Serc

Betahistine dihydrochloride.

Inactive ingredients/Excipients: Microcrystalline cellulose, mannitol (E421), citric acid monohydrate, anhydrous colloidal silica and talc.

Pharmacotherapeutic Group: Antivertigo preparations. ATC Code: N07CA01.
Pharmacology: Pharmacodynamics: The mechanism of action of betahistine is only partly understood. There are several plausible hypotheses that are supported by animal studies and human data: Betahistine affects the histaminergic system: Betahistine acts both as a partial histamine H₁-receptor agonist and histamine H₃-receptor antagonist also in neuronal tissue, and has negligible H₂-receptor activity. Betahistine increases histamine turnover and release by blocking presynaptic H₃-receptors and inducing H₃-receptor downregulation.
Betahistine may increase blood flow to the cochlear region as well as to the whole brain: Pharmacological testing in animals has shown that the blood circulation in the striae vascularis of the inner ear improves, probably by means of a relaxation of the precapillary sphincters of the microcirculation of the inner ear. Betahistine was also shown to increase cerebral blood flow in humans.
Betahistine facilitates vestibular compensation: Betahistine accelerates the vestibular recovery after unilateral neurectomy in animal, by promoting and facilitating central vestibular compensation; this effect characterized by an up-regulation of histamine turnover and release, is mediated via the H₃-receptor antagonism.
In human subjects, recovery time after vestibular neurectomy was also reduced when treated with betahistine.
Betahistine alters neuronal firing in the vestibular nuclei: Betahistine was also found to have a dose dependent inhibiting effect on spike generation of neurons in lateral and medial vestibular nuclei.
The pharmacodynamic properties as demonstrated in animals may contribute to the therapeutic benefit of betahistine in the vestibular system.
The efficacy of betahistine was shown in studies in patients with vestibular vertigo and with Ménière’s disease as was demonstrated by improvements in severity and frequency of vertigo attacks.
Pharmacokinetics: Absorption: Orally administered betahistine is readily and almost completely absorbed from all parts of the gastrointestinal tract. After absorption, the drug is rapidly and almost completely metabolized into 2-pyridylacetic acid. Plasma levels of betahistine are very low. Pharmacokinetic analyses are therefore based on 2-PAA measurements in plasma and urine. Under fed conditions C_max is lower compared to fasted conditions. However, total absorption of betahistine is similar under both conditions, indicating that food intake only slows down the absorption of betahistine.
Distribution: The percentage of betahistine that is bound by blood plasma proteins is less than 5%.
Biotransformation: After absorption, betahistine is rapidly and almost completely metabolized into 2-PAA (which has no pharmacological activity).
After oral administration of betahistine the plasma (and urinary) concentration of 2-PAA reaches its maximum 1 hour after intake and declines with a half-life of about 3.5 hours.
Excretion: 2-PAA is readily excreted in the urine. In the dose range between 8 and 48 mg, about 85% of the original dose is recovered in the urine. Renal or fecal excretion of betahistine itself is of minor importance.
Linearity: Recovery rates are constant over the oral dose range of 8-48 mg indicating that the pharmacokinetics of betahistine are linear, and suggesting that the involved metabolic pathway is not saturated.

Symptomatic relief of vertigo and dizziness of vestibular origin.
Ménière's Syndrome as defined by the following triad of core symptoms: Vertigo (dizziness with nausea/vomiting); hearing loss (hardness of hearing); tinnitus.

Recommended Dose and Mode of Action: Adults: 16-mg Tab: 24-48 mg divided over the day. (See Table 1.)

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24-mg Tab: 48 mg divided over the day. (See Table 2.)

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The dosage should be individually adapted according to the response. Improvement can sometimes only be observed after a couple of weeks of treatment. The best results are sometimes obtained after a few months. There are indications that treatment from the onset of the disease prevents the progression of the disease and/or the loss of hearing in later phases of the disease.
Pediatric: Serc is not recommended for use in children below18 years due to insufficient data on safety and efficacy.
Geriatric: Although there are limited data from clinical studies in this patient group, extensive post-marketing experience suggests that no dose adjustment is necessary in this patient population.
Renal and/or Hepatic Impairment: There are no specific clinical trials available in this patient groups, but according to the post-marketing experience, no dose adjustment appears to be necessary.
Administration: Should be swallowed with water.

A few overdose cases have been reported. Some patients experienced mild to moderate symptoms with doses up to 640 mg (eg, nausea, somnolence and abdominal pain). More serious complications (eg, convulsions, pulmonary or cardiac complications) were observed in cases of intentional overdose of betahistine especially in combination with other overdosed drugs. Treatment of overdose should include standard supportive measures.

Hypersensitivity to the active substance or to any of the excipients. Phaeochromocytoma.

Patient with bronchial asthma or have a history of peptic ulcer need to be carefully monitored during the therapy.
Effects on the Ability to Drive or Operate Machinery: Betahistine is indicated for Morbus Meniere and vertigo. Both diseases can negatively affect the ability to drive and use machines.
In clinical studies specifically designed to investigate the ability to drive and use machines betahistine had no or neglible effects.

Use in 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.
Use in 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.

The following undesirable effects have been experienced with the below indicated frequencies in betahistine-treated patients in placebocontrolled clinical trials [very common (≥1/10); common (≥1/100 to <1/10); uncommon (≥1/1,000 to <1/100); rare (≥1/10,000 to <1/1,000); very rare (<1/10,000)].
Gastrointestinal Disorders: Common: Nausea and dyspepsia.
Nervous System Disorders: Common: Headache.
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 System Disorders: Hypersensitivity reactions, e.g. anaphylaxis.
Gastrointestinal Disorders: Mild gastric complaints (e.g. vomiting, gastrointestinal pain, abdominal distension and bloating). These can normally be dealt with by taking the dose during meals or by lowering the dose.
Skin and Subcutaneous Tissue Disorders: Cutaneous and subcutaneous hypersensitivity reactions, in particular angioneurotic oedema, urticaria, rash, and pruritus.

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.
As betahistine is an analogue of histamine, interaction of betahistine with antihistamines may in theory affect the efficacy of one of these drugs.

Special Precautions for Disposal and Other Handling: Any unused product or waste material should be disposed of in accordance with local requirements.
Incompatibilities: Not applicable.

Do not store above 30°C. Protect from light.
Shelf-Life: 3 years.

Antivertigo Drugs

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

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