Can anyone tell me if my basic understanding of the potential interactions of the P450 system is correct? Both the pharmacist and the LLMD are not too concerned about this, but I would like to know a bit more. Can't be too carefull, and it looks like there are a lot of potential interactions.
I know there are three types of drugs:
- inducers: a drug that increases activity of a certain pathway, so that levels of drugs dependent on this pathway fall. For instance pioglitazone is an inducer of CYP3A4. CORRECT?
- inhibitors: a drug that inhibts/decreases. activity of a certain pathway, so that levels of drugs dependent on this pathway fall. For instance Fluconazole is an inhibitor of CYP3A4?
- substrates: a drug that depends on a certain pathway in order for it to be metabolised / broken down. For instance, Clarithromycine (Biaxin) and Telithromyine (Ketek) is a CYP3A4 substrate. CORRECT?
So, you can not take at the same time:
- an inhibitor with a substrate as that would increase drug levels of the substrate. CORRECT?
- two substrates that use the same particular pathway, since they would compete and that would increase concentration of one of them or of both. CORRECT?
- an inducer with a substrate as that would decrease drug levels of the substrate. CORRECT?
- Is it possible to take two inhibitors at the same time (ie Fluconazole and Clarithromycine (of course you have to make sure that you do not take a substrate at the samne time)?
- Is it possible to take an inhibitor at the same time as an inducer? What would be the effect of that?
- I found that some drugs I found to be both inhibitors as substrates of CYP3A4, for instance clarithromycine. Is this an error or is this possible? How does that work?
I have 2 liver support supplements, Dr Zhang's Hepa formula 2 and milk thistle. Both are potent CYP3A4 inhibitors. It seems that almost all abx that I have taken and that my llmd plans me to take are one way or the other conneceted to CYP3A4. So, it would not be advisable to take them while on any CYP3A4 abx?
posted
I'm sorry, but this pea-sized brain has no clue what you're talking about.
What's a P450 system??
-------------------- --Lymetutu-- Opinions, not medical advice! Posts: 96239 | From Texas | Registered: Feb 2001
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Health
Frequent Contributor (1K+ posts)
Member # 6034
posted
Hello,
I know about this. I was really researching this a year or so ago, because I had a severe reaction while on Azithromycin and St Johns Wort. I also had this happen at another time, while on another drug.
SO, what I can say is that it does happen. Keep phoning around to the pharmacies, the local ones and ask the pharmacists, you will end up most likely, talking to a very knowledgeable one that knows about this.
There was a new study done re. St Johns wort and drugs, they did a study using a cancer drug and St Johns Wort, and found that St Johns Wort made the cancer drug extrete more quickly, somethink like this, my head cannot find the right words to describe more now.
BOttom line, I often wonder if I would be MUCH better had I not taken the St Johsn wort while on the antibitoics. I had taken it with the Biaxin and flagyl, and was ok, but when switched to the Azithro, I had a reaction a few weeks into this drug.
Trish
Posts: 1250 | From Canada | Registered: Aug 2004
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I have done extensive research on the P 450 system. I think that ANY drug (or food) that uses the same pathway causes one to become a poor metabolizer and can cause medication levels to build up causing toxic levels.
There is a chart Flockhart P 450 Drug Interactions that explains the interactions.
Caffeine as well as Motrin and Advil should also be avoided with P 450 drugs.So many doctors and pharmacistsarenot aware of anyP 450 interactions.
Health,
I am curious what interaction you hadwith the Zithromax and St. John's Wart. Zithromax is SUPPOSE to betheonly macrolide that is NOT suppose to have a interaction with Serotonin Inhibitors.
Biaxin and SSRI's interact BIG TIME and cause toxic levels of the SSRI, especially LEXAPRO. No research has been done with Zithromax so I am curious what your interactions were. Thanks,
Posts: 677 | From USA | Registered: Aug 2002
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But, is my basic understanding of the way substrates, inducers and inhibitors function and may interact correct or am I way off base here?
I have asked around pharmacists and MD's, but they are not very helpfull apart of the information that is listed in the Summary of Product Characteristics (kind of a scientific patient information leaflet), and I have read all that but that does often not include all interactions... Sometimes the pharmacist and MD think relatively lightly about the possibilities of these interactions, and I would like to dig a bit deeper just in case...
Barb, Auntybiotic, or anyone else so knowledgeable about these things, could you enlighten me on this and let me know how these interactions work?
Health
Frequent Contributor (1K+ posts)
Member # 6034
posted
Hello,
I had heart racing, and throat swelling with the Zithro/Flagyl and St Johns Wort combined. I may have had some mental problems as well, cannot remember.
It was SEVERE, not mild reaction. I went off St Johns Wort, something I did not want to do because I was dealing with severe depression.
I sunk into depression after going off St Johns Wort, and had to deal with it through prayer and other ways, no drugs, BAD SCENE that was.
Also, candida was contributing to the depression, at that time, later found out.
Maybe it was just a reaction for me, the two combined did this to me, maybe it would not do it to you.
Trish
Posts: 1250 | From Canada | Registered: Aug 2004
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