Drug-Receptor Interaction Flashcards
Dr. Ingram
What isa drug defined as?
A substance that acts, often by interaction with regulatory molecules, to stimulate or inhibit normal physiologic processes
Drug receptors:
Molecules in which a drug will first interact to eventually induce a response (stimulate or inhibit). Drug receptors are specific and usually include endogenous substance (neurotransmitters, hormones), enzymes, transport proteins, ion channels, etc.
Pharmacodynamics:
The study of drugs affecting the body. The does-response relationship and drug receptor interactions for each drug are of particular importance
Pharmacokinetics:
The study of the effects of what the body does to a drug. This includes the absorption, distribution and elimination by the organism
What is of particular importance when studying pharmacokinetics?
The plasma drug concentration as a function of time
What are the four type of drug receptors?
1) Ligand-gated ion channel (cholinergic receptors)
2) G-protein coupled receptors (alpha and beta adrenoreceptors)
3) Enzyme-linked receptors (insulin receptors)
4) Intracellular receptors (steroid receptors)
What are the types of drug binding?
Agonist+receptor
Antagonist+receptor
Allosteric activator+receptor
Allosteric inhibitor+ receptor
What determines the effect of the drug?
drug classification
Affinity?
Tightness of interaction between receptor and drug
Efficacy:
The strength or extent of the pharmacological effect of agonist. The maximal effect an agonist can achieve at the highest practical concentration
Potency:
The amount of drug needed to produce a given effect
What is the difference between potency and efficacy?
Potency is the amount of drug required to reach a desired effect.
Efficacy is the maximal response achieved by a drug at any dose
What factors contribute to what the body can do to a drug?
Absorption
Distribution
Metabolism
Excretion
What factors contribute to what a drug can do to the body?
Mechanism of action
Therapeutic effects
Toxic effects
EC50:
The concentration of drug that produces 50% of maximal effect
Kd equation:
Kd=(L)(R)/(LR)
Kd:
The equilibrium dissociation constant, represents the concentration of free drug at which half-maximal binding is observed
How does Kd relate to affinity?
Inverse relationship:
If the Kd is low= binding affinity is high
If the Kd is high= binding affinity low
Assumption for Kd=EC50
1) Magnitude of responses is proportional to number of receptors present
2) Emax only occurs when all receptors are bound
3) Cooperatively does not exist
Agonist:
A drug which binds to a receptor and results in a biological response
(Promotes)
Antagonist:
A drug which binds to a receptor is not associated with a biological response (inhibit). Will prevent an agonist from binding to the receptor
What are agonist classified as?
Full agonist= maximal efficacy
Partial agonist=efficacy; greater than baseline but less than full (Ra)
Inverse agonists= efficacy less than baseline (Ri)
Partial agonist:
Displaces the full agonist from the receptor. The response is reduced-the partial agonist will act like an antagonist
What happens when an antagonist is added to an agonist in the presence of a spare receptors?
EC50 will increase but will not have an overall increase on the agonist EC50 threshold despite the addition of antagonist. Leads to maximal activity with minimal binding
