Understanding What Drugs are DHT Blockers and How They Work

October 13, 2025 •

4 min read

Dihydrotestosterone (DHT) is a potent androgen derived from testosterone and is the primary cause of androgenetic alopecia, or pattern hair loss, in genetically susceptible individuals. Understanding what drugs are DHT blockers and how they inhibit this hormone is crucial for anyone seeking effective treatment to prevent hair follicles from shrinking and promoting hair growth.

Quick Summary

This guide covers prescription and over-the-counter DHT blockers, including how they work to inhibit the hormone dihydrotestosterone and their common uses for treating hair loss.

Key Points

Prescription Medications: Finasteride (Propecia) and dutasteride (Avodart) are oral 5-alpha reductase inhibitors that significantly reduce systemic DHT levels.
Mechanism of Action: These drugs work by inhibiting the enzyme that converts testosterone into dihydrotestosterone (DHT), the hormone responsible for pattern hair loss.
Natural Alternatives: Supplements like saw palmetto and pumpkin seed oil offer a milder, less potent approach to blocking DHT, often included in over-the-counter hair care products.
Topical Options: Ketoconazole shampoo and compounded topical finasteride or dutasteride provide targeted action on the scalp to reduce DHT effects.
Potential Side Effects: The most common side effects of potent oral DHT blockers include sexual dysfunction and mood changes, which are rare but can occur.
Combined Therapy: DHT blockers can be used alongside other hair loss treatments like topical minoxidil to enhance overall results.

The Role of DHT in Hair Loss

Dihydrotestosterone, or DHT, is an androgen created when the enzyme 5-alpha reductase converts testosterone. In individuals with a genetic predisposition to androgenetic alopecia (pattern baldness), hair follicles on the scalp are sensitive to DHT. When DHT binds to receptors on these follicles, it causes them to gradually shrink in a process called miniaturization. This results in the production of thinner, weaker hairs until the follicle eventually stops producing hair altogether, leading to noticeable hair thinning and baldness.

DHT blockers are designed to counteract this process either by preventing the conversion of testosterone to DHT or by blocking DHT from binding to the hair follicle receptors. These treatments can slow or halt the progression of hair loss and, in some cases, promote regrowth.

Prescription-Strength DHT Blockers

For those with significant androgenetic alopecia, a healthcare provider may prescribe oral or topical DHT-blocking medications. These are the most potent and extensively studied options available.

Finasteride (Propecia, Proscar)

Finasteride is an oral prescription drug that acts as a 5-alpha reductase inhibitor. It primarily blocks the Type II form of the enzyme, which is most active in the scalp and prostate. By inhibiting this enzyme, finasteride significantly lowers the amount of DHT in the body, with studies showing a reduction of up to 70%. Finasteride is FDA-approved specifically for male pattern baldness at a 1mg dose (Propecia). A higher 5mg dose (Proscar) is used for treating benign prostatic hyperplasia (BPH).

How it works: Blocks the 5-alpha reductase enzyme to decrease DHT levels.
Effectiveness: Highly effective for slowing hair loss and promoting regrowth, with consistent use.
Side effects: Potential side effects, though rare, can include sexual dysfunction (decreased libido, erectile dysfunction), mood changes, and breast tenderness.

Dutasteride (Avodart)

Dutasteride is another powerful 5-alpha reductase inhibitor that blocks both Type I and Type II forms of the enzyme, resulting in an even greater reduction in DHT levels—over 90% in the blood. Although it is FDA-approved for treating BPH, it is often prescribed off-label for hair loss in men when finasteride is not sufficiently effective.

How it works: Provides stronger DHT inhibition than finasteride by targeting both enzyme types.
Effectiveness: Can be more effective than finasteride for some individuals, though it carries a higher risk of more intense side effects.
Side effects: Similar to finasteride, but with potentially a higher incidence of side effects like sexual dysfunction.

Spironolactone

This anti-androgen medication is commonly used to treat female pattern hair loss, particularly in women with high androgen levels. It works by blocking androgen receptors, which prevents DHT from binding to hair follicles. Spironolactone is prescribed off-label for this purpose and is considered a safer alternative for premenopausal women than finasteride.

Natural and Over-the-Counter Options

For those seeking alternatives to prescription drugs, several natural supplements and topical products with mild DHT-blocking properties are available.

