Reader Warns of Grapefruit Juice Danger with Finasteride and Dutasteride

Dear Doctor:

This is a follow-up to the post I had sent regarding Cytochrome P-450 enzymes as they relate to drug metabolism, specifically Finasteride and Dutasteride.

As i had mentioned earlier, grapefruit juice is a potent inhibitor of CYP3A4 in the intestines, however, research indicates that it also inhibits hepatic CYP3A4 when 3 250ml (3 8-oz cups) are consumed daily. This is of particular importance to those takeing statin drugs, antihypertensives, antihistamines, and antiepileptics, as GF juice will significantly RAISE serum levels of these drugs. As a result, side effects are magnified.

Now broccoli has been identified as a potent dual inhibitor of both intestinal and hepatic CYP3A4. More precisely, it is the sulforophanes contained within broccoli. As Dutasteride is actively metabolized by CYP3A4, consumption of GF juice and broccoli will elevate serum levels of the drug considerably, as well as Finasteride, as both are substrates of CYP3A4.

I’m sure there are many who are looking for an inexpensive way to elevate serum levels of Dutasteride to get the “better clinical efficacy”. Caution should be taken however. Yes, it would be great to get .5mg of Avodart to be as effective as the 2.5mg through enzyme inhibition. However, most drugs are metabolized by CYP3A4. Those who are considering this approach must take into serious consideration the effect this approach will have on any and all other medications currently being used.

As i stated above, statins, antihypertensives, allergy medications, antiepileptics, and most other drugs are metabolized by the enzyme that GF juice and broccoli inhibit. Elevation of serum concentration of drugs with a low margin of safety may increase negative side effects, or worse, cause death. I would love to get the effect of 2.5mg of Avodart out of only .5mg, however, I would not want to trade my life for it.

Thanks!

Good review of an interesting subject. Thank you for sending this.