St. John's Wort + medications & supplements

[DementiaSavantPlus]

Over the past year or two, I have investigated different supplements to increase my mood (after some years of often mishandled drug and alcohol use). Until recently I avoided St. John's Wort because its mechanism has commonly been compared to an SSRI, and I was concerned about side effects.

I am aware of its interactivity with other medications and supplements, however I am having trouble finding specifics that are consistent throughout the web.

Wanted to know: Has anyone used St. John's Wort with gabapentin or phenibut? I take gabapentin and want to make sure its not blocked somehow by the SJW. One drug interaction list on the web says that SJW can reduce the effects of Xanax (GABA a?) and could cause a benzo withdrawal syndrome, but also says that SJW increases effects of baclofen (GABA b?). It also says that it can increase CNS depressive effects of gabapentin, which I have found so far to be not true.

On bluelight I found one mention of St. John's Wort completely blocking phenibut, which is GABA b, similar to baclofen. I thought some firsthand experience from this forum might shed some light on any rules related to SJW and GABAergics.

 

[Toucan]

SJW's interaction with Xanax is through the induction of an enzyme for which xanax is a substrate. Meaning the xanax will be metabolised more readily if co-administered with st johns wort.
Gabapentin undergoes negligable metabolism in the body, with most of the drug being excreted unchanged. I'm fairly sure that this is the case for phenibut also.
As such I wouldn't expect a similar interaction with these drugs

edit: apparently Hyperforin, an active constituent of SJW, has been shown to prevent reuptake of GABA in vitro. this could perhaps explain an increase in effects.

 

[DementiaSavantPlus]

Thanks, Toucan. I was aware of the enzyme activity, but I've read a few accounts in which a GABA reuptake inhibitor such as hyperforin caused a block of some other GABAergics' effects (which disagrees with my logic). I have started taking the St. John's Wort this week, and it is accumulating and I am feeling some effects. I am wondering what to expect, but am also thinking I should probably not be that worried.

 

[Swimmingdancer]

Yeah what Toucan said.

St John's Wort interacts with many different kinds of drugs based on the way it induces the liver enzyme CYP3A4 (it also affects CYP2C19). So drugs that are metabolized by these enzymes are affected. Gabapentin is not metabolized, it's just absorbed through the small intestine and then almost all of it is excreted through the kidneys. Baclofen and Phenibut are also mostly excreted through the kidneys, around 70%. I don't have much info as far as what happens to that other 30% though. It's possible that if someone felt that SJW lessened the effects of Phenibut it might have been by another mechanism, like SJW's action on P-glycoprotein. I have no idea if Phenibut is a major substrate of P-glycoprotein though.

Sources just say that SJW can increase depressive effects of drugs like gabapentin or baclofen because they have that as a blanket warning on every combination of drugs that can cause sedation etc. SJW can be sedating, so basically the warning is that if you take 2 drugs that are sedating, you can be extra sedated. But personally I don't find SJW very sedating and don't think it increases any effects of gabapentin or benzos for me. I don't have any experience taking SJW with phenibut or baclofen.