Saw Palmetto

This herbal extract is derived from the fruit of the Serenoa repens palm tree and is one of the most popular natural DHT blockers. It is believed to inhibit 5-alpha reductase, though its effects are much milder than those of prescription medications. Saw palmetto is commonly available in oral supplements and is often included in shampoos and hair serums.

Pumpkin Seed Oil

Studies have shown promising results for pumpkin seed oil in promoting hair growth, likely due to its potential to inhibit 5-alpha reductase through phytosterols. A 2014 study on men with androgenetic alopecia showed a 40% increase in hair count after 24 weeks of taking pumpkin seed oil supplements.

Ketoconazole Shampoo

This antifungal medication, available in prescription (Nizoral 2%) and over-the-counter (Nizoral 1%) strengths, has been shown to possess mild anti-androgenic effects. It is not a strong DHT blocker on its own but can be a useful adjunctive therapy, especially for individuals with concurrent dandruff or scalp inflammation.

Other Natural Ingredients

Other ingredients commonly found in natural DHT-blocking supplements and topical products include green tea extract, stinging nettle root, and reishi mushroom. Their efficacy is generally considered less potent and less studied compared to finasteride and dutasteride.

Combining DHT Blockers with Other Treatments

For enhanced results, dermatologists may recommend combining a DHT blocker with other hair loss treatments. For example, Minoxidil (Rogaine) is a popular topical treatment that works differently from DHT blockers—it's a vasodilator that increases blood flow to hair follicles, stimulating growth. A combination of oral finasteride and topical minoxidil has been shown to be highly effective.

Comparing DHT Blockers


Feature	Finasteride (Propecia)	Dutasteride (Avodart)	Saw Palmetto	Ketoconazole Shampoo
Efficacy	High (FDA-approved for men)	Very High (Often used off-label)	Modest (Herbal supplement)	Mild (Adjunctive treatment)
Mechanism	Inhibits Type II 5α-reductase	Inhibits Type I & II 5α-reductase	Mildly inhibits 5α-reductase	Mildly anti-androgenic
Prescription?	Yes	Yes	No (OTC supplement)	OTC or Prescription
Oral/Topical	Oral (1mg), Topical available via compounding pharmacy	Oral (0.5mg), Topical available via compounding pharmacy	Oral/Topical	Topical (shampoo)
Side Effects	Sexual dysfunction, mood changes (rare)	Similar to finasteride, but potentially more intense	Generally mild; stomach upset (rare)	Skin irritation, dryness (local)

Conclusion

Understanding what drugs are DHT blockers and their respective mechanisms is the first step towards effectively managing androgenetic alopecia. While prescription options like finasteride and dutasteride offer the strongest and most reliable results, they also carry a greater risk of systemic side effects. Natural alternatives like saw palmetto and pumpkin seed oil can provide modest benefits with fewer side effects but are generally less potent. Topical treatments, such as ketoconazole shampoo, can also be used as supportive therapy. A consultation with a healthcare professional or dermatologist is recommended to determine the best approach based on your specific condition and health history.

For more information on DHT and hair loss, visit the National Institutes of Health website.

Frequently Asked Questions

The primary cause of pattern hair loss, or androgenetic alopecia, is the hormone dihydrotestosterone (DHT), which causes hair follicles in genetically susceptible individuals to shrink over time.

Yes, for the most effective oral DHT blockers like finasteride and dutasteride, you will need a prescription from a doctor. However, many natural supplements and topical shampoos containing mild DHT-blocking ingredients are available over-the-counter.

Potential side effects, though rare, can include sexual dysfunction, such as decreased libido and erectile dysfunction, as well as mood changes. Women may experience irregular periods or breast tenderness.

No, natural DHT blockers like saw palmetto are generally much less potent than prescription medications like finasteride and dutasteride. They may provide a mild benefit but are not a substitute for medical-grade treatment.

Some DHT blockers, like spironolactone, are used off-label for female pattern hair loss, particularly in postmenopausal women or those with hormonal imbalances. Finasteride and dutasteride are not typically recommended for women of childbearing age due to potential risks to a fetus.

It can take several months of consistent use to see noticeable results with DHT blockers. Initial improvements from prescription medications like finasteride typically appear within 3 to 6 months, with maximum benefits often taking up to a year or more.

No, minoxidil is not a DHT blocker. It works by increasing blood flow to the scalp and is often used in combination with DHT blockers for a more comprehensive treatment approach.