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Risk of resistance?
Mar 21, 2002

I have been on Combivir/Sustiva therapy for a little over 1 year now. This is my first therapy. I have never missed a dose and my viral load has been undetectable since week 8 or so. I usually take the combvir at 7:30am when I wake up and 5PM after work. I take the Sustiva at bedtime which can vary betwen 10PM and 1AM depending on the day. I've been reading recently that the timing of each dose is critical to prevent drug resistance; am I at risk with my current "loose" schedule? Should the Combivir be taken exactly every 12 hrs and the Sustiva at 24hrs? Thanks

Response from Dr. Little

It sounds to me like you are doing an excellent job. Although your schedule is working, treatment guidelines do stress that the doses be taken at the exact intervals recommended. For a once a day drug like sustiva - this is not an issue - the half life of this drug is quite long and thus not nearly as sensitive to 1-2 hour shifts in drug dosing. I generally recommend for the twice daily drugs that you try to keep dosing at 12 hour intervals plus or minus 2 hours - this means that the furthest apart your drugs would ever be taken would be 16 hours apart which is aproaching a window of concern - but if it does not happen often - not likely to be a problem. In general, aim for the recommended dosing intervals - and remember that the interval is much more important for the twice a day drugs - try to get within an hour or so of the recommended time and realize that if you are within 2 hours of the recommended time now and then, it is not likely to be a problem - as long as this is not the usual pattern.

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