Betahistine

Betahistine is a drug used to treat vertigo. It is often prescribed for balance disorders or to relieve symptoms of vertigo, such as those associated with Ménière's disease. It was first approved in Europe in 1970 for the treatment of Ménière's disease. Betahistine is a histamine analogue.

Pharmacodynamics

Betahistine has two mechanisms of action. Primarily, it is a weak agonist at H1 receptors located on blood vessels in the inner ear. Stimulation of H1 receptors in the inner ear causes vasodilation, which leads to increased blood vessel permeability and a reduction in endolymphatic pressure; this action prevents rupture of the labyrinth, which may contribute to the hearing loss associated with Ménière's disease. Betahistine also acts by reducing asymmetric vestibular sensory function and increasing vestibulocochlear blood flow, which relieves symptoms of vertigo. In addition, betahistine also acts as a histamine H3 receptor antagonist by increasing the turnover of histamine from postsynaptic histaminergic nerve receptors, which subsequently leads to an increase in H1 agonist activity.

Pharmacokinetics

Betahistine is available in both tablet and solution form 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 converted to aminoethylpyridine and hydroxyethylpyridine in the liver and excreted in the urine as pyridylacetic acid.

Side effects

Patients taking betahistine may experience the following side effects:

• Headache
• Minor side effects in the gastrointestinal tract
• Nausea
• Hypersensitivity and allergic reactions

Hypersensitivity reactions resolve quickly after betahistine is stopped.