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STI - Last Question!

Nov 20, 2000

Dear Dr. Cohen:

Many thanks for your previous answers which have really helped me decide what to do when on a break from medication. I have a few more questions, though, which I hope you'll be able to answer.

Is it necessary to have resistance testing? I've been on my current combination (Efaverenz + Combivir) for a year now with excellent results. Viral Load has been <50 from one month after commencing, and T4 is now at 625, which is the highest in many years. So I don't think there is any resistance, but of course, I'd rather know. If I do have resistance tests, when is the best time to do so - after stopping the drugs, or before starting up again?

Is there any information as to how long a break can be? I'll be travelling and crossing a lot of time zones and into different countries for about 2 1/2 months and the hassles of timing the drugs and importing them into different countries is a bit overwhelming. (The USA is one of the hardest places for HIV+ people to enter.) Is this (2 1/2 months) a reasonable break?

I'm planning to have regular blood tests: is there a "Magic Number" for either viral load or T4 which would tell me it's time to start meds again? At thi s point I'm thinking that if my load goes over 25,000 and/or T4 below 250 -300. What do you think?

Is there any connection between the time on medication and the length of the break (i.e. how long it takes for results to start deteriorating?)

Thanks again for all your help.

Response from Dr. Cohen

Well - I doubt this will be the last question on STI - it is a hot issue these days - so keep them coming - that is what we are here for!

As for resistance testing - you are in the circumstance where resistance testing will be least useful. As you note - your viral suppression to

If/when you stop, the virus to come back will be the original sensitive virus - the one you had before you started this combo. Drug resistant strains (probably) aren't there now, and are unlikely to emerge when stopping. But even if they are there, they tend to get washed out or diluted by the amount of sensitive virus when people are off of meds. If your concern is the theoretic one - that you might develop resistance to these meds because of the longer half life of the efavirenz - it is not clear when the best time to look for this would be - but perhaps the first few weeks after stopping would be best - since it would take a while for this to happen, but the longer you wait, the more the sensitive virus could dilute the resistant ones. Now, this is perhaps at best educated guessing, and the good news is that resistant HIV is fortunately unlikely to emerge during a stop. But not impossible - so research is going on to better understand this. One way to decrease the chance of this happening is to start a protease inhibitor and stop the EFV while continuing the Combivir - and do this for about a week while the EFV levels fade away - then stopping the combo. This is about the most conservative way to go but does have the benefit of noting that those who stop PI based combos have very low chances of seeing resistance, like below 1% chance so far.

As for how long a break you can take - it is still not clear it will be before you reach your defined trigger to restart. How long you have been on meds probably doesn't tell us much - the factors that are likely to matter are how high your viral load goes, and perhaps how low your CD4 counts were before starting meds at all. If your viral load was 20 thousand before meds, you might have a smaller drop in CD4 cells than if your viral load goes up to 200 thousand. And you didn't mention here what yours was so it is hard to know. On average, if you stop more than a few weeks and your viral load does come back (and after 10 weeks it usually does), you should expect some CD4 cell count drop. Rarely some will also have symptoms of HIV again - we have seen this as have others, and very rarely this can be pretty severe. It would be helpful to know how long you drop however in case you are among the few who have a low enough drop as to prompt us to reinitiate treatment quickly.

As for the "right" trigger to restart - there is on ongoing debate about this. At the lower end, a T4 of 250 is about the lowest anyone is going before suggesting restarting, especially if it is a combo you can tolerate well. Some would choose higher cutoffs, others might choose even shorter periods of time to avoid much CD4 loss at all. It all depends on why you are taking a break, and what happens during it. Your viral load peak of 25 thousand is a bit more arbitrary - this number is useful in part to tell us how quickly you would lose CD4 cells - so restarts are usually based more on either the cell counts, or on shorter periods of time to avoid cell drops. The med combo should work on you whatever your viral load becomes - since it is working well now.

Hope that clarifies for now - but let us know if there are more questions. No doubt this issue is one that many are struggling with.

And as for HIV+ persons reentering - I don't suppose we can expect much to change on this in the near future unless Florida counts dimples...


Cal Cohen, M.D., M.S.

human trials
Ok to continue with hydroxyurea?

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