Important: This page is general information, not medical advice. It does not recommend or prescribe any treatment. Always consult your doctor or pharmacist before starting, stopping or changing any medicine.
Quick facts
- Drug class
- 5-alpha Reductase Inhibitor [EPC], 5-alpha Reductase Inhibitors [MoA]
- How it is given
- oral
- Type
- human prescription drug
- RxNorm ID
- 200172
We do not publish dosing. How much of this medicine to take, how often, and for how long depends on your age, weight, kidney and liver function, other conditions and other medicines. That is a decision for the person who prescribes or dispenses it. Follow the directions on your own pack and ask your pharmacist if anything is unclear.
What it is used to treat
Finasteride tablets USP are indicated for the treatment of male pattern hair loss (androgenetic alopecia) in MEN ONLY. Efficacy in bitemporal recession has not been established. Finasteride tablets USP are not indicated for use in women. • Finasteride tablets USP are 5α-reductase inhibitors indicated for the treatment of male pattern hair loss (androgenetic alopecia) in MEN ONLY ( 1 ). • Finasteride tablets USP are not indicated for use in women ( 1 , 4 , 5.1 ).
About this medicine
Finasteride tablets USP, 1 mg contains finasteride as the active ingredient. Finasteride USP, a synthetic 4-azasteroid compound, is a specific inhibitor of steroid Type II 5α-reductase, an intracellular enzyme that converts the androgen testosterone in to 5α-dihydrotestosterone (DHT). Finasteride is 4-azaandrost-1-ene-17-carboxamide, N-(1,1-dimethylethyl)-3-oxo-, (5α, 17β)-. The empirical formula of finasteride is C 23 H 36 N 2 O 2 and its molecular weight is 372.55. Its structural formula is: Finasteride is a white crystalline powder with a melting point near 250° C. It is freely soluble in chloroform and in lower alcohol solvents but is practically insoluble in water. Finasteride tablets USP for oral administration are film-coated tablets that contain 1 mg of finasteride and the following inactive ingredients: lactose monohydrate, microcrystalline cellulose, pregelatinized starch, sodium starch glycolate, docusate sodium, magnesium stearate and opadry brown (hypromellose, iron oxide red, talc, titanium dioxide, yellow iron oxide). structure6
How it works
12.1 Mechanism of Action Finasteride is a competitive and specific inhibitor of Type II 5α-reductase, an intracellular enzyme that converts the androgen testosterone into DHT. Two distinct isozymes are found in mice, rats, monkeys, and humans: Type I and II. Each of these isozymes is differentially expressed in tissues and developmental stages. In humans, Type I 5α-reductase is predominant in the sebaceous glands of most regions of skin, including scalp, and liver. Type I 5α-reductase is responsible for approximately one-third of circulating DHT. The Type II 5α-reductase isozyme is primarily found in prostate, seminal vesicles, epididymides, and hair follicles as well as liver, and is responsible for two-thirds of circulating DHT. In humans, the mechanism of action of finasteride is based on its preferential inhibition of the Type II isozyme. Using native tissues (scalp and prostate), in vitro binding studies examining the potential of finasteride to inhibit either isozyme revealed a 100-fold selectivity for the human Type II 5α-reductase over Type I isozyme (IC 50 =500 and 4.2 nM for Type I and II, respectively). For both isozymes, the inhibition by finasteride is accompanied by reduction of the inhibitor to dihydrofinasteride and adduct formation with NADP+. The turnover for the enzyme complex is slow (t 1/2 approximately 30 days for the Type II enzyme complex and 14 days for the Type I complex). Inhibition of Type II 5α-reductase blocks the peripheral conversion of testosterone to DHT, resulting in significant decreases in serum and tissue DHT concentrations. In men with male pattern hair loss (androgenetic alopecia), the balding scalp contains miniaturized hair follicles and increased amounts of DHT compared with hairy scalp. Administration of finasteride decreases scalp and serum DHT concentrations in these men. The relative contributions of these reductions to the treatment effect of finasteride have not been defined. By this mechanism, finasteride appears to interrupt a key factor in the development of androgenetic alopecia in those patients genetically predisposed.
