Proscar

The dosage of Finasteride is strictly dependent on the condition being treated. Patients must adhere to the specific dose prescribed by their healthcare provider to ensure safety and efficacy.

• For Androgenetic Alopecia (Male Pattern Hair Loss): The standard recommended dose is 1 mg taken orally once daily. Increasing the dose beyond 1 mg has not been shown to improve hair growth but may increase the risk of side effects. It generally takes three months or more of daily use before an improvement in hair growth or a reduction in hair loss is observed. Continued use is required to maintain results.
• For Benign Prostatic Hyperplasia (BPH): The standard recommended dose is 5 mg taken orally once daily. This dose may be administered as monotherapy or in combination with an alpha-blocker (such as doxazosin or tamsulosin). Patients may notice an improvement in urinary symptoms within a few weeks, but it may take up to six months of treatment to determine if a full clinical response has been achieved.

Finasteride is not approved for use in pediatric patients. The safety and effectiveness of Finasteride in children have not been established. Furthermore, because of its potent anti-androgenic effects, exposure to Finasteride in developing male children could lead to significant hormonal disruptions and abnormalities in the development of sex organs.

Renal Impairment

In patients with varying degrees of renal impairment (creatinine clearance as low as 9 mL/min), no adjustment in dosage is typically required. Studies have shown that the elimination of Finasteride is not significantly altered by kidney function, as a large portion of the drug is excreted via the fecal route.

Hepatic Impairment

Finasteride is extensively metabolized by the liver. While there are no specific quantitative guidelines for dose adjustment in patients with liver disease, caution should be exercised. Patients with significant hepatic impairment should be monitored closely by their healthcare provider, as the drug's half-life may be prolonged, leading to higher systemic exposure.

Elderly Patients

No dosage adjustment is necessary for elderly patients. While the rate of elimination is slightly decreased in men over 70 years of age, the clinical significance is minimal, and the standard 1 mg or 5 mg doses are generally well-tolerated in this population.

• Administration: Finasteride should be swallowed whole with a glass of water. It can be taken with or without food.
• Consistency: For the best results, take the medication at the same time every day to maintain a steady level of the drug in your bloodstream.
• Handling Precautions: Women who are pregnant or may become pregnant should not handle crushed or broken Finasteride tablets. The drug can be absorbed through the skin and may cause birth defects in a male fetus. If contact occurs, the area should be washed immediately with soap and water.
• Storage: Store the tablets at room temperature (59°F to 86°F or 15°C to 30°C), away from moisture, heat, and direct light. Keep the container tightly closed.

If you miss a dose of Finasteride, take it as soon as you remember. However, if it is almost time for your next scheduled dose, skip the missed dose and return to your regular dosing schedule. Do not take two doses at once to make up for a missed one. Regular daily adherence is key to the effectiveness of the treatment, especially for hair loss.

In clinical studies, single doses of Finasteride up to 400 mg and multiple doses up to 80 mg/day for three months did not result in significant adverse effects. However, if an overdose is suspected, contact a poison control center or seek emergency medical attention immediately. There is no specific antidote for Finasteride overdose; treatment is generally supportive and symptomatic.

> Important: Follow your healthcare provider's dosing instructions exactly. Do not adjust your dose or stop taking the medication without medical guidance, as symptoms of BPH may return or hair loss may resume.

While most men tolerate Finasteride well, a small percentage of users may experience side effects related to the drug's effect on hormone levels. The most frequently reported side effects involve sexual function:

• Decreased Libido: A reduction in sex drive or interest in sexual activity. This is often reported early in treatment and may resolve as the body adjusts to the medication.
• Erectile Dysfunction (ED): Difficulty achieving or maintaining an erection. Clinical trials for the 1 mg dose showed this occurred in about 1.3% of patients compared to 0.7% on placebo.
• Ejaculation Disorder: A decrease in the volume of ejaculate or changes in the consistency of semen. This is generally not harmful but can be distressing to some patients.

• Breast Tenderness or Enlargement (Gynecomastia): Some men may notice their breast tissue becoming sensitive or slightly larger. Any changes in breast tissue, including lumps or nipple discharge, should be reported to a doctor immediately.
• Skin Rash: Some patients may develop a mild allergic skin reaction or itching.
• Testicular Pain: A dull ache or discomfort in the testicles has been reported by a small number of users.

• Depression and Anxiety: There have been reports of mood changes, including feelings of sadness, hopelessness, or increased anxiety. In rare cases, suicidal ideation has been reported.
• Hypersensitivity Reactions: This includes swelling of the lips, tongue, or face (angioedema) and hives.
• Male Infertility: Some men have reported poor seminal quality or infertility while taking Finasteride. In many cases, these parameters improved after the medication was discontinued.

