Drugs that CYP2D6 metabolizes include selective serotonin reuptake inhibitors (SSRI), tricylic antidepressants (TCA), beta-blockers, opiates, neuroleptics, antiarrhythmics and a variety of toxic plant substances. Specific notable drugs include Prozac, Zoloft, Paxil, Effexor, hydrocodone, amitriptyline, Claritin, cyclobenzaprine, Haldol, metoprolol, Rythmol, Tagamet, tamoxifen, and the over-the-counter diphenylhydramine drugs, Allegra, Dytuss, and Tusstat. CYP2D6 is also responsible for activating the prodrugs codeine and other opioids into their active forms. The analgesic activity of the drugs is therefore reduced or absent in CYP2D6 poor metabolizers. Refer to list for substrates, inhibitors and inducers of CYP2D6.
Haloperidol is a typical butyrophenone type antipsychotic that exhibits high affinity dopamine D 2 receptor antagonism and slow receptor dissociation kinetics.  It has effects similar to the phenothiazines .  The drug binds preferentially to D 2 and α 1 receptors at low dose (ED 50 = and mg/kg, respectively), and 5-HT 2 receptors at a higher dose (ED 50 = mg/kg). Given that antagonism of D 2 receptors is more beneficial on the positive symptoms of schizophrenia and antagonism of 5-HT 2 receptors on the negative symptoms, this characteristic underlies haloperidol's greater effect on delusions, hallucinations and other manifestations of psychosis.  Haloperidol's negligible affinity for histamine H 1 receptors and muscarinic M 1 acetylcholine receptors yields an antipsychotic with a lower incidence of sedation, weight gain, and orthostatic hypotension though having higher rates of treatment emergent extrapyramidal symptoms .
processing.... Drugs & Diseases haloperidol (Rx) Brand and Other Names: Haldol, Haldol Decanoate, more... Haloperidol LA, Peridol