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Avodart (dutasteride) and Proscar (finasteride) - the 5-ARI drugs


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Avodart (dutasteride) and Proscar (finasteride) - the 5-ARI drugs

Posted in Primary hormone therapy

The drug labeling for 5-alpha-reductase inhibitors (5-ARIs), a class of medications that includes finasteride and dutasteride, must now include a warning that the drugs may increase the risk for high-grade prostate cancer (PCa), according to the FDA.

Finasteride and dutasteride are FDA approved for treating benign prostatic hyperplasia (BPH).

The new safety information is based on the agency's review of two large, randomized controlled trial: the Prostate Cancer Prevention Trial (PCPT) and the Reduction by Dutasteride of Prostate Cancer Events (REDUCT) trial. In both studies, use of the medications was associated with an approximately 25% decreased risk of prostate cancer overall compared placebo. However, data suggested high-grade tumors were more likely to develop in men who took either medication.

The FDA recommends that, prior to initiating therapy with 5-ARIs, clinicians perform evaluations to rule out other urological conditions, including PCa, that might mimic BPH.

Click here to read the reasons given for the FDA warning

Avodart (dutasteride) and Proscar (finasteride) are drugs added by some doctors to hormone treatment (also called Androgen Deprivation Therapy (ADT)) for men with prostate cancer.

They are in a family of drugs called 5-alpha reductase inhibitors (5-ARI)

There is some controversy about the use of these drugs for prostate cancer prevention.

In the PCPT trial of men with no evidence of prostate cancer, men who took Proscar (finasteride) were 25% less likely to develop prostate cancer (as revealed in a final biopsy) than those who took a placebo. The controversy is over whether the extra 1% of aggressive cancers discovered in the finasteride group are caused by the drug or are found more easily because the drug shrinks the prostate.

Despite this controversy about prevention, the rationale for using one of these drugs is, for me, shown by two studies.

The first showed that men on Intermittent Hormone Deprivation (IAD) with Proscar (finasteride) added had, over the period of the study, a total of 15 months extra off hormones than those on IAD without finasteride:


The second, the REDUCE trial, started with men with no sign of high-grade cancer in their initial biopsy, but who were rated "at risk"; because of a PSA between 2.5 and 10 ng/ml. The half the men taking Avodart (dutasteride) had a 23% smaller chance of Gleason score 7-10 or 8-10 cancer being found in their final biopsy than those on the placebo:


Because these drugs lower your base PSA measurements, some have worried that all people are seeing is a PSA-measurement effect, and that there is no effect on the cancer. That the affect is really on the cancer is shown by a study that took biopsies of men on active surveillance and showed fewer progressions (about half) in the men taking 5-ARIs:

The link below is to a PDF file on another site.

If you have not used a PDF before, your browser may ask you to get Adobe Acrobat.

Adobe Acrobat reader is available for free.


One small reason for choosing Avodart (dutasteride) over Proscar (finasteride) is that lab work on cells showed dutasteride to be more effective against prostate cancer cells.


While there is no study to date on the effectiveness of Avodart (dutasteride) and Proscar (finasteride) in treating advanced prostate cancer, some well known American oncologists add it to their mix.

I am not a doctor.

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