Unit 1: Drug Receptors Flashcards
Types of receptors
— orphan receptors — regulatory proteins — enzymes — transport proteins — structural proteins
E max
Efficacy
Maximum effect achievable by the drug
EC 50
Potency
Dose or concentration at which the drug is half maximal
ED 50
Median effective dose
TD 50
Median toxic dose
LD 50
Median lethal dose
Full agonist
Drug can fully activate receptor system
Partial agonist
Full activation is not possible even with full saturation
Neutral antagonist
Does not cause an effect on its own; prevents binding by an agonist (e.g. naloxone and an opioid)
Inverse agonist
Have higher affinity for R sub i than R sub a;
Decrease or abolish constitutive activity
Biased agonism
Agonists in a group that activate the same receptors but have different downstream effects (biased effects)
(Mechanism not well understood)
Competitive antagonists
E.G. naloxone
Drugs that bind to (or close to) agonist receptor site without activating effector system for that receptor (reversible binding)
Shifts dose-response curve to the right; maximal effect remains the same
Irreversible antagonist
Dose-response curve gets decreased but not shifted, so maximum effect is less
Physiologic antagonist
Bind to a different receptor molecule than the agonist does
Antagonize the physiologic response (e.g. glucagon and insulin are antagonists)
Chemical antagonist
Interact directly with drug being antagonized to help remove it
e.g. medicines that chelate heavy metals
Therapeutic effect
Range between median effective dose (ED 50) and median toxic dose (TD 50)
The wider the therapeutic index, the safer the drugs tends to be
Therapeutic window
Doses that give effective treatment without toxicity
Range between minimum effective dose and minimum toxic dose
Which tend to be more selective? Drugs that bind through weak bonds or strong bonds?
Drugs that bind through weak bonds tend to be more selective
orphan receptors
Natural ligands unknown
Receptors of regulatory proteins do what?
mediate actions of endogenous chemical signals
What can binding of a drug do to an enzyme?
Inhibit it
