Patient Impact (K4)

Question 1

Is drug distribution round the body even? ie if there is 10mg/L of a drug in the blood the same conc will be in the liver?

Answer 1

No!
- Different organs have different levels of blood supply so some tissues will absorb more drugs while others less

Question 2

Is Drug metabolism always unwanted?

Answer 2

• No
• We want it to activate pro-drugs
• We want to be able to metabolise and eliminate drugs so they arnt in our system forever

Question 3

What are some patient characteristics that impact pharmacodynamics and pharmacokinetics?

Answer 3

• Age, gender, health, size
• Blood flow
• Tolerance to the drug
• Chance of comorbidity (multiple diseases)
• Pregnancy

Question 4

What is pKa?

Answer 4

• The acid dissociation constant
  -It is a measure of the strength of an acid in water (how well it ionises donating a proton)
• A lower value indicates a stronger acid

Question 5

Why might changing pH be useful in drug absorption?

Answer 5

• We can trap certain acidic drugs in plasma or other solutions by changing the pH

Question 6

How does Ion trapping work? and how does this stop the absorption of some drugs?

Answer 6

• Drugs tend to exist in 2 ionisation states based on their environment
• Weak acids tend to be ionized (protonated) in basic environments, while weak bases tend to be ionized in acidic environments
• For weak acids, in the more acidic intracellular compartments, they become protonated and neutral. As neutral molecules can diffuse across membranes more easily than ionized forms, the drug becomes trapped inside the cell. Similarly, weak bases become ionized in the acidic environment and are then trapped in the intracellular compartments.

Question 7

What is the equation for pH that includes pKa?

Answer 7