Convullex, 50 mg/ml syrup 100 ml

Antioepileptic drug.

It also has sedative and central myorelaxant effects.

The mechanism of action is mainly due to an increase of GABA in the CNS due to inhibition of the enzyme GABA-transferase. GABA decreases excitability and seizure readiness of motor areas of the brain. In addition, the effects of valproic acid on GABA_A receptors (activation of GABA-ergic transmission) and the effect on potential-dependent sodium channels play a major role in the mechanism of action of the drug.

According to other speculations, it acts on areas of postsynaptic receptors, mimicking or enhancing the inhibitory effect of GABA. Possible direct effects on membrane activity are related to changes in conductance for potassium ions. Improves the mental state and mood of patients, has antiarrhythmic activity.

Pharmacokinetics

Absorption

Valproic acid is almost completely absorbed from the gastrointestinal tract, bioavailability when ingested is 100%. Food intake does not reduce the absorption rate. C_max in plasma is noted after 2-3 hours. The therapeutic plasma concentration of valproic acid is 50-150 mg/l.

Distribution

C_ss is reached on days 2-4 of treatment, depending on the intervals between doses.

At plasma concentrations up to 50 mg/L, the binding of valproic acid to plasma proteins is 90-95%; at concentrations of 50-100 mg/L, 80-85%.

The values of the concentration in the cerebrospinal fluid correlate with the value of the non-protein-bound fraction of the active substance. Valproic acid penetrates the placental barrier and is excreted with breast milk. The concentration in breast milk is 1-10% of the concentration in maternal plasma.

Metabolism

Valproic acid undergoes glucuronidation and oxidation in the liver.

Valproic acid (1-3% of dose) and its metabolites are excreted by the kidneys, small amounts in the feces and exhaled air. T_1/2 in monotherapy and in healthy volunteers is 8-20 h.

Pharmacokinetics in special clinical cases

In uremia, hypoproteinemia and cirrhosis, the binding of valproic acid to plasma proteins is decreased.

When combined with other drugs, T_1/2 may be 6-8 h due to induction of metabolic enzymes.

In patients with impaired liver function, elderly patients and children under 18 months of age a significant increase in T_1/2 is possible.

Indications

Active ingredient

Composition

Associates:

maltitol liquid (lycasine 80/55) – 800 µg,

methyl parahydroxybenzoate – 1 mg,

propyl parahydroxybenzoate – 400 µg,

sodium saccharinate – 1 mg,

sodium cyclamate – 3 mg,

sodium chloride – 400 µg,

Raspberry flavoring 9/372710 – 400 mcg,

Peach flavoring 9/030307 – 1.25 mg,

Purified water – up to 1 ml.

How to take, the dosage

Individual. For oral administration in adults and children with body weight more than 25 kg the initial dose is 10-15 mg/kg/day. Then the dose is gradually increased by 200 mg/day at intervals of 3-4 days until clinical effect is achieved. The average daily dose is 20-30 mg/kg. For children with body weight less than 25 kg and newborns the average daily dose is 20-30 mg/kg.

The frequency of administration is 2-3 times a day with meals.

V/v (as sodium valproate) is administered in a dose of 400-800 mg or by drip at a rate of 25 mg/kg for 24, 36 and 48 hours. If concomitant use of oral and IV is necessary, the first administration is by IV infusion at a dose of 0.5-1 mg/kg/h, 4-6 hours after the last oral dose.

Maximum doses: when administered orally for adults and children weighing more than 25 kg, 50 mg/kg/day. Administration at a dose higher than 50 mg/kg/day is possible with monitoring of plasma concentrations of valproate. If plasma concentrations exceed 200 mg/l, the valproic acid dose should be reduced.

The capsules are taken orally, without chewing, 2-3 times daily, during or immediately after a meal, with a small amount of water.

Adults are prescribed in an initial dose of 600 mg/day with gradual increase of the dose by 150-250 mg every 3 days until clinical effect (disappearance of seizures) is achieved.

The initial dose in monotherapy is 5-15 mg/kg/day, then the dose is gradually increased by 5-10 mg/kg/week.

