A nearly free genetic test that just might save your life

    Today I’m going to tell you about a nearly free genetic test that could save you a lot of medical grief and in rare instances might even save your life. In fact, chances are you’ve already performed this test on yourself, you just don’t know what the results mean.
    As always, my disclaimer: I’m not a doctor, although I play one at cocktail parties.
    Everybody loves a story about someone else’s grief and misery, so I’ll share mine. Several years ago I saw a weight-loss ad in the paper and decided to go see a fat doctor, who I will call “Dr. Aflac.” For any of you who might be hard of thinking, what’s the Aflac duck say? Quack, quack!
    Dr. Aflac prescribed me phentermine, generic Prozac, and pig thyroid for weight loss which makes sense. Prozac, an SSRI, does promote weight loss for some patients, although not as effectively as the banned fenfluramine. Phentermine, a mild stimulant, has long been known to cause weight loss. And thyroid supplements will increase metabolism, although the body tends to resist efforts to increase thyroid levels by reducing production.
    The drugs were effective, but after a week I started having trouble sleeping and my legs and arms would have spasms, particularly at night. After two weeks it was much worse, and I could only get to sleep by taking some Ativan, which I had in reserve for airplane rides.
    I reported my problem to Dr. Aflac and he assured me it would go away, and that Prozac never caused these types of problems. So I continued two more weeks. By this time I was totally sleepless and could not hold a fork steady enough to get it to my mouth. I had to hold a drink cup with two hands.
    I must say I had lost some weight, though. The inability to keep food on one’s fork is highly conducive to the loss of weight.
    At this point I decided to take my case to the Internet, where I soon found that Prozac is processed by a liver enzyme known as CYP2D6. Somewhere between three and seven percent of the white population suffers from a severe deficiency of this enzyme. I suspect I produce virtually none of it. At the other end of the spectrum are a few people who produce a lot of this enzyme.
    It’s possible to take a genetic test for the CYP2D6 enzyme. These tests can cost hundreds of dollars. If you don’t want to spring for a test right away, you can just ask yourself one question: What do you think of and how much do you like dextromethorphan? That’s the drug in Robitussen DM. Chances are if you take a good slug you either hate it, feel nothing or perhaps find it mildly pleasurable, or absolutely love it.
    If you really love dextromethorphan you are an ultra-metabolizer and have a lot of CYP2D6. It is from this group that people who use dextromethorphan as a drug of abuse come from. So if you have heard of someone “Robi-running” and asked yourself “Why?”, the answer is because they are getting something from the drug that most people don’t.
    If DM is only slightly pleasurable to you, or not particularly pleasurable at all that’s good news. It means you’re normal, and a whole bunch of drugs are going to work for you just like they are supposed to work. Congratulations.
    If you hate dextromethorphan it is likely because you are a poor metabolizer and have little or no CYP2D6. On a personal level, it makes me feel too bad to stay up, but I can’t go to sleep either. My brain feels likes it’s laying atop a razor blade. Ouch!
    So what does all of this mean and why is it important to you? Well, if you have little or no CYP2D6 dozens of drugs – as many as 25 percent – simply aren’t going to work properly for you. In some cases there will be only a slight loss of efficacy, but in others it can be dangerous. When the doctor prescribed me Prozac for weight loss, my lack of CYP2D6 meant that the drug wasn’t being broken down and removed from my system. Not only wasn’t the drug not working exactly properly, but it was building up in massive amounts because by body couldn’t break it down. Codeine, as a cough syrup, is absolutely ineffective on those without CYP2D6, as the body can’t convert the codeine into the morphine which actually suppresses the cough. (Hydrocodone uses CYP2D6, but provides some but lessened effect in those who don’t have the enzyme). SSRIs don’t break down properly without CYP2D6; a few, such as Paxil, can be downright dangerous. Tamoxifen, the breast cancer hormone drug, doesn’t work well or at all without CYP2D6. Obviously knowing whether or not one has the enzyme to process this drug is pretty darn important when deciding on a cancer treatment.
    Many doctors are amazingly unaware of the important of individual liver enzyme profiles in the treatment of patients. I’ve never had one ask me how I felt about dextromethorphan, and I suspect few know of this shortcut to expensive genetic testing.
    Make no mistake, if your life depends on getting the most out of a particular medicine you ought to pay for genetic enzyme profiling. But everyone’s health could be much improved if they would ask and consider their answer to one simple question:
    How does dextromethorphan make you feel?