Action and use
Silicon dioxide analogue; defoaming agent.
Preparations
Simeticone Suspension for Infants
When activated dimethicone is prescribed or demanded, Simeticone for Oral Use shall be dispensed or supplied.
DEFINITION
Simeticone for Oral Use contains not less than 4.5% and not more than 8.0% w/w of silica, SiO2, and not less than 91.0% and not more than 97.0% w/w of Dimeticone 1000. It is prepared by the addition of finely powdered silica to Dimeticone 1000.
CHARACTERISTICS
A viscous, grey, translucent liquid.
Immiscible with water and with ethanol (96%); almost completely soluble in toluene, leaving a residue of silica.
IDENTIFICATION
A. The infrared absorption spectrum of the supernatant liquid obtained by centrifugation, Appendix II A, is concordant with the reference spectrum of dimeticone (RS 381).
B. Ignite; dense white fumes are evolved leaving a white residue which is insoluble in hydrochloric acid.
TESTS
Acidity
Dissolve 15.0 g in a mixture of 15 mL of toluene and 15 mL of butan-1-ol, previously neutralised to a 0.5% w/v solution of bromophenol blue in ethanol (96%), and titrate with 0.1M ethanolic potassium hydroxide VS using the bromophenol blue solution as indicator. Not more than 0.15 mL is required to change the colour of the solution.
Refractive index
Of the supernatant liquid obtained in Identification test A, 1.4050 to 1.4080, Appendix V E.
Viscosity
Of the supernatant liquid obtained in Identification test A, 950 to 1050 mm2s-1 , Appendix V H, Method I, using a U-tube viscometer (size G).
Weight per mL
Of the supernatant liquid obtained in Identification test A, 0.965 to 0.980 g, Appendix V G.
ASSAY
For silica
To 1 g add 50 mL of toluene, mix well and filter through an ignited silica crucible. Wash the residue thoroughly with toluene, dry at 105° and ignite to constant weight at 500°.
For dimeticone
Place 40 mg in a stoppered centrifuge tube, add 20 mL of toluene and shake for 20 minutes. Filter and record the infrared absorption spectrum, Appendix II A, of a 0.5-mm layer of the filtrate over the range 1330 to 1180 cm-1 (7.52 to 8.47 μm).
Measure the absorbance of the CH3Si stretching band at the maximum at 1261 cm (7.93 μm). Repeat the operation using dimeticone EPCRS in place of the preparation being examined.
