ddI: FDA Approves Additional Indication

On September 28 the U. S. Food and Drug Administration
officially approved an additional indication (use) for ddI -- for
treatment of patients who had already received prolonged prior
treatment with AZT. Previously, ddI had only been officially
approved for persons who could not tolerate AZT or had
significantly worsened while using it. While the new approval
does not give physicians any power which they did not already
have, it will in practice encourage wider use of ddI.
[Physicians can prescribe an approved drug for other than its
approved indications, but many are reluctant to do so. Also,
some third-party payers refuse to reimburse for expensive drugs
which are used "off label" (for conditions other than the FDA-
approved indications) -- despite the fact that FDA indications
were never intended to be used in this way, since the standard of
care in medicine often includes unlabeled use of approved drugs,
especially for serious diseases such as cancer and AIDS.]

The new ddI approval is based on results of a major study by
the AIDS Clinical Trials Group of the U. S. National Institute of
Allergy and Infectious Diseases (James O. Kahn, Stephen W.
Lagakos, Douglas D. Richman and other, "A Controlled Trial
Comparing Continued Zidovudine with Didanosine in Human
Immunodeficiency Virus Infection," New England Journal of
Medicine, August 27, 1992, pages 581-587.) This study enrolled
913 volunteers who had successfully tolerated AZT for at least 16
weeks; they were randomly assigned to either continue AZT, switch
to low-dose ddI, or switch to high-dose ddI. The low-dose ddI
group did best, with significantly fewer deaths and AIDS-defining
events than the group assigned to AZT. The researchers were
surprized that it did not matter how long the patients had been
on AZT before switching.

Another major study (ACTG 116A) has compared first-line use
of ddI vs AZT, but the results are not known yet. They are
expected later this year.