Betahistine

Oral
Meniere's disease
Adult: For the treatment of vertigo, tinnitus, hearing loss, and nausea associated with Meniere's disease: As betahistine dihydrochloride: Initially, 8-16 mg tid. Maintenance: 24-48 mg daily in divided doses. As betahistine mesilate: 6-12 mg tid. Adjust doses according to patient needs.

May be taken with or without food.

Phaeochromocytoma, active or history of peptic ulcer.

Patient with bronchial asthma, CV disease, urticaria, rashes, allergic rhinitis. Patient taking antihistamines. Hepatic impairment. Pregnancy and lactation.

Significant: Rarely, ventricular extrasystoles, hypotension, tachycardia. Gastrointestinal disorders: Diarrhoea, dry mouth, dyspepsia, nausea. Rarely, mild gastric complaints (e.g. vomiting, gastrointestinal pain, abdominal distension, bloating). Immune system disorders: Hypersensitivity reactions (e.g. anaphylaxis). Nervous system disorders: Headache. Skin and subcutaneous tissue disorders: Rarely, rash, pruritus, urticaria, angioneurotic oedema.

Symptoms: Nausea, somnolence, abdominal pain; convulsions, pulmonary or cardiac complications. Management: Supportive and symptomatic treatment. Perform gastric lavage.

Metabolism may be inhibited by MAOIs (e.g. selegiline). May diminish efficacy with antihistamines.
Potentially Fatal: 

Delayed absorption with food.

Betahistine is a histamine analogue that is claimed to improve the microcirculation of the labyrinth resulting in decreased endolymphatic pressure. The exact mechanism is not yet fully determined; however, it is known to act as both a partial histamine H₁-receptor agonist and histamine H₃-receptor antagonist in neuronal tissue, with negligible histamine H₂-receptor activity. It inhibits presynaptic histamine H₃-receptors and induces H₃-receptor downregulation, thus increasing the histamine turnover and release.
Absorption: Readily and almost completely absorbed from the gastrointestinal tract. Delayed absorption with food. Time to peak plasma concentration: 1 hour (inactive metabolite).
Distribution: Plasma protein binding: <5%.
Metabolism: Rapidly and almost completely metabolised into 2-pyridylacetic acid (inactive metabolite).
Excretion: Via urine (approx 91%; mainly as inactive metabolite). Elimination half-life: Approx 3.5 hours (inactive metabolite).

Oral: Store between 15-30°C. Protect from moisture and light.

Antivertigo Drugs

N07CA01 - betahistine ; Belongs to the class of antivertigo preparations.