In general, finasteride is a safe and well-tolerated medication. However, for some individuals who experience side effects, these effects persist even after stopping the medication. This is is known as post-finasteride syndrome.
Currently, it's unclear how many people are affected by post-finasteride syndrome and what the clinical outcomes are. We also don't know definitively whether post-finasteride syndrome is a real thing. However, it's important to take reports of side effects seriously, irrespective of how long they last, because they can have a significant impact on quality of life.
What is post-finasteride syndrome?
Post-finasteride syndrome refers to long term sexual, neurological and/or physical side effects that persist even after stopping finasteride treatment. Although a strict diagnostic time frame has not yet been established, side effects that persist for more than 3 months after treatment discontinuation can be considered long term.
Side effects associated with post-finasteride syndrome include:
- Erectile dysfunction
- Lowered or non-existent sex drive
- Reduced sensitivity to sexual stimulation
- Ejaculatory changes or disorders
- Breast swelling and/or pain
- Chronic fatigue
- Muscle aches/spasms
- Memory problems, feeling 'sluggish'
- Depression, anxiety
- Trouble sleeping
- Suicidal ideation
These side effects can be alarming, but it's important to keep in mind that they are relatively uncommon within the general population and pattern hair loss is still a condition that can be treated safely and effectively.
Post-finasteride syndrome and effects on the brain
Examples of neurological symptoms reported by post-finasteride syndrome patients include depression, anxiety, fatigue, sluggishness and other mood changes. In a round up of studies, the incidence of depressive symptoms is consistently higher in finasteride users than those who have never been exposed to the medication (Traish, 2020).
The cause may be a decrease in hormones that have an effect on brain function. These hormones are called neuroactive steroids and have been studied in connection with mood changes in finasteride users (Diviccaro et al., 2020). Neuroactive steroids can't be produced without the 5-alpha reductase enzyme. When finasteride is taken orally, systemic exposure to the blocking action of the medication may also decrease levels of these key hormones that are involved in mood regulation.
But are these neurological side effects permanent? One study has shown that directly supplementing and boosting neuroactive steroid levels leads to an improvement in mood (Sripada et al., 2013). This seems to suggest that this aspect of post-finasteride syndrome may be reversible. But as we'll discuss later in this article, it's very difficult to directly attribute finasteride to depression (or even sexual side effects), as patients with pattern hair loss may be struggling with these health challenges even prior to starting treatment.
Post-finasteride syndrome and sexual side effects
Across studies of finasteride safety, sexual side effects are the most common category of side effect. Erectile dysfunction and reduced, or loss of sex drive (libido) are more frequently reported than ejaculatory changes and this holds true for patients with post-finasteride syndrome. In fact, the incidence of erectile dysfunction may be as high as 40% in this population (Traish, 2020).
Are any, or all of these sexual side effects permanent? When it comes to reversing erectile dysfunction, time seems to be key. One animal study showed that the severity of erectile dysfunction associated with 5-alpha reductase inhibitor use was partially dependent on the duration of treatment (Sung et al., 2019). Stopping the medication at the first signs of symptoms seemed to result in some degree of recovery of function.
Several years earlier, in 2008, a study was conducted on the effects of finasteride and dutasteride on sexual function in young men over a period of 52 weeks. Researchers found that participants experienced slight reductions in ejaculatory volume during treatment. However, these changes were usually temporary and did not have serious effects on sexual function or satisfaction overall (Amory et al., 2008).
It's a similar story for reduced, or loss of sex drive (libido). A 2016 study focused on identifying common characteristics of men who reported post-finasteride syndrome. Brain imaging studies of participants who were shown erotic imagery revealed abnormal activity in regions of the brain involved in sexual arousal and motivation.
However, despite noting this unusual response to erotic stimuli, researchers were not able to conclude whether finasteride actually caused this response. Additionally, the men in this study did not demonstrate any prior evidence of hormonal or enzyme abnormalities and once participants stopped taking finasteride, brain function seemed to return to normal (Basaria et al., 2016).
This data suggests that sexual side effects associated with finasteride use are typically self-limiting and might even improve over time. But for a small subset of former finasteride users, these side effects do not resolve. The reasons for this are complex and involve genetic, environmental and behavioural effects.
Is post-finasteride syndrome real?
The medical community is unsure if post-finasteride syndrome actually exists. As it stands, post-finasteride syndrome remains a controversial topic and there is a lack of conclusive data directly linking finasteride to permanent side effects. In the end, there does appear to be an element of individual risk and your doctor can help counsel you on this.
There is contradictory data on post-finasteride syndrome for a few reasons. Firstly, some studies have not been appropriately designed to capture side effect information. Secondly, volunteer bias may be present, or even a phenomenon known as the nocebo effect.
Volunteer bias, also known as self-selection bias, occurs when participants who agree to take part in a study have a special clinical status. An example of this is when participants are recruited from websites or forums that focus on the side effects of finasteride. These individuals already identify with symptoms.
Meanwhile, the nocebo effect applies when prior knowledge of possible side effects leads to a negative response to an otherwise safe or well-tolerated therapy.
This effect was observed in a 2007 study that examined the impact of counselling on sexual side effect rates in finasteride users (Mondaini et al., 2007). 43.6% of individuals who were counselled about possible risks went on to report symptoms, compared to only 15.3% of those who were not.
A different 2003 study comparing 5 mg oral finasteride daily to placebo for the treatment of benign prostatic hyperplasia found that among participants who withdrew after initial symptoms of sexual dysfunction, members of the placebo group actually reported more persistent side effects (Pereira & Coelho, 2020). So there is real reason to believe that knowledge of the potential risk of side effects could actually be driving side effect data.
One last thing. Individual predisposition to sexual or psychiatric disorders is also an important consideration when assessing the risk of developing post-finasteride syndrome.
A trial conducted in 2018 assessed the anxiety and depression risk of a group of finasteride users. They found that 55% of study participants had a pre-existing diagnosis of a mood disorder and 28% had a family history of mental illness (Ganzer & Jacobs, 2018). This is not an insignificant finding and reiterates the importance of informing your doctor about your full medical history.
What should I do if I think I have post-finasteride syndrome?
It's key that you let your doctor or another healthcare professional know that you're experiencing side effects. They can offer advice and recommendations including decreasing the dosage or taking you off the medication if needed. They'll also be able to refer you to a specialist that deals with your specific concerns.
In most cases, post-finasteride syndrome research has focused on oral finasteride. There is some data that supports the improved safety profile of topical finasteride, which is applied directly to scalp. If you're worried about long term side effects while on finasteride, connect with a doctor to see if this might be an option for you.