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Finasteride

Finasteride

Overview
Finasteride is a synthetic antiandrogen
Antiandrogen
Antiandrogens, or androgen antagonists, first discovered in the 1960s, prevent androgens from expressing their biological effects on responsive tissues. Antiandrogens alter the androgen pathway by blocking the appropriate receptors, competing for binding sites on the cell's surface, or affecting...

 that inhibits type II 5-alpha reductase
5-alpha reductase
5α-reductases, also known as 3-oxo-5α-steroid 4-dehydrogenases, are enzymes involved in steroid metabolism. They participate in 3 metabolic pathways: bile acid biosynthesis, androgen and estrogen metabolism, and prostate cancer....

, the enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

 that converts testosterone
Testosterone
Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and other vertebrates. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands...

 to dihydrotestosterone
Dihydrotestosterone
Dihydrotestosterone is an androgen or male sex hormone. The enzyme 5α-reductase synthesises DHT in the prostate, testes, hair follicles, and adrenal glands...

 (DHT). Finasteride is approved for the treatment of benign prostatic hyperplasia
Benign prostatic hyperplasia
Benign prostatic hyperplasia also known as benign prostatic hypertrophy , benign enlargement of the prostate , and adenofibromyomatous hyperplasia, refers to the increase in size of the prostate....

 (BPH) and male pattern baldness (MPB).

Finasteride is used for the treatment of benign prostatic hyperplasia
Benign prostatic hyperplasia
Benign prostatic hyperplasia also known as benign prostatic hypertrophy , benign enlargement of the prostate , and adenofibromyomatous hyperplasia, refers to the increase in size of the prostate....

 (BPH) and male pattern baldness (MPB).

Physicians use finasteride for the treatment of benign prostatic hyperplasia (BPH) (also known as enlarged prostate) at a dose of 5 mg once a day.
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Encyclopedia
Finasteride is a synthetic antiandrogen
Antiandrogen
Antiandrogens, or androgen antagonists, first discovered in the 1960s, prevent androgens from expressing their biological effects on responsive tissues. Antiandrogens alter the androgen pathway by blocking the appropriate receptors, competing for binding sites on the cell's surface, or affecting...

 that inhibits type II 5-alpha reductase
5-alpha reductase
5α-reductases, also known as 3-oxo-5α-steroid 4-dehydrogenases, are enzymes involved in steroid metabolism. They participate in 3 metabolic pathways: bile acid biosynthesis, androgen and estrogen metabolism, and prostate cancer....

, the enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

 that converts testosterone
Testosterone
Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and other vertebrates. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands...

 to dihydrotestosterone
Dihydrotestosterone
Dihydrotestosterone is an androgen or male sex hormone. The enzyme 5α-reductase synthesises DHT in the prostate, testes, hair follicles, and adrenal glands...

 (DHT). Finasteride is approved for the treatment of benign prostatic hyperplasia
Benign prostatic hyperplasia
Benign prostatic hyperplasia also known as benign prostatic hypertrophy , benign enlargement of the prostate , and adenofibromyomatous hyperplasia, refers to the increase in size of the prostate....

 (BPH) and male pattern baldness (MPB).

Medical uses


Finasteride is used for the treatment of benign prostatic hyperplasia
Benign prostatic hyperplasia
Benign prostatic hyperplasia also known as benign prostatic hypertrophy , benign enlargement of the prostate , and adenofibromyomatous hyperplasia, refers to the increase in size of the prostate....

 (BPH) and male pattern baldness (MPB).

Benign prostatic hyperplasia


Physicians use finasteride for the treatment of benign prostatic hyperplasia (BPH) (also known as enlarged prostate) at a dose of 5 mg once a day. Six months or more of treatment may be required to see the full effects of finasteride. If the drug is discontinued, any therapeutic benefits will be reversed. Finasteride may improve the symptoms associated with BPH such as difficulty urinating, getting up during the night to urinate, hesitation at the start of urination, and decreased urinary flow.

