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Clinical data
Trade namesPrimalan
AHFS/Drugs.comInternational Drug Names
ATC code
Legal status
Legal status
  • 10-(1-Azabicyclo[2.2.2]octan-3-ylmethyl)phenothiazine
CAS Number
PubChem CID
CompTox Dashboard (EPA)
ECHA InfoCard100.045.005 Edit this at Wikidata
Chemical and physical data
Molar mass322.47 g·mol−1
3D model (JSmol)
  • c1ccc2c(c1)Sc1ccccc1N2CC1CN2CCC1CC2
  • InChI=1S/C20H22N2S/c1-3-7-19-17(5-1)22(18-6-2-4-8-20(18)23-19)14-16-13-21-11-9-15(16)10-12-21/h1-8,15-16H,9-14H2
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Mequitazine (trade name Primalan) is an H1 antagonist and anticholinergic of the phenothiazine chemical class. It is used to treat allergies and rhinitis.

It was patented in 1969 and came into medical use in 1976.[2]



Severe liver disease; premature infants or full-term neonates.

Special precautions


Pregnancy, lactation; severe cardiovascular disorders; asthma; angle-closure glaucoma, urinary retention, prostatic hyperplasia, pyloroduodenal obstruction; renal and hepatic impairment; elderly, children; epilepsy. May impair ability to drive or operate machinery.

Adverse reactions


CNS depression including slight drowsiness to deep sleep, lassitude, dizziness, incoordination. Headache, psychomotor impairment and antimuscarinic effects. Rarely, rashes and hypersensitivity reactions, blood disorders, convulsions, sweating, myalgia, paraesthesias, extrapyramidal effects, tremor, confusion, sleep and GI disturbances, tinnitus, hypotension, hair loss. Photosensitivity, jaundice.

Drug interactions


Enhances effects of CNS depressants e.g. alcohol, barbiturates, hypnotics, opioid analgesics, anxiolytics and antipsychotics. Can mask signs of ototoxicity caused by aminoglycosides. QT prolongation (which can lead to torsades de pointes arrhythmia) reported with spiramycin.



Same precursor as for Quifenadine. Note that the synthesis has changed over the years from the original. One route seems to involve a Johnson–Corey–Chaykovsky reaction of the starting ketone, although another secondary route is also discussed.

Thieme Prec:[3] Synthesis:[4][5][6]


  1. ^ "Active substance: mequitazine" (PDF). List of nationally authorised medicinal products. Amsterdam: European Medicines Agency. 15 October 2020.
  2. ^ Fischer J, Ganellin CR (2006). Analogue-based Drug Discovery. John Wiley & Sons. p. 548. ISBN 9783527607495.
  3. ^ US 4546185, Bondiou JC, Hodac F, Legroux D, issued Pharmuka Laboratoires 
  4. ^ Gonnot V, Nicolas M, Mioskowski C, Baati R (November 2009). "Expedient synthesis of mequitazine an antihistaminic drug by palladium catalyzed allylic alkylation of sodium phenothiazinate". Chemical & Pharmaceutical Bulletin. 57 (11): 1300–2. doi:10.1248/cpb.57.1300. PMID 19881287.
  5. ^ Guminski Y, Fabre V, Lesimple P, Imbert T (June 1999). "An efficient synthesis of mequitazine". Organic Preparations and Procedures International. 31 (3): 319–323. doi:10.1080/00304949909458326.
  6. ^ Leroux S, Larquetoux L, Nicolas M, Doris E (July 2011). "Asymmetric synthesis of (+)-mequitazine from quinine". Organic Letters. 13 (13): 3549–51. doi:10.1021/ol2012567. PMID 21657243.

Further reading

  • "Mequitazine". Drug Information Portal. U.S. National Library of Medicine.