Betavert (Betahistine) – Mechanism of Action

1. Histamine receptor activity

• Weak partial agonist at H1 receptors — located on blood vessels of the inner ear (stria vascularis) and in the CNS.
• Potent antagonist/inverse agonist at H3 receptors — these are presynaptic autoreceptors that normally inhibit histamine (and other neurotransmitter) release. By blocking H3, betahistine increases the synthesis and release of histamine, and indirectly boosts other neurotransmitters (acetylcholine, norepinephrine, serotonin, GABA) from nerve terminals.

2. Peripheral (inner ear) effect

• H1-mediated vasodilation and increased capillary permeability improve microvascular circulation in the stria vascularis of the cochlea.
• This is believed to reduce endolymphatic pressure/hydrops, which is central to Ménière's disease pathology - Scott-Brown's Otorhinolaryngology Head & Neck Surgery, Vol 1.

3. Central (vestibular) effect

• Betahistine also appears to act directly on the vestibular nuclei, inhibiting neuronal activity there, and facilitates vestibular compensation (the brain's adaptive process for balance recovery after vestibular injury) - Scott-Brown's Otorhinolaryngology Head & Neck Surgery, Vol 1.
• Cummings Otolaryngology describes betahistine as a vasodilator historically popular for Ménière's disease, though in the US it is only available via compounding pharmacies.

Summary

1. Vasodilation and improved microcirculation in the inner ear → lowers endolymphatic pressure
2. Increased central histamine turnover → enhances vestibular compensation and modulates neuronal excitability in the vestibular nuclei

Evidence caveat