Who should not take it
Finasteride tablets USP are contraindicated in the following: • Pregnancy. Finasteride use is contraindicated in women when they are or may potentially be pregnant. Because of the ability of Type II 5α-reductase inhibitors to inhibit the conversion of testosterone to 5α-dihydrotestosterone (DHT), finasteride may cause abnormalities of the external genitalia of a male fetus of a pregnant woman who receives finasteride. If this drug is used during pregnancy, or if pregnancy occurs while taking this drug, the pregnant woman should be apprised of the potential hazard to the male fetus. [ See Warnings and Precautions (5.1) , Use in Specific Populations (8.1) , How Supplied/Storage and Handling (16) and Patient Counseling Information (17.1) .] In female rats, low doses of finasteride administered during pregnancy have produced abnormalities of the external genitalia in male offspring. • Hypersensitivity to any component of this medication. • Pregnancy ( 4 , 5.1 , 8.1 , 16 ). • Hypersensitivity to any components of this product ( 4 ).
Warnings and cautions
Finasteride tablets USP are not indicated for use in women or pediatric patients ( 5.1 , 5.4 ). • Women should not handle crushed or broken finasteride tablets USP when they are pregnant or may potentially be pregnant due to potential risk to a male fetus ( 5.1 , 8.1 , 16 ). • Finasteride tablets USP causes a decrease in serum PSA levels. Any confirmed increase in PSA while on finasteride tablets USP may signal the presence of prostate cancer and should be evaluated, even if those values are still within the normal range for men not taking a 5α-reductase inhibitor ( 5.2 ). • 5α-reductase inhibitors may increase the risk of high-grade prostate cancer ( 5.3 , 6.1 ). 5.1 Exposure of Women - Risk to Male Fetus Finasteride tablets USP are not indicated for use in women. Women should not handle crushed or broken finasteride tablets USP, when they are pregnant or may potentially be pregnant because of the possibility of absorption of finasteride and the subsequent potential risk to a male fetus. Finasteride tablets USP are coated and will prevent contact with the active ingredient during normal handling, provided that the tablets have not been broken or crushed. [S ee Indications and Usage (1) , Contraindications (4) , Use in Specific Populations (8.1) , How Supplied/Storage and Handling (16) and Patient Counseling Information (17.1) . ] 5.2 Effects on Prostate Specific Antigen (PSA) In clinical studies with finasteride tablets USP in men 18 to 41 years of age, the mean value of serum prostate specific antigen (PSA) decreased from 0.7 ng/mL at baseline to 0.5 ng/mL at Month 12. Further, in clinical studies with finasteride tablets USP 5 mg when used in older men who have benign prostatic hyperplasia (BPH), PSA levels are decreased by approximately 50%. Other studies with finasteride tablets USP 5 mg showed it may also cause decreases in serum PSA in the presence of prostate cancer. These findings should be taken into account for proper interpretation of serum PSA when evaluating men treated with finasteride. […]
Reported side effects
The most common adverse reactions, reported in ≥1% of patients treated with finasteride tablets USP and greater than in patients treated with placebo are: decreased libido, erectile dysfunction and ejaculation disorder ( 6.1 ). To report SUSPECTED ADVERSE REACTIONS, contact Hetero Labs Limited at 866-495-1995 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch . See 17 for PATIENT COUNSELING INFORMATION and FDA-approved patient labeling. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice. Clinical Studies for Finasteride Tablets USP 1 mg in the Treatment of Male Pattern Hair Loss In three controlled clinical trials for finasteride tablets USP of 12-month duration, 1.4% of patients taking finasteride tablets USP (n=945) were discontinued due to adverse experiences that were considered to be possibly, probably or definitely drug-related (1.6% for placebo; n=934). Clinical adverse experiences that were reported as possibly, probably or definitely drug-related in ≥1% of patients treated with finasteride tablets USP or placebo are presented in Table 1. TABLE 1 Drug-Related Adverse Experiences for Finasteride Tablets USP, 1 mg in Year 1 (%) MALE PATTERN HAIR LOSS Finasteride tablets USP N=945 Placebo N=934 Decreased Libido 1.8 1.3 Erectile Dysfunction 1.3 0.7 Ejaculation Disorder (Decreased Volume of Ejaculate) 1.2 (0.8) 0.7 (0.4) Discontinuation due to drug-related sexual adverse experiences 1.2 0.9 Integrated analysis of clinical adverse experiences showed that during treatment with finasteride tablets USP 36 (3.8%) of 945 men had reported one or more of these adverse experiences as compared to 20 (2.1%) of 934 men treated with placebo (p=0.04). Resolution occurred in men who discontinued therapy with finasteride tablets USP due to these side effects and in most of those who continued therapy. […]
