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Kent Pharmaceuticals Ltd

Joshna House, Crowbridge Road, Orbital Park, Ashford, Kent, TN24 0GR
Telephone: 0845 437 5565
Fax: 0845 437 5567
WWW: http://www.kentpharm.co.uk
Medical Information Direct Line: +44 (0)1233 506 574
Medical Information e-mail: medinfo@kentpharm.co.uk
Customer Care direct line: 0800 220 280
Medical Information Fax: 0845 437 5567

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Summary of Product Characteristics last updated on the eMC: 19/07/2013
SPC Betahistine Dihydrochloride 8mg Tablets


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1. Name of the medicinal product

Betahistine Dihydrochloride 8mg Tablets


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2. Qualitative and quantitative composition

Each tablet contains 8mg betahistine dihydrochloride.

Excipient(s) with known effect: lactose monohydrate.

For the full list of excipients, see section 6.1.


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3. Pharmaceutical form

Tablet.

Betahistine Dihydrochloride 8mg Tablets are white, circular, flat, bevelled edged tablets marked B8 on one side


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4. Clinical particulars

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4.1 Therapeutic indications

Vertigo, tinnitus and hearing loss associated with Ménière's syndrome.


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4.2 Posology and method of administration

Adults, including the elderly: Initially 16 mg three times daily, taken preferably with meals. Maintenance doses are generally in the range 24 to 48 mg daily. Dosage should be altered according to clinical response.

Children: No dosage recommendations are made for children.


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4.3 Contraindications

Use in patients with hypersensitivity to betahistine dihydrochloride or any component of the tablet. Use in patients with phaeochromocytoma.


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4.4 Special warnings and precautions for use

Betahistine dihydrochloride is considered to be unsafe in patients with porphyria

Betahistine dihydrochloride should be administered with caution to patients with bronchial asthma or a history of peptic ulcer.

Betahistine dihydrochloride is not recommended for use in children.

Patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption should not take this medicine.


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4.5 Interaction with other medicinal products and other forms of interaction

No in-vivo interaction studies have been performed. Based on in-vitro data no in-vivo inhibition on Cytochrome P450 enzymes is expected.

In vitro data indicate an inhibition of betahistine metabolism by drugs that inhibit monoamino-oxidase (MAO) including MAO subtype B (e.g. selegiline). Caution is recommended when using betahistine and MAO inhibitors (including MAO-B selective) concomitantly.

Betahistine dihydrochloride should not be used concurrently with antihistamines.


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4.6 Fertility, pregnancy and lactation

Pregnancy:

There are no adequate data from the use of betahistine in pregnant women.

Animal studies are insufficient with respect to effects on pregnancy, embryonal/foetal development, parturition and postnatal development. The potential risk for humans is unknown. Betahistine should not be used during pregnancy unless clearly necessary.

Lactation:

It is not known whether betahistine is excreted in human milk. There are no animal studies on the excretion of betahistine in milk. The importance of the drug to the mother should be weighed against the benefits of nursing and the potential risks for the child.


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4.7 Effects on ability to drive and use machines

No adverse effects known.


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4.8 Undesirable effects

The following undesirable effects have been experienced with the below indicated frequencies in betahistine dihydrochloride-treated patients in placebo-controlled clinical trials (very common (≥ /100 to < 1/10); uncommon (≥ /1,000 to < 1/100); rare (≥ /10,000 to < 1/1,000); very rare (<1/10,000))

Gastrointestinal disorders

Common: nausea and dyspepsia

In addition to those events reported during clinical trials, the following undesirable effects have been reported spontaneously during post-marketing use and in scientific literature. A frequency cannot be estimated from the available data and is therefore classified as “not known”.

Immune systems disorders

Hypersensitivity reactions, e.g. anaphylaxis have been reported

Gastrointestinal disorders

Mild gastric complaints (e.g. vomiting, gastrointestinal pain, abdominal distension and bloating) have been observed. These can normally be dealt with by taking the dose during meals or by lowering the dose.

