Supersaturation mechanism of drugs from solid dispersions with enteric coating agents.
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The crystallization behavior of drugs from supersaturated solutions containing carboxymethylethylcellulose (CMEC) was investigated to clarify the mechanism of supersaturation phenomena from solid dispersions with enteric coating agents in JP XI 2nd fluid (pH 6.8). Nifedipine, griseofulvin and spironolactone were used as drugs. The rate of crystallization of all drugs was remarkably inhibited by the presence of CMEC.It was found that the inhibition was not due to solubilization of the drugs by CMEC.<BR>The crystallization kinetics from supersaturated solutions suggested that the process of crystal growth itself was directly inhibited. Physical properties of the crystallized mass were also investigated in the case of nifedipine. It was thought that the inhibitory effect of CMEC on the drug crystallization was due to the adsorption of CM EC at the solid-water interface at the stage in which a hydrophobic drug crystal surface was formed, and further drug molecules could not deposit easily on the crystal surface for the following reasons;(1) formation of a step or kink, which is necessary for the crystal growth, was inhibited by polymer adsorption, and (2) molecular diffusion to the crystal surface was inhibited by the adsorbed polymer.
- Chemical and Pharmaceutical Bulletin
Chemical and Pharmaceutical Bulletin 36(12), 4941-4950, 1988
The Pharmaceutical Society of Japan