Male pattern baldness


In a 5-year study of men with mild to moderate hair loss, 2 out of 3 of the men who took 1 mg of finasteride daily regrew some hair, as measured by hair counts. In contrast, all of the men in the study who were not taking finasteride lost hair. In the same study, based on photographs that were reviewed by an independent panel of dermatologists, 48% of those treated with finasteride experienced visible regrowth of hair, and a further 42% had no further loss. Average hair count in the treatment group remained above baseline, and showed an increasing difference from hair count in the placebo group, for all five years of the study. Finasteride is effective only for as long as it is taken; the hair gained or maintained is lost within 6–12 months of ceasing therapy. In clinical studies, finasteride, like minoxidil
Minoxidil
Minoxidil is an antihypertensive vasodilator medication which also slows or stops hair loss and promotes hair regrowth. Now off-patent, it is available over-the-counter for the treatment of androgenic alopecia. Minoxidil must be used indefinitely for continued support of existing hair follicles and...

, was shown to work on both the crown area and the hairline, but is most successful in the crown area.

Some users, in an effort to save money, buy Proscar (finasteride 5 mg) instead of Propecia, and split the Proscar pills into several parts to approximate the Propecia dosage. The pills are coated to prevent contact with the active ingredient during handling, and the dust or crumbs from broken Proscar tablets should be kept away from pregnant women or women who may become pregnant.

Adverse effects


Side effects of finasteride include impotence (1.1% to 18.5%), abnormal ejaculation
Ejaculation
Ejaculation is the ejecting of semen from the male reproductory tract, and is usually accompanied by orgasm. It is usually the final stage and natural objective of male sexual stimulation, and an essential component of natural conception. In rare cases ejaculation occurs because of prostatic disease...

 (7.2%), decreased ejaculatory volume (0.9% to 2.8%), abnormal sexual function (2.5%), gynecomastia
Gynecomastia
Gynecomastia or Gynaecomastia, , is the abnormal development of large mammary glands in males resulting in breast enlargement. The term comes from the Greek γυνή gyné meaning "woman" and μαστός mastós meaning "breast"...

 (2.2%), erectile dysfunction
Erectile dysfunction
Erectile dysfunction is sexual dysfunction characterized by the inability to develop or maintain an erection of the penis during sexual performance....

 (1.3%), ejaculation disorder (1.2%) and testicular pain. According to the product package insert, resolution occurred in men who discontinued therapy with finasteride due to these side effects and in most men who continued therapy. The PPI also states that patients have reported persisting erectile dysfunction despite discontinuing the drug. In December 2010, Merck added depression as a side effect of finasteride.

Prostate cancer


The FDA has added warning to finasteride about an increased risk of high-grade prostate cancer
Prostate cancer
Prostate cancer is a form of cancer that develops in the prostate, a gland in the male reproductive system. Most prostate cancers are slow growing; however, there are cases of aggressive prostate cancers. The cancer cells may metastasize from the prostate to other parts of the body, particularly...

. Whilst the potential for positive, negative or neutral changes to the potential risk of developing prostate cancer with finasteride has not been established, evidence has suggested it may temporarily reduce the growth and prevalence of benign prostate tumors, but could also mask the early detection of prostate cancer. The primary area for concern is for patients who may develop prostate cancer whilst taking finasteride for benign prostatic hyperplasia, which in turn could delay diagnosis and early treatment of the prostate cancer, thereby potentially increasing the risk of these patients developing high-grade prostate cancer.

The 2005 Prostate Cancer Prevention Trial (PCPT) showed at a dosage of 5 mg per day, as is commonly prescribed for BPH, participants taking finasteride were 25% less likely to have developed prostate cancer at the end of the trial compared to those taking a placebo. It appeared (incorrectly) that finasteride increased the specificity and selectivity of prostate cancer detection, thus creating an apparently increased rate of high Gleason grade tumor. A 2008 update of this study found that finasteride reduces the incidence of prostate cancer by 30%. In the original study, it turns out that the smaller prostate caused by finasteride means that a doctor is more likely to hit upon cancer nests and more likely to find aggressive looking cells. Most of the men in the study who had both low and high-grade prostate cancer chose to be treated, and many had their prostates removed. A pathologist then carefully examined each of those 500 prostates and compared the kinds of cancers found at surgery to those initially diagnosed at biopsy. This study concluded that finasteride did not increase the risk of high-grade prostate cancer.

