|Viramune Flaws through Research Testing
Dec 31, 2004
Today a report was published about flawed drug tests in regards to Viramnue effectiveness. My partner has been taking viramune for about 2 years and we are now concerned about potential resistance to other classes of drugs due to the use of viramune. Can you please provide any insight of the resistance issue that has been reported? Thank you!
Response from Dr. Sherer
Nevirapine (Viramune or NVP) and efavirenz (Sustiva or EFV) are the main members of the NNRTI class of antiretroviral drugs (ART). In the largest study to date, the 2NN study, the outcomes of people taking three drug regimens with either drug were comparable, with roughly 2/3 of patients achieving good viral control and rising CD4 cell counts after one year.
Sustiva is more widely used initially, and is preferred for initial use in the HHS Guidelines of Oct 2004, for two main reasons. First, it has less liver toxicity than nevirapine (4% vs 8% of patients with hepatitis in the 2NN trial, respectively), and less rash (5% vs 30%). It is also dosed once daily. Though NVP can be dosed once daily as well, this increases liver toxicity to 12%.
The liver toxicity with NVP is more severe when started in ART naive women with CD4 cells above 250 cells/ml, and in men with CD4 cells above 400 cells/ml.
Most importantly, the liver toxicity with NVP can be life-threatening due to fulminant hepatitis. This most commonly occurs in the first 6 weeks of treatment in men and women with higher CD4 cell counts, as noted above.
Thus, your partner has little risk of this liver toxicity, and apparently has gained from the potential benefit of NVP in his regimen.
Regarding resistance, all of the NNRTIs are highly susceptible to resistance in the event of poor adherence or use as a single drug. This resistance can occur in days or a few weeks, and is a reason for patients like your partner to be fastidious with medication adherence.
The reports to which you refer address a different problem - transmission of HIV from pregnant women to their infants - for which single dose NVP has been found to be quite effective. This practice gained popularity in the developing world due to its simplicity and cost effectiveness, i.e. a single pill to a woman in labor and to her child resulted in transmission reductions of 50% or more.
Unfortunately, but not unexpectedly, this practice also led to NVP resistance in the mother and the baby as high as 20-60%. This clearly is undesirable and compromises the chance for subsequent responses to NNRTI-containing regimens for these women. And NNRTI-containing regimens are commonly the only ones avaialable in many regions of the world.
Thus the problem of resistance resulted from the use of NVP as a single drug, and was not unexpected. The use of NVP in a 3 drug combination, as in your partner's case, remains appropriate and consistent with current guidelines and the standard of practice.
Fortunately, there are alternatives to the use of single dose NVP for the prevention of perinatal HIV transmission in the developing world; for example, in a study in South Africa presented at the Bangkok meeting last summer, the addition of only 4 days of combivir (an NRTI combination of AZT and 3TC) resulted in the reduction of resistance in the women from 50% to 5%.
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