> Warning: Stop taking Finasteride and call your doctor immediately if you experience any of the following:

• Signs of a Severe Allergic Reaction: Difficulty breathing, swelling of the throat or face, or severe hives. This may indicate anaphylaxis, which is a medical emergency.
• Breast Changes: The discovery of a lump, persistent pain, or nipple discharge. While rare, male breast cancer has been reported in men taking Finasteride, though a definitive causal link has not been established.
• Severe Mood Changes: If you experience thoughts of self-harm or deep clinical depression, you must seek psychiatric or medical help immediately.

One of the most debated topics regarding Finasteride is the potential for Post-Finasteride Syndrome (PFS). This term is used to describe a constellation of sexual, physical, and neurological symptoms that persist even after the medication has been discontinued. While the medical community continues to study this phenomenon, some patients report long-term erectile dysfunction, loss of libido, and cognitive issues ("brain fog") lasting months or years after stopping the drug.

Additionally, long-term use of Finasteride for BPH has been associated with a decrease in Prostate-Specific Antigen (PSA) levels. While this is expected, it can mask the detection of prostate cancer. Healthcare providers must adjust PSA readings (typically doubling the value) when screening patients who have been on Finasteride for more than six months.

As of 2026, Finasteride does not carry an FDA Black Box Warning. However, the FDA has mandated updates to the professional labeling to include warnings about the risk of high-grade prostate cancer (based on the Prostate Cancer Prevention Trial) and the potential for persistent sexual side effects and suicidal ideation.

Report any unusual symptoms or persistent side effects to your healthcare provider. It is helpful to keep a log of when symptoms started and their severity to discuss during follow-up appointments.

Finasteride is a potent hormonal modulator. Before starting treatment, patients must be aware that it affects the entire body's androgen balance. It is not a "local" treatment for hair or the prostate; it systemicially reduces DHT. Patients should be screened for pre-existing liver disease and baseline PSA levels if they are in the age group where prostate cancer screening is appropriate.

No FDA black box warnings for Finasteride exist at this time. However, the FDA has issued safety communications regarding the potential for Finasteride to increase the risk of being diagnosed with high-grade prostate cancer. While Finasteride reduces the overall risk of low-grade prostate cancer, those who do develop cancer while on the drug may be more likely to have a more aggressive form.

• Pregnancy and Teratogenicity: This is the most critical warning. Finasteride is a potent teratogen (a substance that causes birth defects). It inhibits the development of male external genitalia in a male fetus. Pregnant women must not even handle crushed tablets. If a woman who is pregnant with a male fetus is exposed to Finasteride, the child may be born with ambiguous genitalia or other reproductive abnormalities.
• Prostate Cancer Screening: Finasteride causes a decrease in serum PSA levels by approximately 50% in men with BPH, even in the presence of prostate cancer. Any confirmed PSA increase while on Finasteride should be evaluated carefully, as it may signal the presence of prostate cancer despite the drug's suppressive effect.
• Hepatotoxicity: Because the drug is metabolized by the liver, those with impaired hepatic function may experience higher levels of the drug. While rare, any signs of jaundice (yellowing of the skin or eyes) should be reported.
• Psychological Effects: Patients and their families should be alert for changes in mood. There is an observed association between 5-alpha reductase inhibitors and an increased risk of depression and, in rare instances, suicidal thoughts.

• PSA Monitoring: For men taking the 5 mg dose for BPH, a baseline PSA should be established before starting therapy. Periodic PSA tests are recommended thereafter. A new 'baseline' is typically established after 6 months of treatment.
• Digital Rectal Exam (DRE): Regular prostate exams are recommended for men over 50 (or younger if at high risk) to monitor for prostate changes independently of PSA levels.
• Liver Function: While not routinely required for all patients, those with known liver issues may require periodic liver enzyme tests.

Finasteride is not known to cause drowsiness or significant impairment of motor skills. Most patients can drive and operate machinery safely while taking this medication. However, if you experience dizziness or mood changes, evaluate your reaction to the drug before engaging in potentially dangerous activities.

There are no known direct interactions between Finasteride and alcohol. However, excessive alcohol consumption can exacerbate some of the side effects of Finasteride, such as erectile dysfunction or mood disturbances. Moderation is advised.

There is no physical "withdrawal syndrome" associated with stopping Finasteride, and tapering the dose is generally not required. However, the therapeutic benefits will cease upon discontinuation. For hair loss, any hair gained or preserved will likely be lost within 6 to 12 months of stopping the drug. For BPH, urinary symptoms may gradually return as DHT levels rise and the prostate regrows.

