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Pharmacology and Medical Chemistry I > Exam 1 - Lecture 1 & 2, Drug Action > Flashcards

Exam 1 - Lecture 1 & 2, Drug Action Flashcards

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1
Q

How to study receptors

A
  1. Isolate and purify macromolecular component and study drug “structure-activity” relationships

info inferred from kinetics of drug-receptor interaction = binding sites

  1. Determine amino acid sequence; clone and express receptor in cultured cells

enables study of receptor function in living cells, but isolated from components of native cells in intact tissue

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2
Q

Types of binding of drugs to receptors

A
  1. van der Waals attraction (weakest)
  2. Hydrogen bond
  3. Hydrophobic interaction
  4. Ionic bond
  5. Covalent bond (strongest)
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3
Q

Receptor locations

A

typically cell surface, embedded in cell membrane

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4
Q

Drugs that don’t act through receptors

A

Antacids
Osmotic diuretics and cathartics
Chelating agents which bind heavy metals

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5
Q

Nature of drugs

A

Physical nature (solid, liquid, pH [affect absorption], hydrophilicity and hydrophobicity [changes receptor interaction])

Drug size ( small, large, typically MW 100-1000…as size increases absorption isn’t as effective)

Drug shape (stereoisomerism, ie carvedilol…R+ binds to Beta receptors much worse than S- (Kd = 54 vs 0.5)

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6
Q

Agonist

A

Drug that causes specific physiological effect due to direct interaction with a receptor

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7
Q

Antagonist

A

Compound that is devoid of intrinsic pharmacological activity but blocks the action of a specific agonist or an endogenous substance which produces the effect

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8
Q

Allosteric modulator

A

A drug which binds to a different site on the receptor than that bound by endogenous ligands; can modulate positively or negatively

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9
Q

Addition

A

When two agonist which produce the same effect are administered together, they produce an effect equal in magnitude to the sum of the effects of the individual drugs
A + B = A (solo) + B (solo)

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10
Q

Synergism

A

When two agonist which produce the same effects are administered together, they produce an effect greater in magnitude than the sum of effects of the individual

A + B > A (solo) + B (solo)

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11
Q

Potentiation

A

When drug is itself without effect, but if administered with a second drug, increases the effect of the second drug

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12
Q

Drugs A and B can target….

A

One receptor or two separate receptors producing interacting effects

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13
Q

Quantal ( all or none) dose response curves

A

Relates drug dose to frequency of drug-induced “all-or-none” pharmacological effect

Plot of response frequency vs dose yields normal distribution

Replotting curve in terms of percentage of subjects responding vs log of dose yields a sigmoid (S-shaped) curve

Examples include (dose of barbiturate to induce sleep)

Wide distribution yields shallow cumulative curve (S-shaped)

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14
Q

Graded (quantitative) dose response curves

A

relates dose of drug to size of response of a single biological unit

Plot of magnitude of response vs log doe yields sigmoid curve

Examples include drug induced, graded changes in HR

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15
Q

ED50

A

smallest dose of drug which is effective in 50% of individuals receiving the drug

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16
Q

Linear vs Log plot

A

Linear - intuitive scaling

Semi-log plot - compact scaling

17
Q

Tolerance

A

When repeated admin of given dose of drug produces a decreased effect, or conversely larger doses must be administered to obtain the same effect observed with the original dose.

Time scale: days to months

18
Q

Tachyphylaxis

A

Very rapidly developing tolerance; decreasing effect of a drug following consecutive doses given at short intervals

Time scale: minutes to hours

19
Q

Supersensitivity

A

A heightened state of pharmacological responsiveness of a tissue or organ, leading to an exaggerated effect of an agonist

may be due to a compensatory increase in number of receptors, “up regulation”

Changes can be drug induced (prolonged exposure to antagonist) or due to denervation (destruction of neuronal input to the tissue)

20
Q

Desensitization

A

A reduced state of a pharmacological responsiveness of a receptor due to continuous presence of the agonist at that receptor

Maybe due to decrease in receptor number ie. down regulation or to a change in receptors conformational state to an inactive “desensitized” state

21
Q

LD50

A

smallest dose of a drug which is lethal in 50% of individuals receiving the drug

22
Q

Therapeutic index (TI)

A

LD50 / ED50

23
Q

Margin of safety

A

LD0.1 /ED99.9

More useful expression of drug safety

24
Q

Small Kd

A

its affinity for receptor is high

25
Q

Large Kd

A

its affinity for the receptor is low

26
Q

Kd = [D] when…

A

50% of receptors occupied

27
Q

Kd

A

K2/K1

equilibrium dissociation constant and is related to the affinity of the receptor for the drug

K2 = {D][R]
K1 = [DR]
28
Q

PAM effect on log chart

A

Can be left-ward shift, typically accompanied by an upward shift

29
Q

Agonist + Competitive Antagonist on Semi-log plot

A

Moves to right

30
Q

Agonist + Irreversible or Non-competitive antagonist on semi-log plot

A

lowers efficacy from agonist alone

31
Q

Intrinsic activity or efficacy

A

independent of the slope or position of dose-response curve

degree of effect obtainable for a given level of receptor occupancy, drugs with same efficacy elicit same maximal response

32
Q

Potency

A

used in comparing 2 or more drugs when specifically referring to the doses of each required to produce same effect

Location on access, slope show potency

Efficacy is more important than potency in selecting drugs for use in clinical situation

33
Q

Coupling

A

overall transduction process that links drug occupancy of receptors and pharmacologic response

34
Q

Spare receptors

A

Example:

If 4 coupling events yield max effect and only 4 G proteins are present to transduce signaling, having more receptors does not cause more effect….extra receptors are “spare”

35
Q

Pharmacological antagonism

A

Antagonist prevents an agonist from acting upon it receptor to produce a response

36
Q

Physiological antagonism

A

Occurs when 2 agonist act upon a tissue to produce opposing response, each agonist interacts independently with specific but different receptors

ex. Epinephrine and histamine

37
Q

Antagonism by neutralization

A

2 drugs combine with one another to form an inactive compound

ex. Heparin (-) and Protamine (+) form inactive ionic complex

Pharmacology and Medical Chemistry I (30 decks)

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