There is evidence to suggest that
St John's wort (Hypericum perforatum) may decrease blood levels of
nevirapine (clearance increased by 35%). Similar interactions are possible with delavirdine and
efavirenz.
This supports the advice issued by the CSM in the UK, that St John's wort may decrease blood levels of the
NNRTIs with possible loss of HIV suppression. Combined use should be avoided.