P450 Interactions

[tasar1898]

Seriously what is the deal with this system ?? -e.g azoles inhibit P450 but are induced by it , statins are metabolized except one , Protease inhibitors , oral hypoglycemics are metabolized by p450 , Chloramphenicol induces and on and on and on… Does anyone learn all that jabba jabba or we just learn the interactions in FA??

also don't even get me started on the CYP subtypes … 4A1 , E2A , C2B , I wish humans didn't have a liver...

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[worldbeater]

Relax. You just need a couple of mnemonics for what works with p450, and you can get all the questions right.

So p450 is the mechanism of how the liver metabolizes medications. They can be either 1) inducers 2) inhibitors or 3) dependent.

Inducers of p450 make the liver process medication faster, so it won't have it's intended effect over a long period of time. Warfarin being used up by another drug, and then causing clots, is a great example.

Inhibitors of p450 block the metabolism, so the medication won't be processed at all. Dependent means a handful of drugs work with other.

These are the drugs that we were taught:

1) p450 Inducers - BAG for CPR QTS
Barbiturates, alcohol, griseofulvin, carbamezapine, rifampin, quinidine, tetracyclines, spironolactone

2) p450 inhibitors - ID SMACK QUIN
INH, dapsone, sulfa drugs, macrolides, amiodarone, cimetidine, ketoconazole, quinolones

3) p450 dependent - WEPTD
Warfarin, estrogen, phenytoin, theophylline, digoxin

Match these lists to the questions your working on, you will see the pattern of what's going on.

 

[tasar1898]

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[worldbeater]

I am not sure what you mean by substrates and dependents...but yeah any drug that has a long half life is processed by p450 because they are fat soluble.

p450 dependent I think are the main drugs that affect each other. I just have "p450 dependent" and those 5 drugs listed in my notes, and that's the logic I use to get UWorld questions correct.