Switching from ZLN to TLD in a Patient with Detectable Viral Load

Introduction to Switching Antiretroviral Therapy

The American Academy of HIV Medicine recommends switching from ZLN (Zidovudine/Lamivudine/Nevirapine) to TLD (Tenofovir/Lamivudine/Dolutegravir) for patients with detectable viral load, as dolutegravir-based regimens demonstrate superior efficacy in suppressing viremia, including in patients with NNRTI resistance 1, 2

Dolutegravir plus 2 NRTIs (with at least 1 active drug) is the recommended regimen after initial treatment failure with an NNRTI, which is the most likely scenario here given the detectable viral load on nevirapine-based therapy 2, 3

While resistance testing is ideally recommended before switching regimens, the absence of resistance testing should not prevent this switch, according to the Infectious Diseases Society of America 4, 5
The high genetic barrier to resistance of dolutegravir makes it effective even when NRTI resistance is present, as noted by the World Health Organization 1, 2

Switch to TLD immediately without delay, as continuing on a failing NNRTI-based regimen risks accumulation of additional resistance mutations, advises the European AIDS Clinical Society 2, 3
Check HIV viral load at 1 month post-switch to confirm virologic response, and continue viral load monitoring every 3 months for the first year, then at least every 6 months thereafter if suppression is maintained, recommends the Centers for Disease Control and Prevention 1, 2, 6, 7
Monitor renal function (serum creatinine and eGFR) at baseline and periodically, particularly given the switch to tenofovir, as suggested by the National Institute of Health 6
Assess for hepatitis B co-infection status, as the tenofovir/lamivudine combination in TLD provides dual activity against HBV, notes the American Liver Foundation 2, 3, 6

Continuing ZLN while waiting for resistance testing results is not recommended, as this allows ongoing viral replication and potential accumulation of resistance mutations, warns the British HIV Association 2, 3
Never add dolutegravir alone to the failing ZLN regimen—always switch to a complete new regimen, advises the International AIDS Society 2, 3

TLD has superior tolerability, eliminating zidovudine-related anemia and bone marrow suppression, and nevirapine-related hepatotoxicity and rash risks, notes the American Academy of HIV Medicine 5, 8
Dolutegravir has a much higher genetic barrier to resistance than nevirapine, according to the World Health Organization 1
The single-pill regimen of TLD improves convenience and adherence, suggests the European AIDS Clinical Society 8
TLD reduces long-term toxicity, eliminating concerns about zidovudine-related lipoatrophy and mitochondrial toxicity, recommends the National Institute of Health 8