The purpose of this study was to define liquid or semi-solid excipient base
s for the filling of hard capsules at room temperature. The rise of amphiph
ilic bases rather than strictly hydrophobic or hydrophilic bases allows the
rise of this pharmaceutical form to be extended to a wide range of active
substances. The excipient mixtures used must have the thixotropic propertie
s necessary to meet two essential requirements: perfect fluidity during dis
tribution in the capsule filling machine and recovery of a consistency in t
he resting capsule in order to prevent leaks. A methodology based on the si
mulation of the rheological history of these mixtures from the capsule-fill
ing machine to the capsule has been developed to forecast behaviour during
and after filling. Rheological studies were carried out in permanent flow a
nd oscillating mode. These allow analysis of the excipient flow in the caps
ule-filling machine and evaluation of thixotropy recovery kinetics in rite
capsule. At the same time, the behaviour of these bases was tested on a pil
ot semi-automatic capsule-filling machine. All of these characteristics all
owed a precise definition of the specifications of a preparation compatible
with the "semi-solid content capsule" dosage form.