Monday, September 20, 2010

Prilosec (Omeprazole) and Plavix do NOT mix!

Omeprazole (Prilosec) is a drug we take when we suffer reflux, gastritis or other stomach upset. If we have LPR (Laryngopharyngeal reflux) or Barrett's Esophagus, it's considered a "must". What should we do if we are also on Plavix for clotting or platelet problems?

The basics

Omeprazole is a proton pump inhibitor. It stops the cells in your stomach that are supposed to produce the digestive juices needed to digest your food.

Plavix (clopidogrel) is a drug that is used to prevent your platelets from sticking together and forming clots.

Both of these drugs can be important pieces of the arsenal we use when we have autoimmunity. When used together, unfortunately the Plavix is unable to do its job. You won't know this until it is too late however, so being very aware of this particular drug reaction is really important.

What happens that is so important to my autoimmune symptoms?

Plavis requires cannot prevent clots until it is metabolized in the liver. This requires a special enzyme called CYP2C19. Omeprazole blocks this enzyme, which effectively also blocks the Plavix. The blocking action of the omeprazole appeared consistent no matter if the clopidogrel was taken at the same time as the omeprazole, or later in the day.

The FDA looked into Plavix back in January hoping to identify and warn patients of these interactions. Unfortunately, not only is Omeprazole not the only medicine that blocks CYP2C19, the nature of this reaction is not very well understood. As a result, Plavix labels have been recently updated to reflect the danger of this interaction.

It is unknown at this time if other proton pump inhibitors also block the CYP2C19 enzyme, therefore also causing problems with Plavix. Patients who take clopidogrel and also need to take a drug to reduce stomach acid should discuss their therapy with their doctor. Axid (nizatidine), Pepcid (famotidine) and Zantac (ranitidine) are not known to inhibit the
CYP2C19 enzyme and therefore aren't expected to interfere with the anti-clotting
activity of clopidogrel. Antacids are also discouraged as they may interfere with clopidogrel's ability to block clotting activity.

Although it may be possible to tweak the clopidogrel dosage a little to overcome the interaction with omeprazole, the FDA is silent on what those recommendations might be. Further research is necessary.

Other medicines known to interfere with CYP2C19 include

* Diflucan (fluconazole)
* Felbatol (felbamate)
* Intelence (etravirine)
* Luvox (fluvoxamine)
* Nexium (esomeprazole)
* Nizoral (ketoconazole)
* Prozac (fluoxetine)
* Serafem (fluoxetine)
* Symbyax (fluoxetine)
* Tagamet and Tagamet HB (cimetidine)
* Ticlid (ticlopidine)
* VFEND (voriconazole)

Thankfully, the company that makes Plavix has agreed to continue researching other drug interactions with this potentially helpful drug.

The importance of checking your medicines' warning labels frequently

I am guilty of taking my medicines for granted. When I receive a new prescription I am very diligent about checking for interactions and any other contraindication that would keep me from taking the medicine. I usually try to have patience. I walk out the doctor's door with my prescription in hand, but instead of taking it directly to the pharmacy, I go home and begin searching online for all the information I can find. The same goes for my over-the-counter meds. What I don't do is continually check up on these medicines and catch new warnings such as this. This illustrates again why it is so terribly important to tell your doctor of every single supplement and otc med you're using at any time, as this kind of mistake could be very harmful, even fatal in the right circumstances.

One more important thing...
There is a gene variant that results in reduced production of the enzyme we're concerned about. If you are on clopidogrel and have not had the test to check for this gene variant, you may want to begin a frank discussion with your doctor about it, as this gene variation is very similar in the body to the the reaction of Omeprazole with the clopidogrel.
I posted a while back about genetic testing I had this past spring (see DNA testing - my story, my mystery). One of those tests was for my genetic ability to metabolize clopidogrel. Interestingly enough, I do carry an irregularity that restricts my ability to metabolize the drug. Unfortunately, it is an imperfect world and there are no dosing suggestions for people like me with this genetic variance. Hopefully soon we will have more information that will be easily available to us all.

Have you ever forgotten to tell your doctor about a supplement or OTC medicine you're taking and had a bad reaction? What happened?

Have you ever considered genetic testing to determine your health history or your genetic drug response for medications you might be taking?

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