Comparative Analysis of Experimental Pharmacokinetics of New Neurotropic Peptides

Experimental pharmacokinetics of new pharmacologically active peptides, modified analogues of endogenous neuropeptides, has been investigated in rats and rabbits. The study icluded 3 new drugs: (i) the nootropic drug noopept (phenylacetyl-prolyl-glycine ethyl ester); (ii) dilept (N-caproyl-L-prolyl-L-tyrosine methyl ester) – the antipsychotic with positive mnemotropic action; (iii) compound GB-115 – selective anxiolytic (phenylhexanoyl-prolyl-tryptophan amide). Differences in pharmacokinetics and biotransformation of the studied drugs depended on their structural features. The ether derivatives noopept and dilept underwent intensive metabolism by rat gastrointestinal esterases and peptidases with the formation of active metabolites. Being an amide, the compound GB-115 was more resistant to the enzymatic effects of peptidases and was detected for a longer period in the blood of experimental animals. In rabbits the studied compounds were less exposed to the enzymatic action by gastrointestinal peptidases, and were detected plasma of rabbits for a longer period. The higher stability of the compounds studied in rabbits may be attributed not only to the structural features of the studied dipeptides, but also to differences in the activity of the enzymatic systems of the gastrointestinal tract participating in their metabolism, as well as differences in the rate of hepatic and renal blood flow in rats and rabbits.