Tablets & Capsules

TC0315

Issue link: http://www.e-digitaleditions.com/i/477622

Contents of this Issue

Navigation

Page 41 of 53

40 March 2015 Tablets & Capsules which improves the flow of wet pow- ders by adsorption, hydrophobic silica "floats" on the film of water that forms on the particle, thereby keeping the particles separated. Hydrophobic silica can be wetted by applying high shear forces or by prolonged mixing. The more hydrophobic the silica, the less sensitive it is to over-mixing. In addi- tion to its use as a glidant and anticak- ing agent, this silica is useful as a thickener for non-polar liquids, an hydrophilic fumed and precipitated varieties. Its degree of hydrophobicity depends on the percentage reduction in silanol groups on the surface of the silica, which is controlled by the amount of dich lorodimethyl silane used and the reaction conditions. Being hydrophobic, this material adsorbs less moisture than other sili- cas, which makes it a better glidant in moisture-sensitive or hygroscopic for- mulations. Unlike hydrophilic silica, emul sions stabilizer, a spray-drying aid, and an agent for modifying the release of active ingredients. Suppliers (Wacker Chemie, Evonik Industries, and Cabot) offer various nutraceutical, food, cosmetic, and technical grades of hydrophobic silica. A pharmaceutical grade is Evonik's Aerosil R972 Pharma. The primary particle size of this grade is about 16 nanometers, but it forms loose agglomerates in the range of 10 to 200 microns. The specific surface area is about 110 m 2 /cc. The tap density is low, just of 0.05 grams per cubic cen- timeter. The safety, handling, and toxi- cology are the same as those of hydrophilic silica. The next edition of the column will discuss silica's function and use in tablet and capsule formulations. T&C Reference 1. McCarty, John A. Eye on Excipients. Tablets & Capsules 13:1, pp. 37-39. January 2015. J o h n A . M c C a r t y i s p r e s i d e n t o f McCarty Pharma Consultants, PO B o x 6 6 1 5 6 8 , M i a m i S p r i n g s , F L 33266. Tel. 305 887 9220. E-mail: john.mccarty@comcast.net. He is also a member of Tablets & Capsules' Technical Advisory Board. TABLE 2 Properties of some pharmaceutical grades of precipitated silica Property Syloid 244 FP a Sipernat 160 PQ b Syloid 63FP a Syloid XP 3150 a Particle size 5.5 11 6 150 (microns) Tap density 0.1 0.08 0.41 0.28 (g/cc) Specific surface area 300 170 700 320 (m 2 /cc) Oil adsorption 3.0 2.5 0.8 3.0 (mL/g) pH 5.0-8.0 4.0-8.0 4.0-6.0 4.0-8.0 Pore volume 1.5 NA 0.4 1.7 (ml/g) Application Glidant Glidant Glidant Liquid carrier Tableting aid Tableting aid Tableting aid Moisture-activated Liquid carrier Liquid carrier Anticaking agent dry granulation Moisture-activated Adsorbent Tablet coating Drug carrier dry granulation agent Spray drying aid Disintegrant Drug carrier Adsorbent Disintegrant Notes: a Syloid is a trademark of W.R. Grace Co. b Sipernat is a trademark of Evonik Industries

Articles in this issue

Links on this page

Archives of this issue

view archives of Tablets & Capsules - TC0315