Inventions relate to medicine, pharmacology, biotechnology, molecular biology, genetic engineering and can be used for analgesia. A plasmid DNA for transient expression in mammalian cells is proposed and represented by DNA backbone containing prokaryotic and eukaryotic elements, as well as a fragment providing enhanced capture of plasmid DNA by cells and a polynucleotide encoding beta-endorphin modified for increasing the affinity for receptors and codon-optimized for expression in mammalian cells. There are also proposed a producer of such plasmid DNA on the basis of a bacterial cell and an analgesic agent for application in mammals, in particular, humans, on its basis. The technical result of the use of the developed plasmid DNA and analgesic based on it is to increase the controllability of the synthesis of beta-endorphin exactly, in increasing the efficiency of plasmid DNA from which beta-endorphin is synthesized, and reducing its amount to achieve analgesia, in increasing the duration of analgesia and in expanding the spectrum of analgesic drugs.