Effect of clonazepam and drug combination on driving ability in healthy adults with driving under the influence of drugs

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What is this study about?

The study examines how several commonly prescribed medicines affect a person’s ability to drive safely. The medicines being tested are clonazepam, tramadol, pregabalin, gabapentin, dexamfetamine, and sodium oxybate. The condition of interest is Driving under the influence, which means impaired driving after taking a drug.

The main purpose is to determine how these drugs change driving performance. Participants will receive one of the study medicines or a placebo capsule and then, after a short waiting period, will complete a computer‑based driving simulation and a series of simple memory and reaction tests at specific times. Blood, saliva and other samples will be taken, and heart activity will be recorded with a ECG.

The driving simulation measures how well a person stays within the lane and how fast they travel. Cognitive tests include a digit span test (remembering numbers) and a reaction test (pressing a button quickly when a signal appears). Heart rhythm is monitored, and a mobile tool called the DRUID app records any feelings of impairment. Participants also answer short questionnaires about sleepiness and how they feel while driving.

1 receive study medication

after you join the study, a study staff member will give you one oral capsule. the capsule contains either clonazepam 1.5 mg, sodium oxybate 4.5 g, dexamfetamine 20 mg, pregabalin 300 mg, gabapentin 800 mg, tramadol 100 mg (which also includes paracetamol), or a placebo capsule that has no active drug. you will take the capsule once, on the test day.

2 waiting period and baseline measurements

after taking the capsule you will rest for about 45 minutes. during this time vital signs are checked, electrodes are attached to record your heart rhythm (ecg) continuously, and a baseline blood sample is collected. saliva and urine may also be collected before the medication takes effect.

3 first cognitive assessment

45 minutes after taking the medication you will complete a short set of computer tests that measure attention, memory, reaction time and decision making. the tests include a field of view test, a digit span test (remembering numbers), a stop signal test (ability to stop a response), a digit‑symbol substitution test (matching symbols to numbers quickly), and a four‑choice reaction test (choosing the correct option among four). these tests help determine any changes in thinking caused by the study drug.

4 first driving simulation

2 hours after taking the medication you will sit in a driving simulator for about 10‑15 minutes. the simulator records how well you stay within the lane, your speed and steering movements. the main measurement is the standard deviation of lateral position, which shows how much you drift side to side while driving.

5 subjective and scale assessments after first drive

about 2 minutes after the first drive (approximately 2:25 after intake) you will answer three short questionnaires: the karolinska sleepiness scale (rates how sleepy you feel), the brief biphasic alcohol effect scale (rates feelings similar to alcohol), and a visual analogue scale where you mark perceived driving effort and quality. you will also answer yes/no questions about side effects, feeling drugged, and whether you think you are fit to drive.

6 second cognitive assessment

3 hours and 45 minutes after taking the medication you will repeat the same cognitive test battery described in step 3. this allows comparison of performance over time.

7 second driving simulation

4 hours and 45 minutes after taking the medication you will repeat the driving simulation. the same measurements (lane position, speed, steering) are recorded again to see any changes.

8 final scale assessments

5 hours and 10 minutes after taking the medication you will again complete the karolinska sleepiness scale, brief biphasic alcohol effect scale and visual analogue scale, plus the same yes/no questions about side effects, feeling drugged and fitness to drive.

9 additional biological sampling

blood samples are taken at each testing point (before dosing, after the first drive, after the second drive) to measure the concentration of the study drug. at the same times saliva, dried blood spots, dried saliva spots, urine and a small hair sample are also collected to study how the drug is processed by the body.

10 continuous monitoring

throughout the entire testing day your heart rhythm (ecg) is recorded continuously, and your eye movements are tracked during each driving simulation to assess ocular activity.

Who Can Join the Study?

