An evaluation was made of existing data on concentrations of marijuana, secobarbital, diazepam, diphenhydramine, and methaqualone in blood, saliva and urine to assess the feasibility of establishing chemical tests for detecting drug-impaired driving. The study employed standard pharmacokinetic methods to relate urine and saliva concentrations to blood levels, which were related to measures of behavioral impairment in laboratory tasks. Marijuana was the only drug for which sufficient data were available to suggest the use of urine tests to establish the need to obtain or analyze a blood specimen for THC. Data from numerous studies support the proposal that testing for THC metabolites in urine at or above the 100 ng/ml concentration will provide better than a 50% probability of detecting levels of THC in the blood that may be associated with impairment. Saliva appears to offer more promise as a body specimen for a presumptive screen of the other drugs included in the study. Analysis of data on secobarbital, as a representative of the barbiturate group of sedatives, suggested saliva concentrations in excess of 0.5 microg/ml may serve as a possible threshold for predicting impairing levels of the drug in the blood. Similarly, a combined concentration of 5 ng/ml of diazepam and its primary metabolite in saliva appeared as a reasonable level. The antihistamine diphenhydramine gives high saliva concentrations following its use, thus level of 180 ng/ml in saliva was selected as a threshold for conducting a blood analysis. Evaluation of data on methaqualone suggests a threshold level of 150 ng/ml in saliva. It is cautioned that this was a preliminary study based on existing data. Additional studies and collection of more prevalence data are necessary to further establish the reliability of the suggested threshold levels in order to predict when blood tests for a specific drug are necessary or desirable. Such tests are presently only available for alcohol and marijuana with use limited to the stationhouse or emergency room. At the present state of knowledge, blood is the only body fluid that may serve in a limited manner to relate drug levels to impaired driving.

Media Info

  • Features: Figures; References; Tables;
  • Pagination: 72 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00491240
  • Record Type: Publication
  • Source Agency: National Highway Traffic Safety Administration
  • Report/Paper Numbers: HS-806 920
  • Contract Numbers: DTNH22-84-C-07265
  • Files: HSL, NTL, TRIS, USDOT
  • Created Date: Feb 28 1990 12:00AM