How Often Does Topical Finasteride Need To Be Applied?
Most clinicians recommend using topical finasteride at least once daily. However, its minimum viable frequency of application depends on factors such as daily drug exposure and contact time with the scalp.
For those who can keep topical finasteride on their scalps for 10-12 hours (or longer), once-daily applications of low-dose topical finasteride might suffice. For those who can only keep topical finasteride on their scalps for 4-6 hour periods, twice-daily applications may be more helpful – or higher-dose topical finasteride.
After maximum drug saturation has occurred in the scalp (typically after ~30 days of daily applications), it is possible to reduce the frequency of use from once daily to five times weekly – and perhaps even lower – while still seeing hair parameter improvements. However, doing so with low-dose finasteride may come with a reduction in efficacy.
More explanations can be found below.
Finasteride: How Much Is Enough To Regrow Hair?
Clinical studies have demonstrated a steep, dose-dependent, logarithmic response curve for finasteride’s effects on DHT levels. In other words, a little finasteride reduces almost as much DHT as a lot of finasteride. See this chart:
Clinical studies also show that topical formulations of topical finasteride as low as 0.005% x 1 mL, applied twice daily, can improve hair parameters over 16-month periods.[1]https://www.tandfonline.com/doi/abs/10.3109/09546639709160517
That’s a total daily exposure volume of just 0.1mg daily – or one-tenth that of what is prescribed orally on a daily basis to treat androgenic alopecia (AGA). Needless to say, people with localized hair loss (i.e., just at temples and/or crown) may be able to switch to topical finasteride, reduce their drug exposure, and still see impressive hair growth-promoting effects.
Can Topical Finasteride Be Used Every Other Day?
While usage frequencies lower than once daily haven’t been clinically studied, it’s likely that topical finasteride would still be effective with less frequent dosing schedules.
Why? Because finasteride has a tissue dissociation timing of 4-5 days. In other words, it takes multiple days (and sometimes weeks) for finasteride bound to skin tissue to finally leave that skin tissue and enter the bloodstream, where it is later metabolized and excreted.
Moreover, clinical studies on 1 mg daily of oral finasteride suggest that after one year of use, switching to a 30-days-on, 30-days-off dosing schedule is just as effective as continuing with a once-daily dosing schedule – despite not using the drug for a total of 6 months throughout the same year.[2]https://jaad.org/retrieve/pii/S0190962220319289
For these reasons, finasteride can still have a therapeutic effect on DHT reduction in the scalp skin, even up to ~30 days after quitting the drug.
This is even reflected in withdrawal studies of oral finasteride, which show that blood levels of DHT can still take multiple weeks to rebound to baseline levels prior to starting the drug.[3]https://academic.oup.com/jcem/article/89/5/2179/2844345
The same pharmacokinetic relationships also apply to topical finasteride – provided that enough finasteride has saturated the scalp skin to match the levels of exposure in these oral finasteride withdrawal studies.
For a deeper dive into the pharmacokinetics supporting alternate doses and dosing schedules for finasteride, see these articles:
- How Often Should I Take Oral Finasteride?
- How Long Does Finasteride Stay In The Bloodstream?
- How Long Does Finasteride Remain In Scalp Tissues?
What About Scalp Contact Time?
In most cases, the longer a topical sits on the scalp skin, the better chance it has of absorbing into the skin, where it can positively impact hair follicles.
When it comes to topical finasteride, in vitro studies have measured skin absorption rates of the drug over a 24-hour period, and versus different topical formulations – such as finasteride paired with carrier ingredients such as ethosomes, alcohol, liposomes, or water.
The relationships change depending on the finasteride formulation. Just see this chart from the following study:[4]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2977015/
This chart suggests that absorption of topical finasteride is linear across time. In other words, the longer you leave in topical finasteride, the more of it will absorb into your scalp skin – with no diminishing returns over a 24-hour period.
Moreover, these results reveal that across the same time period, those using liposomal finasteride will absorb up to 30% less finasteride into the skin versus those using alcohol-based finasteride – and across the same time period.
This might explain why there are anecdotal reports of fewer side effects while on liposomal finasteride: less of it is getting into the scalp skin, and thereby less of it is leaching into the bloodstream and causing systemic effects. It causes fewer side effects, because it is perhaps less effective.
Additionally, liposomal finasteride users may need to let their topical sit for twice as long on the scalp to reach the same level of absorption as those using alcohol-based finasteride.
To illustrate this, look at the level of absorption for liposomal finasteride at 22 hours. It’s nearly the same as the level of absorption for hydroethanolic finasteride at 10 hours.
