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low levels of sustiva
Oct 13, 2010

hi, have asked this question before, and the answer was: i, i had to come back with same quaestion since ive got no answer in the first place. im on atripla for 6 months, in my last 3 checks my doctor told me that my levels of efavirenz is under 1000, something between 600 and 800. he dosent know if he should give me an extra 200mg efavirenz pill. he asked other consultants and nobody had an answer. can u please let me know what u think? thank you. a.

Response from Mr. Vergel

Did your doctor measure your blood level of Efavirenz? Are you in Europe? Most doctors in the United States do not measure medication blood levels.

If your doctor measured your blood levels and he has told you that you need more Efavirenz, why are you both questioning it? Also, I am assuming that he or she measured your blood levels because you have not responded to the drug (your viral load has not become undetectable after 26 weeks). If that is the case, make sure that you do not have resistance to Efavirenz. If you have resistance, increasing the dose will do little good.

You can always talk to your doctor about using a Novir boosted protease inhibitor, which usually reach adequate blood levels.

Nelson

QUESTION: yes im from europe(London) yes my doctor measure my drug levels of Efavirenz and he said its not enough, BUT i dont have drug resitance to the drug and im undetectable. the doctor is afraid that maybe in time i will get resitance to Efavirenz if my drug levels are not more than 1000 how it supossed to be, but in the same time im undetactebale now, so might be pointless to get an extra 200mg of Efavirenz, he asked other consultants from the clinic and nobody has an answer. why i didnt got the extra 200mg of Efavirenz is that my sleep is not the best and maybe with the extra pill will be even worse. but i rather be healthy and have dreams than get drug resistance to Efavirenz. dont know what to do... thx very much. A.

Response from Mr. Vergel

I am assuming that you have not developed resistance to efavirenz with your suboptimal levels.

There was a study that found that best blood concentrations were between 1000-4000 microg/l . Since your level in under 1000,I would double the dose and retest a week later. Be careful with large increases since you may have more CNS side effects.

It is strange to me that the lab your doctor used to measure blood levels id not provide a range.

Are you taking other meds that are accelerating the clearance of Efavirenz?

Efavirenz plasma levels can predict treatment failure and central nervous system side effects in HIV-1-infected patients.

Marzolini C, Telenti A, Decosterd LA, et al. AIDS. 2001;15:71-75.

Objective: Limited information exists on the clinical usefulness of drug level monitoring for efavirenz, a once-daily non-nucleoside reverse transcriptase inhibitor (NNRTI). The aim of this study was to determine whether efavirenz plasma concentration monitoring could predict treatment failure and central nervous system (CNS) tolerability. Methods: Blood samples were obtained from 130 HIV-infected patients receiving efavirenz in combination with other antiretroviral agents for more than 3 months. Efavirenz plasma concentrations were measured by high-performance liquid chromatography. An evaluation of CNS side-effects was performed and the viral load, CD4 cell count and other clinical and laboratory data were assessed. In 85 patients, these measures were repeated at 3 month intervals. Results: Efavirenz plasma levels (n = 226) were measured at an average of 14 h after drug intake. Drug concentrations ranged from 125 to 15230 microg/l (median 2188). Large inter-patient (CV 118%) and limited intra-patient (CV 30%) variabilities were observed in efavirenz levels. Virological failure was observed in 50% of patients with low efavirenz levels (< 1000 microg/l) versus 22 and 18% in patients with 1000-4000 microg/l or more than 4000 microg/l, respectively. CNS toxicity was approximately three times more frequent in patients with high efavirenz levels (> 4000 microg/l) compared with patients with 1000-4000 microg/l. Conclusion: Treatment failure and CNS side-effects are associated with low and high efavirenz plasma levels, respectively. The important inter-individual variability in efavirenz levels strongly argues for dose adjustment on the basis of therapeutic drug monitoring to optimize treatment.



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