Pharmacokinetic antagonists can act in many different ways, for example:
- Some act by reducing the amount of agonist in the body
eg by decreasing the absorption of the agonist from the gastrointestinal tract
- Others act by decreasing the length of time that the agonist is in the body
eg by increasing the rate of renal excretion
- Others increase the rate of degradation of the agonist
An example of pharmacokinetic antagonism is the increase in hepatic metabolism of warfarin resulting from the addition of phenobarbitone.