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46 January 2016 Tablets & Capsules HME of felodipine-HPMCAS and evaluation of solid dispersions. A 40:60 felodipine:HPMCAS grade was prepared and extruded under the pro- cessing conditions listed in Table 1. The specific energy (SE) was cal- culated using two equations: kW(motor rating) × % torque rpm max. rpm × 0.97 (gearbox efficiency) kW(applied) kg/hr where kW= kilowatt rating of the motor (kW=horsepower × 0.746) % torque=percentage of maximum allowable torque used rpm=screw revolutions per minute Melt pressures and specific energy inputs were used to indicate ease of extrusion. As Table 1 shows, the felodipine-HPMCAS H grade re- quired much lower melt pressure and specific energy than the L and M grades, which indicates the superior extrudability of the H grade. This was confirmed by the lower melt viscosity observed during frequency-sweep experiments on the API-polymer extrudates that were collected after extrusion at 160ºC (data not shown). The Tg of the felodipine-polymer extrudates were much lower than those of the HPMCAS polymer grades, which indicates that felodipine acts as a plasticizer for these polymers during extrusion (Figure 5). Chemical composition and molecu- lar weight determinations of the felodipine-HPMCAS extrudates were performed to assess the polymer's sta- bility during extrusion. Because felodipine was able to plasticize the polymer, the API-polymer mixture extruded faster than all grades of the HPMCAS alone. It was seen that the substitution levels, free-acid levels, and the molecular weights of the API- Figure 4 Effect of extrusion temperature on pH-solubility behavior Time (s) Time (s) Time (s) LG dissolution HG dissolution MG dissolution 1.5 1 0.5 0 1.5 1 0.5 0 -0.5 -1 -0.5 -1 -1.5 Normalized frequency Normalized frequency Normalized frequency L85 L85B L80B M88A M88C M89F M81C H82A H90A H87E H87D H86B H85A HPMCAS LG at 180°C HPMCAS LG at 150°C HPMCAS LG at initial HPMCAS MG at 180°C HPMCAS MG at 160°C HPMCAS MG at 150°C HPMCAS MG at initial Initial HPMC HG HPMCAS HG at 140°C HPMCAS HG at 120°C HPMCAS HG at 180°C HPMCAS HG at 170°C HPMCAS HG at 160°C LG and its extrudates MG and its extrudates HG and its extrudates 100 600 100 600 1100 1100 1000 0 2000 4000 5000 6000 3000 1600 1600 -100 2100 2600 3100 2600 3100 3600 2100 -100 2.00E+00 1.50E+00 1.00E+00 5.00E-00 0.00E+00 -5.00E-00 -1.00E+00 -1.50E+00 -2.00E+00 -2.50E+00 Figure 5 Effect of felodipine on glass transition temperature of extrudates LG MG HG HPMCAS Felodipine-HPMCAS 140 120 100 80 60 40 20 0 Tg (C°) 1. kW(applied)= 2. SE=