Mechanism of Action and Pharmacokinetics Testosterone Propionate

Testosterone is absorbed in the digestive tract, through the skin and oral mucosa. However, it undergoes extensive hepatic first-pass metabolism when administered orally and, therefore, is usually administered intramuscularly, subcutaneously or transdermally. In addition, the basic testosterone molecule has been modified to obtain active derivatives orally and prolong the duration of the effect. The alkylation of position 17 a produces derivatives that are metabolized more slowly in the liver and, for this reason, can be administered orally. Esterification of group 17 to hydroxyl increases liposolubility and leads to a slower systemic absorption if administered by intramuscular injection. The absorption rate of the esters is related to the size of the ester group. Testosterone esters are hydrolyzed to testosterone after absorption. Testosterone binds approximately 80% to the sex hormone binding globulin. The 19-nostestosterone derivatives and the 17-methylated derivatives are characterized by reduced binding to this globulin. The plasma elimination half-life of testosterone ranges from 10 to 100 min. It is mainly metabolized in the liver through an oxidation in the 17-OH group with the formation of androstenedione, which is further metabolized to androstenolone, weakly androgenic, and ethiocolanolone, inactive, which are excreted in the urine mainly as glucuronoconjugates and sulfates. Approximately 6% is excreted unmodified by feces after undergoing enterohepatic recirculation. Testosterone is transformed into the most active dihydrotestosterone derivative in some target organs by the effect of 5 a-reductase. 19-nortestosterone derivatives are less sensitive to this enzyme. Small amounts of testosterone are aromatized in the body, leading to the formation of estrogenic derivatives in the body. Derivatives with a saturated A ring, such as mesterolone, aromatize less estrogen.

Indications

It is used in the treatment of male hypogonadism. It is usually active in combination with testosterone enanthate.
It is used in acute renal failure in the form of oily solutions for intramuscular route, topical route is used
It is used as an adjunct in postmenopausal breast carcinoma, some postmenopausal disorders and late puberty in children.

Posology

• In male hypogonadism: In adults, in the form of oily solutions for intramuscular route, administered in doses of 10-50 mg, two or three times a week.
• In acute renal failure: in dosages of 25 mg / day, for a maximum of 10 days.

Contraindications

TESTOSTERONES should be avoided in the following cases:

Pregnancy: There are reports of virilization of the female fetus after maternal treatment with testosterone or methyl testosterone during pregnancy.
Breastfeeding: the use of testosterones in nursing mothers should be avoided, due to the potential androgenic effect on the infant.
Porphyria: Androgens are not considered safe in patients with porphyria, although contradictory experimental evidence of porphyrinogenesis is available.

Restrictions of Use

Restrictions of Use

Do not use in case of hypersensitivity to some of its components; during pregnancy and breastfeeding period. Also, do not use in patients with high blood pressure, or in patients with cardiovascular problems, liver and kidney dysfunction.