> Important: Discuss all your medical conditions, especially any history of liver disease or prostate issues, with your healthcare provider before starting Finasteride.

There are currently no drugs that are strictly contraindicated for use with Finasteride due to direct chemical incompatibility. However, the use of Finasteride with other 5-alpha reductase inhibitors (such as dutasteride) is not recommended, as it increases the risk of side effects without providing additional therapeutic benefit.

• Potent CYP3A4 Inhibitors: Drugs such as ketoconazole, itraconazole, clarithromycin, and certain HIV protease inhibitors (like ritonavir) can inhibit the enzyme responsible for breaking down Finasteride. This may lead to increased plasma concentrations of Finasteride, potentially increasing the risk of side effects. While a specific dose adjustment is not usually mandated, patients on these combinations should be monitored for increased adverse reactions.
• Potent CYP3A4 Inducers: Medications like rifampin, carbamazepine, and phenytoin can speed up the metabolism of Finasteride, potentially reducing its effectiveness. Healthcare providers may need to monitor the clinical response (e.g., hair growth or urinary flow) more closely.

• Alpha-Blockers: Finasteride is frequently used in combination with alpha-blockers (e.g., tamsulosin, doxazosin) for the treatment of BPH. While this is a common and effective therapeutic strategy, the combination may slightly increase the risk of orthostatic hypotension (a drop in blood pressure when standing up) or dizziness in some patients.
• Testosterone Replacement Therapy (TRT): Taking testosterone supplements while taking Finasteride may be counterproductive. Since Finasteride works by blocking the conversion of testosterone to DHT, adding exogenous testosterone can overwhelm the enzyme inhibition or negate the drug's effects on the prostate and hair follicles.

• Grapefruit and Grapefruit Juice: Grapefruit is a known inhibitor of the CYP3A4 enzyme. Consuming large amounts of grapefruit while taking Finasteride could theoretically increase the drug's levels in the blood. While not as significant as with other medications (like statins), it is best to consume grapefruit in moderation.
• General Diet: There are no restrictions on dairy, caffeine, or high-fat meals. Finasteride can be taken with any type of food.

• Saw Palmetto: This herbal supplement is often used for prostate health and is believed to have mild 5-alpha reductase inhibitory properties. Taking Saw Palmetto with Finasteride may increase the risk of side effects without clear evidence of added benefit.
• St. John's Wort: This herb is a potent inducer of CYP3A4 and may reduce the blood levels and efficacy of Finasteride.

• Prostate-Specific Antigen (PSA): This is the most significant interaction. Finasteride reduces PSA levels by about 50%. To interpret a PSA test result for a patient who has been taking Finasteride for 6 months or longer, the PSA value should be doubled for comparison with normal ranges in untreated men. Failure to do this can lead to a failure to detect prostate cancer.

For each major interaction, the mechanism typically involves the Cytochrome P450 system. Management strategies usually involve monitoring for clinical efficacy or increased side effects rather than immediate discontinuation.

> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking, including over-the-counter vitamins and minerals.

Conditions where Finasteride must NEVER be used include:

• Pregnancy: Finasteride is classified as FDA Pregnancy Category X. It is known to cause abnormalities in the external genitalia of male fetuses. This contraindication applies not only to the ingestion of the drug but also to the handling of crushed or broken tablets by pregnant women.
• Hypersensitivity: Anyone with a known severe allergic reaction to Finasteride or any of the inactive ingredients in the tablet (such as lactose, microcrystalline cellulose, or magnesium stearate) must not take the medication.
• Pediatric Patients: Finasteride is not indicated for use in children. The hormonal impact on a developing child could be severe and irreversible.
• Women of Childbearing Potential: Because of the risk to a potential fetus, Finasteride is generally not prescribed to women who are or could become pregnant.

Conditions requiring a careful risk-benefit analysis by a physician:

• Liver Disease: Since the liver is the primary site of metabolism, patients with significant hepatic impairment (e.g., cirrhosis, hepatitis) may require closer monitoring or may be advised against the drug if their liver cannot clear it effectively.
• Existing Prostate Cancer: While Finasteride is used to treat BPH, it is not a treatment for prostate cancer. In fact, it may complicate the monitoring of the disease. A thorough screening for cancer should be performed before starting the drug.
• Pre-existing Depression: Given the reports of mood changes associated with 5-ARIs, patients with a history of major depressive disorder or suicidal ideation should be monitored very closely, and alternative treatments should be considered.

There is a potential for cross-sensitivity between Finasteride and other 5-alpha reductase inhibitors, such as Dutasteride (Avodart). If a patient has had a severe allergic reaction to one drug in this class, they should generally avoid all others in the same class unless specifically directed by an allergist or specialist.

