Pharmacodynamics and Pharmacokinetics Flashcards
Define pharmacodynamics and pharmacokinetics
Dynamics - what the drug does to the body.
Kinetics - what the body does do the drug.
What are 3 molecular factors that influence drug absorption?
- Size
- Solubility (drugs must be both hydro- and lipo-philic)
- Polarity/charge (only neutral drugs can cross membranes)
What does P-glycoprotein do?
Efflux pump - returns absorbed drug into lumen.
What is bioavailability?
F = fraction of adminstered does that is absorbed. Usually refers to oral bioavailability.
What are prodrugs?
Prodrugs are drugs that once metabolised become active.
What is volume of distribution?
Dose / plasma concentration.
Lipid soluble drugs have a high Vdist. Highly protein bound drugs have low Vdist.
What are the two phases of drug metabolism and what do they aim to do?
Oxidative metabolism and conjugative metabolism.
Aim to decrease lipophilicity and increase hydrophilicity.
Describe the process of oxidative metabolism.
Involves adding oxygen (e.g. -OH) to a drug.
Catalysed by CYP450 enzymes. CYP 1, 2 and 3 are the most important in human metabolism.
What are the complications with CYP inducers and inhibitors.
Drugs rely on CYP to be metabolised.
CYP inducers (e.g. smoking/alcohol through xenosensors) increase activity of CYP, and cause drug to be metabolised faster.
CYP inhibitors decrease activity of CYP, causing drug to be metabolised slowly (can result in toxicity or reduced efficacy in prodrugs)
What fruit is a CYP inhibitor?
Grapefruit inhibits CYP3A4
What are examples of reactions in oxidative and conjugative metabolims?
Oxidative: Oxygenation, hydroxylation, N-Dealkylation
Conjugative: Sulfonation, glucuronidation, acetylation, methylation.
What does conjugative metabolism do?
Adds a polar endogenous molecule to make the drug more hydrophilic.
E.g. Glucuronidation, sulfonation.
Describe the process of drug passage through kidney filtration.
Glomerular filtration takes all low molecular weight drugs (unbound) from blood into filtrate.
Some drugs can passive diffuse back into blood (lipophilic).
Some drugs are actively transported into filtrate from the blood.
