Estimation of dissolution rate from in vivo studies of synthetic vitreous fibers

Although the dissolution rate of a fiber was originally defined by a measur ement of dissolution in simulated lung fluid in vitro, it is feasible to de termine it from animal studies as well. The dissolution rate constant for a fiber may be extracted from the decrease in long fiber diameter observed i n certain intratracheal instillation experiments or from the observed long fiber retention in short-term biopersistence studies. These in vivo dissolu tion rates agree well with those measured in vitro for the same fibers. For those special types of fibers, the high-alumina rock wool fibers that coul d not be measured in vitro, the method provides a way of obtaining a chemic al dissolution rate constant from an animal study. The inverse of the in vi vo dissolution rate, the fiber dissolution time, correlates well with the w eighted half life of long fibers in a biopersistence study, and the in vivo dissolution rate may be estimated accurately from this weighted half-life.