What is the active ingredient in Bonine (meclizine)?

Active Ingredient in Bonine

The active ingredient in Bonine is meclizine hydrochloride (also called meclizine dihydrochloride). 1

Chemical Composition and Formulation

• Meclizine hydrochloride is chemically designated as 1-(p-Chloro-α-phenylbenzyl)-4-(m-methylbenzyl) piperazine dihydrochloride monohydrate, appearing as a white to slight yellowish crystalline powder. 1

• Each tablet contains meclizine dihydrochloride in varying strengths that correspond to different amounts of meclizine free base:

  • 12.5 mg tablet = 10.53 mg meclizine free base 1
  • 25 mg tablet = 21.07 mg meclizine free base 1
  • 50 mg tablet = 42.14 mg meclizine free base 1

Mechanism of Action

• Meclizine functions as a histamine H1 receptor antagonist, though the precise mechanism by which it exerts its therapeutic effect for motion sickness is presumed to involve antagonism of the histamine H1 receptor. 1, 2

• The drug suppresses the central emetic center to relieve nausea and vomiting associated with motion sickness. 3

Clinical Use

• Meclizine is commonly used for motion sickness at doses of 12.5-25 mg three times daily. 3

• The American Academy of Otolaryngology-Head and Neck Surgery recommends meclizine 25 mg orally as-needed (PRN) rather than on a scheduled basis, with a maximum of 100 mg daily in divided doses if severe symptoms persist. 4

Metabolism

• CYP2D6 is the dominant enzyme for metabolism of meclizine, and genetic polymorphism of this enzyme could contribute to large inter-individual variability in drug exposure. 1, 5

• Meclizine has a plasma elimination half-life of approximately 5 to 6 hours in humans. 1