Optimal Amprenavir/Ritonavir dosages
Apr 11, 2001
I've been on a combination of 1200mg Amprenavir/100mg Ritonavir BID plus Zerit and Ziagen for about six months and my viral load has been undetectable the last two times I tested (i.e., a four month period). While I'm happy with the success of this combination, I'd like to lower my Amprenavir dosage in order to minimize toxicity risks. I've seen some recent pharmacokinetic data on Amprenavir/Ritonavir, but my particular combination doesn't seem to have been studied. Or has it? Am I overkilling with 1200mg? Would it be safe to go to a lower dose? Is there a testing procedure that would help me determine the optimal dosage for ME? Thanks for your guidance.
Response from Dr. Pavia
You probably have seen some of the PK studies. 600/100, 750/100, and 900/100 give pretty similar amprenavir exposure. There was one study at retrovirus this year that suggested that when a non nuke was added, it may be necessary to go up to ritonavir 200 to get everyone up to high levels of amprenavir. So, based on these studies, I would consider somewhere between 600/100 and 750/100 to be reasonable doses for you to consider.
The question you ask at the end is really: "Can I individualize my dose to what is best for me?" In theory the answer is yes, but in practice we are not there yet. We would want to know what the level of drug is (in your body, not in a lab in Belgium or the Bay area)necessary to inhibit your virus completely, and then make sure that the regimen you were on provided at least that level in your blood, brain, semen and lymph nodes at the end of each dosing interval. We are not there yet, but I think monitoring drug levels in the blood will become very useful in the next year or three.
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