Drs. Puzantian and Shaw Reply

Letter to the Editor

Sir: Dr. Yong’s comments regarding our letter raise the interesting
issue of the potential for an interaction between nefazodone
and risperidone via inhibition of the cytochrome P450
2D6 isoenzyme, leading to increased levels of risperidone.
Interaction studies of nefazodone with the triazolobenzodiazepines
triazolam and alprazolam, both metabolized by cytochrome
P450 3A4, have revealed substantial and clinically
significant increases in plasma triazolobenzodiazepine concentrations.
Only the benzodiazepines metabolized by the 3A4
isoenzyme have a potential interaction with nefazodone.2,3