What are 5-Alpha-Reductase Inhibitors (5-ARIs)?

From the Guidelines

5-Alpha-Reductase Inhibitors (5-ARIs) are a class of medications that play a crucial role in the treatment of benign prostatic hyperplasia (BPH) and male pattern baldness by inhibiting the enzyme 5-alpha reductase, which converts testosterone to dihydrotestosterone (DHT). The two main 5ARIs are finasteride and dutasteride, with finasteride being prescribed at 5 mg daily for BPH and 1 mg daily for male pattern baldness, while dutasteride is given at 0.5 mg daily for BPH 1. These medications work by reducing DHT levels, which can shrink the prostate and slow hair loss in men, with studies showing improvements in standardized symptom scores, such as the International Prostate Symptom Score (IPSS), superior to placebo 1. It's essential to note that 5ARIs may take 3-6 months to show noticeable effects, and potential side effects include decreased libido, erectile dysfunction, and a small increased risk of high-grade prostate cancer 1. Regular prostate-specific antigen (PSA) testing is recommended for men taking these medications, and patients should discuss potential benefits and risks with their healthcare provider, especially considering their individual health profile and treatment goals 1. Some key points to consider when prescribing 5ARIs include:

• The reduction of DHT in prostate tissues has been measured at approximately 80% with finasteride and 94% with dutasteride 1
• The ideal candidate for a 5-ARI regimen would be an individual who is concerned about the development of prostate cancer, has a higher-than-average risk of the disease, has urinary symptoms that may be relieved by finasteride, and is not sexually active 1
• Clinicians may consider 5-ARIs as a treatment option to reduce intraoperative bleeding and peri- or postoperative need for blood transfusion after transurethral resection of the prostate (TURP) or other surgical intervention for BPH 1

From the FDA Drug Label

Dutasteride capsules are a prescription medicine that contains dutasteride. Dutasteride capsules are used to treat the symptoms of benign prostatic hyperplasia (BPH) in men with an enlarged prostate Prostate growth is caused by a hormone in the blood called dihydrotestosterone (DHT). Dutasteride capsules lowers DHT production in the body, leading to shrinkage of the enlarged prostate in most men 5 alpha-reductase inhibitors may increase the risk of development of high-grade prostate cancer.

5-Alpha-Reductase Inhibitors (5-ARIs) are a class of drugs that inhibit the production of dihydrotestosterone (DHT), a hormone involved in the growth of the prostate.

• They are used to treat symptoms of benign prostatic hyperplasia (BPH) in men with an enlarged prostate.
• Dutasteride is an example of a 5-ARI, which works by lowering DHT production in the body, leading to shrinkage of the enlarged prostate in most men.
• 5-ARIs may increase the risk of development of high-grade prostate cancer 2, 2, 2.

From the Research

Definition and Mechanism of 5-Alpha-Reductase Inhibitors (5-ARIs)

• 5-Alpha-Reductase Inhibitors (5-ARIs) are a class of drugs that inhibit the conversion of testosterone to 5α-dihydrotestosterone (5α-DHT) 3, 4, 5, 6, 7
• They are commonly prescribed for the treatment of benign prostatic hyperplasia (BPH) and androgenetic alopecia (male pattern baldness) 3, 4, 6
• 5-ARIs work by blocking the action of the 5-alpha-reductase enzyme, which is responsible for converting testosterone to 5α-DHT 4, 5

Types of 5-ARIs

• Finasteride is a type 2 5-alpha-reductase inhibitor, which is primarily used to treat BPH and male pattern baldness 3, 4, 6
• Dutasteride is a dual inhibitor of type 1 and type 2 5-alpha-reductase, which is also used to treat BPH and male pattern baldness 3, 4, 6

Clinical Applications of 5-ARIs

• 5-ARIs have been shown to be effective in treating BPH and improving voiding symptoms, reducing the risk of urinary retention and the need for prostate surgery 6, 7
• They have also been used to treat male pattern baldness, with low-dose finasteride being effective in promoting hair growth 6
• 5-ARIs may also have a role in the prevention of prostate cancer, although the evidence is still emerging and the potential benefits and risks need to be carefully considered 6, 7

Potential Side Effects of 5-ARIs

• 5-ARIs have been associated with several potential side effects, including sexual dysfunction, infertility, mood disorders, gynecomastia, and high-grade prostate cancer 3, 5
• The risk of these side effects varies depending on the individual and the specific 5-ARI being used, and patients should be carefully monitored for any adverse effects 3, 5