Drug absorption Flashcards
Absorption
Process by which unchanged drug enter the circulation
Distribution
Dispersion of a drug among fluids and tissues of the body
Metabolism
Transformation of a drug into daughter components
Excretion
Is the removal of drugs from the body
What is the importance of ADME?
- Essential for safe and intelligent use of medicines by all doctors
- Designing dosing regimens
- Monitoring treatment compliance
- Substance of abuse monitoring
- Medicine licensing requirement
What do different routes of administration result in?
Result in bio-availability and onset
Reasons as to why choice of delivery is a compromise
○ Speed of onset
○ Convenience: Oral or i.v
○ Bioavailability: proportion of administered drug reaching the systemic circulation
○ Side effects/specificity of action
What do drugs have to do in order to reach there target?
Requires drugs to cross biological barriers like lipophilic membranes
Where does most absorption occur but where some can occur?
• Most absorption occurs through cells, however some occurs between cells
How can absorption occur?
○ Active transport
○ Facilitated diffusion through cells
○ Passive diffustion
What is the equation of ficks law?
§ Rate of diffusion=surface area x Concentration difference x permeability
What are key determinants of Ficks law?
§ Lipid solubility/ionization are key determinants of permeability
What are most drugs and hence what are they?
• Most drugs are weak acids or bases and are thus ionisable
What are weak acidic drugs?
Proton donors
what are basic drugs?
Proton acceptors
