Pharmacokinetics Flashcards Preview

BIOL2049 S1 > Pharmacokinetics > Flashcards

Flashcards in Pharmacokinetics Deck (220)
Loading 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?



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?





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 


What is absorption?

The process that takes place between the site of administration and the site of measurement (site of measurement is usually from plasma and its easily accessible)


For rapid and extensive absorption, what does the drug have to do?

The drug has to dissolve i.e. to produce a molecular solution

large particles do not produce a molecular solution to the gut lumen 

Sustained release means you can take it less reguarly in day (may be better for people who forget to take it)


Which subject has the fastest gastric emptying and why?

Subject 1 has the fastest gastric emptying as the drug is getting to the intestine quicker, as you can see the shape is steeper than that seen in subject 2


Whats means by conjugation? 

The combination, especially in the liver, of certain toxic substances formed in the intestine, drug or steroid hormone with glucuronic or sulphuric acid; a means by which the biologic activity of certain chemical substances is terminated and the substances ready for secretion. 


In first pass metabolism, what's used in the gut wall?





In first-pass metabolism, whats used in the liver?