Formation of Sustained Release Wax Matrices Within Hard Gelatin Capsules in a Fluidized Bed

Sustained release wax matrices were formed within hard gelatin capsules during fluidization in a hot air stream. The capsules were filled with drug (propranolol HC1 or dieophylline) - wax (Precirol ATO-5 or Gelucire 50/13) powder blends and suspended in a fluidized bed to induce fusion of the wax. Upon cooling, wax matrices with embedded drug were formed in the ends of die capsules. The use of blends of waxes with different HLB values allowed good control over the drug release pattern. The drug release from the matrices was independent of the pH of the dissolution medium. Differential scanning calorimetry was used to study the physical state of the drugs in the matrices. Propranolol HC1 was insoluble and completely dispersed in the wax matrix while theophylline was partially dissolved in the wax.