Making Sense Of Medical Warnings - What Your Doctor Is Saying - Harvard Commentaries

Life is full of warnings and, clearly, some are more helpful than others. But warning labels are so common that you may begin ignoring them or you may not notice them at all. Just how should one respond to all the red exclamation points, bold print and highlighted advice that you see on food labels, prescriptions, billboards and elsewhere? Many of these do not provide the reason they are there or tell you what may happen if you ignore them. It’s enough to confuse even the most reasonable person who just wants to do the right thing.

Warning labels deal with risk. Some are there solely to inform you that something bad may happen.

Others offer you a warning so you can reduce your risk: There are peanuts in this product; if that’s a problem for you, this would be a good time to choose something else!

Some tell you something you probably already know (In case you missed this news, the cigarettes you are about to smoke may cause serious health problems!) or something that is primarily there to legally protect the manufacturer in case something bad happens in the future (The artificial sweetener you are about to use has been found to cause cancer in laboratory animals; we have no idea if it will harm you but if it does, this warning will help protect us from any legal action you may take against us!).

When you see your doctor, a wealth of recommendations to reduce risk and warnings may accompany a prescription or other treatment. As is the case for food labels, the reasons vary and the consequences of ignoring these warnings vary as well.

Some of the more common warnings that appear on food and alcohol labels have less to do with medical conditions and more to do with common sense. For example, if you drink enough alcohol, your judgment and ability to drive may be impaired. Naturally, ignoring these may lead to medical problems, such as sexually transmitted disease (a potential consequence of exercising poor judgment), head injury (a potential consequence of driving drunk) or even death.

As is the case with cigarette smoking, there are probably few who do not realize that alcoholic beverages may cause health problems; but the specifics may be surprising. For example, women who are trying to conceive should avoid alcohol because its use has been associated with birth defects. Liver disease, including cirrhosis, may result from regular, long-term alcohol abuse, but just how much alcohol is likely to cause liver trouble varies between people and may be hard to predict. And in recent years, it is the medical benefits, rather than risks, of regular, modest alcohol intake that has received the most attention. For example, up to two glasses of wine per day for men, up to one per day for women may be associated with a reduced incidence of cardiovascular disease. Still, don’t expect a label warning against abstinence from alcohol any time soon.

Among the other medically important and common food label warnings I found in my kitchen include:

Aspartame — This sweetener, found in Nutrasweet and many similar products, contains an amino acid (one of the building blocks of protein) called phenylalanine. For people with a rare, inherited condition called phenylketonuria (PKU), phenylalanine builds up in the body and causes serious problems, including brain damage. Newborns are routinely screened for this condition and if detected, they must restrict their dietary intake of phenylalanine. That’s why sweeteners containing aspartame carry a warning: Phenylketonurics: contains phenylalanine.

Peanuts — Serious allergic reaction to peanuts is among the most common of all food allergies, so foods that may contain even minor amounts of peanuts have warning labels to let you know.

Meats — there are warning labels on ground beef to make sure it is cooked thoroughly. One reason is a bacterium that may cause serious bleeding from the intestinal tract. It’s called E. coli O157:H7, a rare strain of a common bug that normally lives in animal and human intestines; this strain makes a toxin that causes disease but can be eradicated by thorough cooking at high temperature.

Eggs — Salmonella enteritidis is a bacterium that can be ingested from raw or undercooked eggs; the warning label on eggs urges you to cook them thoroughly, to wash your hands well after cracking raw eggs and to wash cooking surfaces if they have come into contact with raw eggs.

Your doctor or pharmacist may warn you about a prescription you are about to fill; in fact, pharmacies typically have rolls of stickers to apply to pill bottles with suggestions or warnings about how to take the medicine. Among the most common are:

Take after food — This recommendation is common for many medicines because eating food buffers the acid in the stomach, and that can make medicines such as ibuprofen or aspirin easier to take.

Take on an empty stomach — Some medicines will not be absorbed properly unless taken on an empty stomach; common medicines for osteoporosis, alendronate (Fosamax) and risedronate (Actonel), are examples. In addition, a warning label for these medicines will urge you to take them with a full glass of water and to remain upright — that is, don’t go back to bed if you take it in the morning — to ensure it goes down properly all the way into the stomach; if it does not, it may cause serious irritation and damage to the esophagus called erosive esophagitis.

