Is St. John's Wort Safe To Take With Diovan (Valsartan)?

Answer

Thank you for contacting us! St. John's Wort is one of the most commonly used dietary supplements. Unfortunately, it's known to potentially interact with various medications due to its broad effects on several metabolizing enzymes in the body.

One such enzyme that studies indicate St. John's Wort may affect is Cytochrome P450 2C9 (CYP2C9). It has been reported in some studies as a 'CYP2C9 enzyme inducer'. An inducer is a substance that speeds up the metabolic processes of the body, increasing the rate at which a particular enzyme processes its specific substrate.

Diovan (valsartan), a medication used to treat heart failure and high blood pressure, is classified as a CYP2C9 substrate, meaning it is metabolized by the CYP2C9 enzyme.

If you were to take St. John's Wort along with Diovan, the concern is that it could potentially increase the rate at which Diovan is metabolized. This could lead to decreased levels of the drug in the body, potentially reducing its effectiveness.

Our detailed interaction page provides more insight into this potential interaction.

Conflicting Evidence

It's worth noting that the research on St. John's Wort's effect on CYP2C9 is somewhat conflicting. Some studies suggest it induces CYP2C9 (the linked study reported that St. John's Wort induced the metabolism of warfarin, a CYP2C9 substrate), while other research has found no significant effect on the pharmacokinetics of CYP2C9 substrates.

Guidance

Given this potentially significant interaction, it would be prudent to discuss this with your cardiologist before starting to take St. John's Wort. Overall, until more definitive research is available, caution is advisable when combining St. John's Wort with CYP2C9 substrates like Valsartan, and at the very least, your doctor should be aware of everything you are taking so you can be appropriately monitored.

Final Words

You also mentioned that you are taking metoprolol succinate, a medication used to treat high blood pressure and heart rhythm disorders. This drug is primarily metabolized by different enzymes (CYP2D6), and the interaction with St. John's Wort is likely to be less significant.

I hope this answer was helpful! Thanks again for reaching out.