Phenibut 500
UkraineTable of Contents
INSTRUCTION FOR MEDICAL USE OF THE MEDICINAL PRODUCT PHENIBUT 500 (PHENIBUT 500)
Composition:
Active substance: phenibut;
1 capsule contains 500 mg of phenibut;
Excipients: potato starch; pregelatinized starch (in the form of modified pregelatinized corn starch); calcium stearate;
the capsule shell contains gelatin, titanium dioxide (E 171).
Pharmaceutical form. Hard capsules.
Main physicochemical properties: white hard gelatin capsules. The capsule contents are white or almost white powder.
Pharmacotherapeutic group. Psychostimulants and nootropic agents. Phenibut.
ATC code N06B X22.
Pharmacological properties.
Pharmacodynamics. Nootropics are also called psychometabolic stimulants because they have a beneficial effect on metabolic processes in the brain. The active substance of the medicinal product, phenibut, can be considered both as γ-aminobutyric acid (GABA) and as a derivative of β-phenylethylamine. Phenibut exhibits both nootropic and anxiolytic (tranquilizing) activity typical of GABA derivatives. Phenibut does not affect cholinoreceptors or adrenoreceptors. It reduces anxiety, restlessness, fear, and improves sleep; therefore, the medicinal product can be used in the treatment of neuroses and also prior to surgical procedures. Phenibut prolongs and enhances the effect of hypnotics, narcotic agents, neuroleptics, and antiparkinsonian drugs. It does not exert anticonvulsant activity. Phenibut prolongs the latent period of nystagmus and reduces its duration and intensity. Phenibut significantly reduces manifestations of asthenia and vasovegetative symptoms, including headache, sensation of heaviness in the head, sleep disturbances, irritability, emotional lability, and increases mental performance. Under the influence of phenibut, psychological parameters improve—attention, memory, speed and accuracy of sensorimotor reactions.
In patients with asthenia and emotional lability, phenibut improves subjective well-being from the first days of therapy, increases interest and initiative, and motivation for action, without causing excessive sedation or excitation. In terms of antiasthenic activity (weakness, fatigability, hypodynamia, mental and physical asthenia), phenibut is more active than piracetam.
Pharmacokinetics.
Absorption and distribution
After oral administration, the drug is well absorbed from the gastrointestinal tract and penetrates into all tissues of the body, easily crossing the blood-brain barrier (approximately 0.1% of the administered dose penetrates into brain tissue, to a significantly greater extent in young and elderly individuals). 80% of phenibut is bound in the liver, and this binding is non-specific.
In healthy volunteers, maximum plasma concentration (Cmax) of the active substance is reached approximately 3 hours after a single 250 mg oral dose taken after food. Cmax after a single 250 mg oral dose is approximately 2593 ng/mL, and steady-state Cmax on day 4 after repeated 250 mg oral doses three times daily is approximately 4057 ng/mL.
Biotransformation and elimination
80–95% of phenibut is metabolized in the liver to pharmacologically inactive metabolites. Approximately 5% of the dose is excreted unchanged in urine. No accumulation is observed with repeated administration. Elimination half-life in healthy volunteers after a single 250 mg oral dose taken after food is approximately 7 hours, and on day 4 after repeated 250 mg oral doses three times daily is approximately 8 hours.
Clinical characteristics.
Indications. Asthenic and anxiety-neurotic states: restlessness, anxiety, and fear; elderly patients – insomnia and nocturnal restlessness; prevention of stress prior to surgical procedures.
Menière’s disease and vertigo associated with vestibular dysfunction of various origins.
Prevention of motion sickness (a specific condition characterized by nausea, vomiting, prostration, and vestibular disturbances caused by being in a moving vehicle, such as a ship or airplane).
Adjunctive agent in alcohol withdrawal syndrome.
Contraindications. Hypersensitivity to phenibut or to excipients of the medicinal product. Pregnancy or breastfeeding period.
Interaction with other medicinal products and other forms of interaction. Phenibut may be combined with psychotropic medicinal products, with reduction of the dose of phenibut or the concomitantly administered medicinal products.
Phenibut enhances and prolongs the effects of sedatives, narcotics, antipsychotics, and anti-Parkinson agents.
Special precautions for use.
The medicinal product should be used with caution in patients with peptic ulcer disease of the stomach and/or intestine. To protect mucous membranes from the irritating effect of phenibut, lower doses should be prescribed for these patients.
In case of prolonged treatment, blood parameters and liver function tests should be monitored.
Literature data indicate the development of dependence after using medicinal products containing phenibut at doses exceeding therapeutic ones.
Experience obtained during the post-marketing period with the use of phenibut at therapeutic doses does not indicate withdrawal syndrome. However, literature data suggest that when phenibut is used at doses higher than therapeutic, abrupt discontinuation may lead to withdrawal syndrome, which can be severe and require hospitalization. In such cases, insomnia, psychomotor agitation, psychosis, auditory and visual hallucinations, anxiety, depression, dizziness, seizures, nausea, vomiting, palpitations, and tachycardia have been reported.