Age: You must be between 18 and 45 years old.
Driving licence: You need a European driving licence that you have held for at least one year.
Driving experience: You must have driven at least 200 kilometres (about 124 miles) in the past year.
English language: You must be able to read and understand English.
Vision: Your eyesight must be normal, or you must use glasses or contact lenses to correct it.
Body mass index (BMI): Your BMI, a measure of weight compared to height, must be between 18.5 and 29.9.
Blood pressure: Your blood pressure must be lower than 160/100 mmHg (the pressure of blood in your arteries; higher numbers can indicate hypertension).

Who Cannot Join the Study?

You have a self‑reported history of traumatic brain injury, such as a major concussion.
A pregnancy test is positive at the start of the study (women only).
Your score on the Kennedy simulation sickness questionnaire (KSSQ) is higher than 30 after simulator training.
You have a self‑reported diagnosis of neurological or psychiatric conditions, for example attention‑deficit/hyperactivity disorder.
You report having any cardiovascular, gastrointestinal, hepatic, or renal disease, including high blood pressure (hypertension) or chronic lung disease.
You are currently using any medications that affect driving ability or that could interact with the study drugs or alcohol.
You consume more than 21 units of alcohol per week (high‑risk alcohol consumption).
You smoke more than six cigarettes per day.
You have a history of severe skin reactions such as Stevens‑Johnson syndrome, drug‑induced hypersensitivity syndrome, or a drug rash with eosinophilia and systemic symptoms after taking any of the study drugs.
Your urine pH is outside the range of 4.5 to 8.0 at the beginning of the visit.
You did not pass the required eye‑sight test.

Where you can join this trial?

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Other Sites

Site Name	City	Country	Status
Rvpwlnex Upeywtecwl	Roskilde	Denmark

Trial status

Country	Status	Recruitment Start
Denmark	Not yet recruiting	01.03.2027

Trial locations

Investigated Drugs:

Clonazepam is a medication that belongs to a group of drugs called benzodiazepines. In this study it is given by mouth to see how it might affect a person’s thinking, reaction time, and ability to drive safely. Researchers are watching for any changes in alertness, coordination, or judgment while participants take this drug.

Sodium oxybate (often known as GHB) is a central nervous system depressant that is also taken orally. The trial uses it to understand whether it can cause drowsiness, memory problems, or slower decision‑making that could make driving more difficult. Participants are monitored for any signs of reduced alertness or impaired motor skills.

Dexamphetamine is a stimulant medication that is taken by mouth. In the trial it is used to see if it can improve focus, speed of thinking, or reaction time, and whether any of these effects might make driving performance better or worse. Researchers watch for increased energy, restlessness, or changes in concentration.

Pregabalin is a drug taken orally that is often used for nerve pain and anxiety. The study looks at how it might affect attention, coordination, and the ability to respond quickly while driving. Participants are observed for any feelings of dizziness, drowsiness, or reduced mental sharpness.

Gabapentin is an oral medication commonly used for nerve pain and seizures. In this trial it is examined for its possible impact on thinking skills, reaction speed, and overall driving safety. Researchers check for side effects such as sleepiness, blurred vision, or slowed thinking.

Tramadol (combined with paracetamol) is an oral pain‑relieving medication. The study evaluates whether it can cause drowsiness, affect coordination, or change a person’s ability to stay focused while driving. Participants are monitored for any signs of sedation, dizziness, or slower reaction times.

Driving under the influence – Driving under the influence refers to the state in which a person operates a vehicle while impaired by alcohol, prescription medication, or other psychoactive substances. The impairment can reduce attention, slow reaction time, and affect coordination. As the concentration of the substance in the bloodstream rises, the degree of impairment typically increases, leading to greater deviation from normal driving patterns. The effects may persist for several hours after intake, gradually diminishing as the drug is metabolized. This condition is measured by changes in vehicle control, speed, and lane position.

Trial ID:

2026-526362-24-00

Trial Phase:

Therapeutic confirmatory (Phase III)

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Effect of clonazepam and drug combination on driving ability in healthy adults with driving under the influence of drugs

What is this study about?

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