Piperazines

A piperazine ring — six-membered, two nitrogens — carrying a benzyl or aryl group. The family has two halves with different pharmacology, and they are usually sold together. The benzylpiperazines, BZP and DBZP, act on the catecholamine transporters and read as a coarse stimulant; the phenylpiperazines, TFMPP, mCPP and MeOPP, are serotonin receptor agonists and releasers, and mCPP is also a metabolite of some antidepressants, better known for headache, anxiety and dysphoria than for anything anyone wanted.

Mixtures of the two halves were sold as a legal substitute for ecstasy, and are frequently what a tablet sold as MDMA actually contains. BZP lowers the seizure threshold, the serotonergic half carries serotonin syndrome risk alongside MAOIs and serotonergic antidepressants, and taking one on top of the drug it was substituted for stacks both effects.