Receptor-Mediated Cell Signaling Flashcards Preview

Pharmacology > Receptor-Mediated Cell Signaling > Flashcards

Flashcards in Receptor-Mediated Cell Signaling Deck (17):
1

Antagonist

Block receptors and have no inherent ability to elicit a response

2

Competitive antagonist

molecule that competes for the same binding site as an agonist; low concentrations can be overcome by the agonist; effects depend upon its concentration which is influenced by the rate of metabolic clearance or excretion

3

Non-competitive antagonist

  • have depressive effects on maximal agonist response but do not compete for same binding site as the agonist
  • blockade is fixed and cannot be overcome by the agonist
  • usually have prolonged effects and receptor blockade reversal is slow
  • duration of action depends upon rate of receptor turnover
  • Ex: ketamine blocks channel functioning of NDMA receptor channel for glutamate

4

Chemical antagonist

a drug that binds directly to an agonist and deactivates the agonist (form an inactive compound) e.g. tannins

5

Physiological antagonist

any drug or chemical that has an opposite effect, but through different physiological pathways e.g. histamine and epinephrine (contract vs. dilate sm mm of airway)

6

Pharmacologic antagonist

any drug that binds to a receptor and prevents the activation of the receptor

7

Drug-Receptor Interactions

  • most drugs bind in reversible manner - unbinding and binding occurs very fast
  • drug binding chemical interaction is determined by structure of drug relative to receptor binding site

8

Properties of drug-receptor interactions:

  1. Saturable (maximal) response (finite # of receptors)
  2. Reversibility
  3. Good potency (many drugs act @ very low concentrations)
  4. Chemical sensitivity 
  5. Competitive blockade by antagonists
  6. Amplified responses

9

Dissociation constant (Kd)

  • the concentration at which 50% of the binding sites (receptors) are occupied by the drug; can be determined for an agonist or antagonist
  • expressed as a concentration
  • provides info about affinity of the drug for a receptor
  • High affinity - low Kd; Low affinity - high Kd

10

Affinity

how well a drug binds a receptor; helps define the drug's potency

11

Potency

amount of drug required to produce a desired effect; used as means to compare drugs, (higher potency, less drug required)

12

EC50

drug concentration producing 50% of a maximal effect; typically used for in vitro  studies

13

Efficacy

the maximum effect a drug can produce

 

for drugs w/ similar maximal efficacy, increasing drug potency decreases EC50

14

ED50 or effective dose

dose that causes a desired effect in 50% of the population receiving it; effect must be all or none (quantal effect)

15

Specificity

measure of a drug's ability to produce a desirable effect relative to its ability to produce an undesirable effect

 

Specificity = ED50 (desirable)/ ED50 (undesirable)

 

If ED50 (un) >>>ED50 (des) = high (good) specificity

If ED50 (un) = ED50 (des) = low (bad) specificity

16

Therapeutic Index (TI)

a quantal response; ratio of LD50 (lethal dose in 50%) and ED50; the larger the TI, the safer the drug is

 

TI = LD50/ED50

17

Margin of Safety

ratio of drug that is just within the lethal range (1%) to the dose that is 99% effective; more stringent index of safety

 

MOS = LD1/ED99