Why can’t I have grapefruit juice with my statin?

March 25, 2017 by E.A. Thackaberry in Archives Comments Off

There are a whole lot of people on statins these days. Statins are a class of drugs intended to lower your LDL (the so-called “bad” cholesterol), leading to a reduction in heart disease risk. This is great, but many patients are surprised to learn that they have to avoid grapefruits and grapefruit juice while taking statins, and since statins are generally taken daily for long periods of time, this can essentially mean no more grapefruit products for many people.

What do doctors have against grapefruits? Do people really need to avoid them completely? Aren’t apples supposed to keep doctors away? UseYourBrain has the answers.

Behold: A doctor’s worst nightmare? (source)

Perhaps not surprisingly, grapefruit juice is a mix of many different chemicals.

One class of these chemicals, the “furanocoumarins” is responsible for all the trouble. These chemicals block the activity of particular enzyme in your intestine – cytochrome P450 3A4 (CYP3A4) – which is responsible for breaking down most statins. When pharmaceutical companies produce a statin drug (or most any drug for that matter) they account for the fact that most of the drug is going to be chewed up by your metabolism (generally cytochrome p450 enzymes) long before any of it makes its way to its intended targets. To get around this problem, the dose of the statin that you take is actually higher than the dose needed to produce the desired effect, because drug companies know that most of the drug will be broken down by CYP3A4 or other enzymes before it can do anything. That is, unless you take your statin with grapefruit juice, in which case the statin levels in your blood can be several times higher than they would normally be, because the furanocoumarins from the grapefruit have tied up all the CYP3A4 that should be breaking down the drug.

Not Pictured: pharmacists glaring daggers at the citrus stand across the street (source)

So, is this bad? Well, there’s actually some debate about this in the medical community. Higher exposure to statins could make them more effective (that’s good!), but it will also increase the risk of adverse effects, and that falls squarely in the “bad” category. The major risk of statins is rhabdomyolysis, which is serious damage to the skeletal muscle. In severe cases, rhabdomyolysis can cause secondary kidney damage and require hospitalization. The debate in the field centers around how much of an increased risk there is when grapefruit juice boosts the exposure to statins. This increase in risk is likely not high, but from the point of view of a medical professional, it has a negative risk/benefit profile – meaning that drinking grapefruit juice brings you no medical benefit (other than some tasty juice) while increasing your risk of a serious medical condition (albeit a small increase). As a result, grapefruit and grapefruit juice go on the do-not-fly list for statin users.

Adding to the confusion, there are many different statins on the market, and not all have the same interaction with grapefruit juice. Those that are not heavily metabolized by CYP3A4 are less likely to result in grapefruit-related peril. The worst interactions tend to occur with atorvastatin (Lipitor), simvastatin (Zocor), and lovastatin (Mevacor).

Excessive exercise is another common cause of rhabdomyolysis. Luckily, that’s not a huge concern for *this* blog editor 🙂 (source)

Also, statins aren’t the only drugs that grapefruits and their juices will interact with: these sneaky citrus can also boost the doses of some blood pressure lowering drugs (like nifedipine and verapamil), psychiatric drugs (like valium and BuSpar), anti-arrhythmia drugs (amiodarone), oral contraceptives, and many more. Grapefruit juice actually reduces the effect of fexofenadine (Allegra), albeit through a completely different mechanism.

Some will suggest that it’s ok to time the consumption of grapefruit juice to avoid an interaction (drinking juice in the morning and taking the statin at night, for instance), but this is difficult – both the drug and the grapefruit juice will spend several hours in your GI tract after all. Some doctors simply advise that you’ll be ok if you drink grapefruit juice in moderation (no more than 8 ounces a day). Ultimately, each person will respond differently depending on the drug in question, the amount of grapefruit juice, the timing of consumption, and their own genetics. If you are taking a statin or one of these other classes of drugs, it’s best to talk to your doctor before enjoying your next glass of grapefruit juice. Or maybe just switch to orange juice? You’ll get the same yummy and citrusy source of vitamin C without any of the drug interactions.