> Important: Your healthcare provider will evaluate your complete medical history, including any history of bladder muscle problems or urinary obstructions, before prescribing Finasteride.

Finasteride is strictly contraindicated in women who are pregnant or may become pregnant. In animal studies, administration of Finasteride during pregnancy resulted in the feminization of male offspring. In humans, the inhibition of Type II 5-alpha reductase prevents the conversion of testosterone to DHT, which is essential for the development of male sex organs between the 7th and 12th weeks of gestation. Exposure during this window can lead to hypospadias (the opening of the urethra is not at the tip of the penis) and other malformations. Even the small amount of Finasteride found in the semen of men taking the drug is generally considered below the level that would pose a risk to a partner, but some doctors recommend using a condom if the partner is pregnant.

It is not known whether Finasteride is excreted in human milk. However, because Finasteride is not indicated for use in women, and because of the potential for serious adverse reactions in nursing infants, its use during breastfeeding is not recommended.

Finasteride is not indicated for use in the pediatric population. Androgens are vital for normal growth and pubertal development in boys. Artificially suppressing DHT in a growing child could lead to stunted growth, delayed puberty, and abnormalities in reproductive development.

Clinical studies have shown that Finasteride is effective and generally well-tolerated in men over the age of 65. While the half-life of the drug is slightly longer in older men, no dose adjustment is required. Healthcare providers should be mindful of polypharmacy in the elderly, as older patients are more likely to be taking multiple medications that could interact with the CYP3A4 system.

In patients with chronic renal insufficiency, the pharmacokinetics of Finasteride are not significantly altered. Studies in patients with creatinine clearance ranging from 9 to 55 mL/min showed that the disposition of a single dose of 14C-finasteride was similar to that in healthy volunteers. No dosage adjustment is necessary for patients with kidney disease, including those on dialysis.

Caution should be exercised in patients with hepatic impairment. The liver is the primary organ for Finasteride metabolism. In patients with Child-Pugh Class A, B, or C liver disease, the drug's clearance may be reduced, leading to higher systemic levels. There are no established dose-reduction protocols, so treatment should be based on a careful clinical assessment of the patient's liver enzymes and overall health.

> Important: Special populations require individualized medical assessment. Always inform your doctor if you have any underlying organ dysfunction or if you are planning a family.

Finasteride is a competitive and specific inhibitor of Type II 5-alpha reductase, an intracellular enzyme that converts the androgen testosterone into 5-alpha-dihydrotestosterone (DHT). Finasteride has no affinity for the androgen receptor and possesses no androgenic, anti-androgenic, estrogenic, anti-estrogenic, or progestational effects. Its action is purely enzymatic. By forming a stable complex with the enzyme, Finasteride prevents the conversion of testosterone, leading to a significant rapid decrease in serum and tissue DHT concentrations. In the prostate, this leads to apoptosis (programmed cell death) of epithelial cells and a reduction in gland size. In the scalp, it reverses the miniaturization process of hair follicles.

Following a single oral dose of Finasteride, a rapid decrease in serum DHT concentration is observed, with the maximum effect occurring within 24 hours. In men with BPH, daily 5 mg doses result in a ~70% reduction in serum DHT and an ~85% reduction in intraprostatic DHT. In men with hair loss, 1 mg daily doses reduce scalp DHT by approximately 60%. Importantly, while DHT levels drop significantly, circulating levels of testosterone and estradiol may increase by about 10-15%, though they typically stay within the normal physiological range.

| Parameter | Value |

|---|---|

| Bioavailability | 63% - 65% |

| Protein Binding | ~90% (to Albumin) |

| Half-life | 5 - 6 hours (up to 8 in elderly) |

| Tmax | 1 - 2 hours |

| Metabolism | Hepatic (CYP3A4) |

| Excretion | Fecal (57%), Renal (39% as metabolites) |

• Molecular Formula: C23H36N2O2
• Molecular Weight: 372.5 g/mol
• Solubility: Soluble in chloroform and lower alcohols; practically insoluble in water.
• Description: Finasteride is a white to off-white crystalline powder. It is a 4-azasteroid compound, characterized by the replacement of a carbon atom with a nitrogen atom at the 4-position of the steroid nucleus.

Finasteride is classified as a 5-alpha reductase inhibitor (5-ARI). It is specifically a Type II selective inhibitor. Other drugs in this class include Dutasteride, which is a dual inhibitor of both Type I and Type II 5-alpha reductase. Within the therapeutic area of urology, it is considered a urinary retention preventative and a prostate volume reducer.