Betahistine Dihydrochloride

Betahistine works in more than one way. Meniere's disease is thought to come from a disruption of the fluid balance (endolymphatic fluid homeostasis) in the ear. Betahistine mainly acts as a histamine H1-receptor agonist. When H1-receptors in the inner ear are stimulated, the blood vessels widen, their permeability increases and the endolymphatic pressure falls. This action prevents rupture of the labyrinth, which can contribute to the hearing loss seen in Ménière's disease. Betahistine is also said to reduce the uneven functioning of the sensory vestibular organs and to increase blood flow in the vestibulocochlear region, and that relieves the symptoms of vertigo.

Betahistine also acts as a histamine H3-receptor antagonist. This increases the turnover of histamine from the postsynaptic histaminergic nerve receptors, which in turn increases H1-agonist activity. H3-receptor antagonism also raises the levels of neurotransmitters, including serotonin, in the brainstem. That inhibits the activity of the vestibular nuclei, so proper balance is restored and vertigo symptoms decrease.