PHARMACOLOGICAL PROPERTIES Nebido 250 mg 4 ml
testosterone undecanoate is an ester of natural androgen, testosterone. Active form - testosterone is formed as a result of cleavage of the side chain.
Testosterone is the most important androgen in the male body and is synthesized mainly in the testes and to a lesser extent in the adrenal cortex.
Testosterone is responsible for the formation of male sexual characteristics during prenatal development, in early childhood, as well as during puberty, and over time - for supporting the male phenotype and androgen-dependent functions (e.g. spermatogenesis, sex glands), and also performs some functions, for example, in the skin , muscles, skeleton bones, kidneys, liver, bone marrow and central nervous system.
Insufficient testosterone secretion causes the development of hypogonadism in men, which is characterized by low concentrations of testosterone in the blood serum. Symptoms associated with hypogonadism in patients also include impotence, decreased sex drive, fatigue, depression, lack of, underdevelopment, or regression of secondary sexual characteristics, as well as an increased risk of osteoporosis. Exogenous androgens are prescribed to increase insufficient levels of endogenous testosterone, as well as to eliminate the corresponding symptoms of hypogonadism.
Depending on the target organ, the range of testosterone is mainly androgenic (e.g. prostate gland, seminal vesicles, epididymis) or protein-anabolic (muscles, bones, blood-forming system, kidneys, liver).
The effect of testosterone in some organs appears after conversion of testosterone to peripheral tissues into estradiol, which subsequently binds to estrogen receptors in the nuclei of target cells (e.g., pituitary gland, adipose tissue, brain, bones, and Leydig testicular cells).
In men with hypogonadism, the use of androgens reduces body fat mass, increases lean body mass, muscle strength, and also prevents bone loss. Androgens can improve sexual function, as well as have a positive psychotropic effect by improving mood.
Nebido is a depot preparation that is administered intramuscularly and contains testosterone undecanoate, as a result of which the effect of the first passage through the liver is absent. After a / m injection of testosterone undecanoate in the form of an oil solution, this compound is gradually released from the depot and is almost completely cleaved by serum esterases into testosterone and undecanoic acid. An increase in the concentration of testosterone in serum relative to basal values can be determined the very next day after the injection.
During two separate studies, the average maximum testosterone concentrations of 24 and 45 nmol / L were determined after 14 and 7 days, respectively, after a single IM injection of 1000 mg of testosterone undecanoate in patients with hypogonadism. Postmaximal testosterone levels decreased with a half-life of approximately 53 days.
In male blood serum, about 98% of circulating testosterone binds to sex steroid-binding globulin (SHGS) and albumin. Only the free fraction of testosterone is considered biologically active. After iv infusion of testosterone in elderly patients, the apparent volume of distribution was determined at about 1 l / kg.
Testosterone resulting from the breakdown of the testosterone undecanoate ester is metabolized and excreted from the body in the same ways as endogenous testosterone. Undecanoic acid is metabolized via β-oxidation in the same way as other aliphatic carboxylic acids.
Testosterone undergoes significant metabolism in the liver and beyond. After administration of labeled testosterone, about 90% of the radioactivity was excreted in the urine in the form of glucuronide and sulfate acid conjugates, and 6% (after undergoing intrahepatic circulation) in feces. Products excreted in the urine include androsterone and etiocholanolone.
After repeated intramuscular injections of 1000 mg of testosterone undecanoate in patients with hypogonadism, an equilibrium concentration was reached between the 3rd and 5th injections at a 10-week interval between injections. The average maximum and average minimum concentrations of testosterone in equilibrium were approximately 42 and 17 nmol / L, respectively. The postmaximal serum testosterone level decreased with a half-life of approximately 90 days, which corresponds to the rate of release of the substance from the depot.