pharmachologic effect
Antipsychotic drug (neuroleptic). Quetiapine is an atypical antipsychotic drug that exhibits a higher affinity for serotonin 5HT2 receptors than for brain dopamine D1 and D2 receptors. Quetiapine has affinity for histamine and α1-adrenergic receptors, and less affinity for α2-adrenergic receptors. No significant affinity of quetiapine for cholinergic muscarinic and benzodiazepine receptors was found.
In standard tests, quetiapine exhibits antipsychotic activity.
The results of the study of extrapyramidal symptoms in animals revealed that quetiapine causes mild catalepsy at a dose that effectively blocks dopamine D2 receptors. Quetiapine causes a selective decrease in the activity of mesolimbic A10-dopaminergic neurons, in comparison with A9-nigrostriatal neurons involved in motor functions.
There were no differences between the use of quetiapine (at a dose of 75-750 mg / day) and placebo in the incidence of extrapyramidal symptoms and in the concomitant use of anticholinergic drugs. Does not cause a prolonged increase in the concentration of prolactin in the blood plasma.
Quetiapine maintains long-term clinical improvement in those patients in whom a positive effect developed at the very beginning of treatment.
The duration of the effect of quetiapine on serotonin 5HT2 receptors and dopamine and D2 receptors is less than 12 hours after taking the drug.
Pharmacokinetics
Suction and distribution
Absorption is high, food intake does not affect bioavailability. Plasma protein binding – 83%.
The pharmacokinetics of quetiapine is linear and does not differ between men and women.
Metabolism
It is actively metabolized in the liver with the formation of pharmacologically inactive metabolites under the influence of the CYP3A4 isoenzyme. Quetiapine and some of its metabolites are weak inhibitors of isoenzymes 1A2, 2C9, 2C19, 2D6 and 3A4 of human cytochrome P450, but only at concentrations at least 10-50 times higher than the concentration of the drug when used in the effective dose range from 300 to 450 mg / day. day
Based on in vitro results, co-administration of quetiapine with other drugs should not be expected to result in clinically significant inhibition of cytochrome P450 mediated metabolism of other drugs.
breeding
T1 / 2 is approximately 7 hours. Excreted by the kidneys is approximately 73% and through the intestines – 21%. Less than 5% of quetiapine is not metabolized and is excreted unchanged.
Pharmacokinetics in special clinical situations
The average clearance of quetiapine in elderly patients is 30-50% less than in patients aged 18 to 65 years.
The average plasma clearance of quetiapine in patients with severe renal insufficiency (CC < 30 ml / min / 1.73 m2) and in patients with liver damage (stabilized alcoholic cirrhosis) is reduced by approximately 25%.
Dosage
The drug is prescribed orally, 2 times / day, regardless of the meal.
In the treatment of acute and chronic psychoses, including schizophrenia, the daily dose for the first 4 days is: 1st day – 50 mg; 2nd day – 200 mg; 3rd day – 200 mg and 4th day – 300 mg. Starting from the 4th day, the daily dose is 300 mg. Depending on the clinical effect and tolerability of the drug, its dose may vary individually from 150 mg / day to 750 mg / day. The maximum daily dose in the treatment of schizophrenia is 750 mg.
In the treatment of manic episodes in bipolar disorder, quetiapine is recommended as monotherapy or as adjuvant therapy to stabilize mood.
The daily dose in the first 4 days is: 1st day – 100 mg; 2nd day – 200 mg; 3rd day – 300 mg and 4th day – 400 mg. An increase in the daily dose in the future is possible by 200 mg / day and by the 6th day of therapy is 800 mg. Depending on the clinical effect and tolerability of the drug, its dose may vary individually from 200 mg / day to 800 mg / day. As a rule, the effective dose is from 400 mg to 800 mg / day. The maximum daily dose is 800 mg.
Because plasma clearance of quetiapine in elderly patients is reduced by 30-50%, the drug should be prescribed with caution, especially at the beginning of therapy. Starting dose – 25 mg / day, followed by an increase of 25-50 mg until an effective dose is reached.
In patients with renal and hepatic insufficiency, it is recommended to start therapy with 25 mg / day. In the future, it is recommended to increase the dose daily by 25-50 mg until an effective dose is reached.
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