Interactions of Marihuana Constituents with Centrally-Acting Drugs.

Abstract

Marihuana is a complex mixture containing various biologically active compounds in which cannabinoids are major components. The drug interaction of marihuana with other drugs is a serious problem in some cases since marihuana is often taken with other centrally-acting drugs. Tetrahydrocannabinol (THC), which is a main component responsible for most of the psychomimetic effects of marihuana, can potentiate the effects of many depressants, such as alcohol, barbiturates, anesthetics, morphine and anticonvulsants, in the central nervous system. The drug interaction of THC with other drugs is a functional mechanism in the central nervous system. THC has biphasic effects (stimulant and depressant) depending on, maily, doses. THC, therefore, interacts with stimulants as cocaine and phencyclidine in a complicated manner. Cross-tolerance in some effects of the components of marihuana and of other drugs has been recognized. Cannabidiol (CBD), which is another major component in marihuana but lacks psychomimetic activity, potentiates the effects of some specified drugs that terminates their effects through metabolic inactivation. The interaction of CBD with other drugs is considered to be metabolic in origin since the cannabinoid can suppress the gepatic microsomal drugmetabolizing enzymes. Drug interaction can also occur among cannabinoids, indicating the complexity of the combined effect of marihuana and other drugs. These are additives, synergistic or antagonistic, depending on the conditions used. This review describes the interactions of marihuana components with centrally-acting drugs in relation to their pharmacological and toxicological significance.