Use during pregnancy or breastfeeding. Animal studies have not revealed mutagenic, teratogenic, or embryotoxic effects of phenibut. Well-controlled and adequate studies on the safety of phenibut use in pregnant women and women who are breastfeeding have not been conducted. Therefore, phenibut should not be used during pregnancy or breastfeeding (see section "Contraindications").
There is no information available on the effect of phenibut on fertility.
Ability to influence reaction rate while driving or operating machinery. Patients who experience drowsiness or other central nervous system disorders during administration of the medicinal product should refrain from driving vehicles or operating machinery during the occurrence of these adverse reactions.
Method of Administration and Dosage
Dosage
The medicinal product contains 500 mg of phenibut in one capsule; therefore, if a different dose of phenibut is required, medicinal products allowing such dosing should be used.
Asthenic and anxiety-neurotic conditions. The dose is 250–500 mg three times daily. The maximum single dose is 750 mg; for patients aged 60 years and older – 500 mg.
Duration of treatment: 2–3 weeks. If necessary, the course may be extended to 4–6 weeks.
Meniere’s disease and dizziness associated with vestibular analyzer dysfunction of various origins. In functional disorders of the vestibular analyzer of infectious origin and during exacerbations of Meniere’s disease:
- initially – 750 mg three times daily for 5–7 days;
- upon reduction of vestibular disturbances – continue therapy with 250–500 mg three times daily for 5–7 days;
- thereafter – 250 mg once daily for another 5 days.
In mild cases, administer 250 mg twice daily for 5–7 days, followed by 250 mg once daily for 7–10 days.
Prophylaxis of dizziness caused by vestibular analyzer dysfunction of vascular or traumatic origin: administer 250 mg three times daily for 12 days.
Prevention of motion sickness. The dose is 250–500 mg one hour before the expected onset of motion sickness or at the appearance of the first symptoms. The drug is poorly effective in cases of severe symptoms (e.g., vomiting).
Adjunctive treatment in alcohol withdrawal syndrome. During the first days, administer 250–500 mg three times daily and 750 mg at bedtime, then gradually reduce the dose.
Patients with hepatic impairment
High doses of the drug may cause hepatotoxicity in patients with impaired liver function. The lowest effective dose should be used in this patient group.
Patients with renal impairment
There are no data on adverse effects of phenibut in patients with impaired renal function when the drug is used at therapeutic doses.
Method of Administration
Administer orally after meals. Swallow the capsules with sufficient amount of water.
Children. The medicinal product is not intended for use in children (due to the high amount of active substance per capsule).
Overdose. Phenibut is low-toxic at therapeutic doses.
Symptoms: drowsiness, nausea, vomiting, dizziness. With prolonged use of very high doses, eosinophilia, arterial hypotension, fatty liver degeneration, and impaired kidney function may develop.
Post-marketing data indicate that acute phenibut overdose is associated with symptoms such as depression (including decreased level of consciousness, reduced muscle tone, stupor, respiratory depression), impaired temperature regulation, hypertension or hypotension, and tachycardia. Psychomotor agitation, hallucinations, seizures, and delirium have also been reported. Cases of overdose involved administration of phenibut-containing medicinal products at doses significantly exceeding the therapeutic dose.
Treatment: symptomatic therapy should be administered. There is no specific antidote.
Side effects
Like all medicinal products, Phenibut may cause side effects, although they do not occur in all patients.
Side effects are listed according to the MedDRA system organ classification and frequency classification: very common (≥ 1/10); common (≥ 1/100 to < 1/10); uncommon (≥ 1/1000 to < 1/100); rare (≥ 1/10000 to < 1/1000); very rare (< 1/10000); frequency not known (cannot be estimated from available data).
Immune system disorders: frequency not known: hypersensitivity reactions (including urticaria, pruritus, erythema, rash, angioneurotic edema, facial swelling, tongue swelling).
Nervous system disorders: frequency not known: drowsiness (at the beginning of treatment), headache and dizziness (at doses above 2 g per day; reducing the dose reduces the incidence of side effects).
Gastrointestinal disorders: frequency not known: nausea (at the beginning of treatment).
Hepatobiliary disorders: frequency not known: hepatotoxicity (with prolonged use of high doses).
Skin and subcutaneous tissue disorders: rare: allergic reactions (rash, pruritus).
Reporting of suspected side effects
Reporting suspected side effects after medicinal product registration is important. It allows ongoing monitoring of the benefit-risk balance of the medicinal product. Healthcare professionals and patients, or their legal representatives, are encouraged to report any suspected side effects and lack of efficacy through the Automated Pharmacovigilance Information System at the following link: 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. 10 capsules in a blister, 3 blisters per cardboard box.
Prescription status. Prescription only.
Manufacturer. Limited liability company "Pharmaceutical Company "Zdorovya".
Manufacturer's address and place of business. 22 Shevchenka Street, Kharkiv, Kharkiv Oblast, 61013, Ukraine.