The recommendation for laying down a limiting value of tetrahydrocannabinol (THC) concentration in plasma raises the question of dose-effect relations. For this an essential precondition is the determination of pharmacokinetic parameters as resorption, distribution and elimination constants as well as distribution volume and bioavailability. We have evaluated results of five studies which contain data relating to THC levels in plasma after smoking of marijuana cigarettes with defined content of THC. The pharmacokinetic parameters developed out of these studies under presumption of a two compartment model leads to a time plot of average THC concentrations as well as minimum and maximum curves at which the standard deviation of the pharmacokinetic parameters are taken into account. In particular during resorption and in the late elimination stage estimation of plasma levels of THC is accompanied by a wide dispersion. Nevertheless estimation of THC concentrations out of the amount of consumed marijuana at a stated time or on the other hand interval out of THC concentration in plasma is to be derived using the developed curves of THC concentrations. (A)
Samenvatting