Sexual side effects


There have been case reports of persistent diminished libido or erectile dysfunction, even after stopping the drug. In December 2008, the Swedish Medical Products agency concluded a safety investigation of finasteride and subsequently advised that the use of finasteride may result in irreversible sexual dysfunction. The Agency's updated safety information lists difficulty in obtaining an erection that persists indefinitely, even after the discontinuation of finasteride, as a possible side effect of the drug. The UK's Medical and Healthcare Products Regulatory Agency (MHRA) say that erectile dysfunction that persists once use of finasteride has stopped has been reported to them. Similar labeling changes have been made by the Italian government. For a period of time there was a discrepancy between European and North American warning labels regarding the risks of developing persistent sexual side effects from taking Propecia but after two years Merck revised the United States' warning label to report that they had received reports of patients facing "difficulty in achieving an erection that continued after stopping the medication".

Male breast cancer


In December 2009, the Medicines and Healthcare products Regulatory Agency
Medicines and Healthcare products Regulatory Agency
The Medicines and Healthcare products Regulatory Agency is the UK government agency which is responsible for ensuring that medicines and medical devices work and are acceptably safe....

 in the UK announced new drug safety advice on finasteride and the potential risk of male breast cancer. The agency concluded that, although overall incidence of male breast cancer in clinical trials for finasteride 5 mg was not significantly increased, a higher risk of male breast cancer with finasteride use cannot be excluded. A warning on this risk will be included in the product information.

Teratogenicity


Finasteride is in the FDA pregnancy category
Pregnancy category
The pregnancy category of a pharmaceutical agent is an assessment of the risk of fetal injury due to the pharmaceutical, if it is used as directed by the mother during pregnancy. It does not include any risks conferred by pharmaceutical agents or their metabolites that are present in breast...

 X. This means that it is known to cause birth defects in an unborn baby. Women who are or who may become pregnant must not handle crushed or broken finasteride tablets, because the medication could be absorbed through the skin. Finasteride is known to cause birth defects in a developing male baby. Exposure to whole tablets should be avoided whenever possible, however exposure to whole tablets is not expected to be harmful as long as the tablets are not swallowed. It is not known whether finasteride passes into breast milk
Breast milk
Breast milk, more specifically human milk, is the milk produced by the breasts of a human female for her infant offspring...

, and thus should not be taken by breastfeeding women. Finasteride may pass into the semen
Semen
Semen is an organic fluid, also known as seminal fluid, that may contain spermatozoa. It is secreted by the gonads and other sexual organs of male or hermaphroditic animals and can fertilize female ova...

 of men, but Merck states that a pregnant woman's contact with the semen of a man taking finasteride is not an issue for concern. Finasteride is known to affect blood donations, and potential donors are typically restricted for at least a month after their most recent dose.

Interference with doping assays


Many sports organizations have banned finasteride because it can be used to mask steroid abuse. Since 2005, finasteride has been on the World Anti-Doping Agency
World Anti-Doping Agency
The World Anti-Doping Agency , , is an independent foundation created through a collective initiative led by the International Olympic Committee . It was set up on November 10, 1999 in Lausanne, Switzerland, as a result of what was called the "Declaration of Lausanne", to promote, coordinate and...

's list of banned substances. However, it was removed from the list in 2009. Notable athletes who used finasteride for hair loss and were banned from international competition include skeleton racer
Skeleton (sport)
Skeleton is a fast winter sliding sport in which an individual person rides a small sled down a frozen track while lying face down, during which athletes experience forces up to 5g. It originated in St. Moritz, Switzerland as a spin-off from the popular British sport of Cresta Sledding...

 Zach Lund
Zach Lund
Zach Lund is an American skeleton racer who has competed since 2000. He won two bronze medals at the FIBT World Championships with one in 2007 and one in 2008 . He finished #1 in World Cup standings in 2007.-Personal life:Zach was born and raised in Salt Lake City, Utah. He is the youngest of 5...