The recommended daily dose is about 1-2 g, i.e., 20-25 mg/kg. If necessary, the dose may be increased to a maximum dose of 2.5 g/day (30 mg/kg).

The maximum dose is 30 mg/kg/day (in patients with accelerated valproic acid metabolism, the maximum dose may be increased to 60 mg/kg/day with monitoring of plasma valproic acid concentrations).

In combination therapy the dose is 10-30 mg/kg/day with a subsequent increase of 5-10 mg/kg/week.

In children with a body weight greater than 25 kg, the initial dose is 300 mg/day (5-15 mg/kg/day), with gradual increases of 5-10 mg/kg/week until clinical effect (disappearance of seizures) is achieved, with the dose usually being 1-1.5 g/day (20-30 mg/kg/day).

The maximum dose is 30 mg/kg/day (in patients with accelerated valproic acid metabolism, the maximum dose may be increased to 60 mg/kg/day with monitoring of plasma valproic acid concentrations).

In children with body weight of 7.5-25 kg in monotherapy the average dose is 15-45 mg/kg/day, maximum – 50 mg/kg/day. In combined therapy it is 30-100 mg/kg/day.

The average daily dose of Convulex

Although the pharmacokinetics of valproic acid in the elderly may be different, this is of limited clinical significance, and the dose should be determined by clinical effect. Due to decreased binding to serum albumin, the proportion of unbound drug in plasma increases. This makes it advisable to choose the drug dose more carefully in the elderly, with the possible use of lower doses of the drug.

Patients with renal insufficiency may find it necessary to reduce the drug dose. The dose should be adjusted according to clinical monitoring, since plasma concentrations may be insufficiently informative.

Interaction

Contraindicated combinations

Mefloquine: risk of epileptic seizures due to increased metabolism of valproic acid and decreased plasma concentrations and, on the other hand, the convulsant effect of mefloquine.

Wort: risk of decreased plasma concentrations of valproic acid.

Unrecommended combinations

Lamotrigine: increased risk of severe skin reactions (toxic epidermal necrolysis). Valproic acid inhibits hepatic microsomal enzymes that metabolize lamotrigine, which slows its T1/2 to 70 h in adults and 45-55 h in children and increases plasma concentrations. Careful clinical and laboratory monitoring is required if the combination is necessary.

Combinations requiring special precautions

Carbamazepine: Valproic acid increases the plasma concentration of the active metabolite carbamazepine to signs of overdose. In addition, carbamazepine increases hepatic metabolism of valproic acid and decreases its concentration. These circumstances require the attention of the physician and determination of plasma concentrations of the drugs and possible revision of their doses.

Phenobarbital, primidone: Valproic acid increases plasma concentrations of phenobarbital or primidone to signs of overdose, more often in children. In turn, phenobarbital or primidone increase hepatic metabolism of valproic acid and decrease its concentration. Clinical observation during first 2 weeks of combined treatment with immediate decrease of phenobarbital or primidone dose in case of signs of sedative effect is recommended, determination of blood levels of anticonvulsants.

Phenytoin: changes in plasma concentrations of phenytoin are possible; phenytoin increases hepatic metabolism of valproic acid and decreases its concentration. Clinical monitoring, determination of blood levels of anticonvulsants, change of dosages if necessary are recommended.

Clonazepam: The addition of valproic acid to clonazepam in single cases may increase the severity of absences.

Ethosuximide: Valproic acid may both increase and decrease the serum concentration of ethosuximide due to changes in its metabolism. Clinical monitoring, determination of anticonvulsant blood levels, and dosage changes if necessary are recommended.

Topiramate: increased risk of hyperammonemia and encephalopathy.

Felbamate: increases plasma concentrations of valproic acid by 35-50%, with risk of overdose. Clinical monitoring, determination of valproic acid levels in blood, and changes in valproic acid dosage when combined with felbamate and after discontinuation are recommended.

Neuroleptics, MAO inhibitors, antidepressants, benzodiazepines:Neuroleptics, tricyclic antidepressants, MAO inhibitors that reduce seizure threshold decrease the effectiveness of the drug. In turn, valproic acid potentiates the effect of these psychotropic drugs, as well as benzodiazepines.

