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Tenofovir and DDI EC Interactions: TDF raises ddI levels 50-70%
Reported by Jules Levin
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Gilead Sciences and Bristol Myers Squibb presented a poster at Barcelona on
the pharmacokinetic (interactions) between ddI EC (enteric coated, new ddI)
and Tenofovir (TDF). A previous PK study showed increases in ddI Cmax
(highest drug levels after taking dose) and AUC (overall blood levels during
doseing period) of 28% and 44%, respectively, when TDF was taken with ddI
buffered tablets (old form). Researchers reported when ddI EC is taken with
food , ddI AUC is reduced by 18-27%, compared to the fasting state.
The purpose of this study was to examine interaction between new form ddI EC
and TDF. Patients weighed on average 76 kg (2.2 lbs per kg). 14 men & 12
women. 26/28 caucasian.
RESULTS
--TDF levels (Cmax, AUC). ddI was taken fasted + TDF taken 2 hours later with
light meal: no change in TDF levels.
--TDF levels (Cmax, AUC). ddI taken with TDF and a light meal (373 kcal, 20%
fat): no change in TDF levels.
--ddI EC levels. ddI EC taken fasted + TDF 2 hours later with light meal:
Cmax of ddI increased 50%, AUC of ddI increased 50%.
--ddI EC levels. ddI EC taken with light mealL Cmax increased 70%, AUC
increased 65%.
These data show that taking ddI at the same time as TDF with a light meal may
result in even higher levels of ddI, so separating the dosing appears
important. In speaking with Gilead at Barcelona they are planning to start a
study with 250 mg ddI + TDF. It is not a recommendation to take 250 mg with
TDF and we should wait for study results but perhaps the reduced ddI dose
will work with TDF.
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