ABSTRACT
The metabolism process is very important in the analysis of designer drugs in biological material as, besides the original drug, metabolites can be determined. The compounds being drug candidates are the secondary metabolites. Almost all compounds investigated by pharmacognosy are secondary metabolites: flavonoids, steroids, saponins, terpenes, coumarins, lignans, tannins, etc. From designer drugs' perspective, the most important metabolites are alkaloids. Neurotransmitters are endogenous substances; they are synthesized inside the body. There are substances that increase the activity of neurotransmitters by inhibiting their reuptake. Serotonin is a neurotransmitter and a peripheral hormone. Endogenous opioids are neurotransmitters responsible for pain suppression, antidepressant action, and depression of the respiratory system, diarrhea suppression, and reduction of the vomiting reflex. Adenosine is a purine derivative being also a nucleoside. Chronic use of cannabinoids causes tolerance to antinociception, anticonvulsant activity, catalepsy, depression of locomotor activity, and hypotension.
