DSA - Intro Pharmacodynamics Flashcards
(39 cards)
What is pharmacodynamics?
What is the DIFFERENCE between pharmacodynamics and pharmacokinetics?
Effects of drugs on the body
Pharmacodynamics - Effects of drugs on the body.
Pharmacokinetics - Effects of body on drugs
What is a Receptor?
Specific molecule in a biological system that plays a REGULATORY ROLE. Receptor interacts with a drug and initiates the biochemical events leading to drug effects.
What is an Inert Binding Site?
Component of the biologic system to which a drug binds WITHOUT changing any function.
What is a Ligand?
In the field of pharmacology, it is a molecule, such as a hormone or drug, which binds to a receptor.
Is a covalent bond reversible or irreversible? How does drug removal/receptor reactivation occur?
Covalent Bond = IRREVERSIBLE
Drug Removal/Receptor Reactivation —> Requires re-synthesis of receptor OR enzymatic removal of drug.
Is a non-covalent bond reversible or irreversible?
Non-Covalent Bond = REVERSIBLE
Most drugs bind to receptors via non-covalent bonds.
List Drug/Receptor bond types from STRONGEST —> WEAKEST
Covalent Non-Covalent - Ionic Bonds - Hydrogen Bonds - Hydrophobic Interactions
Define AFFINITY
How readily and tightly a drug binds to its receptor
High Affinity = LESS drug produce response
Low Affinity = MORE drug produce response
How is AFFINITY related to Kd?
Kd is the Equilibrium Dissociation Constant
Kd = [L][R]/[LR]
L=Ligand; R=Receptor; LR=Complex
Unit = Molar concentration
Lower Kd = HIGHER AFFINITY for receptor
Higher Kd = LOWER AFFINITY for receptor
What is Drug Selectivity?
How does Drug Selectivity play into side effects?
Selectivity is a property of a drug determined by its affinities at various binding sites.
- Higher selectivity = FEWER side effects as the drug affects fewer targets over a specific concentration range
- Lower selectivity = MORE side effects as drug affects more targets over a specific concentration range
What is Intrinsic Activity?
Ability of drug to change receptor function & produce physiological response upon binding receptor
How is Intrinsic Activity different in AGONISTS vs. ANTAGONISTS?
Agonists = HAVE INTRINSIC ACTIVITY
- Stabilize conformation —> Produce physiological response
Antagonists = NO INTRINSIC ACTIVITY
- Prevent activation receptor by agonists
What are the 3 types of AGONISTS?
- Full Agonist
- Fully activate receptors
- Produce maximal pharmacological effects when ALL receptors occupied
- Maximal intrinsic activity - Partial Agonist
- Partially activate receptors
- Produce sub-max effect when ALL receptors occupied
- Intrinsic efficacy varies on drug; but ALWAYS sub-maximal - Inverse Agonist
- Produce effect opposite full/partial agonist
- Decrease receptor signaling
- Intrinsic activity present; related to inhibition receptor function
- Decrease response at receptors
What are the 3 types of ANTAGONISM?
- Pharmacologic (Receptor)
- Action at same receptor as endogenous ligands or agonist drugs - Chemical
- Chemical antagonist makes other drug unavailable - Physiologic
- Occurs b/t endogenous pathways regulated by different receptors
What are the 2 MAIN TYPES of Pharmacologic Antagonists?
Competitive
Non-Competitive
What is a Competitive Antagonist?
- Compete with endogenous chemicals/agonists for binding receptor
- Can be displaced from receptor by other drugs
What is a Non-Competitive Antagonist? What are the 2 types?
Non-Competitive Antagonist
- Receptor inactivation NOT surmountable
Irreversible - Irreversibly bind/occlude agonist site on receptor via COVALENT bonds
Allosteric - Bind other site —> prevent/reduce agonist binding or receptor activation
What is a Dose-Response Curve?
Curve showing relationship b/t a drug and its effects.
Differentiate b/t drug dose plotted Arithmetically vs. Logarithm.
Arithmetically
- Drug dose on X-Axis
- Drug effect on Y-Axis
- HYPERBOLIC
Logarithm
- LOG of drug dose on X-Axis
- Drug effect on Y-Axis
- SIGMOIDAL
What is Emax? ED50?
Emax = Max effect produced by drug
ED50 = Dose of drug produces 50% of max effect
What are the 2 main types of dose-response curves?
Graded Response
- Answers: How much?
- Magnitude of response varies continuously
- Typically is mean value w/i population or subject
Quantal Response
- Answers: Does the response occur? In how many?
- Requires pre-defined response
- Used to examine freq. of response w/i population
How does a Non-Cumulative quantal dose response curve vary from a Cumulative quantal dose response curve?
Non-Cumulative
- Number or % individuals responding at one particular drug dose
Cumulative
- Number or % individuals responding at a particular drug dose AND ALL DOSES LOWER
Define:
ED50
TD50
LD50
ED50 = Median effective dose
TD50 = Median toxic dose
LD50 = Median lethal dose
How is Therapeutic Index (TI) calculated?
Therapeutic Index (TI) = TD50/ED50
Higher TI = SAFER DRUG
