Betahistine Dihydrochloride
Indications
Meniere's disease and Meniere-like
syndromes are characterized by attacks of vertigo, tinnitus and/or
progressive loss of hearing, usually accompanied by nausea and vomiting.
Description
Betahistine is a histamine analog that was
developed following successful parenteral use of histamine in patients
with Meniere's Syndrome. Betahistine relieves vertigo symptoms by
improving circulation in the microvasculature of the inner ear which
leads to a pressure reduction on the membranous labyrinth and relieves
the symptoms of Meniere's disease.
Pharmacology
The mechanism of action of betahistine is
multifactorial. Meniere's disease is thought to result from a disruption
of endolymphatic fluid homeostasis in the ear. 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.
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.
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.
Dosage & Administration
The usual initial dose: 8 mg to 16 mg three times daily taken preferably with meals.
Maintenance dose: Up to 48 mg daily has been recommended. Betahistine is not recommended for use in children.
Maintenance dose: Up to 48 mg daily has been recommended. Betahistine is not recommended for use in children.
Interaction
There are no proven cases of hazardous
interactions. Though an antagonism between Betahistine and
antihistamines could be expected on a theoretical basis, no such
interactions have been reported.
Contraindications
Betahistine is contraindicated in pheochromocytoma.
Side Effects
Betahistine is generally well tolerated and
there is no known serious adverse effects. In some circumstances
gastrointestinal disturbances, headache, rashes and pruritus have been
reported.
Pregnancy & Lactation
In Pregnancy: The safety
of Betahistine in human pregnancy has not been completely established,
although there is no known teratogenic effect in animals. A careful
assessment of potential benefits should be made before prescribing
Betahistine in pregnancy.
In Lactation: Betahistine is excreted in the breast milk of nursing mothers in concentrations similar to those found in plasma. Toxicity to the neonate at these concentrations is not known.
In Lactation: Betahistine is excreted in the breast milk of nursing mothers in concentrations similar to those found in plasma. Toxicity to the neonate at these concentrations is not known.
Precautions & Warnings
Caution should be exercised in patients with bronchial asthma and peptic ulceration.
Therapeutic Class
Drugs used in meniere's diseases
Storage Conditions
Keep below 30°C temperature, away from light & moisture. Keep out of the reach of children.
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