Resistance

As with all other anti-HIV drugs, strains of HIV that are resistant to nevirapine (Viramune) may emerge after a period of treatment. The emergence of drug-resistant strains coincides with a fall in the effectiveness of the drug .

A single mutation in the reverse transcriptase gene is sufficient to bring about resistance to nevirapine. The commonest nevirapine-associated mutations are K103N, Y181C, G190A and Y188L.1 2 Other nevirapine-associated mutations include V106A, Y188C, G190S and M230L.

Once resistance to nevirapine has developed, it is very likely that the virus will also be resistant to the non-nucleoside reverse transcriptase inhibitor (NNRTI) efavirenz (Sustiva).3 4 Conversely, previous exposure to an NNRTI may predispose a person to fail a nevirapine-based regimen, even where standard resistance tests indicate that no NNRTI resistance is present.

References

  1. Uhlmann EJ et al. Effects of the G190A substitution of HIV reverse transcriptase on phenotypic susceptibility of patient isolates to delavirdine. J Clin Virol 31: 198-203, 2004
  2. Richman D et al. Nevirapine resistance mutations of human immunodeficiency virus type 1 selected during therapy. J Virol 68: 1660-1666, 1994
  3. Antinori A et al. Cross-resistance among nonnucleoside reverse transcriptase inhibitors limits recycling efavirenz after nevirapine failure. AIDS Res Hum Retroviruses 18: 835-838, 2002
  4. Casado JL et al. Extent and importance of cross-resistance to efavirenz after nevirapine failure. AIDS Res Hum Retroviruses 18: 771-775, 2002
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