Posted by Cam W. on February 20, 2000, at 15:46:25
In reply to Q for CamW, posted by Brandon on February 20, 2000, at 12:58:11
> Hi Cam,
>
> I've been taking a small dose of Dilantin (100mgs. at bedtime) for depression and anxiety. I've wanted to try to augment it with some St. Johns Wort. Unfortunately Dilantin interacts with a lot of substances. Do you know of any interactions posed here? Dilantin is partially cleared by the P-450 enzyme and St. Johns Wort increases the amount of this enzyme so would that mean lower levels of Dilantin? I really dont know squat about all of these enzymes.
> If you know anything I would really appreciate it.
> Thanks
>
>
Brandon - This is a complicated question, complicated further by the number of constituents (chemicals) in the St.John's Wort, many of which we aren't completely certain what they do or don't do. I was not aware that St.John's Wort was an inducer of the cytochrome P450 (CYP) system and my answer would deprend upon which family of cytochromes it induces. Personally, I do not believe that SJW is a very strong inducer of any CYP family or we would have definitely noticed it's effects before now.As to phenytoin (Dilantin), it is a very potent inhibitor of two of the CYP families of enzymes. These are called CYP-3A3/4 and CYP-1A2. These enzyme systems affect and metabolize a multitude of drugs and foods Dilantin can change blood level concentrationsof many psychotropic medications (eg SSRIs, TCAs, some benzodiazepines, calcium channel blockers and other heart drugs, certain anti-AIDs drugs, certain antibiotics, etc. Similar events will happen with the CYP-1A2 emzyme system.
This does not mean the these medications cannot be taken together. It means that 'some' of the drugs may have to have their dosage adjusted, depending on several factors (eg Dilantin dose, extent of metabolism of other drug by that system, therapeutic window of that other drug, how that other drug affects Dilantin's kinetics, etc.). This is where the art of medicine comes into play. Usually interactions due to this system are seen after the fact, by the emergence of side effects. To complicate things even more, different people will naturally produce different amounts of enzyme naturally. Also, there are many more CYP enzymes system involved in the metabolism of drugs. Researchers are just now scratching the surface of all the implication of drug interactions within the CYP system.
As to you question, "Does Dilantin interact pharaceutically with St.John's Wort? Probably to some extennt, given the amount of chemicals in St.John's Wort. But is a potential interaction 'clinically significant"? I would not be able to hazard a guess that I could back up with research.
Would I take St.John's Wort with Dilantin? - No!
Hope this helps - Cam W.
poster:Cam W.
thread:22716
URL: http://www.dr-bob.org/babble/20000220/msgs/22739.html