66 MEMBRANE PERMEABILITY AND DRUG ACTION 



Examples of the Permeability Factor in 

 Drug Action 



To conclude this chapter I shall give three examples in 

 which the importance of the permeability factor in the 

 study of drug action is readily made apparent from the 

 practical point of view. 



Drugs acting on Ascaris. A number of substances are 

 known to be of practical value as anthelminthics. These 

 include thymol and hexyl resorcinol. But resorcinol 



TABLE XV 



EXPERIMENTAL AND CALCULATED VALUES OF 

 THE PERMEABILITY OV Ascaris CUTICLE 



itself is of no practical value. Trim has recently studied 

 the permeability of Ascaris to various drugs. The results 

 are shown in Table xv. The rate of permeation into 

 Ascaris obeys the relationship 



PM^^IB=o.2 approximately, 



i.e. the membrane controlling the permeation of sub- 



