8-11 PharmacoDynamics Flashcards
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Kd= Concentration of Drug that it takes to occupy 50% of the total receptors. [Kd] is the affinity constant and equilibrium dissociation constant.
B: Formula for [Kd] = k2 / k1
and
[Kd] = Drug x Receptor / [DRUG-RECEPTOR BOUND]
C: If there is a high # of [DRUG -RECEPTOR BOUND] then this will DEC the [Kd] which means…
**[small Kd = HIGH AFFINITY] **
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ED50 = Concentration of Drug it takes to reach 50% of the maximal Drug Response. THIS IS ALSO KNOWN AS POTENCY OF A DRUG!
Therapeutic Index = LD50 / ED50 [INC Therapeutic Index = INC Drug SAFENESS]
B: Potency depends on [Affinity of the Drug to a receptor] and [Efficiency of the Coupled Response that occurs after Drug binds]
C: CLINCIAL EFFECTIVENESS depends on a drugs MAX RESPONSE/intrinsic Activity. (not the potency)
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Therapeutic Window = [minimum effective concentration] to the [minimum lethal dose concentration]
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3 Different Phases in Drug Action
- Pharmaceutical = Drug is dissolved in gastric fluids and broken down from its dosage form
- Pharmacokinetics = ADME (Absorption/Distribution/Metabolism/Excretion)
- PharmacoDynamics = how does the drug work in the body and interact with receptors
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B: The way a drug interacts with a receptor depends on its structural and chemical inherent properties. A Drug is any substance that changes the living processes
C: Drug binds to receptors using 1 out of the 4:
- Electrostatic interactions
- Hydrogen bonds
- Van der waal forces
- Hydrophobic bonds
C2: MOST drug-to-receptor interactions ARE REVERSIBLE because most drugs do NOT form covalent bonds with their receptors
D: Drug displacement (1 drug displacing the other) does not typically occur. Drugs typically will only occupy FREE receptors not bound by anything else
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[Binding acceptor sites] vs. [Receptors]
[Binding acceptor sites] = sites that allow the interaction between 2 substances but does NOT elicit a subsequent response (i.e. albumin binding to Acidic Drugs)
vs.
[Receptors] = receptive interaction between substance and receptor that DOES LEAD TO SUBSEQUENT RESPONSE/ACTION. The receptor is the discriminator. The component of the receptor that recognizes a drug is called the Pharmacophore
B: These Receptors are dynamic entities that can be CHANGED and altered pharmacologically//pathologically
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[Fractional Receptor Occupancy] takes into account the affinity of a drug to a receptor and the dose/concentation the drug is in the body.
B: [Fractional Receptor Occupancy] = 1 / [1 + (Kd /Dose of Drug) ]
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A: Bmax = TOTAL NUMBEr of Receptors in the body.
A2: TOTAL # of receptors that are occupied by a drug depends on the [Fraction of Receptors Occupied] and the Total # of receptors period.
INC in Total # of Receptors occupied —> INC Response = [Simple Occupancy Theory].
A3: [Simple Occupancy Theory] states that if ALL TOTAL # of Receptors are occupied –> the ultimate MAX RESPONSE
A4: In vivo, [Modified Occupancy Theory] corrects for the phenomena that occurs, and debunks [Simple Occupancy Theory] (such as cell amplification). [INC # of Receptors does INC response but NOT IN A LINEAR WAY]
(ex. [MAX response/Efficacy/intrinsic activity] of some drugs was achieved before that drug occupied ALL receptors in the body)
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Most Drugs have a propensity to bind to more than 1 receptor in the body
Drug Selectivity = Refers to the idea of 1 drug being MORE inclined to bind to 1 specific receptor over the others. With any drug…[INC Dose/Concentration of that drug] —> [DEC Drug Selectivity]
B: Selectivity window = the window of drug concentration you’ll have to work with before a drug starts to travel around and bind to OTHER UNINTENDED receptors
C: Since NO Drug has only 1 single effect in the body, they are classified based on their PRINCIPAL EFFECT
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A: Full Agonist = at concentration X, this drug CAN reach the MAX Efficacy/Response and [intrisic activity of 1]
B: partial Agonist= at the same concentration X, this drug will ONLY EVER be able to elicit “Part” of the MAX Efficacy and have [intrinsic activity less than 1]
C: Neutral Antagonist = Binds to the same receptors as the Agonist but produce NO biological effects and blocks Agonist in the process. [intrinsic activity of 0]
D: Negative Antagonist = Actually binds to [Constitutively active receptors that are active WITHOUT needing agonist] and DEC their function —> [intrinsic activity LESS than 0]
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A: Physiologic Antagonism = using the downstream effects/response of 1 drug to OPPOSE AND WORK AGAINST downstream effects of another
B: Chemical Antagonism = Positively charged drug binds to negatively charged drug and DeActivates it.
