Mequitazine Explained

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.^[1]

Contraindications

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.

Synthesis

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.

Further reading

• Ramírez Chanona N, del Rio Navarro BE, Pérez Martín J . [Efficacy of mequitazine (Primalan) on the relief of symptoms of allergic rhinoconjunctivitis in children. Documented clinical experience] . Spanish . Revista Alergia Mexico . 52 . 6 . 221–225 . November–December 2005 . 16568706 .
• Theunissen EL, Vermeeren A, van Oers AC, van Maris I, Ramaekers JG . A dose-ranging study of the effects of mequitazine on actual driving, memory and psychomotor performance as compared to dexchlorpheniramine, cetirizine and placebo . Clinical and Experimental Allergy . 34 . 2 . 250–258 . February 2004 . 14987305 . 10.1111/j.1365-2222.2004.01874.x . 23019669 .
• Nakamura K, Yokoi T, Kodama T, Inoue K, Nagashima K, Shimada N, Shimizu T, Kamataki T . 6 . Oxidation of histamine H1 antagonist mequitazine is catalyzed by cytochrome P450 2D6 in human liver microsomes . The Journal of Pharmacology and Experimental Therapeutics . 284 . 2 . 437–442 . February 1998 . 9454781 .
• Persi L, Dupin O, Arnaud B, Trinquand C, Michel FB, Bousquet J . Efficacy of mequitazine in comparison with placebo assessed by ocular challenge with allergen in allergic conjunctivitis . Allergy . 52 . 4 . 451–454 . April 1997 . 9188930 . 10.1111/j.1398-9995.1997.tb01028.x . 34785561 .

External links

• Web site: Mequitazine . U.S. National Library of Medicine . Drug Information Portal .

Notes and References

1. Book: Fischer J, Ganellin CR . Analogue-based Drug Discovery . 2006 . John Wiley & Sons . 9783527607495 . 548 . en.