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.