Following oral administration of oseltamivir phosphate is readily buy halotestin absorbed in the gastrointestinal tract and is highly converted into an active metabolite by the action of hepatic esterases. The concentrations of the active metabolite in the plasma are determined within 30 minutes, reaching almost the maximum level 2-3 hours after administration and significantly (by more than 20 times) greater than the concentration of the pro-drug. Not less than 75% of an oral dose reaches the systemic circulation as the active metabolite of less than 5% – in the form of the parent drug. Plasma concentrations of both pro-drug and active metabolite proportional to dose and independent of food intake.
In humans, the mean volume of distribution of the active metabolite is approximately 23 liters.
As shown by the experiments in ferrets, rats and rabbits, the active metabolite reaches all the main places of localization of influenza infection. In these experiments, after oral administration of oseltamivir phosphate, its active metabolite was detected in the lung, bronchial washings, nasal mucosa, trachea, middle ear, and in concentrations that provide an antiviral effect.
The binding of the active metabolite to human plasma proteins slightly (about 3%). Binding of pro-drug to human plasma proteins is 42%, which is insufficient to cause significant drug interactions.
Oseltamivir phosphate is highly converted into an active metabolite by the action of esterases that are predominantly in the liver and intestine. Neither oseltamivir phosphate nor the active metabolite are not substrates or inhibitors of the cytochrome P450 system.
Suck oseltamivir appears mainly buy halotestin by conversion to the active metabolite. The active metabolite is not subjected to further transformation and is excreted in the urine . In most patients, the half-life of the active metabolite plasma is 6-10 hours.
The active metabolite is displayed in full by renal excretion. The renal clearance exceeds the glomerular filtration rate , indicating that the drug is also displayed by tubular secretion. Since feces output less than 20% of ingested radiolabelled drug.
Pharmacokinetics in special groups
Patients with renal impairment
When assigning Tamiflu 100 mg 2 times a day for 5 days to patients with various degrees of renal lesion area under the curve, “concentration of the active metabolite in plasma – time» buy halotestin inversely proportional to the decrease in renal function.
Patients with liver disease
Experiments in vitro showed that the value of oseltamivir phosphate was not significantly elevated in patients with hepatic disorders and of the active metabolite is not reduced.
In elderly patients buy halotestin of the active metabolite at steady state was 25-35% higher than in younger patients when assigning Tamiflu similar doses. The half-life of the drug in the elderly is not significantly different from that in younger patients adulthood. Given data for and drug tolerability senile patients correct dose in the treatment and prevention of influenza is required.
The pharmacokinetics of Tamiflu was studied in children aged 1 year to 16 years in a pharmacokinetic study with a single dose of the drug in a clinical study in a small number of children aged 3-12 years. In young children, excretion of pro-drugs and active metabolites proceeded faster than in adults, resulting in lower in relation to a particular dose. The drug dose of 2 mg / kg gives a similar oseltamivir carboxylate, which in adults is achieved after a single dose capsules of 75 mg (equivalent to about 1 mg / kg). The pharmacokinetics of oseltamivir in children over 12 years is the same as in adults.
- Treatment of buy halotestin influenza in adults and children older than 1 year.
- Prophylaxis of influenza in adults and adolescents aged over 12 years who are in high-risk groups virus infection (in military units and large production teams, in debilitated patients).
- Prevention of influenza in children older than 1 year.