PHARMACODYNAMICS 2024 Flashcards by Quennie Ann Silverio

The cellular macromolecule or macromolecule
complex with which the drug interacts to elicit a
cellular response.
Selective
Modifiable

DRUG RECEPTOR/ DRUG TARGET

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Molecules that translate the drug receptor

interaction into a change in cellular activity

EFFECTORS

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Binding of ATENOLOL to Beta receptor

stimulates conversion of __

ATP to cAMP

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Binding of AMLODIPINE to Calcium Channel.

ION CHANNELS

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Binding of RAMIPRIL to its receptor inhibits ACE

Angiotensin Converting Enzyme

ENZYMES

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Thiazides (Bendroflumethiazide) block NaCl

transporter at the_____

distal convoluted tubule

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In partial agonist, the magnitude of biologic effect is directly related to the fraction of_________

Active state

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In reversible equilibrium, it favors the _____

inactive

state.

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The strength of the reversible interaction between
a drug and its receptor, as measured by the
dissociation constant

DRUG SPECIFICITY

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Defined as the affinity of one for the other.
Both the affinity of a drug for its receptor and its
intrinsic activity are determined by its chemical
structure.

DISSOCIATION CONSTANT

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A drug that interacts with a single type of receptor
that is expressed on only a limited number of
differentiated cells will exhibit_____

high specificity.

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Once the drug binds to the receptor, it produces a
curve – Receptor Occupancy Theory or Dose
Response Curve and this curve is characterized
by

“Hyperbolic Curve”

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Response emanates from a receptor occupied by

a drug

RECEPTOR OCCUPANCY THEORY

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e maximal response that can

be produced by the drug.

Emax

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the concentration that produces

50% of maximal effect.

EC50

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refers to the “effect”

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refers to

“affinity” of the receptor binding.

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is the total concentration of
receptor sites (ie, sites bound to the drug
at infinitely high concentrations of free
drug).

Bmax

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(equilibrium dissociation constant)
represents the concentration of free drug
at which half-maximal binding is
observed.

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If the

Kd is low, binding affinity is_____

high

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If there are 100 receptors, the concentration of the

drug wherein 50% of the receptors are bound

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If there are 100 receptors, the concentration

wherein 100% of these receptors are bound

Bmax

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Refers to the concentration (EC50) or dose
(ED50) of a drug required to produce 50% of that
drug’s maximal effect

POTENCY

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For this drug, potency is at 1μg, wherein 50% of
half maximal effect is seen. If you give a drug that
would increase the heart rate and the maximum
effect of the drug would be increasing the heart
rate by 50, at what dose wherein you would
appreciate a 25 increase in the heart rate? That is
your_____

ED50

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In case potency, the lowest dose that produces half maximal effect would be the _____ potent

most

A magnitude of response a drug causes when it interacts with a receptor. - Intrinsic Activity

MAXIMAL EFFICACY

The best determinant of which drug to choose | clinical effectiveness depends on_____

maximal efficacy

This parameter reflects the limit of the doseresponse relation on the response axis.

maximal efficacy

Among Potency and Maximal Efficacy, which is | more important in prescribing drugs?

Consider both, but for Clinical Effectiveness, Maximal Efficacy is more important. When you prescribe a drug, we are not only after the dosage, but we’re after the effect of the drug

If you are comparing 2 drugs, for example, ARB and Irbesartan (HPN drugs); They are both efficacious, but which among the 2 is more potent based on the dosage, then ____

Potency

If you are comparing drugs with different mechanisms and you want to choose which is better, then

EFFICACY

In determining the drug of choice what will you | consider is it the potency or efficacy?

Efficacy

In Potency, you look for the

ED50

In Efficacy, you look for the

Receptor and | Response.

A 55-year-old woman with hypertension is to be treated with a thiazide diuretic. Thiazide A in a dose of 5mg produces the same decrease in blood pressure as 500mg of Thiazide B. Which of the following statements best describes these results? a. Thiazide A is more efficacious than Thiazide B b. Thiazide A is about 100 times more potent than Thiazide B c. Toxicity of Thiazide A is less than that of Thiazide B d. Thiazide A has a wider therapeutic window that Thiazide B

Thiazide A is about 100 times more potent than Thiazide B because it only takes 5mg of Thiazide A to produce the same efficacy compared to 500mg of Thiazide B.

t is used in computing the therapeutic index.

