize the risk
of transmission of HIV to others correlates strongly with
adherence to medications and is an important part of
primary care of HIV-infected patients but will not be
addressed in this chapter.
Why is medication adherence so important in
HIV therapy?
Nonadherence to prescribed therapy is a ubiquitous
problem in medicine. In chronic diseases, including
asthma, diabetes, and hypertension, only 50% of
patients take their medication as prescribed more than
80% of the time. The same is true of patients with HIV
infection. However, because of the rapid multiplication
and mutation rate of HIV and the relatively low potency
and short half-life of most antiretrovirals, very high
levels of adherence to antiretroviral schedules are
necessary to avoid viral resistance. In comparison with
patients who are adherent to antiretroviral therapy
(ART), nonadherent patients have: 1) Higher mortality
(2.5 adjusted relative hazard) (Wood, et al, 2003), 2)
Lower increase in CD4 cell count (6 cells/mm 3 increase
for nonadherent patients versus 83 cells/mm 3 increase
for adherent patients) (Paterson 2000), and 3) Increased
hospital days (12.9 days/1000 days of followup for
nonadherent patients versus 2.5 hospital days/1000
days for adherent patients) (Paterson, et al, 2000).
How adherent do patients need to be to avoid
viral resistance?
Results of a study of adherence and response to
therapy among primarily antiretroviral-experienced
patients taking protease inhibitors (PIs) showed that
a >95% adherence rate was necessary for 78% of
patients to achieve an undetectable viral load (Paterson,
2000); however, some patients with significantly less
adherence also had success (see Figure 7-1). Exactly
how adherent individual patients need to be is not
known and probably depends on several factors,
including preexisting antiretroviral resistance, viral
load, viral genetic barriers to the development of
drug resistance, and drug half-life. Patients should be
counseled that the risk of viral resistance increases with
nonadherence and that nearly perfect adherence is the
goal. Of note, patients with very low levels of adherence
may be at decreased risk of developing viral resistance
because there is not enough selective pressure
(Bangsberg, et al, 2003).
ASSESSMENT
What factors impact adherence?
Many factors contribute to a patient’s ability to adhere
to medication schedules (Table 7-1). Note that race,
education level, and income are generally not predictive
of adherence. Providers must remember that factors
predicting adherence or nonadherence are only
associations and are not absolutely predictive. For
example, although patients who use addictive substances
are more likely to be nonadherent, some patients with
heavy alcohol or drug use are adherent to ART.
7
U.S. Department of Health and Human Services, Health Resources and Services Administration, HIV/AIDS Bureau
49