Precursor to metabolite: Trazodone to mCPP

Trazodone is converted to mCPP by CYP3A4.

The pair

Trazodone — Sedating SARI, used mostly off-label at low dose for sleep; priapism is a rare risk.
mCPP — Trazodone and nefazodone metabolite; a 5-HT2C agonist that causes anxiety and dysphoria, and accumulates when CYP2D6 is inhibited.

Anything that inhibits or induces CYP3A4 shifts the balance between Trazodone and mCPP.