Androgenetic or pattern hair loss is a common condition that causes gradual thinning in both men and women. It results from the activity of the hormone dihydrotestosterone (DHT) on genetically sensitive hair follicles. This shortens the growth phase and produces finer hair over time. Finasteride and dutasteride are two medicines that reduce DHT levels by blocking the 5-alpha-reductase enzyme. These two medicines have become increasingly useful in the treatment of pattern hair loss. Whilst oral formulations remain the standard, concerns over serious side effects have propelled topical preparations as an alternative way to target DHT production in the scalp whilst limiting systemic absorption. In this article, we’ll compare topical finasteride vs dutasteride in terms of their actions, effectiveness and safety.
Using DHT Blockers for Hair Loss
Oral finasteride 1 mg has regulatory approval for the treatment of male pattern hair loss in the UK and several countries. It selectively inhibits the type II 5-alpha-reductase enzyme, which is active in hair follicles and the prostate. Oral dutasteride 0.5 mg is licensed for treating benign prostatic hyperplasia (BPH) but not for hair loss. However, some clinicians prescribe oral dutasteride off-label for men who have an inadequate response to finasteride or for more advanced androgenetic alopecia. Neither oral finasteride nor dutasteride has MHRA approval for use in women. However, they are sometimes used off-label for hair loss in postmenopausal women under specialist supervision.
All topical formulations of finasteride and dutasteride are unlicensed prescription medicines in the UK and many other countries. They are available by prescription on an individual basis in compounded solutions, foams, serums or lotions by specialist pharmacies. These preparations differ in concentration, vehicle, and absorption characteristics. As such, their quality and consistency depend on the compounding process.
Why Use Topical Finasteride or Dutasteride?
Topical DHT blockers act directly within the scalp and hair follicles where 5-alpha-reductase is most active. The theoretical benefit lies in reducing DHT at the site of action while maintaining lower levels than with oral administration. They have become increasingly popular due to systemic side effects associated with oral DHT blockers such as sexual dysfunction, breast changes and severe mental health disturbances which can persist. As such some patients may prefer to try topical solutions to minimise these risks. Some doctors may also prefer topicals in order to avoid oral medication for long-term use or to limit cumulative drug exposure.
Use of topical finasteride and dutasteride is usually in formulations containing other hair growth ingredients like minoxidil. Whilst systemic absorption is lower than oral medications, you can still detect some blood levels of these DHT blockers. This means that topical use cannot completely eliminate the risk of side effects. Furthermore, these topical preparations are not standardised between pharmacies. Hence outcomes and tolerance may not be equivalent across different formulations.
Differences Between Topical Finasteride vs Dutasteride
Finasteride inhibits the type II 5-alpha-reductase enzyme, whereas dutasteride inhibits both type I and type II isoenzymes. Type I predominates in sebaceous glands and skin, whilst type II is mainly in hair follicles and the prostate. By blocking both, dutasteride produces a broader suppression of DHT production. This difference explains why oral dutasteride can reduce serum DHT by up to 90% vs about 70% for finasteride.
Topical formulations retain these enzyme actions but use lower concentrations aimed at producing high local effects and lower systemic actions. Research shows that topical finasteride 0.25% reduced scalp DHT by 60-70% and serum DHT by about 25% in men after one week of use. This confirms that there is a clear local effect but with partial systemic absorption. Participants had improvement in hair count over 24 weeks similar to oral finasteride and with fewer systemic side effects. Subsequent studies also show that topical dutasteride 0.02–0.1% can increase growth in men with androgenetic alopecia that may even match or surpass oral finasteride at 24 weeks.
The degree of DHT reduction within scalp tissue depends on the concentration, frequency and base vehicle of topical finasteride or dutasteride. Absorption can also vary due to formulation and scalp condition. The body of evidence for topical finasteride and dutasteride is growing but still limited compared with oral therapy. Direct studies comparing topical finasteride vs dutasteride are rare and sample sizes are small. There is also currently no published data showing any difference in long-term outcomes or relapse rates. Furthermore, there is a paucity of data on the effectiveness and safety of topical DHT blockers for hair loss in women (especially premenopausal).
Can You Use Topical Finasteride & Dutasteride Together?
Although some clinics and doctors may prescribe both finasteride and dutasteride in the same topical treatment, this is not common. The reason for this is they act on the same enzyme pathway with dutasteride providing greater DHT blocking. As such using both together offers no real benefit and only increases cumulative exposure as well as risk of side effects.
So, whilst combination therapy has shown some success in small case studies, the data is not robust and very sparse. As such, the two drugs are more often alternated rather than combined. A switch from finasteride to dutasteride may occur when response to finasteride plateaus or where broader enzyme blocking is necessary. This step should only be part of a careful treatment plan with strict monitoring. This is because both compounds can persist in the body for long periods. The longer half-life of dutasteride (approximately five weeks vs eight hours for finasteride) means washout times and overlap may require extra consideration or planning by your treating doctor.
Safety & Considerations
Topical 5-alpha-reductase inhibitors share the same mechanism of action and therefore the same potential adverse effects as oral therapy. However, the frequency and severity of side effects may differ. Potential risks of topical DHT blockers include:
- Local irritation, dryness or mild scaling are the most common side effects.
- Systemic effects such as reduced libido, erectile dysfunction, breast tenderness and mood changes.
- Both drugs are teratogenic and therefore pregnant individuals should not use or handle them.
- There is no established safety data for breastfeeding, paediatric or elderly populations.
Absorption varies widely between compounded preparations. Vehicle composition, concentration, and scalp integrity all influence systemic uptake. For this reason, we can’t assume that results and tolerability are equivalent between different formulations or people. This is why regular follow-up is essential for anyone using compounded versions to document efficacy, monitor for irritation or systemic symptoms. Additionally, dutasteride’s longer half-life potentially increases the risk of accumulation in the bloodstream and prolonging side effects compared with finasteride.
Combining With Other Non-Surgical Hair Loss Treatments
Hair loss responds best to treatments that act through a number of mechanisms to address its multi-factorial nature. This increases the chances of success as everyone responds differently. Topical DHT blockers are often combined with the following treatments:
- Topical or Oral Minoxidil: This stimulates hair follicle activity and prolongs the anagen growth phase.
- LLLT or Microneedling: These enhance follicular blood flow and may improve drug penetration.
- PRP Therapy: Delivers growth factors from your own blood to support follicle regeneration.
Topical finasteride and dutasteride provide the option of reducing DHT activity in the scalp whilst potentially reducing absorption into the bloodstream. Both drugs have shown meaningful effects on scalp DHT and hair density but neither is currently licensed for use in the UK. As such, they are only available as individually prescribed compounded formulations. Additionally, long-term data regarding safety and effectiveness remain limited. There is also not much research directly comparing topical finasteride vs dutasteride. However, data so far is promising and ongoing research should yield more information regarding their value and optimal use in hair loss.
We believe in a personalised approach to hair care which is why we offer custom topical hair loss and growth treatments for men and women through our online skin clinic. Our doctors provide hair growth treatments which may include actives such as Minoxidil, Finasteride, Dutasteride, Spironolactone, Melatonin, Caffeine and Tretinoin where appropriate for each and every patient. Start your virtual consultation and begin your journey to great hair today.
This article is intended for general informational purposes only and is not a substitute for medical advice, diagnosis or treatment. Always consult a qualified medical provider for any medical concerns or questions you might have.
