Avodart is a 5-alpha reductase inhibitor, or 5-ARI, that is approved to treat enlarged prostates. It works by blocking an enzyme that converts testosterone into dihydrotesterone (DHT). By reducing DHT levels, Avodart can shrink the prostate, and relieve some symptoms of an enlarged prostate. Avodart has also been used “off-label” to treat male pattern baldness and prostate cancer after the surgical removal of the prostate. Avodart is manufactured and marketed by GlaxoSmithKline (GSK).
In 2011, the FDA required that labels be placed on Avodart and other 5-ARIs to warn about a serious prostate cancer risk. This warning was put in place after two studies indicated that men taking Avodart were more likely to develop aggressive prostate tumors compared to men taking a placebo. In the trial REDUCE (reduction of dutasteride of prostate cancer events), the use of Avodart was compared to the use of a placebo. The trial studied more than 8,000 men from age 50 to 79 for four years.
Although men on Avodart had a 23 percent overall lower risk of being diagnosed with prostate cancer compared to the men on the placebo, the incidence of high-grade prostate cancers was increased. The high-grade version of prostate cancer grows and spreads faster than the more common strain of the disease.
Avodart has also been linked to rare male breast cancer incidences along with other serious sexual side effects such as erectile dysfunction, impotence, problems with ejaculations and decreased sperm count.
Side effects may include:
- Decreased libido (sex drive);
- Decreased amount of semen released during sex;
- Impotence (trouble getting or keeping an erection); or
- Breast tenderness or enlargement