QUANTAL DOSE EFFECT CURVES

It is the dose at which 50% of individuals exhibit the specified quantal effect.

Median Effective Dose (ED50)

It is the dose required to produce a particular toxic effect in 50% of individuals

Median Toxic Dose (TD50)

If the toxic effect is the death of the animal. The amount of drug/substance that when administered to a group of experimental animals, will kill 50% of the group in a specified time

Median Lethal Dose (LD50)

- Dose of a drug required to produce a desired | effect to that which produces an undesired effect

THERAPEUTIC INDEX

TI is Defined as the ratio of the______

TD50 to the ED50

TI formula:

Formula = LD50/ ED50

refers to the range wherein the half maximal effect is seen as well as the adverse effect

Therapeutic Window

If TI is_____, a slight change in the dosage | can lead to potential adverse effect.

low/ narrow

If TI is_____, even if there is an increase/ decrease in the dosage of the drug the risk for adverse effect is lower.

large/ wide

Penicillin is an example of a drug with _____ TI

High

Drugs with Low TI:

``` ▪ Antiarrhythmic Drugs - Digoxin ▪ Diabetes - Insulin ▪ Bronchodilator - Theophylline ▪ Anticoagulant - Warfarin ▪ Antiepileptic - Phenytoin ```

If ED50 is 0.1 and the TD50 is 10 what will be the | Therapeutic Window?

0.1 to 10 ug

If ED50 is 0.1 and the TD50 is 10 what will be the | Therapeutic Index?

10/ 0.1 = 100

Determines the ability to fully or partially activate | the receptors

INTRINSIC ACTIVITY

If a Full Agonist binds to the receptor and produces and effect similar to your endogenous ligand, the Intrinsic Activity is

If the drug produces an Intrinsic Activity of 1 and mimics the effect of your endogenous ligand it is considered as a

Full Agonist.

For Partial Agonist, they also bind to the receptor and mimic the effect of your endogenous ligand however the Intrinsic Activity of your Partial Agonist is____

above 0 but less than 1.

are also agonists however when they bind to the receptor, they change the equilibrium/state of your receptor from active to inactive

Inverse Agonist

he Intrinsic Activity of your | Inverse Agonist is

below 0.

For Antagonist, the Intrinsic Activity is

0 -because in the absence of agonist your antagonist will not have any effect.

A ligand that binds to a receptor and produces a conformational change that initiates an intracellular signal

Agonist

Continuous administration of agonist after Emax | would lead to

Desensitization

A ligand that binds to a receptor but does not produce the conformational change that initiates an intracellular signal

ANTAGONIST

- binding site different from active site that is | bound by endogenous ligand.

Allosteric Site

Antagonist that binds to allosteric are ALL

noncompetitive antagonist

reversible - Compete to the binding site of endogenous ligand.

Competitive antagonist

irreversible because if they bind to active site, they form covalent bond. Duration of effect will depend on the regeneration of new receptor

Noncompetitive Antagonist

Do not bind to receptor bound to your endogenous ligand. Can be either chemical or physiologic antagonist.

NON – RECEPTOR ANTAGONIST

Protamine, a protein that is positively charged at physiologic pH, can be used clinically to counteract the effects of heparin, an anti-coagulant that is negatively charged. This is an example of:

a. Chemical Antagonism -Protamine (a positively charged protein at physiologic pH) binds heparin (a negatively charged anticoagulant) making it unavailable for interactions with proteins involved in the formation of blood clots.

One drug may antagonize the action of a second | by binding to and inactivating the second drug.

a. Chemical Antagonism

Ted, 50 – year - old diabetic, was rushed to the ER due to bronchial Asthma in acute exacerbation. He was given Salbutamol nebulization and Hydrocortisone (Glucocorticoid). Insulin was administered to oppose the hyperglycemic effects of glucocorticoid. This is an example of?

Physiologic Antagonism -(Nonreceptor Antagonism) Hydrocortisone can increase blood sugar. Insulin was administered to oppose the effect of the hydrocortisone. Another example: Histamine (bronchoconstriction) and Epinephrine (Bronchodilation).