Finasteride Uses, Dosage, Side Effects, Food Interaction and all others data.

Finasteride, a competitive inhibitor of the 5α reductase enzyme which is used in the treatment of benign prostatic hyperplasia. It is selective for 5α reductase type 2 enzyme and has no affinity for androgen receptors. The development of the prostate gland and subsequent BPH is dependent upon conversion of testosterone to dihydrotestosterone (DHT) within the prostate. Finasteride belongs to a new class of specific inhibitors of 5α reductase, an intracellular enzyme, which metabolises testosterone into the more potent androgen, DHT. Finasteride has no affinity for the androgen receptor.

Finasteride is an antiandrogenic compound that works by suppressing the production of serum and intraprostatic dihydrotestosterone (DHT) in men via inhibiting the enzyme responsible for the biosynthesis of DHT. The maximum effect of a rapid reduction in serum DHT concentration is expected to be observed 8 hours following administration of the first dose. In a single man receiving a single oral dose of 5 mg finasteride for up to 4 years, there was a reduction in the serum DHT concentrations by approximately 70% and the median circulating level of testosterone increased by approximately 10-20% within the physiologic range. In a double-blind, placebo-controlled study, finasteride reduced intraprostatic DHT level by 91.4% but finasteride is not expected to decrease the DHT levels to castrate levels since circulating testosterone is also converted to DHT by the type 1 isoenzyme expressed in other tissues. It is expected that DHT levels return to normal within 14 days upon discontinuation of the drug. In a study of male patients with benign prostatic hyperplasia prior to prostatectomy, the treatment with finasteride resulted in an approximate 80% lower DHT content was measured in prostatic tissue removed at surgery compared to placebo. While finasteride reduces the size of the prostate gland by 20%, this may not correlate well with improvement in symptoms. The effects of finasteride are reported to be more pronounced in male patients with enlarged prostates (>25 mL) who are at the greatest risk of disease progression.

In phase III clinical studies, oral administration of finasteride in male patients with male pattern hair loss promoted hair growth and prevented further hair loss by 66% and 83% of the subjects, respectively, which lasted during two years' treatment. The incidences of these effects in treatment groups were significantly higher than that of the group receiving a placebo. Following finasteride administration, the levels of DHT in the scalp skin was shown to be reduced by more than 60%, indicating that the DHT found in scalp is derived from both local DHT production and circulating DHT. The effect of finasteride on scalp DHT is likely seen because of its effect on both local follicular DHT levels as well as serum DHT levels.. There is evidence from early clinical observations and controlled studies that finasteride may reduce bleeding of prostatic origin.

Trade Name Finasteride
Availability Prescription only
Generic Finasteride
Finasteride Other Names Finasterida, Finasteride, Finasteridum
Related Drugs tamsulosin, estradiol, Flomax, prazosin, tadalafil, doxazosin, Cialis, testosterone, norethindrone, medroxyprogesterone
Weight 1mg, 5mg,
Type Oral Tablet, Tablet
Formula C23H36N2O2
Weight Average: 372.5441
Monoisotopic: 372.277678406
Protein binding

Approximately 90% of circulating finasteride is bound to plasma proteins.

Groups Approved
Therapeutic Class BPH/ Urinary retention/ Urinary incontinence
Manufacturer Mylan, Combiphar
Available Country United Kingdom, United States, Indonesia, Netherlands, Switzerland
Last Updated: September 19, 2023 at 7:00 am


Finasteride is used for the treatment and control of benign prostatic hyperplasia (BPH)-

  • To cause regression of the enlarged prostate
  • To improve urinary flow
  • To improve the symptoms associated with BPH.

Finasteride is also used to associated treatment for these conditions: Androgenetic Alopecia, Benign Prostatic Hyperplasia (BPH), Idiopathic Hirsutism, Symptomatic Benign Prostatic Hyperplasia

How Finasteride works

Finasteride acts as a competitive and specific inhibitor of Type II 5α-reductase, a nuclear-bound steroid intracellular enzyme primarily located in the prostatic stromal cell that converts the androgen testosterone into the more active metabolite, 5α-dihydrotestosterone (DHT). DHT is considered to be the primary androgen playing a role in the development and enlargement of the prostate gland. It serves as the hormonal mediator for the hyperplasia upon accumulation within the prostate gland. DHT displays a higher affinity towards androgen receptors in the prostate gland compared to testosterone and by acting on the androgen receptors, DHT modulates genes that are responsible for cell proliferation. Responsible for the production of DHT together with type I 5α-reductase, the type II 5α-reductase isozyme is primarily found in the prostate, seminal vesicles, epididymides, and hair follicles as well as liver. Although finasteride is 100-fold more selective for type II 5α-reductase than for the type I isoenzyme, chronic treatment with this drug may have some effect on type I 5α-reductase, which is predominantly expressed in sebaceous glands of most regions of skin, including the scalp, and liver. It is proposed that the type I 5α-reductase and type II 5α-reductase is responsible for the production of one-third and two-thirds of circulating DHT, respectively.

