PharmPK Discussion - Increased volume of distribution with age

• On 31 Dec 2009 at 02:19:11, andrew sutton (drandrewsutton.-at-.googlemail.com) sent the message
  

  
  The following message was posted to: PharmPK
  
  Dear Yaning
  
  Thanks. I appreciate the information and note that the observation is
  model based and not physiological.  As I see it your quotation (copied
  below)  from the Benet paper is saying that elimination is reduced
  rather than the volume of distribution being increased.
  
  "The change in half-life is due to the redistribution of body fluids
  with age causing more diazepam to distribute out of the fluids delivered
  to the liver, the organ of elimination".
  
  Which could be explained by a reduced rate of absorption from the gut.
  
  I think the same effect would be caused by a reduced hepatic
  extraction capacity although that seems less likely due to the small
  amounts involved. On the other hand it's perhaps more probable as part
  of a physiological ageing process than a reduced absorption since I
  have not encountered that particular mechanism before.
  
  Andrew
  
  

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