The prevalence of phenotypic drug resistance was assessed in 60 patients with a viral rebound after they received a protease inhibitor (PI)- or nonnucleoside reverse transcriptase inhibitor (NNRTI)-containing regimen (baseline), Resistance testing was done within 36 weeks of viral rebound; no resistance testing was available at baseline, All patients had previously received zidovudine; 86.0% had received lamivudine, In total, 45.1% of the patients had strains resistant to the PI that they started and 88.9% given nevirapine had strains with reduced susceptibility to that drug. Overall, 46 patients (76.7%) harbored a strain resistant to greater than or equal to 1 drug of their initial PI- or NNRTI-containing regimen. Of 53 patients who remained on treatment at the time of the study (40 had switched to a different combination from that at baseline), 6 harbored isolates susceptible to all drugs they had ever received. Thus, patients with viral rebound while on potent antiretroviral therapy usually have reduced susceptibility to greater than or equal to 1 drug. Viral rebound also occurs in persons in whom resistant strains could not be detected by the assay used.
Lepri, AC ; Sabin, CA ; Staszewski, S ; Hertogs, K ; Muller, A. ; et. al. Resistance profiles in patients with viral rebound on potent antiretroviral therapy.5th Annual Meeting of the British-HIV-Association (CAMBRIDGE(England), Mar 20, 1999). In: The Journal of Infectious Diseases, Vol. 181, no. 3, p. 1143-1147 (2000)