Mode of Action
Betahistine has a very strong affinity as an antagonist for histamine H3 receptors and a weak affinity as an agonist for histamine H1 receptors. Betahistine seems to dilate the blood vessels within the middle ear which can relieve pressure from excess fluid and act on the smooth muscle.
Betahistine has two modes of action. Primarily, it has a direct stimulating (agonistic) effect on H1 receptors located on blood vessels in the inner ear. This gives rise to local vasodilation and increased permeability, which helps to reverse the underlying problem of endolymphatic hydrops.
In addition, betahistine has a powerful antagonistic effects at H3 receptors, and increases the levels of neurotransmitters released from the nerve endings. This is thought to The increased amounts of histamine released from histaminergic nerve endings can stimulate receptors. This explains the potent vasodilatory effects of betahistine in the inner ear, which are well documented.
- It is postulated that betahistine increases the levels of neurotransmitters such as serotonin in the brainstem, which inhibits the activity of vestibular nuclei.
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