0408 Molecular Aspects of drug action

Question 1

What are the 4 targets of drugs in the body

Answer 1

Receptors (types 1 - 4), ion channels, enzymes and transporters

Question 2

What are the 4 types of receptors that drugs can act on

Answer 2

Ligand gated ion channels, G protein coupled receptors, Kinase linked receptors, Nuclear receptors

Question 3

Describe a general mechanism of drug action at ligand gated ion channels. Give an example of a drug that works on these receptors

Answer 3

Ligand binds to ion channel. Binding causes a conformational change, opening the channel. Ions travel down a concentration gradient, triggering/initiating an effect. An example of a drug is benzodiazepans

Question 4

Describe the general mechanism of drug action at G-protein-coupled receptors. Give an example of a drug that works on these receptors

Answer 4

Ligand binds to G-protein receptor on membrane. Binding causes a conformational changes in intracellular subunits. Alpha sub unit dissiates from beta/gamma subunit. Sub units trigger/initiate effect. An example of a drug is atenolol (a type of beta blocker)

Question 5

Describe the general mechanism of drug action at kinase-linked receptors. Give an example of a drug that works on these receptors

Answer 5

Ligand binds to extracellular component of receptor on membrane. Binding results in conformational change leading to dimerisation and cross-phosphorylation of intracellular subunits. This action initates/triggers an effect via signal transduction. An example of a drug is trastuzumab (monoclondal antibodies)

Question 6

Describe the general mechanism of drug action at nuclear receptors. Give an example of a drug that works on these receptors

Answer 6

Ligand enters cytosol or nucleus and binds to receptor. Binding causes a conformational change and ligand/receptor complex enters nucleus. This complex acts as a transcriptional regulator or binds to one to produce an effect. An example of a drug prednisolone (a type of steroid)

Question 7

Give an example of a drug that acts on ion channels

Answer 7

Tolazamide (class sulfonylurea) an antidiabetic drug used to treat diabetes 2. Drug binds and inhibits ATP dependant K+ channels. This results in depolarisation of membrane and opens volt. gated Ca2+ channels, resulting in release of insulin from beta cells in pancreas.

Question 8

Give an example of a drug that acts on enzymes

Answer 8

Allopurinol (class xanthine oxidase inhibitors) used to inflammation in gout

Question 9

Give an example of a drug that works on transporters

Answer 9

Omeprazole (class proton pump inhibitors) used to treat gastro-esopahgeal reflux)

Question 10

Give for examples of exceptions of drug that do not target the standard 4

Answer 10

Microtubule inhibitors, antacids, osmodiuretics, DNA structure modifying agents