Class Notes (806,449)
Canada (492,253)
Pharmacology (329)

Module 8 Notes.docx

7 Pages
Unlock Document

Western University
Pharmacology 2060A/B
Angela Nissen

Module 8 Pharmacodynamics – Drug Receptor Interactions 8.1 Theories of Drug Receptor Interactions • Is simply occupying the receptor enough to elicit a response? • What if two drugs occupied the same number of the same receptor, would the response be the same? • Two receptor theories to describe drug receptor interactions o The simple occupancy theory o The modified occupancy theory • Simple Occupancy Theory o The intensity of a drugs response is proportional to the number of receptors occupied o The maximal response occurs when all the receptors are occupied o This implies that two drugs that act at the same receptor should produce the same effect  Not true!!  There are many drugs that at the same receptor yet have different efficacies • Modified Occupancy Theory o Identifies that some characteristics of drug receptor interactions cannot be accounted for by the simple occupancy theory o The intensity of a drug’s response is proportional to the number of receptors occupied o Two drugs occupying the same receptor can have different binding affinities (strengths) o Two drugs occupying the same receptor can have different abilities to activate the receptor (intrinsic activity) o Summary: in addition to accounting for the number of receptors occupied, the modified occupancy theory takes into account the affinity of the drug for the receptor and the ability of the drug to activate the receptor o Modified Occupancy Theory –Affinity  Affinity – attraction that a drug has for its receptor  Drugs with a high affinity are highly attracted to their receptor and therefore bind effectively even at low concentrations  Low affinity drugs are weakly attracted to their receptor and bind ineffectively even at high concentrations  Affinity of the drug is the primary determinant of the drugs potency • Drugs with high affinity have high potency o Modified Occupancy Theory – IntrinsicActivity  Intrinsic activity – ability of drug to activate receptor  Drugs with high intrinsic activity cause intense receptor activation  Low intrinsic activity minimally activate receptor  Intrinsic activity is reflected in its efficacy • Drugs with high intrinsic activity have maximal efficacy 8.2 Classification of Drug Interactions • After drug binds, can either activate receptor or block it • Agonist – molecule that activates receptor – mimic action of endogenous ligands • Antagonists – molecules that do not activate it • Partial agonists – molecules that bind but have minimal ability to activate the receptor • • Agonists o Molecules that activate receptors o Endogenous molecules that activate the receptor are considered agonists  Include nts and hormones o Drugs that we design as agonists are often targeted to mimic action of body’s endogenous molecules o Can be thought of as having both affinity and intrinsic activity  Since able to bind/activate receptor o The action of an agonist does not always increase a physiological response  Agonists may cause either increased or decreased physiological response depending which receptor is activated  Some agonists bind to different receptors (different specificities) • May cause different effects depending on the dose
More Less

Related notes for Pharmacology 2060A/B

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.