Every day, countless drivers get behind the wheel while under the influence of substances that affect their reaction time, coordination, and judgment—often without realizing the risk. While alcohol-related DUIs get most of the attention, drugged driving has become an equally dangerous problem on U.S. roads. Many of these substances are not illegal street drugs but everyday medications—prescriptions, over-the-counter remedies, and even herbal supplements—that can quietly compromise driving skills.

Understanding how drugs that impair driving affect the body, which medications are commonly involved in accidents, and what the law says about impaired driving can help you protect yourself and others on the road.

Understanding Drug-Impaired Driving

Driving under the influence of drugs—often called drugged driving—occurs when a substance, whether legal or illegal, interferes with a person’s ability to operate a vehicle safely. These substances can alter attention, depth perception, reaction time, or coordination, increasing the likelihood of crashes.

Unlike alcohol, which can be measured easily through a breathalyzer, detecting drugs that impair driving is far more complicated. Different drugs affect people in different ways, and combinations of substances (for example, painkillers and sleep aids) can amplify impairment.

Both federal and state laws prohibit driving while impaired by drugs. Under most state statutes, including those modeled after the Uniform Vehicle Code, it’s illegal to operate a vehicle while under the influence of any chemical substance that impairs normal faculties. Drivers can face arrest and prosecution for a DUI involving prescription drugs just as they would for alcohol or illegal drugs.

Common Drugs That Impair Driving

Some medications and substances have well-documented effects on driving ability. These include both prescription and non-prescription drugs.

Prescription Drugs and Driving

Many prescription drugs warn against operating heavy machinery or driving after use. Some of the most common impaired driving drugs prescribed by doctors include:

• Opioid painkillers such as oxycodone, hydrocodone, and morphine. These can cause drowsiness, confusion, and slowed reaction time.
• Benzodiazepines (like Xanax, Valium, or Ativan), used to treat anxiety and sleep disorders. They can cause dizziness, blurred vision, and delayed reflexes.
• Muscle relaxants such as cyclobenzaprine and carisoprodol, which can produce sedation or mental fog.
• Antidepressants and certain antipsychotics, especially tricyclic antidepressants, may cause fatigue and difficulty concentrating.
• ADHD medications like Adderall or Ritalin. While these stimulants can improve focus in prescribed doses, overuse or misuse can lead to agitation, impulsive driving, and poor judgment.

Over-the-Counter Medications and Driving Impairment

Even seemingly harmless over-the-counter medications can affect driving performance. Cold and allergy medicines containing diphenhydramine (found in Benadryl) or doxylamine can cause significant drowsiness. Cough syrups that include dextromethorphan may impair motor control and concentration, especially in higher doses.

Many drivers underestimate the risks of these medications, assuming that because they’re available without a prescription, they’re safe to take before driving. However, mixing multiple medications—especially those with sedative effects—can amplify impairment.

Illegal Drugs and Driving Ability

Illegal drugs and driving create some of the most dangerous situations on the road. The most common substances that affect driving skills include:

• Marijuana: THC can delay reaction time, distort time and distance perception, and reduce motor coordination. Studies have shown that drivers under the influence of cannabis are more likely to be involved in crashes.
• Cocaine and methamphetamine: These stimulants can create false confidence and aggressive driving behaviors, followed by fatigue and impaired judgment as the effects wear off.
• Heroin and synthetic opioids: These drastically depress the central nervous system, slowing reaction times and coordination.
• Hallucinogens (LSD, psilocybin): These drugs alter perception and awareness, making safe vehicle operation nearly impossible.

According to the National Highway Traffic Safety Administration (NHTSA), more than half of all drivers involved in fatal crashes test positive for at least one drug, showing how widespread this issue has become.

The Science of Drug-Impaired Driving

Drugs interfere with the brain’s ability to process information and respond quickly. Reaction time, focus, and decision-making are all essential to safe driving—and even minor impairment can lead to serious consequences.

For example, sedatives like benzodiazepines slow the brain’s response time, while stimulants like cocaine increase impulsivity. Combining drugs, or drugs and alcohol, multiplies impairment. Research shows that even small doses of multiple medications can interact to magnify drowsiness or delay reaction time.

Legal Consequences of Driving Under the Influence of Drugs

In nearly every state, driving under the influence of drugs carries the same penalties as alcohol-related DUI. This includes fines, license suspension, mandatory treatment programs, probation, and even jail time.

Law enforcement officers are trained to identify signs of drug impairment through field sobriety tests and specialized Drug Recognition Experts (DREs). Blood or urine tests may also be used to confirm the presence of drugs. However, unlike alcohol, there is no universal “legal limit” for most drugs, which means officers and prosecutors rely heavily on behavioral evidence.

Importantly, even if you have a valid prescription, you can still be charged with impaired driving if the medication affects your ability to drive safely. Courts and insurance companies treat DUI prescription drug cases seriously, especially if the driver caused injury or death.

Drugs Linked to Car Accidents

Studies have identified several categories of drugs linked to car accidents, especially those that depress the central nervous system. Opioids, benzodiazepines, barbiturates, and cannabis are the most common culprits. Drivers who use these substances—alone or in combination—have significantly higher crash rates than those who are sober.

When accidents occur, toxicology reports often show multiple substances in a driver’s system, highlighting the dangers of drug interactions. In many cases, individuals don’t realize the additive effects of taking multiple prescriptions or mixing alcohol with medications.

Civil Liability and Drugged Driving Accidents

If someone causes a crash while impaired by drugs, they may face not only criminal penalties but also civil liability for injuries and damages. Victims of drugged driving accidents can pursue a personal injury claim to recover compensation for medical bills, lost wages, pain and suffering, and more.

Proving impairment can be complex, requiring medical evidence, toxicology results, and expert testimony. A personal injury lawyer familiar with impaired driving cases can help establish fault and demonstrate how the other driver’s substance use led to the collision.

How to Stay Safe if You Take Medications

If you take prescription or over-the-counter medications, talk with your doctor or pharmacist about possible side effects. Ask specifically whether the drug can affect alertness, vision, or coordination. Avoid driving when starting a new medication until you know how your body reacts. Combining substances—even caffeine or alcohol—with your medication can increase impairment.

You should also review warning labels. If the label says, “Do not operate heavy machinery,” that includes your car.

Call Brandon J. Broderick For Legal Help

If you or someone you love has been injured in a drugged driving accident, you have legal rights. Whether the other driver was impaired by illegal drugs or prescription medications, they can still be held accountable for the harm they caused.

Brandon J. Broderick, Attorney at Law, helps victims of drug-impaired driving crashes pursue compensation for their injuries and losses. Our team investigates each case thoroughly, works with experts to determine impairment, and fights for the justice our clients deserve.

Contact us today for a free consultation and learn how we can help you move forward after an accident caused by drugs that impair driving.