Interactions, drug outside body

Drug interactions outside the body, at site of absorption, during distribution, directly on receptors, during metabolism, during excretion... 

Most physicochemically based drug interactions can take place in the body, or outside it, or during concomitant dmg administration, so it is probably not profitable to consider them separately. Some interactions, such as complexation, which are probably more important in vivo than in vitro are discussed in detail below. 

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