[Column] Is it safe to take medication and drive?

Driving while on medication can be just as dangerous as driving under the influence of alcohol. While drug-related car accidents are often associated with narcotics or psychotropic substances, even common prescription and over-the-counter medications can impair driving ability. The bigger issue is that many drivers are unaware of which drugs pose a risk. A 2023 survey by insurer AXA found that although 91 percent of drivers recognized the dangers of driving under the influence of drugs, 75 percent were unsure which medications could impair their driving.

This is especially true for allergy and rhinitis medications, as well as over-the-counter cold remedies commonly taken during seasonal changes. These drugs often contain antihistamines that relieve symptoms but can also cause drowsiness and impair judgment. The risk is substantial: a 2000 study by the University of Iowa found that drivers who took diphenhydramine -- an antihistamine -- were more impaired than those with a blood alcohol concentration of 0.1 percent. This side effect is not surprising, given that the same ingredient is also found in many sleeping pills.

However, far more medications can cause drowsiness or sedation than people typically realize. These include anti-anxiety drugs, antidepressants, diabetes medications, antihypertensives, muscle relaxants, and anti-inflammatory painkillers. While sedation from anti-inflammatory drugs is rare, it can occur in sensitive individuals -- particularly with indomethacin, which is more likely to cause this effect. Diabetes medications may also induce drowsiness if they lead to hypoglycemia. Even common antidiarrheals like loperamide can have sedating effects, so caution is advised.

The older you are, the more cautious you should be when driving while taking medication. As people age, they are more likely to take multiple medications, increasing the risk of drug–drug interactions that can impair driving or the safe operation of machinery. However, taking medication doesn't mean you shouldn't drive at all. Extra care is needed, especially when starting a new medication or adjusting the dose of an existing one. Drugs such as antihypertensives and antidepressants may initially cause dizziness or drowsiness, which can affect driving. Fortunately, these side effects often subside within a week or two as the body adapts.

That said, alcohol significantly raises the risk of adverse effects. It enhances the sedative properties of many medications, making driving even more dangerous. While drinking and driving is always hazardous, combining alcohol with medication makes it far worse -- and should be strictly avoided.

If you need to take medication to relieve your symptoms, it’s safer to choose a less sedating option. In the study mentioned earlier, the antihistamine fexofenadine -- which does not cause drowsiness -- had little to no effect on driving performance, comparable to a placebo. To stay safe, ask your pharmacist whether your medication is safe to take while driving, and stay indoors the first time you take it to observe how your body responds. If you experience drowsiness, blurred vision, or difficulty concentrating, the safest choice is simply not to drive.

Jeong Jae-hoon is a food writer and pharmacist. He covers a variety of subjects, including trends in food, wellness, and medications. This column was originally published in Korean in Joongang Ilbo on June 19, 2025. – Ed.