Absorption
Vinpocetine is rapidly absorbed, after oral administration, the maximum concentration in the plasma is reached within 1 h. It is absorbed mainly in the proximal part of the intestine. When passing through the wall of the intestine is not exposed to metabolism.
Distribution
With oral administration of radioactively labeled vinpocetine, rats were most concentrated in the liver and in the gastrointestinal tract. The maximum concentration in the tissues was noted 2-4 hours after administration. The concentration in the brain did not exceed the values found in the blood.
In humans, the relationship with plasma proteins is 66%. Bioavailability of about 7%. The volume of distribution is 246.7 ± 88.5 liters, which indicates a high binding to tissues. The total clearance (66.7 l / h) exceeds the rate of hepatic blood flow (50 l / h), which indicates extrahepatic metabolism.
Metabolism
The main metabolite is apovincamine acid (AVK), which is 25-30% of the original compound.
The area under the concentration-time curve AVK after oral administration is twice as high as when intravenously administered vinpocetine. In this way, vinpocetine subject to the pronounced effect of "first passage" through the liver. Other metabolites include: hydroxyvinpocetine, hydroxy-AVK, AVK-dihydroxy glycinate and their conjugates (sulfates and / or glucuronides). Excretion of unchanged vinpocetine is low (several percent). If there is a violation of the liver or kidney function, dose adjustment is not required, since vinpocetine Do not cumulate.
Excretion
With repeated administration in a dose of 5 and 10 mg vinpocetine shows a linear pharmacokinetics, the equilibrium plasma concentration is 1.2 ± 0.27 and 2.1 ± 0.33 ng / ml, respectively. The half-life in humans is 4.83 ± 1.29 hours. In studies with radioactively labeled vinpocetine, it has been established that excretion by the kidneys and intestines occurs in a ratio of 60: 40%.
In rats and dogs, a high concentration is found in bile, but significant enterohepatic recirculation has been noted.
Pharmacokinetics in specific patient groups
Because the vinpocetine is primarily designed for the treatment of the elderly,it is necessary to take into account the slowing of distribution and metabolism, as well as the elimination in this age group, especially with prolonged use. According to the results of clinical studies, it is established that the kinetics of vinpocetine in the elderly does not differ significantly from the young, cumulation does not occur. With violations of the liver and nights, cumulation is not noted, which allows for long-term therapy.