Finasteride

Finasteride is a prescription-only active ingredient for the treatment of hereditary hair loss (androgenetic alopecia) in men. The medication was originally introduced by MSD under the brand name Propecia® and is now available as a generic from various manufacturers.

The active ingredient belongs to the group of 5-alpha reductase inhibitors. It specifically targets the hormonal mechanism responsible for hair loss and can stop hair loss and, in many men, reactivate hair growth.

Important to know: Finasteride is approved exclusively for men. The medication is not suitable for women and, particularly during pregnancy, can cause severe malformations in a male fetus.

The effect does not set in immediately – first results are usually visible after 3 to 6 months, the full effect after about 12 months.

To understand how finasteride works, you need to know the mechanism behind hereditary hair loss:

The background: The male sex hormone testosterone is converted in the body into dihydrotestosterone (DHT) by the enzyme 5-alpha reductase. DHT is a potent androgen that damages the hair follicles on the top of the head in genetically predisposed men. The follicles shrink, the hairs become thinner and eventually fall out.

How finasteride works: Finasteride inhibits the enzyme 5-alpha reductase (type II), thereby reducing the DHT concentration in the blood and in the scalp by about 70%. With less DHT, the hair follicles are spared:

• Hair loss is stopped in about 90% of users
• New hair growth appears in about 65% of users
• Hair quality improves – existing hair becomes stronger

Timeline: The effect builds up slowly. First visible results after 3-6 months, optimal effect after 12-24 months. If finasteride is stopped, hair loss returns within 12 months.

Finasteride is suitable for:

Men with androgenetic alopecia:

• Typical pattern: receding hairline at the temples and/or a thinning area on the top of the head
• Age: 18-41 years (study population), older men can also benefit
• Mild to moderate hair loss (best results)
• Also possible with advanced hair loss, but expectations should be adjusted

Particularly effective with:

• Early intervention – the earlier treatment begins, the better
• Hair loss mainly at the crown and back of the head
• Hair that is still present, even if thinned

Less suitable for:

• Completely bald areas (there are no follicles left to save there)
• Hair loss at the temples (lower effectiveness)
• Women (not approved, can cause malformations in a male fetus)
• Hair loss caused by scarring or disease

Combination therapy: Finasteride is often combined with minoxidil. The two active ingredients have different mechanisms and can complement each other.

For androgenetic alopecia:

• 1 mg per day – the only approved dosage for hair loss

Other dosages (not for hair loss):

• 5 mg is used to treat benign prostatic enlargement
• This higher dose is not necessary for hair loss and increases the risk of side effects

Duration of use:

• Long-term therapy required
• It must be taken continuously to maintain the effect
• If stopped, hair loss returns within 12 months
• After 5 years of use, studies continue to show good effectiveness

Pack sizes: Finasteride 1 mg is available in various pack sizes (28, 84, 98 tablets).

How to take:

• One tablet (1 mg) daily
• With or without food
• Take with a glass of water
• Preferably at the same time of day for consistent drug levels

Important notes:

• Do not split or chew the tablets
• Broken or crushed tablets should not be touched by women who are or could be pregnant (absorption of the active ingredient through the skin is possible)
• If you miss a dose: simply continue as normal the next day, do not take a double dose

Treatment duration and expectations:

• 3-6 months: First results may be visible, hair loss slows down
• 12 months: Full effect can be assessed, visibly thicker hair in many men
• Long term: Continuous use needed to maintain results

What you can expect:

• Hair loss stops in about 90% of men
• Visible regrowth in about 65%
• The effect is best at the crown and back of the head
• Usually a smaller effect at the receding temples

Absolute contraindications:

Women:

• Finasteride is approved only for men
• In pregnant women, it can cause severe malformations of the genitals of male fetuses
• Even skin contact with broken tablets should be avoided

Children and adolescents:

• Not for persons under 18 years of age

Hypersensitivity:

• Known allergy to finasteride or any of the other ingredients

Relative contraindications – special caution with:

Impaired liver function:

• Finasteride is broken down in the liver
• In severe liver disease, elimination may be delayed

Pre-existing mental health conditions:

• If prone to depression or anxiety, close monitoring is recommended
• Inform your doctor if psychological symptoms occur

Prostate cancer screening:

• Finasteride lowers the PSA level by about 50%
• This must be taken into account in prostate cancer screening
• Inform your doctor that you are taking finasteride

Uncommon side effects (0.1-1%):

• Decreased libido (sexual desire)
• Erectile dysfunction
• Ejaculation disorders (including decreased ejaculate volume)
• Depression

Side effects of unknown frequency:

• Hypersensitivity reactions such as skin rash, itching, hives and angioedema (swelling of the lips, tongue, throat and face)
• Anxiety, suicidal thoughts
• Palpitations
• Elevated liver enzymes
• Breast tenderness and enlargement
• Testicular pain, blood in the semen, infertility
• Male breast cancer

Post-finasteride syndrome: In rare cases, men report persistent sexual side effects even after stopping the medication. This "post-finasteride syndrome" is scientifically controversial and is still being researched. Its frequency is very low.

Important notes:

• Most sexual side effects disappear with continued therapy or after stopping
• If side effects persist or are distressing, treatment should be stopped
• Psychological changes (depression) should be taken seriously

Effect on laboratory tests:

• PSA level drops by approx. 50% – important to know for prostate cancer screening

Interactions: Finasteride has relatively few clinically relevant interactions:

No known significant interactions with:

• Blood pressure medications
• Cholesterol-lowering drugs
• Diabetes medications
• Pain relievers

Theoretical interactions:

• CYP3A4 inhibitors (ketoconazole, ritonavir): Could slow down the breakdown of finasteride, but not clinically relevant
• St. John's wort: Could speed up the breakdown, significance unclear

Special notes:

PSA test: Finasteride lowers the PSA level by about 50%. For prostate cancer screening, the doctor needs to know this in order to interpret the values correctly.

Blood donation: Men should not donate blood while taking finasteride and until one month after stopping, as the blood could theoretically be given to pregnant women.

Pregnant partners: If you wish to have children or your partner is pregnant: finasteride passes into the seminal fluid in small amounts. The risk to the fetus is considered very low, but should be discussed with the doctor.