Chemistry Reference
In-Depth Information
10.3 EQUIPMENT SELECTION
HME is a well-established technology in the plastics, metals, and food industries.
Pharmaceutical application of HME has lagged behind these industries, until the past 15
years that have seen intense pharmaceutical industry activity. The opportunity to form
solid dispersions by HME is a primary reason for the increased interest in the technology,
but another factor in driving pharmaceutical industry growth relates to HME processing
equipment. Historically, some barriers to HME use included inadequate laboratory-scale
extruders for performing small-scale R&D formulation and
manufacturing
and quality risks from the high-temperature/high-wearing equipment. These concerns are
no longer signi
“
perceived
”
cant barriers, with recent approvals of commercial oral and parenteral
products using HME processing supporting this conclusion.
A general schematic of a hot melt extruder is provided in Figure 10.2, accompanied
by the commonly targeted before- and after-state of the materials processed by HME. As
outlined below, there are three separate items of processing equipment functioning
during hot melt extrusion: feeder, extruder, downstream process. Equipment is readily
available that meets CGMP standards, with an example of a CGMP extruder shown
in Figure 10.3.
10.3.1 Feeder
The feeding operation delivers rawmaterial or a preblend into the extruder at a controlled
rate and with controlled composition. Feeders are often manufactured and supported by
specialist equipment vendors (e.g., K-Tron, Switzerland; Brabender Technologies,
Germany; and Schenck Process, Germany) and either integrated with the extruder
control panel or operated independently, as preferred. Exceptions are some small-scale
extruders, including Thermo Fishers 11mm model or the Leistritz Nano16 that have
highly integrated feed mechanisms. For powdered material, the simplest option is a
volumetric feeder, designed with a variable-speed auger system to transfer material from
the hopper via a feed chute to an open port on the extruder. The feed rate may be
correlated with the auger speed (rpm) setting before batch manufacture, with the
assumption that the feed rate
-
rpm relationship remains constant thereafter. The feed
Figure 10.2.
Hot melt extrusion process schematic accompanied by before- and after-physical
properties for amorphous solid dispersion applications.
