[Cannabis: toxicokinetic focus and methodology of urinary screening]

Cannabis is the most commonly used illicit drug in the world. The major psychomimetic compound is delta 9-tetrahydrocannabinol. The major effects consist in alterations of sensory perception, cognition, motor coordination and self-perception. Procedures designed to detect cannabis use have been developed since 1988. The traditional approach is to screen urine by immunoassay and to submit positive samples for confirmation by gas chromatography and mass spectrometry. There continue to be many difficulties in interpreting the results because of the biotransformations of delta 9-tetrahydrocannabinol.