J.Jpn. Surg. Soc.. 80(1): 63-70, 1979

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Original article

EXPERIMENTAL STUDIES OF PERMEABILITY AND INTRACEREBRAL DIFFUSION OF VARIOUS NEUROTROPIC DRUGS THROUGH SILASTIC MEMBRANE
PART I. INVITRO STUDY

Numerous drugs are known to permeate silastic membranes. However, among these drugs basic problems such as the volume of permeation remain unknown in many cases. Four drugs, namely lidocaine, 1-dopa, serotonine and 1-norepinephrine come under this category. Since a report was madeon the permeability of 1-dopa in vitro, no other reports are available. The present writers made an in vitro investigation of the volume of permeation and factors influencing the permeability avove drugs via silastic membrane.
1) The permeability of the four drugs under an surrounding temperature of 22℃ after 12 hours was 9.37% for 1-dopa, 4.6% for 1-norepinephrine and 2.3% for lidocaine and serotonine. The rate of permeability per hour of these 4 drugs was approximately constant.
2) An investigation was conducted to clarify or otherwise determine the factors influencing the permeability of silastic membrane. When the environmental temperature is raised from 22℃ to 35.5℃, it was found that the permeability of 1-norepinephrine showed a 3 fold increase. When the thickness of the membrane is increased 2.4 times, whereas the permeability of 1-norepinephrine showed a mere decrease to 89ｰ93%, in the case of lidocaine a remarkable decrease to 16ｰ36% was seen. It was shown that the permeability of lidocaine decreased with the decrease in concentration of lidocaine and while, here a relationship between the concentration of the drug and permeability was recognized, in the remaining 3 drugs little or no influence of the concentration was seen.

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