Differential metabolism of drugs, therapeutic effects and side effects.


We all have an enzyme system in our liver called the Cytochrome P-450 (CP-450) system. It evolved to metabolize poisons, but it is the major enzyme system that metabolizes drugs. This means it breaks drugs down into their metabolites, (or adds sulfate, acetyl, methyl, glucuronidyl gorups) which makes them more water soluble, and gets rid of them.

There are many forms of CP-450, ones that are fast, medium, slow, or super slow. The fast CP-450 breaks down the drug you’ve taken quickly. This hopefully allows enough time for the drug to interact with the proper receptors and have its desired effect before it is removed from your circulation. The slow and super slow CP-450 can be problematic in that they remove the drug so slowly that side effects and worse, adverse effects take place.

I have had genetic testing done to see which form of CP-450 I have. I have the slow form. This explains why I have all the side effects plus some whenever I am on a new medication. My liver doesn’t remove the drugs quickly enough, so they stay in my circulation for too long and I have many side effects and many adverse affects. Also I can take very small doses of medications and have an effect.

Now, knowing this helps my psychiatrist prescribe low doses of some medications, because I cannot take a lot of them. Trying out new medications is always a scary thing for me because I never know how bad the side effects and adverse effects are going to be.

I have only been able to tolerate Zoloft (however, no more SSRI’s) Lithium, and Seroquel. But as my friend who is a psychiatrist says, these are some of the best ones to be able to tolerate.

I would ask all of you to get this genetic testing done, but it is quite expensive ($1500) and it is not covered by some insurance plans, like mine… Anyway, I had it done, and the information gleaned from the testing is valuable. Hopefully insurance companies will start paying for these tests, because in the final analysis, it saves you money, because you don’t have to take drugs you know from the testing are not going to work for you.

5 thoughts on “Differential metabolism of drugs, therapeutic effects and side effects.

  1. Reblogged this on Pieces of Bipolar and commented:
    I’m going to look into this with my doc and see if we have this test available in South Africa. Obviously affordability will be a factor, but after my failed attempts with olanzapine and quetiapine due to adverse side effects, I’d be interested to know. It would be nice to not have to go through the whole ordeal of ‘trying’ a drug out and getting sick, before trying an alternative.


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