E-DRUG: NEVIRAPINE OR PLACEBO? (cont)
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Answer to Prof Walubo's message from 7/26:
Dear Prof. Walubo,
You were wondering about the mechanism of transmission reduction with
Nevirapine or AZT.
AZT monotherapy for prevention of vertical HIV transmission only causes
marginally reduction of the maternal viral titers which can not explain the
observed reduction in transmission. Instead AZT probably is effective
because of passage through the placenta causing fetal AZT levels sufficient
for preexposure prophylaxis.
I received another question asking how intrapartum Nevirapine can work if
it takes up to seven hours to reach therapeutic levels. The executive
summary of the Nevirapine trial that is currently available does not give
data how many hours prior to delivery the women received Nevirapine,
hopefully the full publication will help.
But if indeed the time before delivery was often too short to reach
adequate serum levels this would imply that most of the preventive effect
is due to the postnatal dose to the infant.
As a comparison, a retrospective AZT study published by Wade et al (NEJM,
Nov 1998, 339 (20):1409-14) showed the following transmission rates: 6.1%
if treatment was begun in the prenatal period, 10.0% when begun
intrapartum, 9.3% when begun within first 48 hours of life and 18.4% if
begun on day 3 of life or later. Transmission rate was 26.6% without AZT
(all these variations because of limited prenatal care or patient choice).
At least for AZT it seems that starting prophylaxis intrapartum is not
better than starting within 48 hours after birth.
Best regards,
Tido von Schoen-Angerer, MD
Medecins sans frontieres
tavschoen@aol.com
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