Phenibut 500

INSTRUCTION FOR MEDICAL USE OF THE MEDICINAL PRODUCT PHENIBUT 500 (PHENIBUT 500)

Composition:

Active substance: phenibut;

One sachet contains 500 mg of phenibut;

Excipients: mannite (E 421), aspartame (E 951), orange flavor containing aromatic ingredients, maltodextrin, sodium octenylsuccinate starch (E 1450), glucose, ascorbyl palmitate (E 304 (i)), butylated hydroxyanisole (E 320).

Pharmaceutical form. Oral powder for solution.

Main physicochemical characteristics: white or almost white powder with a yellowish tint. Yellow specks are permissible.

Pharmacotherapeutic group. Psychostimulants and nootropic agents. Phenibut.

ATC code N06B X22.

Pharmacological Properties

Pharmacodynamics. Phenibut is a derivative of γ-aminobutyric acid and phenylethylamine.

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

The drug also possesses tranquilizing properties: it relieves psychoemotional tension, anxiety, fear, emotional lability, and irritability, improves sleep, and prolongs and enhances the effects of hypnotics, narcotic agents, neuroleptics, and anticonvulsants. Phenibut binds exclusively to GABA-ß 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 shortens the duration and intensity of nystagmus, and has antiepileptic activity. It does not affect cholinergic or adrenergic receptors.

The drug significantly reduces manifestations of asthenia and vasovegetative symptoms, including headache and a sensation of heaviness in the head. When used in patients with asthenia and emotionally labile individuals, the drug improves well-being without causing excitation.

In patients with psychogenic erectile dysfunction, the drug, by exerting tranquilizing, anti-asthenic, and psychoenergizing effects, activates central pro-erectile mechanisms.

Pharmacokinetics. The drug is rapidly absorbed after oral administration and penetrates into all body tissues, completely crossing the blood-brain barrier. 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 the administered drug is detected in urine after 3 hours; at the same time, the drug concentration in brain tissue does not decrease, and the drug remains detectable in the brain for up to 6 hours. The following day, the drug can only be detected in urine; it remains detectable in urine for up to 2 days after intake, but the amount detected constitutes only 5% of the administered dose. The highest binding of phenibut occurs in the liver (80%), and this binding is nonspecific. No accumulation is observed with repeated administration.

Clinical characteristics.

Indications. Asthenic and anxiety-neurotic states (emotional lability, impaired memory, decreased concentration), restlessness, fear, anxiety, obsessive neurosis.

In elderly patients – insomnia, nocturnal restlessness.

Prophylaxis of stress states before surgeries or painful diagnostic procedures.

Meniere’s disease, dizziness associated with vestibular apparatus dysfunction, prevention of motion sickness.

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

Treatment of men with psychogenic and mixed etiology erectile dysfunction – as monotherapy, as well as part of combination therapy.

Contraindications. Hypersensitivity to the drug components. Acute renal failure.

Interaction with other medicinal products and other forms of interaction. The drug can be used concomitantly with other medications, including psychotropic agents – tranquilizers and neuroleptics (effects are mutually enhanced).

Special precautions for use.

Patients with gastrointestinal disorders should be cautious due to the irritant effect of the medicinal product. Lower doses should be prescribed for such patients.

With prolonged use, blood cell counts and liver function test parameters should be monitored.

Aspartame is a phenylalanine derivative and may be hazardous for patients with phenylketonuria.

If a patient has known intolerance to certain sugars, a physician should be consulted before taking this medicinal product.

Use during pregnancy or breastfeeding. The use of this medicinal product during pregnancy or breastfeeding is not recommended, as there is insufficient data on its use during these periods.

Ability to influence reaction rate when driving or operating machinery. Patients who experience drowsiness, dizziness, or other central nervous system disturbances during treatment should refrain from driving or operating machinery.

Method of Administration and Dosage

The contents of the sachet should be dissolved in 0.5 glass of boiled water and taken orally before meals. The treatment course lasts 2–6 weeks.

The recommended dose is 500 mg 1–3 times daily.

The drug may be combined with other psychotropic agents, which enhances its efficacy; in such cases, the doses of this drug and of other concurrently administered medications may be reduced.

For treatment of alcohol withdrawal syndrome: during the first days, administer 500 mg 2–3 times daily and 500 mg at bedtime, gradually reducing the daily dose to the usual adult dose.

For treatment of vertigo due to vestibular dysfunction of infectious origin (otogenic labyrinthitis) and Meniere’s disease: during the acute phase, administer 500 mg 4 times daily for 5–7 days; as vestibular symptoms subside, reduce to 500 mg 2–3 times daily for 5–7 days, followed by 500 mg once daily for 5 days. In milder cases, administer 500 mg once daily for 5–7 days, then 100 mg 2–3 times daily for 7–10 days. Other dosage forms of the drug should be used to achieve the recommended dosage.

For treatment of vertigo due to vascular or traumatic vestibular dysfunction: administer 500 mg 1–2 times daily for 12 days.

For prevention of motion sickness: a single dose of 500 mg should be taken 1 hour before the expected onset of motion sickness or at the first signs of symptoms.

The effect of the drug increases with higher doses. However, if pronounced symptoms are present (e.g., vomiting, nausea), the drug is poorly effective even at a dose of 1000 mg.

For treatment of erectile dysfunction of psychogenic or mixed origin in men: 500 mg once daily. Treatment course: 21–28 days.

If one or several doses have been missed, continue treatment according to the previously prescribed dosage regimen.

Children: The use of this drug at the specified dosage is contraindicated in children.

Overdose. The drug is low in toxicity; however, at daily doses of 7–14 g during prolonged use, it may become hepatotoxic.

These doses significantly exceed the recommended dose (average therapeutic dose is 500–2000 mg). Only at higher administered doses have eosinophilia and fatty liver degeneration been observed. When lower doses were used, such changes were not noted.

Symptoms: drowsiness, nausea, vomiting, possible development of arterial hypotension, acute renal failure.

Treatment: gastric lavage. Symptomatic therapy.

In case of complications (e.g., arterial hypotension, renal failure), supportive and symptomatic measures should be applied.

Side effects.

Central nervous system: drowsiness (at the beginning of treatment), headache and dizziness (at doses above 2 g per day; the intensity of this adverse effect decreases when the dose is reduced).

Gastrointestinal tract: nausea (at the beginning of treatment), vomiting, diarrhea, epigastric pain.

Hepatobiliary system: hepatotoxicity (with long-term use of high doses).

Immune system: allergic reactions, including rash, itching, urticaria, skin redness.

Psychiatric disorders: emotional lability, sleep disturbances (these adverse reactions may occur in children when the medicinal product is used contrary to the instructions for use).

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

Reporting of suspected adverse reactions

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

Shelf life. 2 years.

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

Keep out of reach of children.

Packaging. 2.5 g per sachet, 10 sachets (1×10) in a box.

Prescription status. Prescription only.

Manufacturer: LIMITED LIABILITY COMPANY "CORPORATION "ZDOROVIYA".

Manufacturer's address and place of business: 22, Shevchenka Street, Kharkiv, Kharkiv Oblast, Ukraine, 61013.