This paper is devoted to studying the features of the release of medicinal substances (MSs, drugs) (both electrolyte and non-electrolyte) from solutions of polyelectrolytes through a semipermeable membrane. Polycation chitosan and polyanion sodium salt of chitosan succinyl are used as polymers, and cefazolin (CFZ) sodium salt, lidocaine hydrochloride (LH), and dioxidine (DO) are used as MSs. In the course of the study, the fact of the interaction between polyelectrolytes and drugs and the influence of the conformational and supramolecular state of polymers in a solution on the values of diffusion coefficients for the release of drugs from polymer solutions through a semipermeable membrane are established. It is shown that the interaction between drugs and polyelectrolytes has a number of characteristic features due to the ionogenic nature of the polymers used and the manifestation of the conformational-supramolecular effect. These features lead to the fact that a significant difference in the amount of the drug firmly retained by the polymer chain and the values of the diffusion coefficients of its release appear only in the region of dilute solutions. Upon transition to the region of semidilute solutions, due to changes in the structure of polymers in solution, these differences mitigated, which is accompanied by convergence of the diffusion coefficients for the release of various of kinds of drugs from polymer solutions through a semipermeable membrane.