, bobsledder
Bobsleigh
Bobsleigh or bobsled is a winter sport in which teams of two or four make timed runs down narrow, twisting, banked, iced tracks in a gravity-powered sled that are combined to calculate the final score....

 Sebastien Gattuso
Sebastien Gattuso
Sébastien Gattuso is a Monegasque athlete specializing in the 100 metres. He was born in Menton, France. In 2006 he was banned for six months after testing positive for finasteride, a drug that can be used to mask use of steroids....

, footballer
Football (soccer)
Association football, more commonly known as football or soccer, is a sport played between two teams of eleven players with a spherical ball...

 Romário
Romário
Romário de Souza Faria , better known simply as Romário , is a former footballer who played striker,manager and current politician where is currently running for a mayor like position in his hometown...

 and ice hockey goaltender
Goaltender
In ice hockey, the goaltender is the player who defends his team's goal net by stopping shots of the puck from entering his team's net, thus preventing the opposing team from scoring...

 José Théodore
José Théodore
José Théodore is a French Canadian professional ice hockey goaltender currently playing for the Florida Panthers of the National Hockey League...

.

Mechanism of action


Testosterone in males is produced primarily in the testicles, but also in the adrenal gland
Adrenal gland
In mammals, the adrenal glands are endocrine glands that sit atop the kidneys; in humans, the right suprarenal gland is triangular shaped, while the left suprarenal gland is semilunar shaped...

s. The majority of testosterone in the body is bound to sex hormone-binding globulin (SHBG), a protein produced in the liver that transports testosterone in the bloodstream, prevents its metabolism, and prolongs its half-life. Once it becomes unbound from SHBG, free testosterone can enter cells throughout the body. In certain tissues, notably the scalp, skin, and prostate, testosterone is converted into dihydrotestosterone
Dihydrotestosterone
Dihydrotestosterone is an androgen or male sex hormone. The enzyme 5α-reductase synthesises DHT in the prostate, testes, hair follicles, and adrenal glands...

 (DHT) by the enzyme 5-alpha reductase
5-alpha reductase
5α-reductases, also known as 3-oxo-5α-steroid 4-dehydrogenases, are enzymes involved in steroid metabolism. They participate in 3 metabolic pathways: bile acid biosynthesis, androgen and estrogen metabolism, and prostate cancer....

. DHT is a more powerful androgen than testosterone (as it has a much higher affinity for the androgen receptor
Androgen receptor
The androgen receptor , also known as NR3C4 , is a type of nuclear receptor that is activated by binding of either of the androgenic hormones testosterone or dihydrotestosterone in the cytoplasm and then translocating into the nucleus...

), so 5-alpha reductase can be thought to amplify the androgenic effect of testosterone in the tissues in which it's found. In addition to blocking the 5-alpha reductase enzyme, finasteride is a competitive inhibitor of the 5-beta reductase type 2 enzyme.

Finasteride is an inhibitor of 5-alpha reductase by being an aza analog of testosterone, thereby initially binding to 5-alpha reductase similarly to testosterone, but with the effect of remaining bound to it rather than being converted, thereby blocking the space that testosterone would otherwise have taken. By blocking 5-alpha reductase, finasteride blocks the conversion of testosterone into the more powerful androgen DHT. This reduces androgenic activity in the scalp, treating hair loss at its hormonal source. In the prostate, inhibition of 5-alpha reductase leads to a reduction of prostate volume, which improves the symptoms of benign prostatic hyperplasia (BPH) and reduces the risk of prostate cancer. Inhibition of 5-alpha reductase also leads to a reduction in the weight of the epididymis
Epididymis
The epididymis is part of the male reproductive system and is present in all male amniotes. It is a narrow, tightly-coiled tube connecting the efferent ducts from the rear of each testicle to its vas deferens. A similar, but probably non-homologous, structure is found in cartilaginous...

 and a decrease in the percentage of motile and morphologically normal spermatozoa found in the epididymis.

