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Nicotine Base Permeation through Silicone Elastomers: Comparison of Dimethylpolysiloxane and Trifluoropropylmethylpolysiloxane Systems

1974; Elsevier BV; Volume: 63; Issue: 12 Linguagem: Inglês

10.1002/jps.2600631205

1520-6017

Timothy S. Gaginella, Peter G. Welling, Paul Bass,

Analytical Chemistry and Chromatography

The rate of release of nicotine base from several silicone polymer systems was studied relative to diffusivity and solubility characteristics. Tubes composed of dimethylpolysiloxane released nicotine base rapidly: >75% in 4 hr. The same tubing with two external fluorosilicone laminations reduced release to about 40% in 4 hr. Tubes made of the silicone derivative trifluoropropyl- methylpolysiloxane caused a substantial reduction in transmission of nicotine base. Drug permeability through dimethylpolysiloxane was >20 times more rapid than through the trifluoropropylmethyl- polysiloxane system. Solubility of nicotine base in the dimethylpolysiloxane and trifluoropropylmethyl derivative membranes was estimated to be 201.4 and 112.9 mg/ml, respectively. The decreased permeability through the trifluoropropylmethylpolysilox- ane polymer appears to be due to reduced diffusivity and solubility. The lower diffusivity cannot be explained on the basis of an increased effective diffusional path length since tortuosity values of about 1.0 were calculated for both polymers. Drug adsorption to filler and greater molecule-polymer interaction within the free volume matrix of the trifluoropropylmethylpolysiloxane polymer appear to be the predominant factors retarding the efflux of the nicotine. The release process was found to obey first-order kinetics by utilizing sigma-minus plots. It appears that the dimethylpolysiloxane membrane is much less suitable than the trifluoropropylmethyl derivative if one wishes to use nicotine experimentally as a timed-release preparation. Of major import is that, for other small molecules having physical-chemical characteristics similar to nicotine base, trifluoropropylmethylpolysiloxane polymers may be the most suitable drug vehicles if timed release is desirable.