Man looking at pills.

5-Alpha Reductase Inhibitors for BPH

If your doctor has recommended a 5-alpha reductase inhibitor for your enlarged prostate, you may want to know more. We’ve got you covered! Learn about how these medications work.

All BPH Articles / BPH Treatment Options / 5-Alpha Reductase Inhibitors for BPH

What are 5-alpha reductase inhibitors?

Having trouble passing urine is one of the most prevalent symptoms of BPH. 5-alpha reductase inhibitors are a type of medication that helps reduce the size of your prostate by blocking the change of your body’s natural testosterone into a hormone called DHT.1,2 DHT is a male hormone like testosterone that builds up in the prostate and can increase its size.1,2 By blocking DHT, 5-alpha reductase inhibitors can stall the growth of the prostate and eventually cause it to shrink.1,2 This can help your urine to flow freely again and manage the symptoms of your enlarged prostate.1,2

Types of 5-alpha reductase inhibitors 

There are two 5-alpha reductase inhibitors usually prescribed for the treatment of BPH.1,2 Depending on your previous medical history and your specific symptoms, the doctor may prescribe one of these as a treatment for your BPH.3 The medications are: 

  • Finasteride (Proscar®)5
  • Dutasteride (Avodart®)6

These medications are usually prescribed to those patients who have a larger prostate volume (more than 30cc – it can be anywhere from the size of a Ping-Pong ball to a tennis ball).3,4 It’s also important to note that it can take a while to feel the effects of 5-alpha reductase inhibitors.1,2 While they reduce the levels of the DHT hormone, it may take anywhere from three to six months to see an improvement in urine flow.1,2

Other considerations and potential side effects 

A key thing to remember with 5-alpha reductase inhibitors is that it’s possible for your BPH symptoms to return if you stop taking these medications.1 
Another consideration is the potential side effects. As with any BPH treatment, these medications may also have certain side effects including: 

  • Trouble getting or keeping an erection (impotence)5,6
  • Decrease in sex drive5,6
  • Decreased volume of ejaculate5
  • Ejaculation disorders5,6
  • Breast disorders (painful or enlarged breasts)5,6

Choose relief 

There are other medications which can be prescribed in combination with 5-alpha reductase inhibitors such as alpha blockers or phosphodiesterase-5 inhibitors.3 Your doctor will decide if a single medication or a combination therapy is the best approach to manage your BPH. 
If medications do not work or if the potential side effects worry you, you can also speak with your doctor about minimally invasive treatment options. Rezūm™ Water Vapor Therapy treats the cause of BPH by removing prostate tissue, and provides lasting relief while preserving sexual function.7 And what’s more, it’s covered by Medicare and most private insurers.   
You can manage your BPH with medication, which you may need to take every day for the rest of your life. Or you can treat your BPH with one 10-minute procedure.7
Choose sustained BPH relief. Talk to your doctor about the benefits and risks associated with all treatment options.

*Most men experience symptom relief as soon as 2 weeks after the Rezum treatment, and maximum improvement may occur within 3 months. Patient responses can and do vary.

Most patients report relatively minor discomfort during the procedure. Potential risks associated with Rezūm Water Vapor Therapy include but are not limited to painful or frequent urination, blood in the urine or semen, decrease in ejaculatory volume, urinary tract infection (UTI), inability to urinate or completely empty the bladder, and urgent need to urinate. During healing, symptoms may continue or worsen. Most men require a catheter for several days post-procedure.7,8 A complete list of risk information can be found here.

Find a Doctor

Use our Doctor Finder to get in direct contact with urologists who specialize in using Rezūm Water Vapor Therapy to treat BPH. 

Man Leaving Public Bathroom

Are BPH symptoms bothering you?

If your symptoms aren’t going away with medications, then it may be time to consider other treatments.

Take the quiz

Read more about medications for BPH


  1. Benign Prostatic Hyperplasia (BPH). Urology Care Foundation. Accessed May 3, 2022.
  2. Your benign prostatic hyperplasia medication: When to consider a change. Harvard Health Publishing. Accessed April 25, 2022.
  3. Lerner LB, McVary, KT, Barry MJ, et al.: Management of lower urinary tract symptoms attributed to benign prostatic hyperplasia: AUA Guideline part I, initial work-up and medical management. J Urol. 2021 Oct;206(4):806-17.
  4. What We Know About Your Prostate. UT Southwestern Medical Center. Accessed May 11, 2022.
  5. Proscar Tablets Patient Information. U.S. Food and Drug Administration. Accessed October 14, 2021.
  6. Avodart Prescribing Information. U.S. Food and Drug Administration. Accessed October 14, 2021.
  7. McVary KT, Gittelman MC, Goldberg KA, et al. Final 5-year outcomes of the multicenter randomized sham-controlled trial of Rezūm water vapor thermal therapy for treatment of moderate-to-severe lower urinary tract symptoms secondary to benign prostatic hyperplasia. J Urol. 2021 Sep;206(3):715-24.
  8. Mooney R, Goldberg K, Wong D, et al. Convective radio frequency thermal therapy for treatment of benign prostatic hyperplasia: single office experience with 255 patients over 4 years. Urol Pract. 2020 Jan;7(1):28-33. 

Caution: U.S. Federal law restricts this device to sale by or on the order of a physician.
Content on this web page is for Informational Purposes only and does not constitute medical advice and should not be used for medical diagnoses. Boston Scientific strongly recommends that you consult with your physician on all matters pertaining to your health or to address any clinical/medical questions. is a website sponsored by Boston Scientific.
All images are the property of Boston Scientific. All trademarks are the property of their respective owners.