Phenibut

INSTRUCTIONS FOR MEDICAL USE OF THE MEDICINAL PRODUCT PHENIBUT Phenibut

Composition:

Active substance: phenibut;

1 tablet contains phenibut 250 mg;

Excipients: lactose monohydrate; corn starch; modified pregelatinized corn starch; stearic acid.

Pharmaceutical form. Tablets.

Main physicochemical properties: tablets from white to white with a yellowish tint, flat cylindrical shape, with a bevel and a notch on one side.

Pharmacotherapeutic group. Other psychostimulants and nootropic agents.

ATC code N06B X22.

Pharmacological properties

Pharmacodynamics

Phenibut is a derivative of γ-aminobutyric acid (GABA) and phenylethylamine.

Its primary effects are anti-hypoxic and anti-amnestic. Phenibut improves memory and attention, facilitates learning processes, and increases physical and mental performance. Psychological parameters (attention, memory, speed and accuracy of sensorimotor reactions) improve under the influence of phenibut. It has been established that phenibut increases the neuron's energy potential by improving mitochondrial function.

Phenibut also has tranquilizer properties: it reduces psychoemotional tension, anxiety, fear, emotional lability, irritability, and improves sleep. It prolongs and enhances the effects of hypnotics, narcotic agents, neuroleptics, and anticonvulsants. Phenibut binds exclusively to GABA-β receptors in the brain, thus exerting a moderate calming effect without causing undesirable sedative effects such as drowsiness, dizziness, reduced attention, or impaired performance. The drug prolongs the latent period and reduces the duration and intensity of nystagmus, and has antiepileptic activity. It does not affect cholinergic or adrenergic receptors.

Phenibut significantly reduces manifestations of asthenia and vasovagal symptoms, including headache and a sensation of heaviness in the head. In patients with asthenia and emotionally labile individuals, treatment with Phenibut improves general well-being without causing excitation.

Pharmacokinetics

Absorption and distribution

The drug is well absorbed after oral administration and penetrates well into all tissues of the body, readily crossing the blood-brain barrier (approximately 0.1% of the administered dose enters brain tissue, and penetration is significantly greater in both young and elderly individuals). The highest binding of phenibut occurs in the liver (80%), and this binding is non-specific.

Biotransformation and excretion

80–95% of phenibut is metabolized in the liver; the metabolites are pharmacologically inactive.

Distribution in the liver and kidneys is close to uniform, while in the brain and blood it is lower than uniform. A significant amount of administered phenibut is detectable in urine within 3 hours; simultaneously, the concentration of the drug in brain tissue does not decrease—phenibut remains detectable in the brain for up to 6 hours. On the following day, phenibut can only be detected in urine; it remains detectable in urine for up to 2 days after administration, but the amount detected constitutes only 5% of the administered dose. No accumulation is observed upon repeated administration.

Clinical characteristics.

Indications.

Asthenic and anxiety-neurotic states: restlessness, fear, anxiety.

Insomnia, nocturnal restlessness in elderly people.

Prophylaxis of stress condition prior to surgery or painful diagnostic procedures.

Meniere's disease, vertigo associated with vestibular analyzer dysfunction of various origins.

Prophylaxis of kinetosis (a specific condition characterized by nausea, vomiting, prostration, and vestibular dysfunction caused by being in a moving object, such as a ship or airplane).

Stuttering, tics in children aged 8 to 14 years.

As an adjunctive agent in the treatment of alcohol withdrawal syndrome.

Contraindications.

Hypersensitivity to the components of the drug.

Acute renal failure.

Pregnancy and breastfeeding period.

Interaction with other medicinal products and other forms of interactions.

The drug can be combined with psychotropic medicinal products, reducing the doses of Phenibut and concomitantly used drugs.

Phenibut enhances and prolongs the effect of hypnotics, narcotics, neuroleptics, and antiparkinsonian drugs.

Special precautions for use.

The medicinal product should be used with caution in patients with stomach or intestinal disorders. To protect the mucosa from the irritating effect of phenibut, lower doses should be prescribed to these patients.

In case of prolonged treatment, blood and liver parameters should be monitored.

The medicinal product Phenibut contains lactose and therefore should not be used in patients with rare hereditary forms of galactose intolerance, lactase deficiency, or glucose-galactose malabsorption syndrome.

Use during pregnancy or breastfeeding.

Animal studies have not revealed mutagenic, teratogenic, or embryotoxic effects of phenibut. However, there are insufficient and well-controlled clinical studies on the safety of phenibut use during pregnancy. Therefore, the use of Phenibut during pregnancy or breastfeeding is contraindicated.

Ability to influence reaction rate while driving or operating machinery.

Patients who experience somnolence, dizziness, or other central nervous system disturbances during treatment with the medicinal product Phenibut should refrain from driving vehicles or operating machinery.

