are med interactions dose-dependent?

[domovoi]

i take tegretol, which is gotta be the most annoying med for interactions. it lowers plasma levels of everything else i take. so i had a question, for which i will use an example:

according to med checker and NIH data, 400 mg of tegretol lower the plazma concentration of 30 mg abilify by 70%. recommendation: double the abilify. the way i understand it, if i take 400 mg of tegretol with 30 mg abilify, that means that i'm actually taking, like 15 mg abilify. right?

what if i take 1200 mg tegretol and 10 mg abilify, like in my sig? does that still mean that i'm absorbing half the abilify that i take? even though it's not the same ratio of dosages? in my case, the dose of tegretol is much higher and the dose of abilify is much lower than in the example above. does that mean the tegretol decreases abilify plasma levels by even larger percentage?

thanks.

[notfred]

What does your doc a pharmisist say ? I would not adjust my meds based on what a web page, which has a clear disclaimer not to make adjustments based on the info presented there. I realize it says "The manufacturer recommends that aripiprazole dosage be doubled when carbamazepine is added to therapy" I would defer to the experience of your doc in these matters.

nf

[AirMarshall]

I don't think there is a single answer that covers the hundred plus drugs commonly used.

One drug where this question comes up, and where docs take action is Lamictal which has several drug-drug interactions. In Lamictals' case, it is common for doctors to increase the dosage to make up for inactivation.

One confounding factor for any attempt to compensate is the drugs' toxicity and range of action. Lamictal has a very wide range of action and lots of margin above before any toxic effects occur. In contrast, Lithium has a narrow range of action and very little margin before toxicity occurs.

What we really need are blood tests that would tell us each drugs' blood levels, and the status of our liver enzymes function. Unfortunately we just don't have that for most drugs.

Your pdoc is the one who can tell you whether your meds can be adjust to compensate for interaction.

best, a.m.

[domovoi]

What does your doc a pharmisist say ? I would not adjust my meds based on what a web page, which has a clear disclaimer not to make adjustments based on the info presented there. I realize it says "The manufacturer recommends that aripiprazole dosage be doubled when carbamazepine is added to therapy" I would defer to the experience of your doc in these matters.

nf

oh no, by no means am i trying to change any dosages of any of my medications without a consultation with my pdoc. i take everything exactly as prescribed. i just haven't asked my doc that question specifically and it's a while until i see her next so just thought if anyone here knew anything about this... as for pharmacists, well, there's a language barrier.

I don't think there is a single answer that covers the hundred plus drugs commonly used.

One drug where this question comes up, and where docs take action is Lamictal which has several drug-drug interactions. In Lamictals' case, it is common for doctors to increase the dosage to make up for inactivation.

One confounding factor for any attempt to compensate is the drugs' toxicity and range of action. Lamictal has a very wide range of action and lots of margin above before any toxic effects occur. In contrast, Lithium has a narrow range of action and very little margin before toxicity occurs.

What we really need are blood tests that would tell us each drugs' blood levels, and the status of our liver enzymes function. Unfortunately we just don't have that for most drugs.

Your pdoc is the one who can tell you whether your meds can be adjust to compensate for interaction.

best, a.m.

thanks, AM.