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J Pharm Sci. 2018 Feb;107(2):745-755. doi: 10.1016/j.xphs.2017.09.009. Epub 2017 Sep 20.

Relating Observed Psychoactive Effects to the Plasma Concentrations of Delta-9-Tetrahydrocannabinol and Its Active Metabolite: An Effect-Compartment Modeling Approach.

Author information

1
Division of Pharmaceutics and Translational Therapeutics, College of Pharmacy, University of Iowa, Iowa City, Iowa 52242.
2
Division of Pharmaceutics and Translational Therapeutics, College of Pharmacy, University of Iowa, Iowa City, Iowa 52242; Positron Emission Tomography Imaging Center, Department of Radiology, University of Iowa, Iowa City, Iowa 52242. Electronic address: laura-ponto@uiowa.edu.

Abstract

The medical use of marijuana is increasing, yet little is known about the exposure-response relationship for its psychoactive effects. It is well known that the plasma concentrations of the principal psychoactive component of marijuana, Δ9-tetrahydrocannabinol (THC), do not directly correlate to the observed psychoactive effects. The purpose of this research was to use an effect-compartment modeling approach to predict and relate the concentrations of the psychoactive components (THC and its active metabolite) in the "hypothetical" effect-site compartment to the observed psychoactive effects. A "hypothetical" effect-compartment model was developed using literature data to characterize the observed delay in peak "highness" ratings compared with plasma concentrations of the psychoactive agents following intravenous administration of THC. A direct relationship was established between the reported psychoactive effects ("highness" or intoxication) and the predicted effect-site concentrations of THC. The differences between estimated equilibration half-lives for THC and THC-OH in the effect-compartment model indicated the differential equilibration of parent drug and the active metabolite between plasma and the effect-site. These models contribute to the understanding of the pharmacokinetic-pharmacodynamic relationships associated with marijuana use and are important steps in the prediction of pharmacodynamic effects related to the psychoactive components in marijuana.

KEYWORDS:

clinical pharmacokinetics; metabolism; metabolite kinetics; pharmacokinetic/pharmacodynamic models; pharmacokinetics; pharmacokinetics/pharmacodynamics; population pharmacokinetics

PMID:
28942005
DOI:
10.1016/j.xphs.2017.09.009
[Indexed for MEDLINE]

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