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X Pharmacological Treatment Of Disease > Histamine and Antihistamine > Flashcards

Histamine and Antihistamine Flashcards

(71 cards)

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1
Q

what chemical mediators are involved in inflammation?

A 
complement
Eicosanoids
Cytokines
histamine
other agents
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2
Q

what role do eicosanoids have in inflammation?

A

eicosanoids -> prostaglandins -> main pathway

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3
Q

what other agents are involved in inflammation?

A

brankinin, platelet activating factors

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4
Q

what is 5-HT involved in?

A

haemostasis

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5
Q

what are leukotrienes involved in?

A

asthma

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6
Q

what are peptide mediators?

A

e.g. bradykinin

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7
Q

what are the 4 cardinal signs of inflammation?

A

dolor - heat
calor - redness
rubor - swelling
tumor - pain

(+ restriction of movement)

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8
Q

what are the most important cardinal signs of inflammation?

A

dalor, calor, rubor - drug targets. blood vessels

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9
Q

what is histamine?

A

a basic amine

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10
Q

where does synthesis of histamine occur?

A

mast cells and circulating basophils

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11
Q

where is histamine stored?

A

in granules in mast cells and circulating basophils

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12
Q

where is histamine found?

A

skin, lungs, face, GI tract and CNS

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13
Q

what complex does histamine occur in?

A

in a complex with heparin

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14
Q

how is histamine synthesised?

A

histidine —deoxycarbolates—> histamine

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15
Q

how is histamine released?

A
  • > degranulation by mass

- > individual mediators

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16
Q

where is histamine metabolised?

A

locally

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17
Q

what is the half life of histamine?

A

~4 mins

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18
Q

what is the mechanism of the metabolism/excretion of histamine?

A

histamine -> Imidazoleacetic acid by Diaminase
oxidase

histamie -> N-methyl histamine by N-methyl transferase
-> N-methyl imidazoleacetic acid by Monoamine oxidase (MAO)

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19
Q

what is Monoamine oxidase (MAO)?

A

breaks down monoamine

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20
Q

what is Monoamine oxidase (MAO) associated with?

A

presynaptic neurone

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21
Q

what kinds of histamine receptors are there?

A

H1
H2
H3
H4

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22
Q

what is the location of H1?

A

Smooth muscle
Endothelium
Brain

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23
Q

what is the location of H2?

A

Gastric mucosa
Cardiac muscle
Mast cells
Brain

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24
Q

what is the location of H3?

