Single administration of finasteride in a dosage of 5 mg leads to a rapid decrease in serum DHT concentrations to achieve maximum effect after 8 hours. While that finasteride plasma concentration undergoes fluctuations over 24 hours, the concentration of DHT is constant. This halotestin side effects means that finasteride plasma concentration is not directly related to the concentration of DHT in the blood plasma. Patients with DHT, which Finasteride 5 mg per day was administered for 4 years, there was a decrease of concentration of blood DHT of approximately 70%, which It was associated with a decrease in prostate volume of approximately 20%. Additionally, approximately 50% decreased the concentration of prostate-specific antigen (PSA), compared with its initial concentration, which implies a reduction of growth of prostate epithelial cells. Reducing the concentration of DHT and reducing the severity of prostatic hyperplasia, accompanied by a decrease in PSA concentration remained in studies of up to 4 years.
In these studies, the blood testosterone increased by about 10-20% and remained within physiological values. In applying the drug PROSCAR ® for 7-10 days in patients referred for prostatectomy decreased DHT concentration in the prostate tissue is approximately 80 % and an increase in the concentration of testosterone in the prostate tissue by 10 times compared with the concentration before treatment. it was established that long-term (up to 4 years) use PROSCAR preparation ® patients with DHT and moderately expressed or significantly pronounced symptoms of the disease reduced the risk of all urological complications (surgery: transurethral resection of the prostate, halotestin side effects or prostatectomy, urinary retention requiring catheterization) by 51% and was accompanied by a marked and persistent decrease in prostate volume, and persistent increase in maximum urinary flow rate and improvement in symptoms (PLESS Research). patients taking PROSCAR ® for 3 months and achieving reduction in prostate volume by about 20%, at the termination of treatment the volume of the prostate gland returned to the same size after 3 months. Thus, treatment with PROSCAR ® contributes to downsizing an enlarged prostate gland, increases the rate of urine flow and reduce symptoms associated with DHT. Pharmacokinetics Absorption The maximum concentration of finasteride in plasma is reached after approximately 2 hours after ingestion. Finasteride absorption from the gastrointestinal tract is completed in 6-8 hours after ingestion.
The bioavailability when administered finasteride is about 80% of an intravenous reference dose and independent of food intake. Distribution Communication plasma proteins is approximately 93%. Plasma clearance is approximately 165 ml / min, volume of distribution -.. 76 l With prolonged therapy has been a slow accumulation of finasteride in small quantities. When receiving finasteride daily oral dose of 5 mg its lowest equilibrium concentration in blood plasma reaches 8-10 ng / mL and remained stable over time. Patients treated with finasteride. 7-10 days, the drug was detected in the cerebrospinal fluid. When receiving the preparation PROSCAR ® 5 mg per day of finasteride is also found in the seminal fluid. The content of finasteride in semen was 50-100 times less than the dose of finasteride (5 mg), which had no effect on the concentration of the circulating DHT in adult males. Metabolism
The half-life (T 1/2 ) of finasteride averages 6 hours. Excretion In men after a single oral dose of finasteride labeled with 14 C, 39% of the dose is excreted by the kidneys as metabolites (unchanged finasteride hardly excreted by the kidneys); 57% – through the intestines. This study identified two metabolites of finasteride, which have little inhibitory effect on 5-alpha reductase inhibitor finasteride compared. In old age finasteride elimination rate is halotestin side effects somewhat reduced. With age, the elimination half-life (T 1/2 ) is increased: men 18-60 years, the average T 1/2 is 6 hours, and in men older than 70 years – 8 hours. These changes are not clinically significant and, therefore, reduce the dose of the drug in men of advanced age is not required. In patients with chronic renal insufficiency (creatinine clearance (CC) from 9 to 55 ml / min.) The distribution of labeled 14C finasteride when receiving a single dose It did not differ from that in healthy volunteers. Contact finasteride plasma protein also did not differ in patients with impaired renal function. In renal failure of the metabolites of finasteride, which is normally excreted by the kidneys, is derived through the intestines. This increase in the amount shown finasteride metabolites in feces with a corresponding decrease of their concentration in urine. In patients with renal failure who are on dialysis, the dose correction PROSCAR ® is not required.
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