Pharmacokinetics Flashcards
Recall the 7 major routes by which drugs can be administered
- IV
- Intraperitoneal
- Oral
- Intramuscular
- Dermal
- Subcutaneous
- Inhalation
Recall an advantage and disadvantage of intraperitoneal administration
Advantage: richly perfused area
Disadvantage: requires training
Recall an advantage and disadvantage of drug inhalation
Advantage: well perfused region
Disadvantage: Danger with powder
Recall an advantage of dermal administration of a drug
Slow, sustained release
Recall an advantage and disadvantage of IV administration of a drug
Advantage: very rapid onset
Disadvantage: requires training
Recall 4 methods by which a drug might pass through a lipid bilayer
- Diffusion (if non-polar)
- Diffuse across aqueous pore (if polar)
- Carrier molecule
- Pinocytosis
Why do drugs often exist in both ionised and non-ionised forms?
Non-ionised form will easily cross lipid bilayer, ionised form will travel around body more easily
What affects the ratio of ionised: non-ionised drug?
pH
What is the pKa of aspirin?
3.4
Where does the majority of aspirin absorption take place and why?
Stomach - more of the unionised form here (driven by low pH) and so diffuses across lipid bilayer more easily
What is “ion trapping”?
Drug gets stuck in ionised form in aqueous compartment (?)
Recall the 4 factors affecting drug distribution
- Regional blood flow
- Extracellular binding to plasma proteins
- Capillary permeability
- Tissue localisation
How does protein-binding affect drug distribution?
Protein-bound drug no longer available for absorption
What sort of drugs are most likely to sjow tissue localisation?
Lipophillic drugs - accumulate in fatty tissue such as testes and brain
What are the 2 major routes of excretion of drugs?
Liver and Kidney
