Switch to efavirenz (EFV) after protease-inhibitor (PI)-failure: explorative analysis of outcome by baseline viral VS tolerability failure.

The aim of this database analysis was to investigate the efficacy and safety of efavirenz (EFV)-based highly active antiretroviral therapy (HAART) after switching from failed protease inhibitor (PI)- and boosted PI (PI/r)-based regimens. Data were analyzed from 17 adult patients previously treated with a PI-based HAART with substitution of PI with EFV because of virologic failure and from 14 patients previously treated with a PI-based HAART, with substitution of PI due to tolerability issues. Of 17 patients who switched therapy because of virologic failure, 5 patients maintained EFV-therapy for more than 1 year. In 11/17 patients, EFV-based HAART was discontinued during follow-up and one patient was lost to follow-up. Reasons for discontinuation were: virologic failure in 4, adverse events in 6 (5 CNS-adverse events and 1 rash) and non-compliance in 1 of 17 patients. Of 14 patients who stopped PI-therapy and switched to EFV due to tolerability issues, 6 patients maintained EFV-therapy for more than 1 year. In 8/14 patients EFV-based HAART was discontinued during follow-up. Reasons for discontinuation were: virologic failure in 3, adverse events in 3 (2 CNS-adverse events and 1 patient had rash) and non-compliance in 2 of 14 patients. Instable switch to an EFV-based regimen due to virologic failure or toxicity reasons with a boosted or unboosted PI does not show significant differences but outcome was worse than had been described previously for stable switch settings, likely due to multiple prior virologic failures in many patients.