Merislon

Tablets 6 mg: White, round tablet with beveled edge, plain on one side, engraved
Click on icon to see table/diagram/image
on the other side.
Each white plain tablet contains 6 mg of betahistine mesilate.
Tablets 12 mg: White, round tablet with beveled edge, engraved
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on one side and
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above scored line on the other side.
Each white plain tablet contains 12 mg of betahistine mesilate.
Betahistine mesilate occurs as white crystals or crystalline powder. It is odorless, or has a faint, characteristic odor, and has a bitter taste. It is very soluble in water, freely soluble in methanol and in acetic acid (100), sparingly soluble in ethanol (99.5), very slightly soluble in acetic anhydride, and in practically insoluble in diethyl ether.
It is hygroscopic.
Nonproprietary name: Betahistine Mesilate (JAN), Betahistine (INN).
Chemical name: N-Methyl-2-pyridin-2-ylethylamine dimethanesulfonate.
Molecular formula: C₈H₁₂N₂·2CH₄O₃S.
Molecular weight: 328.41.
Excipients/Inactive Ingredients: Hydrated silicon dioxide, microcrystalline cellulose, calcium stearate, talc, low substituted hydroxypropylcellulose and hydroxypropylcellulose.

Merislon dilates pre-capillary sphincters thus increasing the blood flow in the inner ear. It controls the permeability of capillaries in the inner ear, thereby removing endolymphatic hydrops. It also improves cerebral circulation, increasing blood flow in the internal carotid artery. MERISLON is clinically useful for the relief of vertigo and dizziness.
Pharmacology: Pharmacodynamics: Improvement of circulatory disturbances in the inner ear: In the inner ear of the guinea pig with experimentally-induced microcirculatory disturbances, the blood flow increases to 148% of the control level within 30 min after the intraperitoneal injection of betahistine mesilate. This effect is specific for pathological conditions.
Increase of blood flow in the scala media of guinea pigs with endolymphatic hydrops: When betahistine mesilate was administered to guinea pigs with endolymphatic hydrops, it produced a significant increase in blood flow in the scala media. The blood flow increased significantly from 5.5 mL/min/100 mg to 8.1 mL/min/100 g. It is considered that the increase in blood flow is due to relaxation of smooth muscle of the cochlear radial arteria.
Improvement of intracerebral blood flow: In the experiment in rhesus monkeys, betahistine mesilate after intravenous administration increases blood flow in the cerebral and cerebellar tissues from 70.4 to 81.4 mL/min/100 g/min and 73.2 to 84.0 mL/min/100 g/min, respectively.
Clinical Studies: Clinical efficacy: In clinical trials on a total of 875 patients including double blind clinical trials, it has been demonstrated that MERISLON is useful for relieving dizziness or feeling of dizziness associated with Meniere's disease, Meniere's syndrome or vertigo, etc.
Pharmacokinetics: Betahistine mesilate was administered orally to 20 healthy adult male volunteers at a single dose of 24 mg. The main metabolic product was 2-pyridylacetic acid and its plasma concentration was determined. The time to reach the peak plasma concentration (T_max) was 0.98±0.47 h, the peak plasma concentration (C_max) was 339.4±213.4 ng/ml, eliminated half-life (t_½) was 5.17±2.66 h and the area under the plasma concentration-time curve (AUC_0-t) was 1,153±729 ng·h/ml.

Vertigo and dizziness associated with the following diseases: Meniere's disease^{(Note 1)}, Meniere's syndrome^{(Note 1)}, Peripheral vertigo.
Note 1): Meniere's disease/syndrome is a disorder of the inner ear which results in vertigo, hearing loss and tinnitus.

The usual adult dosage for oral use is 6-12 mg of betahistine mesilate, three times daily after meals. The dosage may be adjusted depending on the patient's age and symptoms.

There is no experience to date with deliberate overdose.
No specific antidote is known.

(MERISLON is contraindicated in the following patients): Patients with a history of hypersensitivity to any ingredients of MERISLON.

Careful administration (MERISLON should be administered with care in the following patients): Patients with a history of peptic or active ulcer: [Since Merislon has a histamine-like action, it may enhance gastric acid secretion through the intervention of H₂-receptors].
Patients with bronchial asthma: [Since Merislon has a histamine-like action, it may cause respiratory tract contraction through the intervention of H₁-receptors].
Patients with pheochromocytoma: [Since Merislon has a histamine-like action, it may cause an increase in blood pressure due to adrenaline hypersecretion].
Effects on ability to drive and operate machine: Based on the pharmacodynamic properties and the adverse events profile, it is unlikely that Merislon would cause an impairment of driving performance or compromise the ability to use machinery.
Use in Children: The safety in children has not been established (insufficient clinical experience).
Use in the Elderly: Since the elderly, often have a physiological hypofunction, it is advisable to take measures, such as reduction in dosage under careful supervision.

MERISLON should only be used in pregnant women or women suspected of being pregnant, if the expected therapeutic benefits are evaluated to outweigh the possible risk of treatment. [The safety of MERISLON in pregnant women has not been established.]
It is not known whether betahistine is excreted in human milk so the therapeutic benefit of Merislon for lactating women should be evaluated to outweigh the possible risk to the child.

Adverse reactions were reported in 26 of 2,254 patients (1.15%). (Post-marketing clinical investigation.) See table.

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Interaction between MERISLON Tablets and other drugs has not been documented. Theoretically, the effect of betahistine is antagonized by antihistamines.

Precautions Concerning Use: Caution in handling over drug: For drugs that are dispensed in a press-through package (PTP), instruct the patient to remove the drug from the package prior to use. [It has been reported that, if the PTP sheet is swallowed, the sharp corners of the sheet may puncture the esophageal mucosa, causing perforation and resulting in serious complications such as mediastinitis.]

Shelf Life: 6 mg: 36 months from manufacturing date.
12 mg: 24 months from manufacturing date.
Storage and Handling: Do not store above 30°C.

Antivertigo Drugs

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

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