Avodart & Proscar

BY MARK SCHOLZ, MD

Frequently I am asked about Proscar and Avodart, two medications that are FDA approved to reduce urinary side effects from prostate enlargement (BPH).  It turns out that these medications have a much wider spectrum of application than simply treating BPH. They function by blocking a type of testosterone called dihydrotestosterone (DHT) that occurs primarily inside the prostate. A short blog can’t summarize this vast field.  However, I think even a brief review might be helpful.  Here is a list of their potential applications:

• Lower the risk of being diagnosed with prostate cancer
• Improve the detection rate of high-grade prostate cancer
• Cause Gleason 6 cancer to regress or be suppressed
• Synergize with other hormone therapy medications (such as Casodex)
• Help maintain men on active surveillance to avoid surgery or radiation
• Prolong the “holiday period” in men on intermittent hormone therapy
• Reduce male pattern baldness
• Delay orgasm in men with premature ejaculation

The occasional side effects that can occur, such as reduced libido, impotence and breast enlargement, are manageable or preventable as long as the medication is stopped in a timely fashion when side effects occur.

In a randomized study comparing Proscar with placebo, 10,000 men underwent a prostate biopsy. The Proscar-treated men were diagnosed with cancer 25% less frequently compared to placebo. However, enthusiasm for the routine use of Proscar to prevent cancer was dampened when the same study reported a 1% increased incidence of diagnosing high-grade prostate cancer. Even though many experts hypothesized that Proscar was increasing the detection rate, not causing high-grade disease, Peter Scardino, a prominent urologist from Memorial Sloan Kettering published an opinion that Proscar could be causing high-risk cancer, raising all kinds of consternation and inciting the FDA to place a warning. Fortunately, subsequent follow up published in the August 15, 2013 issue of the New England Journal of Medicine showed that after 18 years of observation there was no increased prostate cancer mortality from Proscar.

Much of what is known about Proscar can also be said about Avodart. Both agents block 5- alpha reductase (5-AR), an enzyme that converts testosterone into DHT.  A possible advantage of Avodart is that it blocks two of the three forms of 5-AR whereas Proscar only blocks one.  No clinical trials, however, have been performed to compare clinical efficacy of the two agents.  In our in-house trials we have found that DHT blood levels are lower with Avodart than Proscar.

Since both Proscar and Avodart lower PSA by about 50%, the question arises, “Are they masking the capacity of PSA to signal cancer progression?”  Briefly, the answer is no. These medications do not stop a PSA rise in men with progressive cancer. However, after starting Proscar or Avodart the PSA baseline does reset 50% lower. On average, a man with a PSA of 6.0 before starting Proscar will drop to 3.0 within a few months. Subsequently, if the PSA rises consistently above 3.0, cancer progression should be entertained as a possible cause.

The rationale for concluding these agents are beneficial when added to other hormonal agents is based on the known fact that no pharmaceutical drug by itself can totally eradicate or block testosterone. So logically, the addition of a nontoxic 5-AR inhibitor to further lower DHT is likely to be helpful. Studies show that these agents suppress PSA in men with relapsed disease, delaying the rise in PSA, on average, for a couple of years.  It has also been shown that these agents can double the duration of the “holiday period” in men on intermittent hormone blockade.

Proscar and Avodart—mild agents with mostly reversible side effects—almost never interact with other medications.  They can be taken anytime of the day, with or without food. Proscar is available as a generic called finasteride and is very affordable. There is certainly an important role for these well-tolerated medications though in this era of new, high-powered hormonal agents such as Zytiga and Xtandi, Proscar and Avodart often get forgotten.  

Read another Prostate Snatchers blog written on Avodart & Proscar here:  http://prostatesnatchers.blogspot.com/2011/05/avodart-proscar-for-men-on-active.html