Pharmacodynamics:
Gabapentin is similar in structure to the neurotransmitter gamma-aminobutyric acid (GABA), but its mechanism of action differs from other drugs that interact with GABA receptors (valproic acid, barbiturates, benzodiazepines, GABA transaminase inhibitors, GABA uptake inhibitors, GABA agonists and prodrugs). GABA). It does not have GABAergic properties and does not affect GABA uptake and metabolism. Preliminary studies have shown that gabapentin binds to the α2-σ subunit of voltage-dependent calcium channels and reduces calcium ion flux, which plays an important role in neuropathic pain. Other mechanisms of action of gabapentin in neuropathic pain are a decrease in glutamate-dependent neuronal death, an increase in GABA synthesis, and suppression of the release of monoamine neurotransmitters. Gabapentin at clinically relevant concentrations does not bind to receptors that are sensitive to other drugs (drugs) or neurotransmitters, including GABAd, GABAb, benzodiazepine, glutamate, glycine, or N-methyl-d-aspartate receptors. Unlike phenytoin and carbamazepine, gabapentin does not interact with sodium channels in vitro. Gabapentin partially attenuated the effects of the glutamate receptor agonist N-methyl-d-aspartate in some in vitro tests, but only at concentrations greater than 100 µmol, which is not achieved in vivo. Gabapentin slightly reduces the release of monoamine neurotransmitters in vitro.
Pharmacokinetics:
The bioavailability of gabapentin is not dose proportional. So, as the dose increases, it decreases. After oral administration, the maximum concentration (Cmax) of gabapentin in plasma is reached after 2-3 hours. The absolute bioavailability of gabapentin in capsules is about 60%. Food, including those with a high fat content, does not affect the pharmacokinetics. The half-life (T1 / 2) from plasma does not depend on the dose and averages 5-7 hours. Pharmacokinetics does not change with repeated use; Steady-state plasma concentrations can be predicted from the results of a single dose of the drug. Gabapentin is practically non-plasma protein bound (<3%) and has a volume of distribution of 57.7 liters. It is excreted exclusively by the kidneys in unchanged form, it is not metabolized. The drug does not induce mixed-function liver oxidative enzymes involved in drug metabolism. Plasma clearance of gabapentin is reduced in the elderly and in patients with impaired renal function. The rate constant of excretion, plasma clearance and renal clearance are directly proportional to creatinine clearance. Gabapentin is removed from plasma by hemodialysis. In patients with impaired renal function and patients receiving hemodialysis treatment, dose adjustment is recommended (see Dosage and Administration).
Indications for use:
epilepsy: partial convulsions with and without secondary generalization in adults and children over 12 years of age (myotherapy); partial convulsions with and without secondary generalization in adults (additional drug); resistant form of epilepsy in children older than 3 years (additional drug).
Neuropathic pain in adults (18 years and older).
Contraindications:
Hypersensitivity to any of the components of the drug, age up to 12 years (due to the impossibility of accurate dosing).
Carefully
Renal failure (see “Method of application and doses”).
Use during pregnancy and lactation:
There are no data on the use of the drug in pregnant women, so gabapentin should be used during pregnancy only if the expected benefit to the mother justifies the possible risk to the fetus.
Gabapentin is excreted in breast milk, its effect on a breast-fed child is unknown, therefore, breast-feeding should be discontinued during treatment.
Dosage and administration:
Inside, swallowing whole, regardless of the meal and drinking plenty of liquid. If it is necessary to reduce the dose, discontinue the drug, or change to an alternative agent, this should be done gradually over a period of at least one week.
Neuropathic pain in adults
The initial daily dose is 900 mg divided into three doses; if necessary, the dose is gradually increased to a maximum of 3600 mg / day. Treatment can be started immediately with a dose of 900 mg / day (300 mg 3 times a day) or during the first 3 days the dose can be increased gradually to 900 mg per day according to the following scheme:
Day 1: 300 mg once a day
2nd day: 300 mg 2 times a day
3rd day: 300 mg 3 times a day
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