Vectra

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.

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.

Adults : Initial oral treatment is 8 to 16mg three times daily, taken preferably with meals. Maintenance doses are generally in the range 24-48 mg daily. Daily dose should not exceed 48mg. Dosage can be adjusted to suit individual patient needs. Sometimes improvement could be observed only after a couple of weeks of treatment. There is no data available for patients with hepatic impairment. There is no data available for patients with renal impairment. There is limited data in the elderly, betahistine should be used with caution in this population. Children and adolescents : Betahistine tablets are not recommended for use in children and adolescents below age 18 due to lack of data on safety and efficacy.

There are no proven cases of hazardous interactions. There is a case report of an interaction with ethanol and a compound containing pyrimethamine with dapsone and another of potentiation of betahistine with salbutamol. Vectra is a histamine analogue, concurrent administration of H1 antagonists may cause a mutual attenuation of effect of the active agents.

Betahistine is contraindicated in patients with phaeochromocytoma. As betahistine is a synthetic analogue of histamine it may induce the release of catecholamines from the tumour resulting in severe hypertension. Hypersensitivity to the active substance.

Vectra is generally well tolerated and there is no known serious adverse effects. In some circumstances gastrointestinal disturbances, headache, rashes and pruritus have been reported.

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.

Caution is advised in the treatment of patients with peptic ulcer or a history of peptic ulceration, because of the occasional dyspepsia encountered in patients on betahistine. Caution should be exercised in patients with bronchial asthma. Caution is advised in prescribing betahistine to patients with either urticaria, rashes or allergic rhinitis, because of the possibility of aggravating these symptoms. Caution is advised in patients with severe hypotension. Patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption should not take this medicine. Effects on ability to drive and use machines: Rare reports of drowsiness associated with betahistine have been made. Patients should be advised that they are affected in this way they should avoid activities requiring concentration, such as driving and operating machinery.

The symptoms of betahistine overdose are nausea, vomiting, dyspepsia, ataxia and seizures. More serious complications (convulsion, pulmonary or cardiac complications) were observed in cases of intentional overdose of betahistine especially in combination with other overdosed drugs. No specific antidote. Gastric lavage and symptomatic treatment are recommended.

Keep below 30°C temperature, away from light & moisture. Keep out of the reach of children.