Pharmacokinetics: Absorption, Distribution, Protein Binding, Metabolism (including first-pass and Phase I and II)

 


 	
Absorption

 	
Affected by weight, solubility, and other factors: Influences how a drug enters the bloodstream.
 	
GI factors like food can change absorption: Presence of food can alter drug absorption rates.


 	
Distribution

 	
Membrane permeability (e.g., blood-brain barrier): Determines which drugs can enter the CNS.
 	
Plasma protein binding

 	
If not bound, higher levels in blood and tissues: Only unbound drugs are active.


 	
Storage

 	
Lipophilic drugs accumulate in fats, calcium in teeth: Affects drug storage and release.




 	
Metabolism

 	
Phase I (non-synthetic): drugs are oxidized or reduced to more polar forms
 	
Phase II (synthetic): polar groups like glutathione are conjugated to the drug
 	
Cytochrome P450 metabolism

 	
Mixed function, catalyzes the metabolism of many drugs, delays metabolism or extends life of competing drugs: Plays a crucial role in drug interactions.





Excretion: Renal, Biliary, Other (e.g., for volatile drugs)

 	
Renal

 	
Organic anion transport: HCTZ, furosemide, PCN G, salicylates: Mechanism for drug excretion through kidneys.


 	
Biliary excretion

 	
Drugs excreted into bile and eliminated in feces: Alternative route of excretion.


 	
Other

 	
Volatile drugs excreted through lungs: e.g., anesthetic gase