Perspiration versus saliva--basic aspects concerning their use in roadside drug testing

Various aspects concerning the practical application and forensic interpretation of data obtained by saliva drug testing and drug monitoring from the skin surface are discussed. Basic information on the composition of saliva and skin secretions and their particular transport mechanisms, as far as known, are given. For drugs of abuse secretion into saliva is suggested to be by passive diffusion and to depend on lipid solubility, pKa, plasma protein binding and on the pH of saliva. Drug molecules from blood are considered to reach the skin surface by various routes such as by sweat and sebum as well as by inter- and/or transcellular diffusion. The role of the stratum corneum as a temporary drug reservoir exceeding positive drug findings in urine is outlined. Current data on opioids, cocaine metabolites, cannabinoids and amphetamines detected in saliva and on the skin surface are reviewed. Aspects of collection, processing and analysis of the samples for implementation in roadside testing are addressed. The requirement of test sensitivity covering the broad concentration ranges and the importance of test specificity bearing in mind that the parent drug is the main analyte present in those specimens is stressed. Theoretical and practical findings on frequently abused drugs are discussed with regard to the possibilities and limitations of drug monitoring from saliva and perspiration to support a suspicion of actual or recent drug administration.