The equilibrium level within the plasma drug reaches 10-20 minutes from the beginning of the infusion. This indicator is linear depending on the speed of the infusion (if it is 3 ng / kg / min, then the concentration level of the substance will be approximately 135 ± 24 pg / ml). Upon completion of the infusion, the plasma index of the active component of the drug rapidly decreases (due to the increased intensity of its metabolism process).
The metabolic coefficient of plasma clearance is 20 ± 5 ml / kg / minute. The plasma half-life (terminal phase) is 30 minutes. As a result, after 2 hours after completion of the infusion, the medication will be less than 10% of the equilibrium level.
The drug can not interact with other drugs at the level of protein synthesis, since most of its active component is synthesized with plasma albumin (with protein synthesis is 60%), resulting in a very small amount of free iloprost. Along with this, the likelihood of exposure to iloprost on the processes of bioconversion of other drugs is extremely low (due to the ways of its metabolism and low absolute dosage).
The metabolism of the substance is carried out with the help of the b-oxidation process in the side carboxyl chain. Excretion of the unchanged component does not occur. The main product of decomposition is tetranor-iloprost, which falls into the urine (conjugated, as well as free form) under the guise of 4 diastereoisomers. This metabolite has no pharmacological activity (this has been shown by testing in animals). In vitro tests show that with inhalation or with / in the introduction, the metabolism of the substance inside the lungs is very similar.
In people with healthy renal and hepatic activity, the excretion of iloprost after the infusion procedure often occurs in 2 phases with half-lives of 3-5 or 3-5 minutes, respectively, and 15-30 minutes. At the same time, the total clearance of the component is about 20 ml / kg / minute, which demonstrates the presence of extrahepatic metabolic pathway of the substance.
With the participation of volunteers, testing was carried out to identify the mass fraction of the decay products (here, 3H-iloprost was used). After the infusion, the total radioactivity index was 81%, while in the stool with urine, respectively, 12% and 68% were detected. The decay products are excreted in the urine, and also from the plasma in a 2-phase way. In this case, the half-life in the 1-st phase is equal to about 2 hours, and in the second - about 5 hours. Of urine, the half-life lasts 2, and also 18 hours, respectively.
With reduced renal activity (terminal phase of kidney failure). Studies in people with this disorder, who also underwent periodic dialysis, show that after intravenous medications the clearance rate is much lower (on average 5 ± 2 ml / minute / kg) than the similar level in people with kidney failure, not who underwent periodic dialysis procedures (with an average of 18 ± 2 ml / minute / kg).
With decreased hepatic activity. Since most of the active substance of the drug passes the metabolism inside the liver, changes in its work affect the plasma values of drugs. Test results with the participation of 8 people with cirrhosis showed that the average level of clearance of the substance was 10 ml / minute / kg.