Inhibition of 5α-reductase also reduces epididymal weight, and decreases motility and normal morphology of spermatozoa in the epididymis.Neurosteroids like 3α-androstanediol (derived from DHT) and allopregnanolone (derived from progesterone) activate the GABAA receptor in the brain; because finasteride prevents the formation of neurosteroids, it functions as a neurosteroidogenesis inhibitor and may contribute to a reduction of GABAA activity. Reduction of GABAA receptor activation by these neurosteroids has been implicated in depression, anxiety, and sexual dysfunction.In accordance with finasteride being a potent 5α-reductase inhibitor but a weak inhibitor of 5β-reductase, the medication decreases circulating levels of 5α-reduced steroids like allopregnanolone but does not reduce concentrations of 5β-reduced steroids like pregnanolone. Pregnanolone acts as a potent GABAA receptor positive allosteric modulator similarly to allopregnanolone. Pharmacokinetics
The mean oral bioavailability of finasteride is approximately 65%. The absorption of finasteride is not affected by food. At steady-state with 1 mg/day finasteride, mean peak concentrations of finasteride were 9.2 ng/mL (25 nmol/L). Conversely, following a single 5 mg dose of finasteride, mean peak levels of finasteride were 37 ng/mL (99 nmol/L), and plasma concentrations increased by 47 to 54% following 2.5 weeks of continued daily administration. The volume of distribution of finasteride is 76 L. Its plasma protein binding is 90%. The drug has been found to cross the blood–brain barrier, whereas levels in semen were found to be undetectable.Finasteride is extensively metabolized in the liver, first by hydroxylation via CYP3A4 and then by aldehyde dehydrogenase. It has two major metabolites, which are the tert-butyl side chain monohydroxylated and monocarboxylic acid metabolites.
Capillaritis is where the capillaries, usually of the legs or lungs, are inflamed, allowing blood cells to pass through.It may occur in the lungs as pulmonary capillaritis, or in the skin as pigmented purpuric dermatosis. Capillaritis usually affects otherwise healthy people. Capillaritis can take many forms but is made up of tiny red or brown dots that may be spread out or in a group forming a red or brown patch on the skin. One variation, Majocchi purpupa,  forms concentric rings.Capillaritis is a mild condition not requiring treatment. There is no known cure, however capillaritis can disappear within a few weeks, recur from time to time, or persist for years. == References ==