Finasteride: Permanent Side Effects?

The drug has been linked to sexual and psychological issues that persist long after discontinuation. In some cases, finasteride might have permanent side effects.

By William Llewellyn

Finasteride is one of those “standard” ancillary drugs you find listed in every steroid-related website or book. It is used to combat steroid-related side effects – specifically the androgenic side effects that may be caused by excess DHT (dihydrotestosterone) levels. Finasteride targets the enzyme responsible for the metabolism of testosterone to DHT in the scalp and prostate. It is believed to help with issues like excess acne, prostate enlargement and hair loss.

But let’s face it – finasteride is far from the most popular ancillary drug. In my experience, it is not widely used at all. Steroid users tend to be much more concerned with estrogenic bloat and gynecomastia, than a little androgenic activity. It is starting to look like this disinterest may be a good thing. With some patients, the drug has been linked to sexual and psychological issues that persist long after discontinuation. In other words, in some cases finasteride might have permanent side effects. One paper may help us understand what exactly is going on here.1’

This report begins with a group of Italian researchers examining a series of patients that have reported persistent side effects from finasteride. Their complaints varied somewhat in number and severity, but included muscle stiffness, cramps, tremors, chronic fatigue, anxiety, low libido, erectile dysfunction and depression. The scientists decided to look at a large series of potentially affected steroids, both in blood and the cerebrospinal fluid. The results were matched against healthy controls. Researchers found a variety of disturbances. In cerebrospinal fluid, they noticed levels of progesterone and its metabolites dihydroprogesterone (DHP) and tetrahydroprogesterone (THP) were significantly lower in the previous finasteride users, while the precursor pregnenolone (PREG) was higher. There was also a significant decrease in dihydrotestosterone (DHT), as well as increases in testosterone and the DHT metabolite 3 alpha-diol. In blood, similar changes were observed, along with an increase in estradiol (the primary estrogen).

We know that the enzyme inhibitor finasteride produces substantial changes in basic steroid metabolism. That is what makes it useful medically (and off-label). The potential for lasting changes in steroid metabolism is relatively new, however, and is something that scientists are trying to better understand. The U.S. Food and Drug Administration (FDA) did announce changes to finasteride labeling back in 2012, addressing the potential for persistent sexual side effects. However, no steps were taken to remove the drug from market. The number of affected users is believed at this time to be very small. More research is definitely needed, especially considering the nature of hormonal changes and side effects. As with low testosterone due to aging, some men might be enduring seemingly less-than-extreme symptoms. If so, the issues can go underreported.

William Llewellyn is widely regarded as one of the world’s foremost authorities on the use of performance-enhancing substances. He is the author of the bestselling anabolic steroid reference guide ANABOLICS and CEO of Molecular Nutrition. William is an accomplished researcher/developer in the field of anabolic substances, and is also a longtime advocate for harm reduction and legislative change. He built the website, an extensive online database of information on anabolic steroids and other performance-enhancing drugs.


1. Caruso D, Abbiati F, et al. Patients treated for male pattern hair with finasteride show, after discontinuation of the drug, altered levels of neuroactive steroids in cerebrospinal fluid and plasma. J Steroid Biochem Mol Biol 2015;Feb;146:74-9. doi: 10.1016/j.jsbmb.2014.03.012. Epub, 2014 Apr 6.

2. More Rogues and Ninjas (Yes, Ninjas) Invade LegitScript Database.










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