Inter-Laboratory Reproducibility of Release Tests for Suppositories

AbstractInter-laboratory reproducibility of representative release tests, namely paddle, Muranishi and dialysis tubing methods for suppositories were investigated using two kinds of suppositories of indomethacin, oily and water-soluble types. The inter-laboratory differences for the water-soluble suppository determined by paddle and modified Muranishi methods were small whereas the differences for the oily suppository determined by Muranishi and dialysis tubing methods were large. The release rate of oily suppository by Muranishi method was significantly reduced when the cylindrical cell containing suppository was placed slightly lower. The release rate by dialysis tubing method was decreased by addition of a small volume of test fluid into the dialysis tube. These variables probably contributed to the inter-laboratory differences for the oily suppository. Neither Muranishi or dialysis tubing method should be employed for quality control of oily suppositories unless their reproducibility is significantly ...