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  AIDS 2002 Barcelona
Barcelona, Spain July 7-12 2002
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Tenofovir and DDI EC Interactions: TDF raises ddI levels 50-70%
Reported by Jules Levin
  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.
--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.