Distribution

Question 1

What two factors affect the distribution of a drug in the body

Answer 1

Protein Binding

Fat or Water Solubility

Question 2

What is Distribution in Parmcokinetics

Answer 2

Distribution is the movment of the drug from the blood to different compartments of the tissue

Question 3

How does Protein binding affect distribution of drugs

Answer 3

• Drugs like to bind to plasma proteins
• When bound to protiens drugs have no clinical impact (no effect, cant be excreted or metabolised)
• If a drug is highly bound, a change in the binding site can mean a rapid change in the unbound activity of the drug
• This can lead to Toxcicty due to a rise in drug concentration
• Drug to drug interactions can also occur with different drugs competing for the protein binding sites
• For example Warfrin is highly bound, and if Non Steroid anti inflammattorys are taken too they would also like to bind to the protein. The NSAID displace some of the Warfrin leading to more unbound/Free Warfrin in the plasma to act as an anticoagulant leading to increased risk of heamorage

Question 4

How does Fat or Water solubility affect distribution of drugs

Answer 4

• If water content in the body reduces the plasma concentration of a drug will increase e.g. dehydration If water content in the body increases the plasma concentration of a drug will increase e.g. fluid retention
• If Fat content in the body increases, then a lipid soluble drug will have more tissue to dissolve in taking longer for the drug to to release back into circulation prolonging the half life of the drug