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1. Principles > Pharmacology > Flashcards

Pharmacology Flashcards

1
Q

What are pharmacodynamics?

A

What a drug does to the body

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2
Q

What are pharmacokinetics?

A

What the body does to a drug

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3
Q

What is an agonist?

A

Drug that binds to a receptor to produce a cellular response

possesses affinity and efficacy

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4
Q

What is an antagonist?

A

Drug that blocks the actions of an agonist

Possess affinity but lack efficacy

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5
Q

What is affinity?

A

Strength of association between ligand and receptor

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6
Q

What is efficacy?

A

Ability of an agonist to evoke a cellular response

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7
Q

What does competitive antagonism cause on a response curve?

A

Cause parallel rightward shift of agonist concentration response curve with no depression in maximal response

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8
Q

What does non competitive antagonism cause on a response curve?

A

Depress the slope and maximum response curve, but do not cause a rightward shift

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9
Q

What factors control drug absorption?

A

-Solubility
-Chemical stability
-Lipid to water partition coefficient – rate of diffusion of drug increases with lipid solubility
-Degree of ionisation – only unionised forms readily diffuse across the lipid bilayer
Depends upon pKa of the drug and local pH
pKa = pH at which 50% of drug is ionised and 50% unionised
Henderson-Hasselbalch = pH – pKa = log(A-/AH) = acid

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10
Q

What is oral availability?

A

Fraction of drug that reaches the systemic circulation after oral ingestion

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11
Q

What is systemic availability?

A

Fraction of drug that reaches the systemic circulation after absorption

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12
Q

Describe the routes of administration

A 
Enteral 
-	Oral 
-	Sublingual 
-	Rectal 
Parenteral 
-	Intravenous 
-	Intramuscular and subcutaneous 
-	Inhalational 
-	Topical
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13
Q

What is the volume of distribution?

A

Apparent volume in which a drug is dissolved with a concentration equal to that of plasma

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14
Q

What does the therapeutic ratio = ?

A

MTC/MEC
MEC – minimum effective concentration
MTC – maximum tolerated concentration
Higher the TR the safer the drug

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15
Q

What is clearance?

A

The volume of plasma cleared of drug in unit time

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16
Q

What does rate of elimination =

A

Clearance x Plasma concentration

17
Q

Describe first order kinetics?

A
  • Rate of elimination directly proportional to drug concentration
  • Plasma concentration falls exponentially
  • Half-life is inversely proportional to elimination rate constant
  • T½ = 0.69/Kel
18
Q

When is steady state concentration achieved?

A

after 5 half lives

19
Q

Describe zero order kinetics?

A
  • Initially eliminated at a constant rate

- Then return to first order kinetics

20
Q

Describe positive feedback voltage activated channels?

A

Activation of Na channels self-reinforcing, opening of a few channels causes further depolarisation

21
Q

Describe negative feedback voltage activated channels?

A

Activation of K channels is self-limiting, outward movement of K causes repolarisation which turns off the stimulus

22
Q

Where does the sympathetic system come from?

A

Thoraco-Lumbar outflow (T1-L2)

23
Q

Where does the parasympathetic system come from?

A

Cranial Nerves 3/7/9/10

24
Q

What is Potency?

A

a measure of drug activity required to produce an effect of given intensity

25
Q

What factors affect drug distribution in the body?

A 
ADME – 
Absorption
Distribution
Metabolism
Excretion
26
Q

How do ACh (acetylcholine) and Noradrenaline act in the sympathetic system?

A

ACh - preganglionic: opens ligand-gated ion channels in the postganglionic neurone
Noradrenaline -postganglionic: activates G protein coupled receptors - adrenoceptors

27
Q

How does ACh act in the parasympathetic system?

A

ACh acts on post and preganglionic neurones

ACh always the transmitter used by postganglionic neurones
ACh activates G protein coupled muscarinic acetylcholine receptors in target cell membrane

28
Q

Describe a G protein?

A
  • Peripheral membrane protein
  • 3 polypeptide subunits (alpha = binding site)
    Couple with muscarinic ACh receptors
29
Q

How are G proteins activated?

A
  • Agonist activates receptor
  • G protein couples with receptor
  • GDP dissociates from and GTP binds to alpha subunit
  • G protein dissociates
  • Alpha subunit combines with and modifies activity of effector
  • Agonist may dissociate from the receptor, but signalling persists
30
Q

How are G proteins turned off?

A
  • Alpha subunit acts as an enzyme to hydrolyse GTP GDP

- G protein alpha subunit recombines with the By subunit completing G protein cycle

31
Q

Describe the G protein coupled adrenoceptor subtypes at sympathetic neuroeffector junctions?

A

B1 – Gs – stimulation of adenylyl cyclase – Increased HR and force
B2 – Gs – stimulation of adenylyl cyclase – Relaxation of bronchial and vascular smooth muscle
A1 – Gq – stimulation of phospholipase C – contraction of vascular smooth muscle
A2 – Gi – inhibition of adenylyl cyclase – inhibition of NA release

1. Principles (9 decks)

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