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Drug Info

Learn finasteride side effects and how to avoid them

Cropped SingleCare logo By | May 18, 2020
Medically reviewed by Marissa Walsh, Pharm.D., BCPS-AQ ID

Finasteride is a steroid-like medication frequently prescribed to treat benign prostatic hyperplasia (enlarged prostate) and male pattern baldness. You’ll most likely find it in medicine cabinets and pharmacies as the brand names Proscar or Propecia, although a generic version is also available. 

The drug works by preventing the conversion of testosterone to dihydrotestosterone (DHT), which causes prostate gland growth and hair follicle shrinkage. It’s successful in decreasing prostate size for most patients and two-thirds of men taking it for hair loss report regrowth, according to Harvard. While certain finasteride studies have suggested female hair restoration as well, it’s not typically prescribed to women or children, especially pregnant women, as it can cause birth defects.

Simultaneously treating male pattern hair loss and BPH, two widespread concerns for men, makes finasteride seem like a male health superdrug. So is it? While it’s incredibly useful, finasteride isn’t perfect. Look beyond the surface-level benefits, and you’ll find various finasteride side effects, warnings, and drug interactions. Read on for an in-depth look at all three. 

Side effects of finasteride

Propecia and Proscar are generally well-tolerated, but they come with a whole range of potential side effects. Finasteride belongs to a drug class called 5-alpha reductase inhibitors, which affect hormone levels and reduce male hormone activity, occasionally causing reproductive side effects like:

  • Impotence/erectile dysfunction (reversed with discontinuation of medication)
  • Ejaculation disorder
  • Decreased volume of ejaculate
  • Reduced sperm count
  • Reduced sex drive

In addition to the side effects listed above, other common side effects reported with an incidence of approximately 1%-10% of patients taking the medication include:

  • Orthostatic hypotension (low blood pressure upon standing)
  • Dizziness
  • Headache
  • Weakness

Finally, less-common adverse effects, generally observed in less than 1%-2% of patients taking finasteride, include:

  • Runny nose
  • Skin rash
  • Low blood pressure
  • Testicular pain
  • Breast tenderness

Patients taking finasteride might also experience increased urination. However, in the treatment of BPH (which often restricts urination), this can represent a return to healthy urinary flow. 

Serious side effects of finasteride

Common finasteride side effects are enough to be an inconvenience, but they’re nothing out of the ordinary for prescription medications. In rare cases, however, more severe side effects can occur that require medical attention. These include:

  • Persistent erectile dysfunction: In a recent study, 1.4% of men who began 5-alpha reductase inhibitor treatment developed sexual dysfunction that persisted at least 90 days after ceasing the medication. It’s not permanent impotence like some media sources have reported, but it can affect day-to-day sex life during and after treatment. 
  • Infertility: To be clear, this isn’t life-long infertility. Some men may experience poor semen quality while taking finasteride, which typically improves after discontinuation of the medication.
  • Depression: Finasteride can cause alterations to the hippocampus, which processes emotional responses, leading to depressive states and suicidal thoughts. Stress and anxiety can also stem from potentially inhibited sexual function.
  • Increased risk of breast cancer: Certain studies have questioned a connection between finasteride therapy and male breast cancer, while others have found no correlation. Still, anyone taking the drug should be aware of cancer indicators like breast enlargement, swelling, pain, lumps, or nipple discharge, and visit a doctor if these side effects persist.
  • Higher risk of high-grade prostate cancer: According to a study by the New England Journal of Medicine, finasteride reduces the risk of low-grade prostate cancer, but can increase the risk of high-grade prostate cancer. Long-term outcomes revealed no difference in survival outcomes comparing patients receiving finasteride versus placebo, and presumed contributors to this finding is that finasteride actually improves the ability to detect this type of cancer. 
  • Allergic reaction: In rare cases, finasteride can cause a severe allergic reaction. Indicators like hives, difficulty breathing, and tongue or throat swelling warrant immediate medical attention.

