PSEUDOEPHEDRINE HCL MICROSPHERES FORMULATED INTO AN ORAL SUSPENSION DOSAGE FORM

Pseudoephedrine HCl, a highly water-soluble drug, was entrapped within polymeric microspheres by either an oil-in-water (dispersion or cosolvent method) or a water-in-oil-in-water (multiple emulsion method) emulsion-solvent evaporation method. Acceptable drug loadings were achieved with the three methods. The microspheres were characterized by dissolution studies, scanning electron microscopy and differential scanning calorimetry. The microsphere structure or porosity depended strongly on the polymer selected and, to a lesser extent, on the method of preparation. The drug was partly soluble in cellulosic polymers (ethyl cellulose, cellulose acetate butyrate) but insoluble in poly(methyl methacrylate) and poly(D,L-lactide). The microspheres were formulated into an oral suspension dosage form, using concentrated sucrose or sorbitol solutions, glycerol, propylene glycol or Neobee M-5 oil as suspending vehicles. The amount of drug leached into the storage vehicle leveled off after 2-3 weeks and did not change significantly during further storage. After six months, between 77 and 93% of the original drug loading was still present within the microspheres. The storage of the microspheres in the vehicles had little influence on the drug release profiles.