Ion-exchange fibers and drugs: an equilibrium study

Abstract

The purpose of this study was to investigate the mechanisms of drug binding into and drug release from cation-exchange fibers in vitro under equilibrium conditions. Ion-exchange groups of the fibers were weakly drug binding carboxylic acid groups (-COOH), strongly drug binding sulphonic acid groups (-SO H), or combinations thereof. Parameters determining 3 the drug absorption and drug release properties of the fibers were: (i) the lipophilicity of the drug (tacrine and propranolol are lipophilic compounds, nadolol is a relatively hydrophilic molecule), (ii) the ion-exchange capacity of the fibers, which was increased by activating the cation-exchange groups with NaOH, (iii) the ionic strength of the extracting salt (NaCl), which was studied in a range of 1.5 mM to 1.5 M, and finally (iv) the effect of divalent calcium ions (CaCl ) on the release 2 of the model drugs, which was tested and compared to monovalent sodium ions (NaCl), and combinations thereof. It was found that the lipophilic drugs, tacrine and propranolol, were retained in the fibers more strongly and for longer than the more hydrophilic nadolol. The more hydrophilic nadolol was released to a greater extent from the fibers containing strong ion-exchange groups (-SO H), whereas the lipophilic drugs were attached more strongly to strong ion-exchange groups and 3 released more easily from the weak (-COOH) ion-exchange groups. The salt concentration and the choice of the salt also had an effect: at lower NaCl concentrations more drug was released as a result of the influence of both electrostatic and volume effects (equimolar drug:salt ratio). Incorporation of CaCl in the bathing solution increased drug release considerably 2 as compared to NaCl alone. The equilibrium distribution of the drug species between the fiber and external solution phases was also simulated and it was found that the theoretical modelling proposed describes adequately the basic trends of the behavior of these systems.

Fabrication and Evaluation of Taste Masked Resinate of Risperidone and Its Orally Disintegrating Tablets

“…25) Electrostatic interaction governs the equilibrium distribution of the drug species between the resin and solution phases. [26][27][28] The drug resinate is stable in salivary pH during its disintegration in the oral cavity. Taste masking evaluation by volunteers also indicated that the resinate formation was an efficient method of taste masking for this drug (Table 3).…”

Molecular properties of ciprofloxacin-indion 234 complexes

“…[27][28][29] Increasing the electrolyte concentration decreases the Donnan potential and, hence, the electrostatic affinity between the drug and the ion exchanger, thus tending to increase drug release. The influence of salt concentration on the release rate can be explained by solute diffusion.…”

Formulation and Evaluation of Taste Masked Oral Reconstitutable Suspension of Primaquine Phosphate

“…It has been reported that PRM depolarize taste cells by closing K + channels and produce bitterness (2). Palatable formulation development is one of the most difficult tasks, although various taste masking techniques such as the addition of sweeteners and flavors (3), coating with polymers (4), adsorption to ion-exchange resin (5,6), and chemical modifications such as the use of insoluble prodrugs (7,8) have been reported. Each technique has its own disadvantages.…”