Pharmacokinetics Flashcards
Whats pharmacodynamics?
The effects of the drug in the body
D–>R interactions processes specific to each class of drug
Whats pharmacokinetics?
The effect of the body on the drug delivery to site of action
Generally the same for most drugs (ADME- Absorption, distribution, metabolism, excretion) irrespective of their therapeutic activity

In the following timetline, where does Pharmacokinetics and Pharmacodynamics come into play and what sort of effects do they have?
Adminitered dose –> Compound at site of action –> Therapeutic response

What factors can affect pharmacokinetics?
- Age
- dietary factors
- Disease
- Genetic differences
- Other chemicals
What factors can affect pharmacodynamics?
- Age
- gender
- disease
- Genetic predisposition
- Other chemicals
What processes are helped to be understood by pharmacokinetics ?
- Time of onset of action
- Intensity and duration of effect
- Accumulation
- Inter-individual differences
Intra-individual differences - Drug interactions
- Inter-species differences
What are the key pharmacokinetic processes, which of those are considered to be part of the elimination stage?

What are the locations which drugs can go?

What does this graph show…

- The relationship between the plasma concentration of the beta-adrenoreceptor antagonist propranolol and the reduction in exercise-induced tachycardia in different individuals
- There is a linear relationship and the two can be correlated together
- As plasma concentration increases the response also increases
- Key message: as the plasma concentration of the drug increases the response increases
- The concentration of the drug in the plasma is proportional to the therapeutic effect
What are the different routes of drug administration?
When taken by each route, what part of the body does it have an effect on?
- Intravenous- General circulation
- Oral- Liver
- Intramuscular- Body tissues
- Inhaled- Lungs

Whats First-pass metabolism?
The first pass effect is a phenomenon of drug metabolism whereby the concentration of a drug, specifically when administered orally is greatly reduced before it reaches systemic circulation.
It is the fraction of drug lost during the process of absorption which is generally related to the liver and gut wall
Our bodies need to be able to deal with this vast vareity of structures, how is it able to do this?

We have a large range of metabolic enzymes which can break down a variety of products
How many low molecular weight compounds does coffee contain?
200

What are the key pharmacokinetic processes?
- Absorption
- Distribution
- Metabolism
- Excretion
What are the 3 potential routes which drugs can take in order to cross the membrane and state the types of compounds which can use each route?

What are some factors affecting absorption?
How could each of these factors possibly affect absorption?
1. Lipid solubility
- Rapid from gut
- Slow from intra-muscular
2. Ionisation
- Poor for ionic drugs
- (from gut)
- pH partitioning
3. Formulation
- May limit rate of absorption
- May limit extent of absorption
4. Gastro-intestinal function
- May limit rate of delivery to site of absorption
- May limit time available for absorption
5. First-pass metabolism
- May limit extent of absorption
What factors of pharmacokinetics does ionisation of drugs effect?
Absorption
Excretion
Metabolism
Whats the extent of the ionisation of drugs?
What can be used to calculate it?
pKa of the drug and pH of the drug
Use the Henderson-Hasselbach equation
Whats the Henserson-Hasselbach equation?
When is there 50% ionisation seen?
- H-H equation calculates what percentage of the drug is ionised or not
- If a drug has a pKa of 4 and a pH of 4, then 50% of drug is in ionised form and 50% of drug is in unionised form

Tell me about conjugate acids and bases for acids and tell me their solubility, how pH effects them and if they can cross the membrane?
- Conjugate acid: weak acid as has COOH group, unionised
- Conjugate base: ionised
- pH can affect whether its ionised or unionised

Tell me about conjugate acids and bases for bases and tell me their solubility, how pH effects them and if they can cross the membrane?
- weak base, conjugate acid form, ionised
- base, unionised

Explain the following diagram

- determine if weak base or acid by looking at chemical structure
- for stomach pKa would be 3 as there’s a 1:1 ratio so therefore, pH=pKa
- moves across membrane to plasma, has different pH, so consequently the ratio of ionised to unionised form changes
- The same happens when it moves across the membrane to the urine
- Only the unionised form which is moving across the membrane

Graph to show % absorption of acids and bases vs the pKa

























































































