Adsorption of Charged Non-albumin Bound Drugs by Amorphous Silica

Abstract

We investigated the in vitro drug adsorption of PQ 10150 sodium silicate gel (AIS, Santa Clara, CA) with particle size of 230 microns and surface area of 400 m2/g. We observed 99% to 88% adsorption of gentamicin; a mean 91% of disopyramide; a mean 89% of quinidine at low concentration, falling to 75% at higher concentration. Insulin was 88% adsorbed at low concentrations but less so (65%) at higher concentrations. We observed a mean 83% adsorption of procainamide, a mean 84% of N-acetyl procainamide, 74% of lidocaine, 73% of amitriptyline, and 44% of desipramine. We found an average of 14% reduction of total digoxin concentration when serum containing digoxin (2 to 33 ng/mL) was exposed to sodium silicate, while the reduction in free digoxin concentration was 16%. Five percent ethosuximide was also removed. The adsorption of theophylline, phenobarbital, acetaminophen, phenytoin, ethylene glycol, methotrexate, salicylate, thiocyanate and diazepam was minimal and not significant. We conclude that significant amounts of charged, non-albumin bound drugs can be removed by PQ 10150 sodium silicate gel.