Drug Movement Flashcards
What are the X4 Elements of Pharmacokinetics? (ADME)
- How body responds to drug (kinetics-moves)
1) Absorption
2) Distribution
3) Metabolism
4) Excretion/Elimination
What is Absorption?
Absorption from site of distribution (once left bloodstream,)
What is Distribution?
How the drug reversibly leaves the bloodstream and is dispersed into extracellular and intracellular compartments. (via plasma)
What is Metabolism?
Drug transformation by organs
What is Excretion?
How drug exits the body
What are X2 mechanisms how a drug moves around the body?
- Bulk flow- (via bloodstream)
- Diffusion
What is Passive Diffusion?
- Directly through lipids/aqueous pores in the membrane
- Aquaporins (channel proteins)-transport water
What is Facilitated Diffusion?
-Uses specialised carrier proteins-change conformation in order to move the molecules across the membrane
What is the difference between Passive and Facilitated Diffusion?
-Facilitated uses channel/carrier proteins
What is Active Transport?
- Transport molecules against concentration gradient so requires energy
- Energy is obtained by the hydrolysis of ATP
What is Endocytosis/Pinocytosis (fluid form)
- The drug contacts the plasma membrane
- Vesicle forms around drug and invaginates into plasma membrane.
- The drug is taken in and released
What is Saturation Kinetics?
enzyme reaction reaching a maximal velocity at high levels of Substrate
What X2 types of diffusion does Saturation Kinetics Effect?
-Facilitated and Passive
What are Weak Acids/Bases?
-Weak- Partially dissociate into ions
What are Strong Acids/Bases?
-Fully dissociate into ions
What determines the form of a drug?
pH of the local compartment
What are Acids and Bases?
Acid- Proton Donator ‘a’-away
Base-Proton acceptor
What does the Henderson-Hasselbalch Equation calculate?
-Calculates pKa
What is the pKa
- The strength of an acid
- Log of Ka (Acid Dislocation constant-a-acid)
What is Ka?
-Acid Dissociation constant
What is ion trapping?
-Is the trapping of toxins in their ionised form so they cannot be reabsorbed and are excreted from the body.
Where do Weak Acids and Bases Accumulate?
-Weak bases-accumulate in compartments of low pH.
-Weak Acids- accumulate in compartments in high pH
(Try balance it out)
Name the X5 Body Compartments
-Total Body Water-
-Extracellular Water-
-Blood Plasma-
-Adipose tissue-
Bone and Teeth
What is Volume Distribution? (Vd)
- Is how a drug partitions (splits) between plasma and tissue compartments. The pull of drug between blood and tissue.
What is Vd used for?
-Calculates drug dosage/volume required
What Physiochemical Properties affects the Vd?
( pH and ionisation, method transport, half-life)
What samples are taken from volunteers in a trial to calculate the Vd?
-Blood Samples
What is the formula for Vd?
Vd=Dose
{Drug}plasma
How is {Drug}plasma calculated?
Amount Added/Volume of Beaker
Will type of Vd value will require a high drug dosage?
-Higher Vd=High drug dosage
What can Plasma Protein binding have an impact on?
-Vd
