The Importance of
HIV Therapy Adherence
Importance of Adherence
Anti-HIV drugs must be taken reliably to ensure
that they reach and are maintained at high enough concentrations in infected cells to
inhibit HIV replication. A fall in the concentration of a drug to below a critical level
allows the virus to continue replicating and provides ideal conditions for the development
of drug resistance. This ultimately leads to a need for increasing drug concentrations to
control viral replication (Figure 1).
Figure 1: The importance of regular
|As drug levels in the body drop, due to
missed or delayed dosing, replication and mutation takes place. Mutations lead to drug
resistance, which increases the amount of drug needed to prevent replication (IC100). The
time spent when the bodys drug concentration is lower than the IC100 therefore
increases, allowing replication to continue for longer. Eventually, the IC100 will rise
above the maximum drug concentration in the body and the drug will have no affect on viral
Adherence to prescription instructions is
one of the most important factors in ensuring maximum benefit from drug treatment (Figure
2). This is important for all types of medication, including all types of anti-HIV drugs
and treatments for opportunitistic infections such as CMV retinitis and candida. Adherence
to drug schedules also allows individuals to play an active part in their treatment;
providing an opportunity to participate in the management of their disease1 - something most people value.
|This graphic clearly demonstrates the direct
relationship between the number of daily doses taken (ie.adherence to therapy regimen) and
the development of mutations and plasma viral load; when therapy is adhered to viral load
declines, when doses are missed viral load rises.
Person A is relatively consistent in his/her medication
taking, missing few doses during the 150 days monitored. Most of the viral replication is
therefore suppressed and the viral load, which is represented by log RNA, declines
accordingly. Person B does not adhere to the therapy regimen as well as Person A, missing
many doses and at one point taking less then 2 doses a day. Viral replication takes place
and the viral load rises.
(Adapted from JAMA, 1996:276;24)