Nervous systems disorders

Headache

Skin and subcutaneous tissue disorders

Cutaneous and subcutaneous hypersensitivity reactions have been reported in particular angioneurotic oedema, urticaria, rash and pruritus


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4.9 Overdose

A few overdose cases have been reported. Some patients experienced mild to moderate symptoms with doses up to 640 mg (e.g. nausea, somnolence, abdominal pain). More serious complications (e.g. convulsion, pulmonary or cardiac complications) were observed in cases of intentional overdose of betahistine especially in combination with other overdosed drugs.

There is no specific antidote to betahistine dihydrochloride. Gastric lavage and symptomatic treatment is recommended.


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5. Pharmacological properties

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5.1 Pharmacodynamic properties

Betahistine dihydrochloride is a histamine-like drug in which pharmacological activity can be attributed to a specific effects and/or more direct influences on recovery mechanisms the vestibular nuclei. It has weak agonist activity at histamine H1 receptors and moderate antagonist activity at H3; receptors. The antagonist action of betahistine dihydrochloride at the H3: receptor can be expected to potentiate the release of presynaptic histamine in vivo by blocking the auto-inhibitory feedback at histaminergic terminals, its action on medial vestibular nucleus cells is to significantly reduce their responsiveness to histamine. This action of betahistine dihydrochloride occurs at post-synaptic H1 receptors, since betahistine dihydrochloride lacks any effect at H2 receptors. The effects of betahistine dihydrochloride are thus consistent with a partial agonist action at these receptors, with betahistine dihydrochloride having little excitatory action on its own but reducing the excitatory responses to histamine by occupying H1 receptor sites.

The reduced response of the medial vestibular nucleus cells to histamine in the presence of betahistine dihydrochloride may be the result of the activation of H2 receptor-coupled second-messenger pathways alone rather than the normal activation of both H1 and H2 second-messenger systems together. Thus, simultaneous stimulation of the H1 and H2 receptor pathways is know to cause a large amplification of the cellular cAMP response, above that caused by stimulation of the H2 receptor pathway alone. The reduction in the amplitude and total duration of the histamine-induced excitation in medial vestibular nucleus cells in the presence of betahistine dihydrochloride is suggestive of such a mechanism. This partial agonist action of betahistine dihydrochloride at H1 receptor may be an important part of its mechanism of action.


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5.2 Pharmacokinetic properties

Betahistine dihydrochloride is completely absorbed after oral administration, and peak plasma concentrations of 14C-labelled betahistine dihydrochloride are attained one hour after oral administration to fasting subjects.

Betahistine dihydrochloride is eliminated by the kidney with 85 - 90% of the radioactivity of an 8 mg dose appearing in the urine over 56 hours. Maximum excretion rates are reached within 2 hours of administration. Plasma levels of the parent drug are below the limits of detection of the assay.

Bioavailability has therefore been assessed from urinary excretion of its main metabolite, 2- pyridylacetic acid.

There is no evidence for presystemic metabolism. Biliary excretion is not important as a route of elimination of either the drug or its metabolites in the rat and is unlikely to be so in man.


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5.3 Preclinical safety data

No pre-clinical data exists which gives additional information to the prescriber which is not included in other sections of the SPC.


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6. Pharmaceutical particulars

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6.1 List of excipients

Povidone K90

Microcrystalline cellulose

Lactose monohydrate

Colloidal anhydrous silica

Crospovidone

Stearic acid


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6.2 Incompatibilities

None known.


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6.3 Shelf life

3 years.


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6.4 Special precautions for storage

Do not store above 25° C. Store in the original package. Keep container in the outer carton.


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6.5 Nature and contents of container

Blister strips consisting of 250 µm transparent PVC, a 60 g/m2 PVDC layer and 20µm hard temper aluminium foil, contained in a carton.

Pack sizes: 60, 84, 90, 100 and 120 tablets.


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6.6 Special precautions for disposal and other handling

Not applicable.


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7. Marketing authorisation holder

Athlone Pharmaceuticals Limited

Ballymurray

Co. Roscommon

Ireland


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8. Marketing authorisation number(s)

PL 30464/0019


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9. Date of first authorisation/renewal of the authorisation

23/03/2000


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10. Date of revision of the text

01/07/2013



More information about this product

Link to this document from your website: http://www.medicines.org.uk/emc/medicine/26291/SPC/


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