Fluoxetine modestly raises the levels of
ritonavir. A few cases of
serotonin syndrome have been attributed to the use of fluoxetine and
ritonavir. Darunavir/ritonavir and fosamprenavir/ritonavir reduced
paroxetine levels and darunavir/ritonavir reduced sertraline levels. Fluoxetine would be expected to be similarly affected. These reductions in SSRI levels are opposite to the effect originally predicted.
It would be prudent to anticipate some reduction in
efficacy when starting these
protease inhibitors (and probably any ritonavir-boosted
protease inhibitors) in patients taking fluoxetine, sertraline or
paroxetine. Monitor the
clinical effect and increase the SSRI dose as necessary. The general relevance of the few cases of
serotonin syndrome, is also uncertain.