Pharmacokinetic interactions elements

A study on the CNS depressing effects of toluene (2.73), ethylbenzene (3.15), and xylene (3.15), singly and in combinations, showed that CNS effects were increased when exposures were to mixtures. The enhanced effects observed were modest when employees were at rest, but were significantly higher when workers were exercising or performing manual work. The authors attributed the observed effects to pharmacokinetic interactions of the mixture elements. 44 ... 

In the rest of this chapter, the drugs discussed will be grouped by drug class or by body system, as many may have both a pharmacodynamic and a pharmacokinetic element to their spectrum of interactions, and these will be described together. 

The broad definition of a drug as "any chemical that affects living processes" (Benet, Mitchell, and Sherner 1990a) is helpful in understanding the relationship between the body and administered medications. This is a fluid and interactive process, composed of two elements pharmacodynamics and pharmacokinetics. 

The controlled study suggests that no special precautions are necessary if both drugs are given. However, the case report introduces an element of caution, especially if other drugs that may affect rifabutin pharmacokinetics are used. If indeed rifabutin absorption is affected by antacids (there appear to be no clinical data on this), then giving the drugs at least 2 hours apart, or using the enteric-coated didanosine preparation should avoid the interaction. ... 

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