Medications and Driving: How Common Drugs Impair Your Ability to Drive and What It Means Legally

Driving While on Medication Isn’t Just Risky-It’s Often Illegal

You take your pills like clockwork. Your blood pressure is under control. Your sleep’s better. But if you’re getting behind the wheel after taking them, you might be driving while impaired-even if you feel fine.

It’s not just alcohol that clouds your judgment on the road. Prescription drugs, over-the-counter cold meds, and even sleep aids can slow your reactions, blur your vision, and make you drowsy. And unlike alcohol, most people don’t realize how dangerous it is. The Medications and Driving issue isn’t a fringe concern-it’s a leading cause of preventable crashes, second only to drunk driving.

Which Medications Are Most Dangerous Behind the Wheel?

Not all drugs affect driving the same way. Some hit you hard. Others sneak up on you. Here’s what the data shows:

• Benzodiazepines (like Xanax, Valium): These anti-anxiety meds slow brain processing by 25-40%. Drivers on these drugs are 40-60% more likely to crash. The risk spikes even higher if mixed with alcohol.
• Opioids (oxycodone, fentanyl): These painkillers cause droopy eyelids, blurred vision, and reaction times that drop by up to 300 milliseconds-enough to miss a stop sign at 50 mph.
• First-generation antihistamines (diphenhydramine in Benadryl, Tylenol PM): These are the hidden danger. One dose can impair you as much as a 0.10% blood alcohol level-higher than the legal limit in every U.S. state. And the drowsiness doesn’t vanish after you wake up. A driver who took Tylenol PM at 10 p.m. might still be impaired at 9 a.m.
• Tricyclic antidepressants (amitriptyline) and mirtazapine: These increase crash risk by 40%. They don’t just make you tired-they mess with coordination and attention.
• NSAIDs (ibuprofen, naproxen): You’d think these are safe. But research shows users have a 58% higher crash risk. Why? They can cause dizziness, especially in older adults.
• Zolpidem (Ambien): This sleep aid can impair driving for up to 11 hours after taking it. Most people think they’re fine after 8 hours. They’re wrong.

Why You Think You’re Fine-But You’re Not

Here’s the cruel trick: most people who drive on these meds feel perfectly normal. That’s the problem.

A 2021 AAA survey found that 68% of patients were never told by their doctor that their medication could affect driving. Another 50% didn’t even understand the warning labels. “May cause drowsiness” isn’t enough. It doesn’t say when the drowsiness hits. Or how long it lasts. Or whether it gets worse with other meds.

One Reddit user, u/SafeDriver2023, shared how he took Tylenol PM before bed, woke up at 7 a.m., felt “fine,” and drove to work at 9 a.m.-only to fail a field sobriety test because the diphenhydramine was still in his system. He didn’t know the drug lingers. Neither did his doctor.

And it’s not just older people. A 2022 study found that 70% of drivers who took three or more potentially impairing medications still got behind the wheel within two hours of the last dose. They thought they were safe. They weren’t.

The Legal Side: You Can Be Charged Even Without Alcohol

In the UK and most U.S. states, you don’t need to be drunk to get a DUI. If a drug-prescription or not-impairs your ability to drive safely, you’re breaking the law.

Twenty-eight states in the U.S. have specific legal limits for prescription drugs in your blood. In the UK, the law is even stricter: you can be prosecuted for driving with certain medications in your system-even if you’re taking them as prescribed. The list includes morphine, codeine, diazepam, and others.

Police use Drug Evaluation and Classification (DEC) programs to spot impairment. Officers trained in this method look for signs: slow pupil reaction, eyelid droop, poor balance, and erratic steering. If you’re pulled over and they suspect drugs, you’ll likely be asked to take a blood or saliva test.

And here’s the kicker: there’s no breathalyzer for drugs. That’s why enforcement is hard. But it’s not impossible. In 2023, NHTSA rolled out saliva-based roadside tests that can detect 12 common prescription drugs with 92.7% accuracy. These are being used in 47 U.S. states now.

Who’s Most at Risk-and Why

People over 65 are at the highest risk. Why? Their bodies process drugs slower. Their liver and kidneys don’t clear medications as quickly. And they’re more likely to be on multiple prescriptions.

The American Geriatrics Society’s Beers Criteria lists over 30 medications that should be avoided in older adults because of their driving risks. Yet only 41% of physicians routinely discuss driving safety when prescribing these drugs.

And it’s not just seniors. Younger drivers taking stimulants for ADHD or opioids after surgery are also at risk. A 2020 study found that 22% of drivers involved in trauma crashes had multiple drugs in their system-often mixing alcohol, marijuana, and prescriptions. The effects aren’t just added together-they multiply.

What You Can Do to Stay Safe (and Legal)

You don’t have to give up your meds. But you do need to be smarter about them.

1. Ask your doctor or pharmacist: “Can this medicine make me unsafe to drive?” Don’t assume it’s okay because it’s prescribed.
2. Check the label: Look for “do not operate heavy machinery.” That includes cars. If it’s there, take it seriously.
3. Wait it out: For first-gen antihistamines, wait at least 6 hours. For sleep meds like Ambien, wait 8-12 hours. If you’re unsure, don’t drive.
4. Track your own reactions: After starting a new med, try driving only in safe, low-traffic areas. Pay attention: Are you slower to react? Do your eyes feel heavy? Is your steering wobbly? If yes, don’t drive.
5. Use a driving simulator: The University of Iowa developed a simple test that checks your reaction time and lane control. You need to complete 15 maneuvers with less than 1.5 lane deviations. If you fail, don’t drive until you retest.

The Future Is Here-And It’s Watching You

Car makers are already building tech to detect impairment. By 2027, 85% of new vehicles will have biometric sensors that track eye movement, steering patterns, and even heart rate. If you’re drowsy or impaired, your car might warn you-or even slow down and pull over.

Meanwhile, the FDA now requires “Driving Risk Scores” on all CNS-acting drug labels, rating impairment from 1 (minimal) to 5 (severe). That’s a big step forward.

But tech won’t fix the real problem: people don’t know the risks. And doctors aren’t talking about them.

Final Reality Check

One in 20 drivers admit to getting behind the wheel within two hours of taking an impairing prescription drug. Nearly 40% of people admit to riding with someone who just took a risky med. Yet 85% say they’d be terrified to do it.

That’s the disconnect. We know it’s dangerous. But we do it anyway.

Medication doesn’t make you a bad person. But ignoring its effects on your driving makes you a danger-to yourself and others.

Ask the questions. Read the labels. Wait the hours. Your life-and someone else’s-could depend on it.