The influence of pellet shape and film coating on the filling of pellets into hard shell capsules.

Pellets of different shape, varying from spherical to cylindrical, were filled into hard shell capsules. When no film coat was applied, the pellets had not to be perfectly spherical in order to be filled reproducibly. An aspect ratio of 1.2 or less appeared to be the threshold value. However, pronounced surface roughness hindered the filling process, and hence it appears necessary to monitor this parameter. After coating of the pellets with an ethylcellulose film, none of the batches could be filled to an acceptable standard, because electrostatic loading led to a blockage of the filling mechanism. However, the addition of 1% talcum powder was sufficient to remove all charges, and again filling became a function of the pellet shape, confirming the threshold aspect ratio value of 1.2.