Discard after one year — Although many (or even most) medications are good for more than one year, this warning is present just to be on the safe side. And while this approach seems sensible, it is rare that “old” or “stale” medications have caused harm.

Interactions — Because mixing medications (including over-the-counter medicines) can lead to a variety of problems, warning labels often mention not to take certain medicines if you are already taking another one. Common examples of how problems occur include:
- Additive dose — Avoid taking Motrin and Advil together. Because these are identical medications, taking both just increases the dose higher than intended. With higher than recommended doses comes a higher risk of side effects, such as stomach upset or even a bleeding ulcer.
- Additive effect — Avoid alcohol with sedatives. Some medicines are mildly sedating and are well tolerated on their own, especially if taken before bed; but alcoholic beverages are also sedating, and the combination is sometimes much more than bargained for.
- Counteracting drugs — Avoid taking birth control pills with phenytoin The effectiveness of the first medication is reduced due to the addition of the second medicine; this may not mean the second medicine has to be avoided, but the dosage of the first medication may need to be changed or, in the case of birth control pills, another contraceptive method may be necessary.

Avoid the sun — Certain medications are called “photosensitizers” because they increase one’s sensitivity to the effects of the sun. Examples include tetracycline and sulfa antibiotics (such as Bactrim). Sun exposure while taking these medicines may include rash, fever, and a general feeling of sickness after only a short time in the sun. For this reason, warning labels that recommend avoiding prolonged or direct sun exposure often accompany prescriptions for these medicines.

Allergic reactions — While a drug allergy is a clear enough reason to avoid that drug, some warning labels are not intuitive; for example, the warning that accompanies the flu shot states that you should avoid the vaccination if you are allergic to eggs; that’s because the vaccine is prepared from chicken eggs and persons with serious allergic reactions to eggs may have a bad reaction to the flu shot; similarly, a person who is allergic to aspirin should not take Advil or Alleve or other nonsteroidal anti-inflammatory drug (NSAID). It’s not that they contain aspirin, but because they are chemically similar, a bad reaction to one is more likely if you have a bad reaction to any one of the others.

Besides asking about allergies to dyes that may be used in a test or a procedure, the most common warning is to avoid eating or drinking after midnight. For some tests, such as colonoscopy, the intestinal contents should be as empty as possible to allow adequate inspection. Another reason is that for some procedures, an anesthetic agent is used and if you should vomit as a reaction to the anesthesia, the contents of your stomach could be inhaled into your lungs, causing lung injury or pneumonia. It’s better to play it safe with an empty stomach prior to surgery. That's why "eat nothing after midnight" is a common recommendation before surgery.

With so much risk and so many warnings, what's a person to do? There may be too many warnings about risks that are quite small. In fact, there is a risk of providing too many warnings, including the possibility that warnings will be ignored simply because heeding them all seems impossible. There's also the risk of not taking a medication for fear of taking it incorrectly. I know patients with arthritis who often skip their medications because they are not having a meal – they lose the benefit of the medicine because they were trying to follow the warning label's recommendation — in fact, most of the time, a single dose on an empty stomach is not likely to cause problems. Or, a snack, rather than a full meal, is all they need to take their medication safely.

Do your best to read about your medications and follow instructions — if they contradict each other (which does sometimes occur), call your doctor or pharmacist to sort it out.

Risk is a part of the human condition — there is risk associated with eating, breathing and crossing the street. And although we may worry most about the risk of developing disease, we should also consider the risks of its treatment. Of course, for any given condition there may also be risks associated with not getting treatment. You can reduce your risks related to the medicines by asking questions, and by learning more about what your doctor and pharmacist (and their little stickers) are saying. When you understand why a warning is there in the first place, it's a lot easier to assess its importance.

Robert H. Shmerling, M.D. is associate physician at Beth Israel Deaconess Medical Center and associate professor at Harvard Medical School. He has been a practicing rheumatologist for over 20 years at Beth Israel Deaconess Medical Center. He is an active teacher in the Internal Medicine Residency Program, serving as the Robinson Firm Chief. He is also a teacher in the Rheumatology Fellowship Program.