Opioid Use and Driving Impairment

Opioids (also known as opiates or narcotics) are a class of drugs used legally for pain relief and cough reduction, and also used illegally for their ability to produce a form of intense pleasure known as euphoria. They achieve all of these effects by binding to nerve cells (neurons) in the central nervous system and altering the signals produced by those cells. People who have grown accustomed to the effects of properly used prescription opioids typically experience no real reduction in driving skills. However, people unaccustomed to properly used opioids, as well as people who abuse prescription or illegal opioids, can develop a number of serious driving impairments.

Opioid Basics

Opioids get their name because all drugs in this class stem directly or indirectly from mind-altering substances found in the sap of Papaver somniferum, a plant known popularly as the opium poppy. The three active substances derived directly from this plant are opium, morphine, and codeine. Drugs derived from manmade alterations of these three naturally occurring substances include heroin, hydrocodone (Lortab, Vicodin), and oxycodone (OxyContin). Completely synthetic drugs derived from the chemical structure of naturally occurring opioids include synthetic codeine, methadone, meperidine (Demerol) and, fentanyl (Actiq, Fentora).

Opioids have specific effects that vary somewhat according to the medication or illegal drug under consideration. However, all substances in this class share basic effects that include production of euphoria, pain relief, reduction of the normal rate of communication in central nervous system and reduction of the normal rate of communication in the peripheral nervous system, which connects to the central nervous system through the spinal cord and includes all of the nerves found throughout the body. Effects associated with these nervous system slowdowns include anxiety reduction (sedation), drowsiness, abnormally shallow breathing, reduced mental clarity, increased urine output and, constriction (narrowing) of the pupils. Some opioids produce these effects directly by binding to sites on the neuron surfaces called opioid receptors. Others, like heroin, break down in the body and release opioid byproducts that bind to those receptors.

Effects on Task Performance

An agency within the US Department of Transportation, called the National Highway Traffic Safety Administration (NHTSA), regularly reviews the risks associated with driving under the influence of various legal and illegal drugs. This review includes an assessment of the ability to perform certain basic tasks while influenced by any given substance, as well as an assessment of the specific effects that substance has on the ability to control a motor vehicle. Task performance impairments found in people who abuse opioids, as well as in people unaccustomed to the effects of their prescription opioid doses, include sleepiness, fatigue, a general decrease in consciousness, lack of normal reaction times to changing events, a decreased ability to concentrate, an inability to perform multiple tasks simultaneously, and poor integration of conscious thoughts and bodily responses. These deficits typically remain in effect for several hours after drug use.

Effects on Driving Impairment

Opioid abusers and people unaccustomed to their prescribed opioids can develop driving impairments that range from moderate to severe, the NHTSA notes. Specific manifestations of these impairments include poor ability to control driving speed, poor ability to follow other vehicles at a safe distance, poor ability to maintain proper position within a traffic lane, and poor decision-making that increases the risks for accidents with other vehicles, as well as single-vehicle accidents. The length of time during which these impairments remain active varies according to the specific substance in question, the dose of that substance taken, and the level of tolerance a person has to that substance’s effects.

Considerations

Numerous modern studies have examined the issue of driving while taking long-term doses of prescription opioid medications, such as those commonly used by cancer patients and other people dealing with chronic pain. According to an extensive study review published in 2003 in the Journal of Pain and Symptom Management, as well as a study published in 2005 in the Clinical Journal of Pain, people who have become accustomed to their prescribed opioid pain medications do not usually experience a significant reduction in their ability to control a motor vehicle. Findings in these studies come from both driving simulation tests and actual driving in real-world road conditions. Despite these findings, doctors and drug manufacturers routinely (and sensibly) caution users of opioid medications about the risks of operating a motor vehicle. Doctors typically evaluate the mental and motor skills of their opioid-using patients on a case-by-case basis.