Ritonavir is predicted to increase the effects of dihydrocodeine, oxycodone, and tramadol. However, there is no
clinical evidence that this occurs. Ritonavir may also decrease the effects of
codeine by inhibiting its
metabolism to an active
metabolite.
Caution and careful monitoring of effects is warranted with dihydrocodeine, oxycodone, and tramadol as high levels may lead to
CNS depression. Smaller initial doses may be appropriate. In contrast,
codeine may be less effective than expected. Low-dose
ritonavir would be expected to have a less potent effect on the
metabolism of these
opioids and dose adjustments would not generally be required.