BETAHISTINE Uses, Side Effects, and More

BETAHISTINE

BRAND NAME:- VERTIN 8mg tab .

BETAHISTINE is an orally active,somewhat H1 selective Histamine analogue, which is used to control vertigo in patients of Meniere's disease: possibly acts by causing vasodilation in the internal ear. It is contraindicated in asthmatics and ulcer patients.

PHARMACODYNAMIC:-

Betahistine is a strong antagonist of the histamine H3 receptor and a weak agonist of the histamine H1 receptor.[1]

Betahistine has two mechanisms of action. Primarily, it is a weak agonist on the 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.

More importantly, betahistine has a powerful antagonistic effects at H3 receptors, thereby increasing the levels of neurotransmitters histamine, acetylcholine, norepinephrine, serotonin, and GABA released from the nerve endings. The increased amounts of histamine released from histaminergic nerve endings can stimulate receptors. This stimulation explains the potent vasodilatory effects of betahistine in the inner ear, that are well documented.

Betahistine seems to dilate the blood vessels within the inner ear which can relieve pressure from excess fluid and act on the smooth muscle.

It is postulated that betahistine's increase in the level of serotonin in the brainstem inhibits the activity of vestibular nuclei.

PHARMACOKINETICS:-

Betahistine comes in both a tablet form as well as an oral solution, and is taken orally. It is rapidly and completely absorbed. The mean plasma elimination half-life is 3 to 4 hours, and excretion is virtually complete in the urine within 24 hours. Plasma protein binding is very low. Betahistine is transformed into aminoethylpyridine and hydroxyethylpyridine and excreted with the urine as pyridylacetic acid. There is some evidence that one of these metabolites, aminoethylpyridine, may be active and exert effects similar to those of betahistine on ampullar receptors.

MECHANISM OF ACTION:-

Vertigo is a disturbing sensation of movement caused by dysfunction of the labyrinth (inner ear), vestibular nerve, cerebellum, brainstem, or Central Nervous System (CNS). Vestibular forms of vertigo are often accompanied by auditory dysfunctions such as hyperacusis, hearing loss, and tinnitus.3 In most cases, adaptive mechanisms of the CNS lead to functional recovery after episodes of vertigo, however, syndromes such as Ménière's disease tend to cause the recurrence of vertigo symptoms. This significantly impacts the quality of life and the ability to carry out daily activities.

H1-RECEPTOR ACTIVITY

The mechanism of action of betahistine is multifactorial. Ménière's disease is thought to result from a disruption of endolymphatic fluid homeostasis in the ear.6 Betahistine mainly acts as a histamine H1-receptor agonist. The stimulation of H1-receptors in the inner ear causes a vasodilatory effect leading to increased permeability of blood vessels and a reduction in endolymphatic pressure; this action prevents the rupture of the labyrinth, which can contribute to the hearing loss associated with Ménière's disease. Betahistine is also purported to act by reducing the asymmetrical functioning of sensory vestibular organs and increasing vestibulocochlear blood flow, relieving symptoms of vertigo.

H3-RECEPTOR ACTIVITY

In addition to the above mechanisms, betahistine also acts as a histamine H3-receptor antagonist, increasing the turnover of histamine from postsynaptic histaminergic nerve receptors, subsequently leading to an increase in H1-agonist activity. H3-receptor antagonism elevates levels of neurotransmitters including serotonin in the brainstem, inhibiting the activity of vestibular nuclei, thus restoring proper balance and decreasing vertigo symptoms.

USED:-

Betahistine is used for Meniere's disease. It helps to reduce the episodes of vertigo associated with Meniere's disease.

SIDE effects:-

Headache, Nausea, Palpitations.

DOSE:- ½ TO 1 tab OD.

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