Adult: For vertigo, tinnitus and hearing loss associated in patients with Meniere’s disease: As betahistine dihydrochloride: Initially, 8-16 mg tid or 24 mg bid, adjusted according to individual response. Maintenance: 24-48 mg daily. Max: 48 mg daily. As betahistine mesilate: 6-12 mg tid.
May be taken with or without food.
Patients with bronchial asthma, CV disease, active or history of peptic ulcer disease. Hepatic impairment. Pregnancy and lactation.
Significant: Rarely, ventricular extrasystoles, hypotension (including orthostatic hypotension), tachycardia. Gastrointestinal disorders: Nausea, dyspepsia. Rarely, vomiting, bloating, abdominal distension or pain. General disorders and admin site conditions: Rarely, fatigue, malaise. Immune system disorders: Hypersensitivity reactions (e.g. anaphylaxis). Rarely, urticaria. Nervous system disorders: Headache. Rarely, dizziness, convulsions, somnolence. Psychiatric disorders: Rarely, confusion, hallucination. Respiratory, thoracic and mediastinal disorders: Rarely, dyspnoea, bronchospasm. Skin and subcutaneous tissue disorders: Rarely, rash, pruritus. Vascular disorders: Rarely, vasodilation.
Serum concentration may be increased by MAOIs (e.g. selegiline). Therapeutic effects may be decreased by antihistamines. May decrease the bronchodilator effects of β2 agonists.
Delayed absorption with food.
Description: Betahistine is a histamine analogue. The exact mechanism is not yet fully determined; however, it is known to act as both partial histamine H1-receptor agonist and histamine H3-receptor antagonist in neuronal tissue, with negligible histamine H2-receptor activity. It may also improve the microcirculation in the labyrinth, thus reducing endolymphatic pressure. Pharmacokinetics: Absorption: Rapidly and completely absorbed from the gastrointestinal tract. Delayed absorption with food. Time to peak plasma concentration: 1 hour (2-pyridylacetic acid). Distribution: Plasma protein binding: <5%. Metabolism: Rapidly and almost completely metabolised in the liver to its inactive metabolite, 2-pyridylacetic acid. Excretion: Via urine (Approx 91%, mainly as inactive metabolite). Elimination half-life: Approx 3.5 hours (2-pyridylacetic acid).
Store below 25°C. Protect from moisture and light.