Short Questions Flashcards
What is an agonist, partial agonist, and antagonist?
Agonist - drugs that bind and activate receptors
Partial agonists - drugs that bind but only weakly activate receptors
Antagonist - drugs that bind but do not activate receptors and can block the effects of an agonist.
Types of antagonist
Competitive - compete with the agonists for the same binding site on the same receptor, e.g. propranolol is a competitive agonist at B adrenoreceptors,
Non competitive - reduce agonist effects by interacting with other sites, either at another recognition site on the receptor itself or somewhere else in the cell., e.g. picrotoxin inhibits GABA responses in neurons by blocking Cl- channel.
Therapeutic index
Definition = The ratio of the dose of the drug that produces a toxic effect to a therapeutic effect. is used as a measure of the relative safety of a drug.
Formula = TI = Median Toxic Dose/ Median Effective Dose
What is pharmacodynamics
Quantitative study of the relationship between drug exposure and pharmacologic or toxicologic response.
What is Pharmcokinetics?
pharmacokinetics is the study of what the body does to a drug. It refers to the change in conc. of a drug and its metabolites in blood, plasma urine etc.
First order kinetics definition & formula
Definition = the t 1/2 is constant & rate of elimination depends on how much drug is present, being higher at higher plasma conc drug.
formula = Ke = Cl/Vd
Non cYP540 oxidation reactions, name the enzyme responsible.
3
1. Diamine oxidase - DAO substrates include histamine and polyamides
2. Alcohol and Aldehyde Dehydrogenase - non-specific enzymes found in the soluble fraction of the liver.
3. Flavin monooxygenases - catalyse oxygenation of nitrogen, phosphorous and sulfur, enzymes are FMO1, FMO2 etc.
Types of receptors & examples
G - G protein-coupled receptors, adreno receptors
E - Enzyme Linked Receptors, insulin
N - Nuclear Receptors, oestrogen
L - Ligand - gated ion channels, K+
4/5 Human P450s that account for approximately 95% of the oxidative metabolism
CYP2C19 - 11% - paracetamol
CYP2C9 - 14% -paracetamol
CYP1A2 - 14% - paracetamol
CYP2D6 - 23% - codeine
CYP3A4-5 - 33% - Zidovudine
Plasma protein.
Albumin _ binds Many acidic drug
Thyroxin _> 99% bound to plasmaproteins
Tissue reservoir & examples
Bone reservoirs - - tetracycline antibiotics and heavy metals may accumulate in bone, they can become a reservoir for slow release of hour agents into the blood.
Adipose reservoir -lipid soluble drugs are stored in fat, i.e. 70% of thiopental dose found in fat 3hr after administration.
