Consensus report. Drug concentrations and driving impairment. Consensus Development Panel.

Most drugs that affect the central nervous system have the potential to impair driving ability. For many years, alcohol (ethanol) has been the drug of greatest concern, since it is, by far, the most frequently recognized cause of drug-impaired driving. Yet as more therapeutic agents, such as benzodiazepines, are introduced and widely used, and as social use of unsanctioned drugs such as cannabis (marijuana) increases, attention must be directed toward other drugs. The National Institute on Drug Abuse sponsored a conference on drugs and driving in Durham, NC, in October 1983. The objective was to reach a consensus on several key issues associated with the current state of knowledge about the relationship between body fluid concentrations of drugs and their pharmacologically active metabolites and degree of driving impairment. It was also of interest to ascertain whether a sufficient body of knowledge exists for an expert to form an opinion, which will meet the applicable standards of proof for legal proceedings, that a person's driving ability was impaired based on body fluid concentrations of a drug. The consensus panel, representing the disciplines of clinical pharmacology, analytical and forensic toxicology, law, and forensic medicine agreed on answers to the following questions: Is ethanol a good model for other drugs? What drugs might have a potential for impairing a driver? How is driving impairment measured? What is known about correlations between driving impairment and drug concentrations? Could "per se" concentrations be established for drugs other than alcohol? Can impairment be established from body fluid concentrations?