Finally, we also have (at least) three other variables at play that will affect finasteride absorption rates, and thereby the frequency at which we should apply topical finasteride on a daily or weekly basis:
- The total dilution of finasteride (i.e., 0.005%, 0.025%, 0.1%, etc.)
- The mL per application (i.e., 1 mL for those with localized hair loss, or 2 mL for those with diffuse hair loss)
- The application frequency (i.e., twice-daily, once-daily, once every-other-day, etc.)
For an example of how important these factors are, just see the results of this 2014 study exploring the effects of once- versus twice-daily dosing of topical finasteride on serum DHT levels:[5]https://pubmed.ncbi.nlm.nih.gov/25074865
As we can see from the following chart, a doubling of the daily dose had a dramatic effect on serum DHT reductions.
Which Factors Influence How Often We Can Use Topical Finasteride?
If it isn’t already obvious, it’s impossible to answer the question, “Can I use topical finasteride less than once-daily?” without more context.
Each of the variables we’ve mentioned is critically important, because minor differences in any variable can dramatically change your total weekly finasteride exposure, and thereby the actual effectiveness of the drug.
This is particularly important for those who are trying to build a topical finasteride application schedule that prevents inadvertent exposure to family members, or for those who are opting for topical finasteride to lower their risk of side effects.
So, here’s a recap of the five critical factors influencing how much topical finasteride will actually penetrate into the scalp skin:
- Topical Dilution (i.e., % finasteride). The higher the dilution, the less frequently you need to apply topical finasteride.
- Carrier Vehicles (i.e., liposomes, alcohol, etc.). Liposomal vehicles are significantly less effective versus alcohol.
- Application Dose (i.e., how many mL you apply each time). The higher the mL applied, the more drug exposure.
- Application Frequency (i.e., how often you apply). The more frequent the application, the more drug exposure.
- Scalp Contact Time (i.e., how many hours before washing out?). This is influenced by your % dilution and carrier vehicles.
Moreover, there’s a sixth factor that hasn’t yet gotten discussed: adjuvant treatments alongside topical finasteride.
If you’re combining topical finasteride with other ingredients or therapies that augment skin penetrability – i.e., retinoic acid, topical corticosteroids, or even microneedling – then you can expect more of the drug to penetrate the skin over the same time period.
That’s because these therapies wear down the stratum corneum (i.e. the outermost layer of skin), decrease the side of the epidermis, or create channels into the dermis for better drug penetration – all of which influence topical drug absorption.
What’s The Minimum Days Per Week I Can Apply Topical Finasteride?
To reiterate: the answer depends entirely on your topical dilution, carrier vehicles, application dose, how long you leave in that topical before washing it out, and your use of adjuvant therapies alongside topical finasteride.
Moreover, if someone isn’t experiencing side effects from finasteride, or if someone isn’t trying to limit other household members’ inadvertent exposure to the drug, then it doesn’t make much sense to adopt an alternate dosing schedule. It just introduces a level of complexity to your life that is, largely, unnecessary.
Nonetheless, if you are troubleshooting side effects, trying to limit a loved one’s inadvertent exposure to the drug, or simply traveling and wondering how long you can stop using topical finasteride before your hair starts falling out, you can lower your dosing frequency without necessarily hurting your hair gains.
The exact strategy will depend on why you’re doing this. For instance:
- If you’re troubleshooting side effects, you’ll likely want to lower your total weekly drug exposure. This is because total finasteride exposure is tied to side effect risks.
- If you don’t have any side effects, but you’re just trying to limit the amount of time you’re wearing topical finasteride around a partner, pregnant person, or family member – you may not want to lower your total weekly drug exposure. Instead, you may want to increase the dilution of your finasteride by a factor of 2x or more, but decrease the amount of time you wear in-the-house by washing it out more frequently, or only applying it on certain days of the week.
- If you don’t want to take topical finasteride with you on a vacation, chances are you can stop using it for 1-2 weeks (or more) without seeing much of a negative effect. After all, oral dosing studies showed that every-other-month daily doses were just as effective as every-month daily doses in the second year of use. Just make sure you reach scalp skin saturation points for finasteride before opting for this strategy – which you can likely achieve after ~30 days worth of applications.
Rob English is a researcher, medical editor, and the founder of perfecthairhealth.com. He acts as a peer reviewer for scholarly journals and has published five peer-reviewed papers on androgenic alopecia. He writes regularly about the science behind hair loss (and hair growth). Feel free to browse his long-form articles and publications throughout this site.