Effect of Drug Substances of the Electrolyte Nature on the Conformational and Supramolecular State of Pectin Macromolecules in Solution

Effect of a number of low-molecular-weight drug substances on the viscous and rheological behavior of pectin solutions in dilute and semidilute solutions regimes is studied. It is shown that the introduction of a drug substance, which is a low molecular weight electrolyte, into a dilute pectin solution leads to a change in the intrinsic viscosity of the polymer and the degree of aggregation of its macromolecules. Upon introduction of the drug substance into a semidilute pectin solution the rheological behavior of the solution changes. Presence of a drug substance of the nonelectrolyte nature in pectin solution has almost no effect on the conformational and supramolecular state of pectin and, accordingly, the viscosity characteristics of solution. It is demonstrated that the electrolyte drug substances, especially polyvalent cations, affect some practically important properties of liquid and soft dosage forms produced from pectin solutions, specifically the yield stress and the rate of drug substance release. The results obtained are explained by the polyelectrolyte nature of pectin.