EFFECTS ON DRIVING ABILITY
This section of the report begins with a general overview of medication use and crash risk. Next, recently conducted epidemiological and experimental studies conducted to determine the consequences of a single class of medication on the ability to drive safely are reviewed. These studies are limited to the medications most frequently used by the older community-dwelling population (benzodiazepines, opioids, antidepressants, and antidiabetics). It concludes with three studies that analyzed multiple medication use as follows: one study that evaluated medication use and fitness to drive, one evaluation using a pharmacy database linking a recent crash event to medication use, and one study evaluating substances found in the blood of drivers killed in crashes. Unfortunately, there is a dearth of research on the effects of combinations of specific medications or even combinations of drug classes on driving ability per se.
In theory, all psychoactive compounds (depending on dose), may have detrimental effects on psychomotor performance underlying driving skills (Walsh, de Gier, Christopherson, and Verstraete, 2004). The most common psychoactive substances can be divided into depressants (e.g., alcohol, sedatives/hypnotics, volatile solvents), stimulants (e.g., nicotine, cocaine, amphetamines, ecstasy), opioids (e.g., morphine and heroin), and hallucinogens (e.g., PCP, LSD, cannabis). For some drugs, the effect may be evident for acute use, but may become reduced after tolerance has developed (Morland, 2000). Carr (2004) states that in this era of polypharmacy, there are a myriad of sedating medications that could contribute to driving impairment. A simple drug review may identify benzodiazepines, anticholinergics, narcotics, alcohol, or other medications that, once discontinued, may decrease crash risk.
In Wilkinson and Moskowitz’s (2001) review of 11 epidemiological studies of medication use and traffic safety risk (primarily in older drivers) in the United States and Canada between 1991-2000, it was concluded that the prescription drugs most likely to be associated with motor vehicle crashes by older drivers include the same CNS medications found to increase risk in adults younger than age 65—namely, benzodiazepines (especially long-acting), cyclic antidepressants, and opioid analgesics. Further, they cite a study by Stuck et al. (1994) who found that depressed, community-dwelling elderly were eight times as likely as their nondepressed counterparts to be prescribed a long-acting benzodiazepine in addition to their antidepressant medication.