The mechanism of action of Finasteride is based on its preferential inhibition of Type II 5α-reductase through the formation of a stable complex with the enzyme in vitro and in vivo. Finasteride works selectively, where it preferentially displays a 100-fold selectivity for the human Type II 5α-reductase over type I enzyme. Inhibition of Type II 5α-reductase blocks the peripheral conversion of testosterone to DHT, resulting in significant decreases in serum and tissue DHT concentrations, minimal to moderate increase in serum testosterone concentrations, and substantial increases in prostatic testosterone concentrations. As DHT appears to be the principal androgen responsible for stimulation of prostatic growth, a decrease in DHT concentrations will result in a decrease in prostatic volume (approximately 20-30% after 6-24 months of continued therapy). It is suggested that increased levels of DHT can lead to potentiated transcription of prostaglandin D2, which promotes the proliferation of prostate cancer cells. In men with androgenic alopecia, the mechanism of action has not been fully determined, but finasteride has shown to decrease scalp DHT concentration to the levels found in the hairy scalp, reduce serum DHT, increase hair regrowth, and slow hair loss. Another study suggests that finasteride may work to reduce bleeding of prostatic origin by inhibiting vascular endothelial growth factor (VEGF) in the prostate, leading to atrophy and programmed cell death. This may bestow the drug therapeutic benefits in patients idiopathic prostatic bleeding, bleeding during anticoagulation, or bleeding after instrumentation.


Finasteride dosage

The recommended dosage is one 5 mg tablet daily. Although early improvement may be seen, treatment for at least six months may be necessary to assess whether a beneficial response has been achieved. Thereafter, treatment should be continued.

Side Effects

Finasteride is well tolerated. In clinical studies, the following adverse experiences have been reported as possibly drug related in 1% of patients treated for 12 months with 5 mg Finasteride daily: impotence (3.7%), decreased libido (3.3%), and decreased volume of ejaculate (2.8%).



Oral LD50 is about 418 mg/kg in rats and there have been cases of lethality in rats receiving a single oral dose of 400 mg/kg in males and 1000 mg/kg in females.

Nonclinical toxicology

In a 24-month rat study, there were no signs of the tumorigenic potential of finasteride. In a 19-month carcinogenicity study in CD-1 mice, high doses of finasteride, at 1824 times the human exposure (250 mg/kg/day), resulted in an increase in the incidence of testicular Leydig cell adenomas and an increase in serum LH levels. In vitro mutagenesis assays demonstrated no evidence of mutagenicity. In an in vitro chromosome aberration assay, using Chinese hamster ovary cells, there was a slight increase in chromosome aberrations with much higher doses of finasteride.


There were no reported significant adverse events in clinical trials of male patients receiving single oral doses of finasteride up to 400 mg and multiple doses of finasteride up to 80 mg/day for three months. As there have been no cases of overdose or clinically significant toxicity with finasteride, there are no specific recommendations in case of an overdose.

Significant adverse events

Common reproductive adverse events seen with finasteride therapy include erectile dysfunction, ejaculatory dysfunction, and loss of libido. These adverse events tend to disappear after discontinuation or chronic use of the drug. Only causal adverse event occurring at the male reproductive system that is caused by finasteride is decreased ejaculatory volume because of the predominant action of DHT on the prostate.

Special populations

Finasteride can be safely used in elderly patients or those with renal impairment with no specific dosing adjustment recommendations. Finasteride is indicated for male patients only, and it is advised that exposure to finasteride is avoided in pregnant women carrying male fetuses as it may lead to abnormal development of external genitalia in male fetuses.


General: Since the beneficial response to Finasteride may not be manifested immediately, patients with large residual urine volume and/or severely diminished urinary flow should be carefully monitored for obstructive uropathy.

Prostate cancer: Digital rectal examination, as well as, other evaluations for prostate cancer, should be performed on patients with BPH prior to initiating therapy with Finasteride and periodically thereafter. Finasteride causes a decrease in serum concentration of markers of prostatic cancer such as prostate specific antigen (PSA); therefore, reduction of serum levels of these markers in patients with BPH treated with Finasteride does not rule out concomitant prostate cancer. No clinical benefit has yet been demonstrated in patients with prostate cancer treated with Finasteride.


No clinically important drug interactions have been identified. Finasteride does not appear to significantly affect the cytochrome P450 linked drug metabolising enzyme system. Compounds which have been tested in man include Propranolol, Digoxin, Glibenclamide, Warfarin, Theophylline, and antipyrine.

Food Interaction

  • Take with or without food. The absorption is unaffected by food.

Finasteride Disease Interaction

Moderate: liver disease, urinary obstruction

Volume of Distribution

The volume of distribution is 76 L at steady state, ranging from 44 to 96 L. Finasteride has been shown to cross the blood brain barrier but does not appear to distribute preferentially to the CSF. It is not known whether finasteride is excreted in human milk.

