Saw Palmetto Drug Interactions

In our latest question and answer, the pharmacist discusses known drug interactions with saw palmetto.

Saw Palmetto Drug Interactions
Apr 08, 2019

F.G. asked

Does saw palmetto react or interfere with lisinopril, levothyroxine, gabapentin, or ibuprofen? (I've read that saw palmetto shouldn't be taken with hormones, so I'm more concerned about the levothyroxine even though it's not a sex hormone.) Also, is saw palmetto contraindicated if one is taking certain dietary supplements or herbal medications? Thank you very much for your answer!

At a glance

  • Saw palmetto has few known drug interactions since it is not known to affect CYP metabolizing enzymes. It should, however, be used cautiously with 5-alpha reductase inhibitors, hormone replacement therapy and blood thinners.


Saw Palmetto Drug Interactions

Saw palmetto is one of the most popular and commonly used over the counter nutritional supplements. In fact, in 2010 alone, it had over $700 million in total sales![1]

As with most nutritional supplements, comprehensive and conclusive data on the effectiveness, side effect profile and potential drug interactions, is difficult to come by.

Nevertheless, based on the data we do have available, it appears that saw palmetto has few drug interactions and is generally well tolerated.

In fact, saw palmetto has only a few reported drug interactions. These drug interactions include:

  • Anticoagulants
  • Antiplatelets
  • Hormone-containing drugs
  • 5-alpha-reductase inhibitors

Additionally, since you mentioned you are taking Synthroid (levothyroxine), saw palmetto doesn't have any known interaction with it but you should try and take Synthroid by itself, on an empty stomach, at least 30-60 minutes before food or other medications for optimal absorption.[2]

I discuss the potential drug interactions for saw palmetto in the next section.

Drug Interactions

As mentioned, saw palmetto has few known drug interactions.

This is most likely because it is not known to affect any CYP metabolizing enzymes, the main mechanism behind the majority of drug interactions.[3]

Nevertheless, there are a few potential interactions that have been reported.

5-Alpha Reductase Inhibitors

This is less of an interaction and more of a precaution.

One of the supposed mechanisms behind saw palmetto's effectiveness is that it acts as a '5-alpha-reductase' inhibitor. 5-alpha reductase is an enzyme that is responsible for (among much else), the conversion of testosterone to dihydrotestosterone. Inhibiting 5-alpha reductase, therefore, inhibits this conversion.[4]

Two prescription 5-alpha-reductase inhibitor drugs are available in the United States:

These drugs are used to treat benign prostatic hyperplasia (BPH) in men with an enlarged prostate to improve symptoms and for male pattern hair loss (i.e., androgenetic alopecia).

Since saw palmetto may also work as a 5-alpha-reductase inhibitor, the effects of combining it with Proscar or Avodart has unknown effects. The cumulative effects could potentially additive (and positive) but may also increase the risk of certain side effects.

There are some studies that have used both to evaluate their combined effectiveness and few side effects have been reported, but overall, since data is sparse, you should discuss the use of saw palmetto with your doctor if you are already taking a 5-alpha-reductase inhibitor.[5]

Hormone-Containing Drugs

Saw palmetto may interact with hormone containing drugs, including testosterone and estrogen.

Multiple studies show that saw palmetto has both antiandrogenic and anti-estrogen effects. Therefore, in theory, saw palmetto could antagonize the actions of these hormones, so potential drugs that could decrease in effectiveness include testosterone or estrogen replacement therapy and oral contraceptive pills.[6][7]

Blood Thinners

Although far from conclusive, saw palmetto is reported to prolong bleeding time in several published case reports.[8]

It should, therefore, be used cautiously with anticoagulant and antiplatelet drugs, including:

Final Words

Although data on effectiveness is mixed, most studies indicate that saw palmetto is at least safe and has few drug interactions to be concerned about.

In regard to the medication list you gave in your inquiry, there doesn't appear to be any major interactions to be concerned with.

The use of ibuprofen is likely okay, even though it can thin the blood. The blood thinning effects of saw palmetto seem to occur only rarely but you should still watch for easy bruising/bleeding.

Additionally, as mentioned at the beginning of this answer, be sure to separate the administration time of saw palmetto and levothyroxine.

If you are considering taking saw palmetto, be sure to discuss its use first with your doctor so you can be appropriately monitored.

  1. ^ Leading Saw Palmetto Producer Reports That Consumers May Be Using Saw Palmetto Incorrectly in Support of Prostate Health. PR NewsWire
  2. ^ Synthroid Prescribing Information
  3. ^ Multiple doses of saw palmetto (Serenoa repens) did not alter cytochrome P450 2D6 and 3A4 activity in normal volunteers. PubMed
  4. ^ A randomized, double-blind, placebo-controlled trial to determine the effectiveness of botanically derived inhibitors of 5-alpha-reductase in the treatment of androgenetic alopecia. PubMed
  5. ^ Saw palmetto extracts for treatment of benign prostatic hyperplasia: a systematic review. PubMed
  6. ^ An Update on Plant Derived Anti-Androgens. PubMed
  7. ^ Evidence that Serenoa repens extract displays an antiestrogenic activity in prostatic tissue of benign prostatic hypertrophy patients. PubMed
  8. ^ Intraoperative haemorrhage associated with the use of extract of Saw Palmetto herb: a case report and review of literature. PubMed

Ready for a more personal experience with your meds?