Method of Administration and Dosage

Phenibut is taken orally before meals. The tablet should be swallowed whole with sufficient amount of water.

For asthenic and anxiety-neurotic conditions in adults: 250–500 mg (1–2 tablets) three times daily. Maximum single doses: for adults – 750 mg; for elderly patients – 500 mg.

The treatment course lasts 2–3 weeks. If necessary, the course may be extended to 4–6 weeks.

Children aged 8 to 14 years: 250 mg (1 tablet) three times daily.

The treatment course lasts 2–6 weeks.

Meniere’s disease, dizziness associated with vestibular dysfunction of various origins. In cases of infectious-origin vestibular dysfunction and Meniere’s disease during exacerbation, Phenibut is administered at 750 mg (3 tablets) three times daily for 5–7 days; as vestibular symptoms subside, the dose is reduced to 250–500 mg (1–2 tablets) three times daily for 5–7 days, followed by 250 mg once daily for 5 days. In milder cases, Phenibut is administered at 250 mg (1 tablet) twice daily for 5–7 days, followed by 250 mg once daily for 7–10 days.

For relief of dizziness in vestibular dysfunction of vascular and traumatic origin: Phenibut is administered at 250 mg three times daily for 12 days.

For prevention of kinetosis: the drug should be taken once at a dose of 250–500 mg one hour before the expected onset of motion sickness or upon the appearance of the first symptoms of motion discomfort.

For management of alcohol withdrawal syndrome: during the first days of treatment, Phenibut is administered at 250–500 mg three times daily and 750 mg at night, with gradual reduction of the daily dose to the standard adult dose.

Patients with hepatic insufficiency

High doses of the drug may cause hepatotoxicity in patients with hepatic insufficiency. Lower doses should be prescribed for this patient group.

Patients with renal insufficiency

There are no data indicating adverse effects of Phenibut on patients with impaired renal function when administered at therapeutic doses.

Drug dependence or withdrawal syndrome has not been observed during use of this medication.

Scientific publications report isolated cases of tolerance to phenibut.

Children

The drug may be used in children aged 8 years and older.

Overdose

Phenibut is a low-toxicity drug: hepatotoxicity may occur only with prolonged use of daily doses of 7–14 g. Data on overdose are limited.

These doses are significantly higher than the recommended dose (average therapeutic dose is 500–2000 mg).

Symptoms: drowsiness, nausea, vomiting, dizziness.

With prolonged use of high doses, arterial hypotension, acute renal failure, eosinophilia, and fatty liver degeneration may develop.

Treatment: gastric lavage. Symptomatic therapy.

There is no specific antidote.

Adverse Reactions

Phenibut, like other medicinal products, may cause adverse reactions, although they do not occur in all patients.

Classification of adverse reactions by frequency of occurrence: very common (≥ 1/10); common (≥ 1/100 to < 1/10); uncommon (≥ 1/1000 to < 1/100); rare (≥ 1/10,000 to < 1/1000); very rare (< 1/10,000); frequency not known (cannot be estimated from the available data).

Central nervous system: frequency not known – drowsiness (at the beginning of treatment), headache and dizziness (at doses above 2 g per day; reducing the dose decreases the intensity of these adverse effects).

Gastrointestinal disorders: frequency not known – nausea (at the beginning of treatment), vomiting, diarrhea, epigastric pain.

Hepatobiliary disorders: frequency not known – hepatotoxicity (with prolonged use of high doses).

Immune system disorders: frequency not known – hypersensitivity reactions, including urticaria, erythema, rash, angioneurotic edema, facial swelling, tongue swelling.

Skin and subcutaneous tissue disorders: rare – allergic reactions (rash, pruritus).

Psychiatric disorders: frequency not known – emotional lability, sleep disturbances (these adverse reactions may occur in children if instructions for use are not followed).

If any adverse reactions not listed in this instruction occur during treatment, or if any of the listed adverse reactions are severe, please consult your physician.

Reporting of suspected adverse reactions after registration of the medicinal product is important. It allows ongoing monitoring of the benefit-risk balance of the product. Medical and pharmaceutical professionals, as well as patients or their legal representatives, are encouraged to report all suspected adverse reactions and lack of efficacy via the Automated Information System for Pharmacovigilance at: https://aisf.dec.gov.ua.

Shelf life. 3 years.

Storage conditions.

Store at a temperature not exceeding 25 °C.

Keep out of reach and sight of children.

Packaging. 10 tablets in a blister; 2 blisters per cardboard pack.

Prescription status. Prescription only.

Manufacturer/Marketing Authorization Holder. Ternopharm LLC.

Address of manufacturer and location of its business activity / address of Marketing Authorization Holder.

4 Fabrychna St., Ternopil, 46010, Ukraine.

Tel./fax: (0352) 521-444, www.ternopharm.com.ua.