What's the Most Dangerous Over-the-Counter Drug?

Answers to your questions about the news.
Dec. 8 2011 6:39 PM

What's the Most Dangerous Over-the-Counter Drug?

Hint: It's not Plan B.

Medicine aisle at a drugstore.
What would it take for Tylenol to be harmful to your health?

Comstock/Thinkstock

Health and Human Services Secretary Kathleen Sebelius overruled the FDA's recommendation that emergency contraception be made available over the counter to patients of all ages on Wednesday. Her argument was that its effects on 11-year-olds have not been thoroughly studied. Critics pointed out that many over-the-counter drugs are far more dangerous than emergency contraceptives. What’s the most dangerous drug you can buy without a prescription?

It's hard to say. As far as the Explainer can tell, no researcher has ever compared the fatality rates of every drug available over the counter—probably because the number of deaths from overdose of antacids and many other products is so small as to make the study a waste of time. There is, however, a large body of research on pain relievers. Analgesic overdoses are pretty common in the United States. In 2000, poison-control centers received more than 130,000 calls from people who believed they had taken a dangerous amount of an over-the-counter painkiller. Nearly one-half of those calls concerned acetaminophen, best known as the active ingredient in Tylenol. Approximately 0.2 percent of those cases ended in death. That’s higher than the reported death rate for nonsteroidal anti-inflammatory drugs like Advil (ibuprofen) and Aleve (naproxen), but lower than the fatality rate for aspirin. (Aspirin is technically in the same category, but is often separated for research purposes.)* However, most of the aspirin deaths appear to have been suicides, while accidental overdose is more common than intentional overdose for acetaminophen. Between the years 1990 and 1998, 458 people died from taking too much acetaminophen.*

Pseudoephedrine, a very common cold medication, is also implicated in a number of deaths every year. In 2004, for example, poison-control centers reported 21 deaths in which the chemical was involved. However, most of those patients took a cocktail of drugs—often including acetaminophen—and many of the cases were ruled suicides. It’s also not entirely correct to call pseudoephedrine an over-counter drug. A 2005 act of Congress forced retailers to move it behind the counter because of its use in the production of methamphetamine.

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Of course, many other drugs can be fatal if you go way overboard. Even Epsom salts, which are commonly used as a laxative, can cause cardiac arrest. A hospital in Scotland reported a case of attempted suicide by Epsom salts in 2009. The woman ingested an incredible 4.4 pounds of the stuff. She suffered some acute cardiac complications, but doctors were able to save her.

It’s not easy to determine the fatal dose of over-the-counter drugs. Take the example of acetaminophen. A person’s ability to handle the drug depends on a variety of factors, including the condition of their liver, how much they’ve eaten, and whether they take the pill in conjunction with alcohol. (Bad idea.) Compared to other over-the-counter drugs, acetaminophen has a relatively narrow safety margin—that is, the difference between a safe-but-effective dose and an overdose is relatively small. Doctors have reported liver failure from as little as 2.5 grams in a day, which is 1.5 grams less than the approved limit.

The FDA has considered reducing the approved daily dose (PDF) of over-the-counter acetaminophen, but that wouldn’t help in all cases. Many patients don’t realize how much of the drug they’re taking. Those who are prescribed the painkiller Percocet, for example, might take over-the-counter acetaminophen as an adjunct for different or breakthrough pain. The problem is that Percoset contains acetaminophen, and the combination can easily put them over the dose limit.

What’s the fatal dose of emergency contraceptive? Nobody knows. The drug certainly has side effects, like nausea, vomiting, dizziness, fatigue, and the like. Women who use the morning-after pill as their regular form of contraception can also experience some menstrual irregularities. But no one has taken a fatal dose of Plan B.

Got a question about today’s news? Ask the Explainer.

Correction, Dec. 8 2011: The original stated that 458 people die annually from acetaminophen overdoses. In fact, that was a figure from the years 1990 through 1998. (Return to corrected sentence.) This article also originally misspelled Advil and Percocet. (Return to corrected sentence)

Brian Palmer is Slate's chief explainer. He also writes How and Why and Ecologic for the Washington Post. Email him at explainerbrian@gmail.com. Follow him on Twitter.