Cimetidine, erythromycin: inhibit hepatic metabolism of valproic acid and increase its plasma concentration.

Zidovudine: Valproic acid increases the plasma concentration of zidovudine, which leads to increased toxicity.

Carbapenems, monobactams: meropenem, panipenem, and aztreonam and imipenem decrease the plasma concentration of valproic acid, which may lead to a decrease in anticonvulsant effect.

Combinations to be considered

Acetylsalicylic acid: Increase the effects of valproic acid due to its displacement from plasma protein binding. Valproic acid enhances the effects of acetylsalicylic acid.

Indirect anticoagulants: Valproic acid increases the effect of indirect anticoagulants, close monitoring of prothrombin index is required when combined with vitamin K-dependent anticoagulants.

Nimodipine: enhancement of hypotensive effect of nimodipine due to increase of its concentration in plasma due to inhibition of its metabolism by valproic acid.

Myelotoxic drugs: increased risk of suppression of medullary hematopoiesis.

Ethanol and hepatotoxic drugs: increase the likelihood of liver damage.

Other combinations

Peroral contraceptives: Valproic acid does not cause induction of microsomal liver enzymes and does not reduce the effectiveness of hormonal oral contraceptives.

Special Instructions

With regard to reports of severe and fatal cases of hepatic failure and pancreatitis when using valproic acid preparations, the following should be kept in mind:

Contraindications

With caution:

Side effects

In general, Convullex® is well tolerated by patients. Side effects are mainly possible at plasma concentrations of the drug above 100 mg/l or during combination therapy.

Digestive system disorders: nausea, vomiting, gastralgia, decreased or increased appetite, diarrhea, hepatitis, constipation, pancreatitis, up to severe lesions with fatal outcome (in the first 6 months of treatment, more often in 2-12 weeks).

CNS side: Tremor, diplopia, nystagmus, flickering “flies” before the eyes, changes in behavior, mood or mental state (depression, fatigue, hallucinations, aggressiveness, hyperactive state, psychosis, unusual agitation, motor anxiety or irritability), ataxia, dizziness, somnolence, headache, encephalopathy, dysarthria, enuresis, stupor, impaired consciousness, coma.

Hematopoietic system disorders: anemia, leukopenia, thrombocytopenia, decrease of fibrinogen and platelet aggregation, leading to hypocoagulation (accompanied by prolongation of bleeding time, petechial hemorrhages, bruises, hematomas, bleeding).

Metabolic side: decrease or increase in body weight.

Endocrine system disorders: dysmenorrhea, secondary amenorrhea, breast enlargement, galactorrhea.

Laboratory findings: hypercreatininemia, hyperammonemia, hyperbilirubinemia, slight increase in liver transaminases activity, LDH (dose-dependent).

Allergic reactions: skin rash, urticaria, angioedema, photosensitization, erythema malignant exudative (Stevens-Johnson syndrome).

Others: peripheral edema, hair loss (usually recovered after discontinuation of the drug).

Overdose

Symptoms: nausea, vomiting, dizziness, diarrhea, respiratory dysfunction, muscle hypotonia, hyporeflexia, miosis, coma.

Treatment: gastric lavage (no later than 10-12 hours) followed by administration of activated charcoal, hemodialysis. Forced diuresis, maintenance of function.

Pregnancy use

Pregnancy should be prevented during treatment.

The teratogenic effect of valproic acid was found in animal experiments.

The incidence of neural tube defects in children born to women who took valproate in the first trimester of pregnancy is 1-2%. In this connection it is advisable to use folic acid preparations.

The treatment with Convulex should not be started in the first trimester of pregnancy. If a pregnant woman is already receiving the drug, treatment should not be interrupted due to the risk of increased seizures.

The drug should be used in the lowest effective doses, avoiding combination with other anticonvulsants and, if possible, regularly monitoring the plasma concentration of valproic acid.

Pediatric use

Pediatric contraindication: children under 3 years of age (for prolonged-acting tablets).

Similarities