Absorption and Distribution of Drugs Flashcards
How would a graph of blood concentration / time differ for drugs administered parenterally as opposed to orally?
With oral administration, there would be a slight initial delay as concentration increases, but a similar constant decline thereafter.
What forms of metabolism occur in the liver?
Almost all forms of metabolism.
What forms of metabolism occur in the kidneys, skin and lungs?
Mainly biotransformation phases I and II (oxidation and conjugation).
What forms of metabolism occur in the microbiome?
Oxidation via cytochrome p450 enzymes (biotransformation phase I).
Where in the body do sulfation pathways occur?
In almost all places in the body.
What chemical change is made to molecules during biotransformation phase I?
Introduction of hydroxyl groups.
What chemical change is made to molecules during biotransformation phase II?
Charged groups, such as sulfates and glucuronidates are conjugated to the compound.
Define absorption (of a drug).
Movement of a drug from its site of administration into the plasma.
Define distribution (of a drug).
Reversible transfer of a drug from one location to another within the body.
What is pinocytosis?
A process involving facilitated diffusion and active transport to facilitate the movement of fluid into a cell.
What makes an acid or base ‘weak’?
An acid or base is considered weak if their pKa values are in the physiological pH range, meaning the degree of ionisation depends on the local pH.
Define pKa.
The pH at which there is an equal amount of the ionised and unionised forms of a molecule.
Why is it that weak bases are absorbed well from basic environments and weak acids are absorbed well from acidic environments?
In an environment that is acidic / basic, an acid / base will shift to the side of the dissociation curve with the unionised form, which is lipid soluble and will therefore be able to be absorbed across lipid membranes.
List 5 factors that affect drug absorption.
1 - Route of administration.
2 - Blood flow at the site of administration.
3 - Dose of drug.
4 - Active vs passive diffusion.
5 - Drug solubility.
What are the 3 types of routes of drug administration?
1 - Enteral.
2 - Percutaneous.
3 - Parenteral.
