How Long Can a Single Dose of Propecia Stay in the Body?

Dear Dr. Rassman,

I’ve read here that a single dose of Finasteride can stay in one’s body for up to 7 days or more: regrowhair.com

Do you think it’s true?

Thank you! Best Regards

There are many resources for information as well as misinformation. Some sources say finasteride half life is 4-5 hours. Some say it is 8 hours. My Epocrates drug database says it is 6 hours. Half life is the time it takes for 50% of the drug to be out of your bloodstream. So if you assume that the half life is 6 hours, then most of the medication should be out of your bloodstream and excreted out of your body in a day or so (it is excreted in your feces and urine). But being out of the bloodstream does not always correlate with it being out of your body per se, because some form of the medication is left in your tissue. In general, this minute amount is not enough to affect the physiologic goal that was intended, so we have to take the medication at the corresponding interval to keep a consistent level in your body. Propecia (finasteride 1mg) has a recommended dosing of one pill, once a day. This makes sense, because most of the drug is out of the bloodstream in one day.

For the conspiracy theorists…

Now, the confusing part to those who scour the Internet for conspiracy theories and mistrust in the medical and scientific world is that it has been shown that after stopping Propecia there seems to be a suppression of the DHT levels even after one day (when Propecia is out of your bloodstream). There is no clear explanation of why this is. You can also theorize that maybe it takes a while for the DHT to return back to its normal levels in a few days after stopping Propecia. There is no clear answer that I can find, but I suppose some may advocate taking Propecia every other day. I personally would follow the recommended dosing and discuss any changes with your doctor.

For those that still don’t believe…

You want more science? Let’s use the finasteride packaging study as the source: Following an oral dose of 14C-finasteride (radioactive dose) in men, approximately 39% (32-46%) of the dose was excreted in the urine in the form of metabolites. Virtually no unchanged drug was excreted in the urine and 57% (51-64%) of the total dose was excreted in the feces. The elimination rate of finasteride decreases somewhat with age. Mean terminal plasma half-life is approximately 5-6 hours (3-14 hours) and in men more than 70 years of age the half life rises on average to 8 hours (6-15 hours range). These findings are of no clinical significance and hence, a reduction in dosage in the elderly is NOT warranted.

To conclude…

To all who are utterly confused by now, I say this: Propecia is a medication to help men who have androgenic alopecia. Propecia does not cure androgenic alopecia, but it does slow it down. Propecia has its side effects, but as with all drugs you have to consider the risks as well as benefits and after discussing all the options with your physician you have a choice! Finally, the recommended dose of Propecia is once a day. If you want to take it any other way, that’s between you and your doctor. This is not rocket science and there should not be confusion in this matter. It is a simple drug to take with clear instructions. The rest are just mental masturbation, hypotheticals, and Internet hype.