Phenibut

INSTRUCTIONS FOR MEDICAL USE OF THE MEDICINAL PRODUCT FENIBUT (PHENIBUT)

Composition:

Active substance: phenibut;

1 tablet contains 250 mg of phenibut;

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

Pharmaceutical form. Tablets.

Main physicochemical properties: flat cylindrical tablets of white to off-white color, with a bevel and a score line 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 main action is antihypoxic 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 tranquilizing properties: it relieves psychoemotional tension, anxiety, fear, emotional lability, irritability, improves sleep, and 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, or reduced attention and performance. The drug prolongs the latent period and reduces the duration and severity of nystagmus, and exerts an antiepileptic effect. It does not affect cholinergic or adrenergic receptors.

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

Pharmacokinetics.

Absorption and distribution

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

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, whereas in the brain and blood it is below uniform levels. A significant amount of administered phenibut is detected in urine within 3 hours; simultaneously, the drug concentration in brain tissue does not decrease, and phenibut remains detectable in the brain for up to 6 hours. On the following day, phenibut is detectable only in urine; it can be found in urine for up to 2 days after administration, but the amount detected constitutes only 5% of the administered dose. No accumulation is observed with repeated dosing.

Clinical characteristics.

Indications.

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

Insomnia, nocturnal restlessness in elderly people.

Prevention of stress states before surgeries or painful diagnostic procedures.

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

Prevention 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 interaction.

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

Phenibut enhances and prolongs the effects of sedatives, narcotics, neuroleptics, and antiparkinsonian drugs.

Special precautions for use.

The medicinal product should be used with caution in patients with gastric 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 contains lactose; therefore, it 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 studies on the safety of phenibut use during pregnancy. Therefore, the use of PHENIBUT during pregnancy or breastfeeding is contraindicated.

Ability to affect reaction rate when driving or operating machinery.

Patients who experience drowsiness, 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.

The medicinal product PHENIBUT is taken orally before meals with sufficient amount of water.

For asthenic and anxiety-neurotic conditions in adults: 250−500 mg (1−2 tablets) three times a day. 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 up to 4−6 weeks.

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

The treatment course lasts 2−6 weeks.

Meniere’s disease, dizziness associated with vestibular apparatus dysfunction of various origins.

In vestibular dysfunction of infectious origin and Meniere’s disease during exacerbation, the medicinal product PHENIBUT is prescribed at 750 mg (3 tablets) three times a day for 5−7 days; when vestibular disturbances decrease in severity – 250−500 mg (1−2 tablets) three times a day for 5−7 days, followed by 250 mg once daily for 5 days. In relatively mild cases, PHENIBUT is administered at 250 mg twice daily for 5−7 days, followed by 250 mg once daily for 7−10 days.

For relief of dizziness in vestibular apparatus dysfunction of vascular and traumatic origin: PHENIBUT is prescribed at 250 mg three times a day for 12 days.

For prevention of motion sickness: the medicinal product is taken as a single dose of 250−500 mg one hour before the expected onset of motion or at the appearance of first symptoms of motion discomfort.

For management of alcohol withdrawal syndrome: during the first days of treatment, PHENIBUT is prescribed at 250−500 mg three times daily and 750 mg at night, with gradual reduction of the daily dose to the usual adult dose.

Patients with hepatic insufficiency

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

Patients with renal insufficiency

There is no data on adverse effects of the medicinal product Phenibut in patients with impaired renal function when administered at therapeutic doses.

No drug dependence or withdrawal syndrome has been observed during use of this medicinal product.

There have been isolated reports of tolerance to phenibut described in the literature.

Children

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

Overdose

PHENIBUT is a low-toxicity medicinal product. It may become hepatotoxic only at daily doses of 7−14 g with prolonged use. Data on overdose are limited. The doses mentioned significantly exceed 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

FENIBUT, 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 (≥ 1/1,000 to < 1/100); rare (≥ 1/10,000 to < 1/1,000); very rare (< 1/10,000); frequency not known (cannot be estimated from available data).

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

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

Reporting of suspected adverse reactions

Reporting suspected adverse reactions after medicinal product authorization is of great importance. It allows continuous monitoring of the benefit-risk balance of the medicinal product. Healthcare professionals and 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 the following link: https://aisf.dec.gov.ua.

Shelf life.

3 years.

Do not use after the expiry date stated on the packaging.

Storage conditions.

Store in the original packaging at a temperature not exceeding 25 °C.

Keep out of reach and sight of children.

Packaging.

10 tablets per blister; 2 blisters per cardboard box.

Prescription status.

Prescription only.

Manufacturer.

LLC "Pharmaceutical Company "FARCoS".

Manufacturer's address and location of business activity.

360 Sviato-Pokrovska Street, settlement of Hostomel, Irpin, Kyiv region, 08290, Ukraine.