Betahistine Hydrochloride
Betahistine hydrocholoride which is also known as Serc is the most common drug prescribed for Meniere's Disease. The chemical name is 2 (2' meihylaminoethyl) pyridine dihydrochloride. There is some similarity in structure between betahistine and histamine. This drug improves the blood flow of the small blood vessels in the inner ear. The vasodilating properties of histamine were the basis for treatment of vertigo and other inner ear dysfunctions.
Betahistine was found to have a histamine-like action in animals. Since parenteral histamine has been used in the treatment of Meniere's disease, studies were conducted to test the action of betahistine in this condition. Unlike some other anti-vertigo drugs, testing with nystagmus induced by caloric and rotational stimulation has demonstrated that betahistine does not decrease the vestibular response, as recorded by electronystagmography. In addition, the absorption, metabolism and action of betahistine when administered by the oral route are not known. However, clinical studies indicate that SERC may be useful in reducing the vertigo of Meniere's disease.
Meniere's disease, or idiopathic labyrinthine hydrops, is characterized clinically by recurrent episodes of vertigo accompanied by, usually unilateral, tinnitus and hearing loss. Nausea and vomiting may also occur. The vertigo lasts from a few minutes to several hours. Other forms of aural vertigo may be distinguished only because they tend to last longer. As a rule, between dizzy spells there are no other complaints save for varying levels of hearing and tinnitus. The prognosis in individual patients with Meniere's is difficult to predict. Some patients have mild or major dizzy spells in frequent clusters, possibly once or twice weekly, for a period of several weeks or months, then have remission of episodes which may last for months or years. Others may have vertiginous attacks only once or twice yearly. Virtually none have daily spells, and continuous vertigo in the sense of dizziness without remission for many days or weeks. In general, hearing is poorer and tinnitus loud when vertiginous attacks are frequent. Hearing may return to normal between attacks in early cases, but as time progresses, hearing slowly deteriorates, whether dizzy spells occur or not. In general, early Meniere's is featured by hearing levels which become worse with vertiginous attacks and improve even to normal between the attacks, while in late Meniere's hearing loss is less directly related to dizziness. The pathology of Meniere's disease consists of distention of the membranous labyrinth associated with accumulation due to overproduction or under absorption of endolymph.
Betahistine Hcl resembles the naturally occurring antihistamine in some of its effects. When taken regularly betahistine reduces the frequency and severity of the attacks of nausea and vertigo that characterise this condition and is thought to work by improving blood flow in the small blood vessels of the inner ear, but the treatment is not always successful and surgery is sometimes required.
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