Biology 122

Question 1

Define Pharmacokinetics and what it is the study of:

Answer 1

Pharmacokinetics is what the body does to the drug/ how the body acts on the drug.

• drug absorption
• distribution
• metabolism
• excretion

Question 2

Define bioavailability:

Answer 2

Proportion of administered does that reaches systemic circulation intact (so how much actually gets into the bloodstream)

• variable (for each drug)
• pharmacokinetics*

Question 3

Define drug absorption:

Answer 3

Passage of a drug from its site of administration into the plasma (getting the drug into the bloodstream)

I.e parentally, orally, subcutaneously, rubbing it in etc

pharmacokinetics

Question 4

Explain diffusion in drug transport:

Answer 4

passive diffusion:

Diffusion is movement of liquid or gases from a high area of concentration to an area of low concentration

pharmacokinetics

Question 5

Explain active transport In drug transport:

Answer 5

Active transport needs ATP (energy) to move the drug across cell membranes

pharmacokinetic

Question 6

Explain carrier-mediated transport in drug transportation:

Answer 6

A host that assists in moving the liquid of gas from one area to another

pharmacokinetics

Question 7

Explain filtration in drug transport:

Answer 7

Moving of drug through membrane openings: If the drug is small enough it can filter through any pores in the cell membrane

pharmacokinetics

Question 8

Explain the nature of absorbing surface as determinants of drug absorption:

Answer 8

Number of cell membrane layers:
Fewer layers the faster absorption will occur.

Surface area:
The larger the surface area the faster the rate of absorption, for example the lungs have a larger surface area than the GI tract.

Blood supply:
Areas that have better blood supply are going to facilitate absorption. Cartilage is avascular (no blood supply) therefore requires an intramuscular injection

Question 9

Explain the nature of chemical structure as determinants of drug absorption:

Answer 9

Lipid solubility:
Lipid soluble substances easily cross cell membranes because the cell membrane is made of lipids.

Charge of drugs molecule:
Ionisation is whether or not a molecule is changed, both positively or negatively. Charged molecules DO NOT cross cell membranes very easily, and will have to use their channels.

Molecular weight:
If it is a big molecule it is less likely to be absorbed

Dissolution rate: how well a drug is dissolved. Subcutaneous drugs are already in a solution.

pH of aqueous phase (solution the drug is put into): acids are better absorbed in acidic, basics better absorbed in basic media.