indication

For the reduction of episodes of vertigo association with Ménière's disease.

pharmacology

Betahistine primarily acts as a histamine H1-agonist with 0.07 times the activity of histamine. Stimulating the H1-receptors in the inner ear causes a vasodilatory effect and increased permeability in the blood vessels which results in reduced endolymphatic pressure. Betahistine is believed to act by reducing the asymmetrical functioning of sensory vestibular organs as well as by increasing vestibulocochlear blood flow. Doing so aids in decreasing symptoms of vertigo and balance disorders. Betahistine also acts as a histamine H3-receptor antagonist which causes an increased output of histamine from histaminergic nerve endings which can further increase the direct H1-agonist activity. Furthermore, H3-receptor antagonism increases the levels of neurotransmitters such as serotonin in the brainstem, which inhibits the activity of vestibular nuclei, helping to restore proper balance and decrease in vertigo symptoms.

toxicity

Symptoms of overdose (< 640 mg) include mild to moderate nausea, dry mouth, dyspepsia, abdominal pain and somnolence. More serious complications such as convulsions, pulmonary or cardiac complications, may occur with higher intentional overdoses (> 640 mg).

biotransformation

Betahistine is metabolized primarily into 2-pyridylacetic acid and is subsequently excreted in the urine.

absorption

When given orally, betahistine is rapidly absorbed from the gastrointestinal tract.

half life

3-4 hours

route of elimination

Renal