Drug release from spray-dried and spray-embedded microparticles of diltiazem hydrochloride

Spray-dried and spray-embedded ethylcellulose microparticles were prepared using a spray-drying technique. The structure of the microparticles (microcapsules or microspheres) changed according to whether the drug (diltiazem hydrochloride) was dispersed or dissolved in the ethylcellulose solution to be spray-dried. The drug release rate from the microparticles was not affected by the physical state of the drug (amorphous or crystalline state), but by the microparticle structure