There are a few very important things to know about Finasteride use for hair loss.
- Blood donation: Men using Finasteride should not donate blood while on the medication or for one month afterward. The reason for this is that the blood could be used to transfuse a woman who is pregnant with a male fetus. The finasteride in the transfused blood could then negatively affect the normal genital development of the fetus.
- Prostate specific antigen: Prostate specific antigen (PSA) is a blood test used to screen men for prostate cancer. The problem with Finasteride is that it can make the PSA level very low in the men who take Finasteride—even men with prostate cancer. This fact makes interpreting levels more difficult. A man with a normal PSA level while on Finasteride may still have prostate cancer. Interpreting levels must always be done with this knowledge. Every physician involved in your care must know you are on Finasteride. Also, any increases of PSA while on Finasteride must be evaluated. The PDR states, “Any confirmed increase from the lowest PSA value while on Finasteride tablets may signal the presence of prostate cancer and should be evaluated, even if PSA levels are still within the normal range for men not taking a 5 α-reductase inhibitor (e.g., Finasteride).”
- Increased risk of high-grade prostate cancer with Finasteride and similar drugs (such as dutasteride): There is the possibility that Finasteride may increase the number of men who eventually get high grade prostate cancer. In one study, men aged 55 and over with a normal digital rectal examination and normal PSA “taking Finasteride 5 mg/day (5 times the dose of Finasteride tablets used for hair loss)...had an increased risk” of higher grade prostate cancer. Some feel that the Finasteride makes it easier to detect these higher grade cancers, but it is a risk that should be acknowledged.The PDR does state, “Whether the effect of 5α-reductase inhibitors (like Finasteride) to reduce prostate volume, or study-related factors, impacted the results of these studies has not been established.”