Medically reviewed by Kristin Hall, FNP
Written by Our Editorial Team
Last updated 2/02/2021
Whether you’re noticing some thinning on your crown or seeing some receding hair line evidence in the front, you may be looking into finasteride as a possible solution for your problems. And if you’re here, you’re probably worried about its safety—not just its efficacy.
Finasteride is one of the most effective treatments for androgenic alopecia, also known as male pattern hair loss. Those effects have been proven in numerous tests over decades, but risks and side effects remain, even if they’re rare.
But that doesn’t mean you shouldn’t be careful to examine whether finasteride may have unintended interactions with prescriptions or other drugs you’re taking. In fact, you should be more careful, as the rare but possible complications and risks can be far more serious if you combine the wrong things.
To understand how finasteride might present some risks and side effects, let’s first discuss how hair loss happens, and what finasteride does about it.
Hair is a more complicated part of your body than you might realize. Each follicle has an independent life cycle of several years, and it can be broken into three phases: the anagen or growth phase, the catagen or pause phase, and the telogen or rest phase.
To keep it simple, the average person will have most of their hair in the anagen phase, and a little under 10 percent of your hair will be in this phase at any one time, unless something is going wrong.
So yes, a little hair in the sink or the hat is normal. Since there are more than 100,000 hairs on your head, losing as many as 100 a day isn’t really a reason to worry.
Hair loss happens when either the hair follicle stays in the telogen phase permanently, or the anagen phase is altered, producing a weaker or thinner hair.
There are different types of hair loss, but the most common is androgenetic alopecia, which is also known as male pattern baldness. And that occurs when the hair follicle stays in the telogen phase because hormones are preventing it from returning to the anagen phase.
Research shows that finasteride (also known as Propecia®) is proven to treat male pattern baldness by inhibiting an enzyme called 5 alpha reductase and reducing a key compound in the reduction of hair growth: dihydrotestosterone, also known as DHT.
DHT is a male androgen linked to balding, and though we don’t fully understand the mechanism behind how and why it works, we know that increased DHT levels are one of the primary causes of male pattern baldness.
Finasteride is an oral reductase inhibitor that is taken daily, and when Finasteride tablets are taken correctly it can reduce the amount of DHT by more than 90 percent.
It’s also considered overall very safe and effective to use, and can be used in conjunction with other treatments, including chemical and clinical therapies, lifestyle changes and alongside Minoxidil.
But it’s not without risks. Side effects and drug interactions can cause complications, so you should consult your healthcare provider before using finasteride and clarify what, if any, medications you’re taking that might cause problematic interactions.
Before we get into the bad news, it’s important to know that not all medication interactions are bad. In fact, some drugs can compound the positive effects of finasteride, including minoxidil, commonly known as Rogaine®.
Minoxidil is a topical solution, but isn’t a DHT blocker. Instead, it works by increasing blood flow to the parts of your body which need it most.
Because it doesn’t have the same mechanism of action as finasteride, using the two together can increase the effectiveness of both compounds in fighting and even potentially reversing the effects of hair loss.
The primary concern when using finasteride alongside other medications is accidentally causing unusually high concentrations of the drug in your blood, which can lead to more serious side effects.
However, per finasteride's FDA label, there are no major drug interactions associated with this drug.
That said, the best thing you can do is bring it up with your healthcare provider. Be honest with them about your medical history, as well as about what other medications you're currently taking.
They'll be able to decide whether or not finasteride is a good choice for you.
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When using finasteride, a small number of men may experience various sexual and other side effects.
These occurrences are rare, but they do happen. Finasteride has gotten a bit of a bad rap on occasion.
In 2012, the FDA issued a warning that it could increase the risk of sexual symptom appearances, but those effects are pretty rare.
We’ve written more extensively about the myths and facts about finasteride side effects, but here are a few key items that you should know:
In clinical studies of finasteride, less than two percent of finasteride users experienced erectile dysfunction, decrease in libido or an ejaculation disorder.
A slightly increased risk of high grade prostate cancer prostate cancer has been shown in some finasteride research, but that was at a dosage of 5mg, which is significantly higher than the Hims recommended dose of 1mg.
It’s also worth noting that a small number of men who take finasteride continue to experience some side effects even after cessation of treatment. This has been occasionally referred to as Post Finasteride Syndrome.
If you’re one of the few people who experience side effects as a result of taking finasteride, make sure that you contact your healthcare provider for further instructions.
Are you interested in starting a treatment program for male pattern baldness? If so, ask your healthcare provider about finasteride to see if it’s a good fit for you.
And ask your health care professional about combining finasteride with other hair loss treatments like minoxidil if you want an even stronger treatment plan against male pattern baldness.