Vision problems aren’t a typical finasteride side effect, although one study found a correlation. However, it was a fairly small sample size, so further testing might be necessary for confirmation. But this doesn’t mean it’s completely harmless to your vision. According to Dr. Yuna Rapaport, MD, MPH, the director of Manhattan Eye, “finasteride itself can cause subclinical damage to the retina and optic nerve, which may not affect your actual vision, but could be discovered on a special image.” Additionally, comparable prostate medications like Flomax can “affect the way the iris constricts and makes certain surgeries, particularly cataract surgery, more challenging.”

Dementia may be a concern, mainly because dihydrotestosterone affects cognitive function. The Journal of Neurological Sciences found higher risks of dementia during the first two years of 5-alpha reductase inhibitor therapy, but no increased risk after that.

After experiencing (or reading about) some of these side effects, some men will want to cut off their finasteride treatment. There aren’t any severe consequences or withdrawals after quitting finasteride cold turkey, but hair loss and prostate growth will likely resume unless another treatment takes its place.

Finasteride warnings

Generally, finasteride is a safe treatment option. That said, perhaps the biggest takeaway from all these side effects is that it’s not for everybody. According to the Propecia drug information from its manufacturer, Merck, and the FDA, finasteride “is not indicated for use in women or pediatric patients.” And this is especially true for pregnant women. The drug’s effect on unborn male children can be so detrimental that the FDA warns expecting mothers against even handling broken or crushed Propecia tablets. 

Anyone with pre-existing liver disease or liver function abnormality should exercise caution when using finasteride because it’s primarily metabolized in the liver. No specific dose adjustments are advised.

There are two standard finasteride dosages: 1 mg and 5 mg. When used for hair growth in patients with male pattern baldness or androgenetic alopecia, doctors typically prescribe 1 mg doses, while BPH patients often require 5 mg. Doses larger than 5 mg are not recommended. 

Although finasteride can treat hair loss, continued use is required to maintain its effects. A patient who begins finasteride treatment sees results, then stops, will see those results reverse. The 1 mg dose is safe for long-term use, but can also cause extended side effects. 

Finasteride interactions

Despite its side effects and warnings, finasteride hasn’t shown significant interactions with any other drugs in clinical trials. Still, there are common questions about taking certain common medications alongside Propecia or Proscar.

Patients who worry about finasteride’s propensity to cause erectile dysfunction (ED) and other reproductive disorders might wonder if they can take it simultaneously with Viagra, Cialis, or other ED drugs. The answer is yes. Not only can they be used together, but simultaneous use could help mitigate or prevent certain sexual side effects. 

But what about other hair growth treatments like Rogaine (minoxidil) or biotin? Yes, both of these are safe for simultaneous use with finasteride. Keep in mind, however, that Rogaine has its own set of side effects, which a patient might experience alongside finasteride side effects. 

Testosterone replacement treatment is also safe for use with finasteride in patients with low testosterone. 

And what about alcohol? Generally, alcohol and finasteride are a safe combination. However, certain studies show that daily, heavy drinking can increase the risk of high-grade prostate cancer, as does finasteride. So, using this drug with high daily alcohol consumption theoretically may compound the risk. 

How to avoid finasteride side effects

Unfortunately, side effects aren’t always avoidable. Sometimes, they just happen. Still, some measures and precautions can reduce the risk of finasteride side effects. 

The most basic precaution is to take the medication as prescribed by a healthcare professional. Patients can take it with or without food, but should only take one dose per day (any time of day). Typically, the drug’s effects aren’t visible for three months, after which consistent use is necessary for sustained benefits. 

Also, keep in mind that some side effects might only be temporary. “The side effects can diminish as you continue to take the medication, and they completely subside after you stop the medication,” according to Dr. Rapaport. So, patients experiencing adverse events can often stop them by ceasing the medication. There are some instances of sexual dysfunction that might persist longer before eventually tapering off. 

The bottom line is this: Do finasteride’s benefits outweigh the potential side effects? But the answer isn’t simple. It varies for each person, depending on their condition, medical history, priorities, and more. The best move for anyone considering a medication like Propecia or Proscar is to get medical advice from a doctor.