What are the Side Effects of Finasteride (Propecia)?

A picture of Accord brand Finasteride with 14 unblistered tablets in front of the box

Finasteride is a popular hair loss treatment for men and is one of the few drugs that has been approved for treating male pattern baldness. It is available as a branded version known as Propecia. Medical studies have shown finasteride to be effective in 83% of individuals that take it, either slowing down the balding process, or reversing it. But what are the side effects of finasteride?

Finasteride Side Effects

According to the Patient Information Leaflet, side effects of finasteride are:

  • Loss of sexual desire
  • Difficulty getting an erection
  • Decrease in the production of semen
  • Depression

These side effects are classified as ‘common’, which means that around 1%-10% of users may experience them. All drugs come with a risk of side effects and there appears to have been a lot of negative press surrounding the use of finasteride (Propecia).

We decided to look at the side effects in more detail.

Does Finasteride cause Erectile Dysfunction?

The use of finasteride has been associated with sexual dysfunction, such as loss of sex drive and erectile dysfunction. It is important to note that most studies looking at the side effects of finasteride include the higher dose of 5mg. This dose is used to treat BPH (benign Prostatic Hyperplasia), an enlarged prostate. It is also important to note that the condition BPH can cause erectile dysfunction and other sexual side effects.

A study published in the British Medical Journal researched the risk of erectile dysfunction over a  9-year period, in men taking both finasteride 1mg and 5mg. The conclusion was that there was no obvious link between erectile dysfunction and finasteride at either dose.

Another study that analysed sexual side effects of finasteride 1mg tablets, found that 4.4% of patients experience sexual side effects in comparison with 2.2% in the placebo group.

A study looking at the sexual side effects of finasteride 1mg tablets found that 75.7% of men experienced no sexual dysfunction, 21.6% experienced mild dysfunction and 2.7% reported sexual dysfunction. In non-finasteride users, sexual side effects were higher with 61.6% experiencing no sexual dysfunction, 26.3% experiencing mild dysfunction and 12.1% experiencing sexual dysfunction.

One study suggests that sexual side effects were higher in patients taking finasteride who had been informed about potential side effects. This was in comparison to a group of patients who were not informed of any sexual side effects before starting treatment. The psychological impact of knowing that a drug can potentially cause sexual side effects can also impact patients. This is known as the nocebo phenomenon, where negative expectations of a treatment can lead to side effects. This study suggests that the fear of developing sexual side effects can bring about or enhance these adverse effects.

Does finasteride cause depression?

There is limited research that has investigated mood changes in those taking finasteride 1mg tablets. Mood disturbances have been reported in a minority of individuals, but the scientific research around this area is limited. Similar to the sexual side effects, there are conflicting reports. Some reports and studies have shown that finasteride can cause erectile dysfunction, which may lead to a drop in mood. At the same time, some reports and studies have shown that finasteride does not affect mood at all.

Are Finasteride side effects permanent or reversible?

Most research shows that the side effects of finasteride are not permanent and reversed when treatment is stopped. Finasteride has a short half-life of around 7 hours and in theory, it will leave your body after one and a half days. However, finasteride accumulates in your system and it can take slightly longer. Because finasteride leaves your body relatively quickly, side effects should go away shortly after stopping treatment.

Can I take finasteride if my partner is trying to conceive?

If your partner is trying to get pregnant, there is no evidence that finasteride will make it harder to conceive, or that there is a risk of birth defects to the unborn child. There have been concerns previously, but evidence from scientific research has not been able to prove this. Pregnant women should not handle finasteride, as it can potentially cause harm to the development of sex organs of the foetus. Although the amount of finasteride in sperm is minimal and not considered to be harmful, you should use a barrier method such as a condom if your partner is pregnant or planning to get pregnant as a matter of caution.

Will Finasteride cause cancer?

There is an ongoing debate whether finasteride causes cancer or prevents it. A study conducted over 10 years found that finasteride reduces the risk of developing prostate cancer by 25%. However, during the trial, the incidence of developing ‘high-grade’ cancer was higher in the group that took finasteride. The argument for this is that finasteride shrinks the prostate, and sampling a smaller area increases the likelihood that the cancer sampled from a smaller area is likely to be more aggressive. Another argument for this is that finasteride improves sensitivity to the PSA test (the test that is used to detect prostate cancer). This can also have contributed to these findings.

However, a professor in urology from John Hopkins Medicine has argued that this study is flawed and finasteride hides the level of PSA (the markers that are used to detect prostate cancer). Therefore, it provides a false sense of security as PSA markers are lowered, but this does not reduce the risk of developing prostate cancer. Hiding these markers will not have a direct impact on preventing prostate cancer but make it undetectable at an early stage when it is curable.

Research in this area is conflicting but the consensus is that finasteride lowers the risk of developing prostate cancer and increases the risk of developing high-grade prostate cancer.

Verdict: Is Finasteride safe to take?

There are reports of some men experiencing side effects of finasteride that mainly relate to sexual dysfunction, such as loss of sex drive, ejaculation problems and erectile dysfunction. It is important to note that most of these studies are carried out using finasteride 5mg used for BPH and not with finasteride 1mg. Most of these studies do not look at data from before these men started taking finasteride; and reports in newspaper articles and blogs do not analyse important data such as BMI, age and pre-existing medical conditions, which can all play a part. Pre-treatment surveys are important in gathering accurate scientific data. As a man gets older, his sexual function decreases.

However, there are reports of sexual dysfunction and we must acknowledge that there are some studies that show finasteride does cause such side effects, albeit in a small number of cases. These effects are usually mild with large studies indicating that they do improve with time; and that they are reversible when treatment is stopped.

Many large studies have shown no link in the cases of prostate cancer when taking finasteride, but a possible rise in high-grade cancer. Some studies also suggest that finasteride lowers the risk of prostate cancer.

There is a lack of evidence to suggest a direct link between finasteride and depression, but some small studies suggest that there may be a correlation. For this reason, depression is listed as a warning on the patient information leaflet.

All medication, including over the counter remedies for minor ailments such as coughs and colds come with a risk of side effects. Most people will never read into the side effects of these medicines and will never have a problem. If they read the list of side effects, they may not want to take the medication. Finasteride is no different and many men take finasteride without any problems.

Finasteride side effects are uncommon, but it is important for users and potential users to have all the information, enabling them to make their own decision. Hair loss can have a negative psychological impact on many men and finasteride has helped to reverse and slow the balding process. If you are taking finasteride, or wishing to start, you should discuss any concerns relating to its use with your doctor or pharmacist. Ultimately, the patient should be provided with as much information and knowledge as possible, so that they are empowered to make their own decision about starting treatment with finasteride.

Sources

https://www.cancer.gov/news-events/cancer-currents-blog/2019/prostate-cancer-prevention-finasteride-parnes

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3481923/

https://academic.oup.com/jcem/article/101/12/4669/2765035

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