Question
Can tenofovir and ddI EC be used in the same combination?
21 March 2006. Related: All topics, Changing treatment, Side effects, Starting treatment.
My doctor has put me on a combination, which includes ddI EC and tenofovir. I have a high VL (500,000) and low CD4 23%. I have had a bad time with this part of my combination before, suffering with fatigue. He said it should only be for up-to six months. Is this right? I am worried that it might affect my ability to work.
Answer
ddI EC and tenofovir are not recommended to be used together because of a higher risk of side effects and a higher risk of the treatment not working ‘unless it is strictly necessary’. The combination is particularly not recommended in people with high viral loads or a low CD4 count.
Guidelines recognise that in some cases both drug may have to be used together. Most doctors though would be very cautious, even when using the reduced dose of ddI EC (250mg), and you certainly shouldn’t be using ‘full-dose’ 400mg of ddI EC with tenofovir.
Where this becomes more difficult, is if your previous treatment history means that you only have a limited choice of drugs to use for you HIV combination. If you have resistance to other drugs, then you may be relying on both drugs, plus other in your combination to get your viral load undetectable. If you are using a combination with 4, 5 or more drugs, this may be behind your doctors choice – as you may then be able to drop one of these drugs afterwards (probably the ddI EC).
Without your previous drug history though, and without information about resistance it is not possible to know if this is the case. However, the prospect of 6-month fatigue does not sound good – especially if the fatigue was related to side effect caused by the increased levels of ddI EC (as the interaction with tenofovir causes this). Your would also expect very close monitoring of your kidney function, which could be a serious outcome from the interaction.
If this combination caused you difficulty before, and the symptoms stopped when you stopped treatment, then be very careful using this again. If you get the same symptoms of tiredness, contact your doctor to discuss other options. If you have resistance to protease inhibitors, then using TMC114, which is available in the UK on expanded access, with T-20, may be an option.
A CD4% of 23 in not particularly low, and you do not give your CD4 count, which is usually a more reliable marker of your immune system. Your current CD4% would normally be linked to a CD4 count that is over 200, and this is still a strong immune system.
The European Medicines Agencies’ letter sent to doctors by the manufacturers of both drugs in March 2005 cautions not to use tenofovir and ddI EC together.
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