The problems most often occurred in patients 65 or older, who suffered adverse effects twice as often as those under 65 and were nearly seven times as likely to need hospitalization. Though many of the common conditions reported weren’t life-threatening (like rashes or stomach aches), all were serious enough to require a hospital visit. The most common culprits included insulin, blood thinners and antibiotics; but some of the most popular over-the-counter pain medications were also on the list. Are patients misreading labels or are doctors prescribing inappropriate doses or drugs? NEWSWEEK’s Jennifer Barrett spoke with the study’s lead author, Dr. Daniel Budnitz, a medical epidemiologist at the Centers for Disease Control and Prevention’s National Center for Infectious Diseases, about the results. Excerpts:

Budnitz: ‘A cookie-cutter approach to medicine doesn’t always work’

NEWSWEEK: You estimate that at least 700,000 Americans suffered adverse drug effects in 2004 and 2005 that were bad enough to require a hospital visit. Were you surprised by the number?

Daniel Budnitz: Actually, it is most likely an underestimate. It might just pick up a third of the emergency visits—the number could be much higher. We don’t know how much. But we are confident that there were at least 700,000 emergency department visits. Another point to remember is that these are medications that we’re giving to patients to help them, and they are experiencing some degree of harm. So some might argue that even one of these events is bad. All drugs have benefits and risks, so it’s probably unfair to say that every ER visit is unavoidable. But many of these events—especially the most severe—are due to this handful of drugs that we already knew we need to closely monitor.

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Which drugs produced the most adverse effects in patients?

Insulin, warfarin [a blood thinner], and amoxicillin [an antibiotic commonly used to treat infections] were the most common. And we knew that this could be a problem with them.

Why? Are people misreading the label or are doctors not being clear about the instructions on how to take it?

In the case of insulin, we found cases where patients would take insulin but then forget to eat their meals, or they might be confused about the proper dose. Insulin is a more severe case. Diabetics can get hypoglycemic and have complications like passing out if they don’t eat.

What about warfarin?

The key point for that drug is to ensure patient education about the proper dose. Also, it commonly reacts with other drugs and even foods. So patients need to inform their doctor if they are taking other drugs, other antibiotics, and even if they change their diet. Certain foods like some green leafy vegetables and grapefruit juice are known to change anticoagulation [the blood’s ability to clot]. So if a patient suddenly starts or stops drinking grapefruit juice every morning, he should tell his doctor. It’s also important to keep up with lab monitoring to check their level of coagulation [the drug is intended to decrease the blood’s tendency to clot but not to prevent clotting altogether, so dosing is often adjusted based on blood tests].

What problems were associated with amoxicillin?

The most common adverse effect is a rash but patients can have more serious allergic reactions [such as] anaphylaxis [a potentially life-threatening reaction]. With this one, it’s not so much a dosing issue. But it’s important to assure its appropriate use to prevent complications.

Adverse effects were also reported in several patients who took common over-the-counter drugs like aspirin and ibuprofen. Were you surprised?

Whether or not a drug makes it onto this list is a function of how commonly the adverse effects occur and how many people take the drug. So, you have to remember that many millions of people take aspirin and ibuprofen [but adverse effects only occurred in a small proportion of users].

Are doctors not monitoring use of these drugs closely enough?

Well, one could say it’s sobering that we know these may cause problems yet the problems are still happening. But it may be encouraging too because we know what we can do to do better … For doctors, this is a reminder to be sure to inform patients about potential complications, be sure patients receive indicated monitoring and follow-up and to be sure that the dose and frequency of the drug is right for that particular patient. The key to drugs that require monitoring is that one drug doesn’t typically fit all patients. The doses need to be individualized and that’s challenging for patients and physicians. A cookie-cutter approach to medicine doesn’t always work.

Were there any drugs on the list that surprised you?

There weren’t any that were particularly surprising to me. But if you asked physicians to come up with a list without seeing these, I think they would come up with a very different list.

What would be on theirs?

They’re more likely to report what’s in the news, the newer drugs like the Cox-2 inhibitors [like Vioxx, which was voluntarily pulled from the market based on concerns about the risk of heart problems or stroke]. But these data should remind patients and doctors that often it’s older drugs that we know cause problems that we need to be more vigilant about. I think 16 of the top 18 drugs implicated have been on the market for 20 years or more.

What should we take away from these findings?

What I find most important is the fact that with many of these drugs we know the adverse effects and we know ways to prevent them, and yet they are still happening. I’m not saying no one should ever have an emergency-department visit for bleeding, for example. But we should strive to minimize the complications as much as we can. And patients, too, should be cognizant that just because a drug is prescribed or over-the-counter doesn’t mean it can only have beneficial effects. Drugs can have harmful effects as well.