4.1. AIDS General Treatment Information: Duration of Therapy
Description
This article is from the AIDS FAQ, by Dan Greening with numerous contributions by others.
4.1. AIDS General Treatment Information: Duration of Therapy
A second difficult question in the field of HIV management is how long
to continue initial zidovudine. Again, the ACTG 019 experience would
suggest that zidovudine monotherapy has a prolonged period of benefit,
especially in patients with higher CD4 cell counts (300-500) when
therapy is begun. On the other hand, ACTG 116A seemed to indicate that
the initial superiority of zidovudine was lost after as little as two
to four months of treatment with this drug prior to treatment with
didanosine. Here again, the State of the Art panel could find little
room for consensus. When therapy is begun in individuals with CD4
counts above 300, the panel suggested that it should be continued
until the CD4 cell count fell below 300. When zidovudine monotherapy
is begun in patients with CD4 counts under 300, the additional option
of switching to ddI monotherapy after a fixed interval was raised, but
again this interval was not defined. Once zidovudine monotherapy has
been used, and when it is no longer felt to be effective for an
individual, secondary therapy must be initiated. The choice of this
therapy, however, is also uncertain. In moderate disease, with CD4
cell counts below 300, switching to ddI was superior to continuing
with zidovudine in ACTG trials 116a and 116b/117, while switching to
ddC was not of benefit in ACTG 155. On the other hand, from data
gathered in CPCRA Trial 002, in patients with more advanced disease,
ddI and ddC were equivalent in secondary treatment of patients
previously treated with zidovudine who had progressed despite taking
that drug or who were intolerant of zidovudine toxicity. In fact, ddC
had a slight but significant superiority compared to ddI in terms of
survival in this trial. It was hoped that combination therapy
following zidovudine would be beneficial but questions have been
raised following the results of ACTG 155. In this study, patients
previously treated with zidovudine with CD4 cells below 300 were
randomized to stay on zidovudine, start ddC monotherapy, or begin
zidovudine and ddC combination therapy. Overall, there was no
difference in clinical progression or survival among the three study
arms. When the baseline CD4 counts are examined, however, it was found
that combination therapy was superior in patients with higher CD4 cell
counts, especially between 150 and 300. Therefore, it might seem
advisable not to delay the introduction of combination therapy until
patients have very advanced disease but rather to use such therapy
earlier in the disease course. Whether zidovudine and ddI would be as
good as zidovudine and ddC has not been investigated.
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