Interactions with other medicines
7.1 Cytochrome P450-Linked Drug Metabolizing Enzyme System No drug interactions of clinical importance have been identified. Finasteride does not appear to affect the cytochrome P450-linked drug-metabolizing enzyme system. Compounds that have been tested in man include antipyrine, digoxin, propranolol, theophylline, and warfarin and no clinically meaningful interactions were found. 7.2 Other Concomitant Therapy Although specific interaction studies were not performed, finasteride doses of 1 mg or more were concomitantly used in clinical studies with acetaminophen, acetylsalicylic acid, α-blockers, analgesics, angiotensin-converting enzyme (ACE) inhibitors, anticonvulsants, benzodiazepines, beta blockers, calcium-channel blockers, cardiac nitrates, diuretics, H 2 antagonists, HMG-CoA reductase inhibitors, prostaglandin synthetase inhibitors (also referred to as NSAIDs), and quinolone anti-infectives without evidence of clinically significant adverse interactions.
Use in specific groups
8.1 Pregnancy Teratogenic Effects : Pregnancy Category X [ see Contraindications (4) ]. Finasteride tablets USP is contraindicated for use in women who are or may become pregnant. Finasteride tablets USP are Type II 5α-reductase inhibitor that prevents conversion of testosterone to 5α-dihydrotestosterone (DHT), a hormone necessary for normal development of male genitalia. In animal studies, finasteride caused abnormal development of external genitalia in male fetuses. If this drug is used during pregnancy, or if the patient becomes pregnant while taking this drug, the patient should be apprised of the potential hazard to the male fetus. Abnormal male genital development is an expected consequence when conversion of testosterone to 5α-dihydrotestosterone (DHT) is inhibited by 5α-reductase inhibitors. These outcomes are similar to those reported in male infants with genetic 5α-reductase deficiency. Women could be exposed to finasteride through contact with crushed or broken finasteride tablets or semen from a male partner taking finasteride tablets USP. With regard to finasteride exposure through the skin, finasteride tablets USP are coated and will prevent skin contact with finasteride during normal handling if the tablets have not been crushed or broken. Women who are pregnant or may become pregnant should not handle crushed or broken finasteride tablets USP because of possible exposure of a male fetus. If a pregnant woman comes in contact with crushed or broken finasteride tablets , the contact area should be washed immediately with soap and water. With regard to potential finasteride exposure through semen, a study has been conducted in men receiving finasteride tablets USP 1 mg/day that measured finasteride concentrations in semen [ see Clinical Pharmacology (12.3) ]. In an embryo-fetal development study, pregnant rats received finasteride during the period of major organogenesis (gestation days 6 to 17). […]
If too much is taken
In clinical studies, single doses of finasteride up to 400 mg and multiple doses of finasteride up to 80 mg/day for three months did not result in adverse reactions. Until further experience is obtained, no specific treatment for an overdose with finasteride can be recommended. Significant lethality was observed in male and female mice at single oral doses of 1500 mg/m 2 (500 mg/kg)and in female and male rats at single oral doses of 2360 mg/m 2 (400 mg/kg)and 5900 mg/m 2 (1000 mg/kg), respectively.
Before you take anything new
Tell your pharmacist or doctor about every medicine you take — including ones bought without a prescription, herbal products and supplements. Interactions are one of the most common avoidable causes of harm from medicines, and a pharmacist can check your full list in a couple of minutes.
This page is built from the openFDA record of the U.S. Food and Drug Administration's approved labelling for this product, effective 28 July 2017. Label text has been shortened and reformatted for readability; safety wording has not been altered in meaning. FDA labelling describes products approved in the United States — brand names, strengths, formulations and approved uses may differ in your country. Always read the leaflet that comes with your own pack. PocketsInfo is not affiliated with, and is not endorsed by, the FDA. Retrieved 2026-07-30.