Title: Azacyclonol
CAS Registry Number: 115-46-8
CAS Name: a,a-Diphenyl-4-piperidinemethanol
Additional Names: a-(4-piperidyl)benzhydrol; diphenyl (g-pyridyl)carbinol; gamma-pipradrol
Manufacturers' Codes: MER-17
Molecular Formula: C18H21NO
Molecular Weight: 267.37
Percent Composition: C 80.86%, H 7.92%, N 5.24%, O 5.98%
Literature References: Prepd by hydrogenation of a,a-diphenyl-4-pyridinemethanol: Schumann et al., US 2804422 (1957 to Merrell).
Properties: Crystals, mp 160-161°.
Melting point: mp 160-161°
Derivative Type: Hydrochloride
CAS Registry Number: 1798-50-1
Trademarks: Frenquel (Cassenne); Frenoton (Draco)
Molecular Formula: C18H21NO.HCl
Molecular Weight: 303.83
Percent Composition: C 71.16%, H 7.30%, N 4.61%, O 5.27%, Cl 11.67%
Properties: Crystals from butanone, mp 283-285°. Slightly bitter taste. Moderately sol in water.
Melting point: mp 283-285°
Therap-Cat: Anxiolytic.
Status: This monograph has been retired and is no longer subject to revision or update.
Azafenidin Azafrin Azamethonium Bromide Azanidazole Azaperone

Systematic (IUPAC) name
Clinical data
Legal status Prescription only
Routes Oral
CAS number 115-46-8 N
1798-50-1 (HCl)
ATC code None
PubChem CID 15723
ChemSpider 14952 YesY
Synonyms MER-17, MDL-4,829
Chemical data
Formula C18H21NO 
Mol. mass 267.37 g/mol
 N (what is this?)  (verify)

Azacyclonol (trade names Ataractan, Calmeran, Frenoton, Frenquel, Psychosan), also known as γ-pipradol, is a drug which is a so-called ataractive, or agent which diminishes hallucinations in psychotic individuals.[1][2] It has also been called a tranquilizer and antipsychotic, though these definitions are not accurate as it does not actually possess such properties. Despite being a positional isomer of pipradrol, it is not a psychostimulant, and instead has mild depressant effects.[1][3]

The drug was introduced in Europe in the mid-1950s for the treatment of schizophrenia likely on account of the fact that it was found to attenuate the subjective psychedelic effects of LSD and mescaline in humans.[1][4] However, due to poor and mixed clinical effectiveness[4] it never gained widespread acceptance and was eventually discontinued.

The antihistamine agent terfenadine produces azacyclonol as an active major metabolite.[5]