Elimination Route

Finasteride is well absorbed following oral administration and displays a slow accumulation phase after multiple dosing.[lablel] In healthy male subjects receiving oral finasteride, the mean oral bioavailability was 65% for 1 mg finasteride and 63% for 5 mg finasteride, and the values ranged from 26 to 170% for 1 mg dose and from 34 to 108% for 5 mg dose, respectively. It is reported that food intake does not affect the oral bioavailability of the drug. The peak plasma concentrations (Cmax) averaged 37 ng/mL (range, 27-49 ng/mL) and was reached 1-2 hours post administration. The AUC(0-24 hr) was 53 ngxhr/mL (range, 20-154 ngxhr/mL). The plasma concentrations and AUC are reported to be higher in elderly male patients aged 70 years or older.

Half Life

In healthy young subjects receiving finasteride, the mean elimination half-life in plasma was 6 hours ranging from 3 to 16 hours. In elderly patients over the age of 70 years, the half-life is prolonged to 8 hours.


In healthy young subjects (n=15), the mean plasma clearance of finasteride was 165 mL/min with the range between 70 and 279 mL/min.

Elimination Route

In healthy subjects, about 32-46% of total oral dose of finasteride was excreted in the urine in the form of metabolites while about 51-64% of the dose was excreted in the feces. In patients with renal impairment, the extent of urinary excretion of finasteride is expected to be decreased while the fecal excretion is increased.

Pregnancy & Breastfeeding use

Finasteride is contra-indicated in women who are or may become pregnant. Finasteride is not indicated for use in women. It is not known whether finasteride is excreted in human milk.

Exposure to finasteride- risk to male fetus: Crushed or broken Finasteride Tablets should not be handled by women who are or may become pregnant because of the possibility of absorption of finasteride and the subsequent potential risk to a male fetus. Similarly, small amounts of finasteride have been recovered from the semen in subjects receiving Finasteride 5 mg/day. It is not known whether a male fetus may be adversely affected if his mother is exposed to the semen of a patient being treated with finasteride. Therefore, when the patients sexual partner is or may become pregnant, the patient should either avoid exposure of his partner to semen (e.g. by use of a condom) or discontinue Finasteride.


Hypersensitivity to any component of this medication. Finasteride use is also contraindicated in women and paediatric patient

Special Warning

Renal insufficiency: Dosage adjustments are not necessary in patients with renal insufficiency since pharmacokinetic studies did not indicate any change in the disposition of Finasteride.

Hepatic insufficiency: There are no data available in patients with hepatic insufficiency.

Elderly: No dosage adjustment is required in elderly patients.

Storage Condition

Store at 20-25° C. Protect from light.

Innovators Monograph

You find simplified version here Finasteride

Finasteride contains Finasteride see full prescribing information from innovator Finasteride Monograph, Finasteride MSDS, Finasteride FDA label


What is Finasteride used for?

Finasteride is used to treat men with an enlarged prostate.

How safe Finasteride is?

Finasteride is generally safe to take for a long time. Many people take it for many months or even years without any problems.

what are the common side effects Finasteride?

The more common side effects that can occur with finasteride include:

  • decreased sex drive.
  • trouble getting or keeping an erection.
  • ejaculation disorder.
  • increase in breast size and tenderness.
  • skin rash.

Is Finasteride safe during pregnancy?

Women should not use this medicine. Women who are pregnant or may become pregnant should not handle crushed or broken tablets. Finasteride can be absorbed through the skin and cause birth defects in male babies

Can I take Finasteride while breastfeeding?

Finasteride is not indicated for use in females, and no data are available on its transfer into human milk.

Can I drink alcohol with Finasteride?

You can drink alcohol with Finasteride.

When should take I Finasteride?

There is no best time of day to taking Finasteride. But you should try to take Finasteride at the same time every single day to maximize its effectiveness. You pick the time morning, noon, or night just make sure you stick with it.

Can Finasteride work forever?

Finasteride does not work forever, and if you stop taking Finasteride, the natural balding process will resume.

Does Finasteride cause weight gain?

Weight gain is not a known side effect of Finasteride.

Can I take Finasteride everyday?

Some patients will half dose Finasteride and take a dose every other day to decrease chance of side effects.

Can I take Finasteride for a long time?

Finasteride is generally safe to take for a long time. Many people take it for many months or even years without any problems.

How long can Finasteride be taken?

In general Finasteride can daily use for 3 months or more.

Is Finasteride worth taking?

Finasteride can slow down or stop hair loss from male pattern baldness, and even stimulate hair growth.

Does Finasteride build muscle?

Finasteride significantly increases muscle strength and BMD and reduces body fat without causing prostate enlargemen.

Does Finasteride affect sperm?

Finasteride daily does not affect spermatogenesis or semen production in young men.

Can Finasteride cause nerve damage?

Finasteride is a drug with side effects far more serious than the diseases it treats. Side effects may be irreversible and include persistent erectile dysfunction, depression, suicidal tendencies, loss of libido, anxiety, and other neurological issues.

Does Finasteride make me angry?

Finasteride had 4 times the risk of experiencing depression and anxiety, as well as an increased risk of reporting suicidal feelings.

Does Finasteride effect memory?

In some very rare circumstances, Finasteride has been linked to memory loss.

Does Finasteride affect heart?

Finasteride Improves Cardiac Function and Reduces Mortality in Heart Failure.
*** Taking medicines without doctor's advice can cause long-term problems.