Pharmacokinetics Flashcards
1
Q
What is pharmacokinetics?
A
- Absorption (first-pass effect)
- Distribution
- Biotransformation (metabolism)
- Excretion
2
Q
What is absorption?
A
- Rate and extent at which a drug leaves its site of administration and enters the circulatory system
3
Q
What is passive diffusion?
A
- Drug dissolves and passes through membranes from a high to a low concentration
4
Q
What is facilitated diffusion?
A
- Drug diffuses from an area of high concentration to an area of low concentration but requires a carrier protein
5
Q
What is active transport?
A
- Operates against a concentration gradient, which requires ATP and invovles a carrier
6
Q
What is phagocytosis?
A
- Drug molecules engulfed by cell membrane using active transport
7
Q
What is the first-pass effect?
A
- Once a drug has been absorbed into the circulatory system, it is transported to the liver via the hepatic portal system where it is metabolised
8
Q
What is distribution?
A
- Once a drug has been metabolised by the liver, it enters the systemic circulation and travels in the plasma to its site of action
- Then combines with cellular receptors to create an action
9
Q
What are the factors affecting distribution?
A
- Drug formulation
- Blood flow to the specific area
- Binding/unbinding of the drug to plasma proteins
- Presence of anatomic barriers
10
Q
Describe drug formulation
A
- Lipophilic or hydrophilic
- Intravenous or intramuscular, so hydrophilic drugs best
- Orally or subcutaneous, so lipophilic drugs best
11
Q
What are the 2 different types of binding?
A
- Plasma-protein binding
- Anatomic binding
12
Q
Which drugs can pass the the blood brain barrier?
A
- Lipophilic drugs
- Hydrophilic can’t
13
Q
What is metabolism?
A
- Enzyme activity modifies the molecules of the drugs to make them hydrophilic to enable them to eliminated by the kidneys
- 2 stages
14
Q
What are the factors affecting metabolism?
A
- Species
- Age
- Nutritional status
- Health status causing toxic accumulation
15
Q
What is metabolism phase 1?
A
- Original drug molecule chemically transformed by cytochrome P450 system using hydrolysis, reduction or oxidation
- Catabolic reaction
16
Q
What is metabolism phase 2?
A
- The metabolite from phase 1 is combined with another molecule (glucuronic acid, sulfate or glycine) in a process called conjugation
- Makes the metabolite hydrophilic to be excreted by the kidneys
- Anabolic reaction
17
Q
What is excretion?
A
- Drug is removed from the body via the kidneys or liver by filtration
18
Q
What are the 4 aims of pharmacokinetics?
A
- Bioavailability
- Volume of distribution
- Clearance
- Half-life
19
Q
What is bioavailability?
A
- The quantity of the administered drug reaching the systemic circulation
20
Q
What is volume distribution?
A
- Amount of drug absorbed within the plasma and body tissues/cells
21
Q
What is clearance?
A
- The volume of blood cleared of a drug from an eliminating organ
22
Q
What is half-life?
A
- The time it takes for a drug to be reduced by 50%
