ortho-Substituted

• 2-Chlorophenylpiperazine (oCPP)
• 2-Methylphenylpiperazine (oMPP)
• 2-Methoxyphenylpiperazine (oMeOPP)
• Mefeclorazine
• Vortioxetine

Enpiprazole is known to produce oCPP as a metabolite. It was initially anticipated to produce oMeOPP as a metabolite, but this proved not to be the case.

meta-Substituted

• 3-Chlorophenylpiperazine (mCPP)
• 3-Methoxyphenylpiperazine (mMeOPP)
• 3-Trifluoromethylphenylpiperazine (TFMPP)
• 1-(3-Chlorophenyl)-4-(2-phenylethyl)piperazine (3C-PEP)

Trazodone, nefazodone, etoperidone, mepiprazole, and others produce mCPP as a metabolite.^[3]

para-Substituted

• 4-Chlorophenylpiperazine (pCPP)
• 4-Fluorophenylpiperazine (pFPP)
• 4-Methylphenylpiperazine (pMPP)
• 4-Methoxyphenylpiperazine (pMeOPP, MeOPP)
• 4-Nitrophenylpiperazine (pNPP; PAL-175) – selective partial serotonin releasing agent^[4]
• 4-Trifluoromethylphenylpiperazine (pTFMPP)

Multiple substitutions

• 2,3-Dichlorophenylpiperazine (2,3-DCPP)
• 3,4-Dichlorophenylpiperazine (3,4-DCPP)
• 2,3-Dimethylphenylpiperazine (DMPP)
• 3-Trifluoromethyl-4-chlorophenylpiperazine (TFMCPP; PAL-179) – selective partial serotonin releasing agent^[4]

Others

• 1-Phenylpiperazine (PP)