TreatmentUpdate 71, Volume 8, No 7; October 1996
Although people living with HIV/AIDS using AZT are usually
prescribed 500 or 600 mg/day, anecdoctal reports suggest that
people may be taking 300 or 400 mg/day. This dose reduction may
reduce side effects and the cost of the drug. Doctors in Mexico
city conducted a small study to find out the effect of
different doses of AZT on the development of drug-resistant
virus. Doctors recruited 15 HIV-infected subjects who had
between 200 and 500 CD4+ cells. Subjects were assigned to the
* AZT 500 mg/day
* AZT 300 mg/day
* no AZT (or any other anti-HIV drugs)
Blood samples were taken from the subjects for analysis before
they entered the study and at regular intervals.
During the course of the study, technicians isolated HIV from
blood samples and exposed the virus to AZT in lab experiments.
They found at the end of the study, HIV from subjects who used
the high dose of AZT required huge quantities (750 times the
normal amount) of the drug to suppress production of HIV in the
test tube. Virus taken from subjects using AZT 300 mg/day
needed less drug (93 times the normal level) to block its
activity. Subjects not receiving AZT had HIV that required even
less drug to suppress its production. The difference between
the concentrations of AZT required to suppress the virus before
and after entering the study was [statistically] significant.
Although researchers are not sure which dose of AZT is best,
300 mg/day in combination with other anti-HIV agents may be a
reasonable dose to use. The study could have been a more useful
piece of research had the doctors also measured changes in
1. Soto-Ramirez L, Renjifo B, Marlink R, et al .
Dose-dependent HIV-1 Zidovudine resistance. Abstract I111.