Effect of gelation conditions and dissolution media on the release of paracetamol from alginate gel beads

Paracetamol was entrapped in alginate beads gelled with calcium or zinc at 0.1, 0.34 or 0.7M. The payloads were of the order of 60-70% w/w which represented an entrapment yield of > 75%. The release of drug from the beads was observed in three media; water, Simulated Gastric Fluid USP without pepsin (SGF) and 0.1% trisodium citrate solution. Release was slowest in water and was complete within 4-5 h. The zinc beads released more slowly than calcium beads prepared at the same molar concentration of cation. Complete release of drug from the alginate gel beads in SGF occurred within 2 h and was unaffected by the cation type and concentration. Except for beads prepared from 0.1M zinc, paracetamol was released rapidly in the citrate solution. All release profiles could be described by first-order kinetics with half-lives which ranged from 25-73 min. Due to the rapid release in acidic conditions, it is unlikely that alginate beads loaded with a relatively water soluble drug will provide satisfactory prolonged release orally.