A

Presynaptic: Brain
Myenteric plexus
Other neurones

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25
what is the location of H4?
Hematopoetic cells | Gastric mucosa
26
what is the post receptor mechanism of H1?
Gq -> ↑IP3 DAG
27
what is the post receptor mechanism of H2?
Gs -> ↑ cAMP
28
what is the post receptor mechanism of H3?
Gi -> ↓ cAMP
29
what is the post receptor mechanism of H4?
Gi -> ↓ cAMP
30
what are the selective antagonists of H1?
Mepyramine Triprolidine Certirizine
31
what are the selective antagonists of H2?
Cimetidine Ranitidine Tiotidine
32
what are the selective antagonists of H3?
Thioperamide Iodophenpropit Impromidine
33
what are the selective antagonists of H4?
Tioperamide
34
what is the Triphasic skin response?
``` • Flush Red line at site of injury • Flare Redness extending around the site • Wheal Swelling due to local oedema ```
35
what is Flush- | Red line at site of injury?
liberation of mast cells in the skin
36
what is Flare- | Redness extending around the site?
due to vasodilation around site vasodilators and dilation of sensory nerve -> release vasodilator -> dilation in blood vessel
37
what is Wheal- | Swelling due to local oedema?
increased vascular permeability
38
what is the difference in vasculature in normal/acute inflammation?
normal - closed precapillary sphincter, most capillaries empty acute inflammation - open precapillary sphincter, most capillaries full
39
what is the mechanism of increased vascular permeability?
1. endothelial cells contract 2. separate at their boundaries 3. basement membrane exposed 4. gap formed 5. leakage of fluid and plasma proteins 6. oedema
40
5 effects of histamine
- vasodilation - increased vascular permeability - bronchoconstriction - mucus secretion - itching
41
how does histamine cause a fall in blood pressure?
1) histamine -> Vasodilation in microvasculature -Direct effect via H1 receptors (rapid) - Indirect effect via H2 receptors (slow) - Fall in: • peripheral resistance, • venous return • cardiac output = fall in blood pressure 2) histamine -> Increased permeability in microcirculation - oedema -loss of blood volume =fall in blood pressure
42
how does histamine cause itching?
stimulation of nerve endings - H1 receptor mediated
43
what do H1-histamine antagonists cause
oedema itching fall in blood pressure (so stop the fall in blood pressure)
44
what does the immunological release of histamine involve?
Mast cells & basophils IgE molecules attached Antigen exposure => degranulation.
45
how does an allergen cause inflammation?
allergen -> B cell -> release of IgE antibodies -> antibodies bind to mast cell surface -> rexposure to allergen -> Antigen-antibody complex causes degranulation -> histamine and other mediators -> inflammation
46
how can you DISPLACE histamine?
basic amines- displace histamine from the histamine-heparin complex. e.g. Tubocurarine and Morphine (Receptors are not involved) (release is not associated with mast cell damage or degranulation)
47
what is tubocarine?
muscle relaxant
48
how can you DEGRANULATE histamine?
Compound 48/80, a diamine polymer specifically releases histamine from mast cells by exocytotic degranulation
49
what is a physiological antagonist of histamine?
adrenaline
50
what are release inhibitors of histamine?
Cromolyn | Nedrocromil
51
what are receptor antagonists of histamine?
H1:- Mepyramine H2:- Ranitidine
52
what is the difference between physiological and pharmacological antagonist of histamine?
physiological - creating opposing affect | pharmacological - blod H1 receptor
53
what do H1 Antihistamines do?
(in vitro): - reduce contraction of bronchial smooth muscle by histamine - reduce histamine-induced contraction of intestinal and uterine smooth muscle - reduce vascular permeability caused by histamine
54
what other receptors do H1 Antihistamines work as antagonists at?
muscarinic, 5-HT and alpha-1 adrenoceptors
55
what would be an adverse effect of blocking H1 receptor?
sedating -useful to reduce awareness of itching | travel sickness
56
what would be an adverse effect of blocking muscarinic receptor?
(muscarinic - parasympathetic) loss of GI motility - constipation dry mouth urinary retention
57
what would be an adverse effect of blocking alpha-1 adrenoreceptor?
(vasoconstriction) so would cause vasodilation leads to reflex tachycardia, fainting
58
what are the uses of H1 antihistamines in allergic reactions? - hay fever - Urticaria - Insect bites - Drug hypersensitivites
Histamine = main mediator: H1 antihistamines effective
59
what is the use of H1 antihistamines in asthma?
H1 antihistamines not v. effective
60
what is the use of H1 antihistamines in * Motion sickness * Morning sickness * Vertigo
Cyclizine, cinnarizine • Promethazine Act via CNS H1 receptors. Antimuscarinic effects may also play a part
61
how do you combat sedation?
-blood brain barrier lipid solubility molecular size efflux pumps
62
what are antimuscarinic effects?
dry mouth blurred vision (loss of accommodation) anti-nausea antiparkinson
63
2 older antihistamines that produce antimuscarinic effects and sedation?
Promethazine, mepyramine
64
what are newer antihistamines?
Loratadine, certirizine
65
what is the difference in newer antihistamines than older?
Fewer CNS effects - cross BBB only slowly | Negligible antimuscarinic effects
66
what are H2 Receptor Antagonists used for?
treatment/prevention of gastric and duodenal ulcers
67
what is an example of an H2 Receptor Antagonist?
cimetidine and ranitidine
68
how do H2 Receptor Antagonists affect gastric ulcers?
Reduce secretion of gastric acid stimulated by histamine, gastrin, ACh
69
how do H2 Receptor Antagonists affect duodenal ulcers?
Promote healing of duodenal ulcers
70
what is the dosage of H2 Receptor Antagonists?
Once (ranitidine) or twice (cimetidine) daily
71
how do H2 receptor antagonists work?
histamine -> vagal stimulation -> cholinomimetics -> gastrin -> H2 receptor antagonists block ->>>>> acid secretion

X Pharmacological Treatment Of Disease (9 decks)

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