Pharmacokinetic Drug Interactions

       

Alteration (Increase or Decrease) of concentration of one drug, by the administration of another drug in the system, is termed as “Pharmacokinetic Drug Interaction”.

·       Interacting drugs have unrelated actions and it is difficult to predict pharmacokinetic drug interactions.

·       Pharmacokinetic interactions involve in the alteration of drugs’

v Absorption

v Distribution

v Metabolism

v Excretion

·       Absorption interactions involve

v Changes in gastrointestinal pH

v Adsorption, chelation and other complexing mechanisms

v Changes in gastrointestinal motility

v Induction or inhibition of drug transporter proteins

v Malabsorption caused by drugs

·       Distribution interactions involve

v Protein-binding interactions

v Induction or inhibition of drug transporter proteins

·       Metabolism interactions involve

v Changes in first-pass metabolism

ü Changes in blood flow through the liver

ü Inhibition or induction of first-pass metabolism

v Enzyme induction

v Enzyme inhibition

·       Excretion interactions involve

v Changes in urinary pH

v Changes in active renal tubular excretion

v Changes in renal blood flow

v Biliary excretion and the entero-hepatic shunt

v Enterohepatic recirculation

v Drug transporter proteins