INCREASING COMPLEX FORMATION OF WEAK ACID DRUG WITH ION EXCHANGE RESIN

Functionality of Ion Exchange Resin (IER) mainly depends on solubility and degree of ionization and molecular weight of drug. For this reason the application of IER is limited to only strong acidic and basic drugs or drug existing as salt; not for weak acidic and weak basic drugs due to their low ionization properties. If we increase the ionization of weak acid and bases, then application of IER will not only be limited to salts or strong acid or strong bases but also for weak acid and bases and hence almost all drugs will be complexed with IER and total exploitation of application of IER can be achieved. Solubility increasing approach such as cosolvent and 2 Hydroxypropyl betacyclodextrin and ionization increasing approach such as keeping the pH above drug ionization constant (pKa) were followed to evaluate their effect on loading of a weekly acidic drug, Repaglinide (taken as model drug) and found that keeping the pH of the complexation medium more than drug pKa had maximum percentage drug loading to resin, where percentage of drug resin complexation increased by four times. However the best approach of increasing drug loading was achieved by combination of solubility increasing approach and ionization increasing approach i.e. using cosolvent and making the pH more than pKa of drug that resulted in percentage of drug loading more than 90%.