By inhibiting 5AR in the central nervous system, finasteride has been shown to diminish the biosynthesis of neurosteroids, which require 5AR function. Neurosteroids and neuroactive steroids play a role in memory enhancement, sedative, hypnotic, anesthetic, anxiolytic, antistress, sleep modulating, anticonvulsant, and antidepressant properties. It has therefore been suggested that alterations in neurosteroid levels explain some of the mental and sexual side-effects of finasteride.

Preparations


Drug trade names include Propecia and Proscar, the former marketed for male pattern baldness (MPB) and the latter for benign prostatic hyperplasia (BPH), both are products of Merck & Co. There is 1 mg of finasteride in Propecia and 5 mg in Proscar. Merck's patent on finasteride for the treatment of BPH expired on June 19, 2006. Merck was awarded a separate patent for the use of finasteride to treat MPB. This patent is set to expire in November 2013.

Some studies have shown that the dose of finasteride needed to treat male pattern baldness may be smaller than 1 mg. Petitions to the FDA to re-examine the approved dosage in light of the statistical evidence and possible long-term risks, were met with the response that a study had shown increased effect of a 1 mg dose compared to 0.2 mg without added risks; the same study also concluded that doses of 0.01 mg per day were found to be ineffective in treating hair loss.

Chemical synthesis


Finasteride is synthesized from progesterone
Progesterone
Progesterone also known as P4 is a C-21 steroid hormone involved in the female menstrual cycle, pregnancy and embryogenesis of humans and other species...

:

History


In 1974, Julianne Imperato-McGinley of Cornell Medical College in New York attended a conference on birth defects. She reported on a group of hermaphroditic
Hermaphrodite
In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.Many taxonomic groups of animals do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both...

 children in the Caribbean
Caribbean
The Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north...

 who appeared sexually ambiguous
Ambiguity
Ambiguity of words or phrases is the ability to express more than one interpretation. It is distinct from vagueness, which is a statement about the lack of precision contained or available in the information.Context may play a role in resolving ambiguity...

 at birth, and were initially raised as girls, but then grew external male genitalia and other masculine characteristic post-onset of puberty. Her research group found that these children shared a genetic mutation, causing deficiency
5-alpha-reductase deficiency
5-Alpha-reductase deficiency is an autosomal recessive intersex condition caused by a mutation of the 5-alpha reductase type 2 gene.-Normal function:...

 of the 5-alpha reductase
5-alpha reductase
5α-reductases, also known as 3-oxo-5α-steroid 4-dehydrogenases, are enzymes involved in steroid metabolism. They participate in 3 metabolic pathways: bile acid biosynthesis, androgen and estrogen metabolism, and prostate cancer....

 enzyme and male hormone dihydrotestosterone (DHT), which was found to have been the etiology behind abnormalities in male sexual development. Upon maturation, these individuals were observed to have smaller prostates which were underdeveloped, and were also observed to lack incidence of male pattern baldness.

In 1975, copies of Imperato-McGinley's presentation were seen by P. Roy Vagelos
P. Roy Vagelos
Pindaros Roy Vagelos, better known as P. Roy Vagelos or Roy Vagelos , was president and chief executive officer and chairman of the multinational pharmaceutical company Merck. He attracted research scientists who developed many major new drugs...

, who was then serving as Merck's basic-research chief. He was intrigued by the notion that decreased levels of DHT led to the development of smaller prostates. Dr. Vagelos then sought to create a drug which could mimic the condition found in the pseudo-hermaphroditic children in order to treat older men who were suffering from benign prostatic hyperplasia.

In 1992, finasteride (5 mg) was approved by the U.S. Food and Drug Administration (FDA) for treatment of benign prostatic hyperplasia
Benign prostatic hyperplasia
Benign prostatic hyperplasia also known as benign prostatic hypertrophy , benign enlargement of the prostate , and adenofibromyomatous hyperplasia, refers to the increase in size of the prostate....

 (BPH), which Merck marketed under the brand name Proscar.

In 1997, Merck was successful in obtaining FDA approval for a second indication of finasteride (1 mg) for treatment of male pattern baldness (MPB), which was marketed under the brand name Propecia.

External links