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** Pharmacology - CF > drugs and histamine receptors > Flashcards

drugs and histamine receptors Flashcards

1
Q

What 4 conditions occur when inflammation goes wrong?

A
  • Anaphylaxis
  • Asthma
  • Rheumatoid arthritis
  • Atherosclerosis
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2
Q

Which step of inflammation do medicines such as steroid, antihistamines and anti-inflammatory drugs target?

A

Release of chemical mediators

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3
Q

Which 2 mediators cause vasodilation?

A
  • Histamine
  • Prostaglandins (PGE2 & PGI2)
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4
Q

Which 2 mediators cause increased vascular permeability?

A
  • Histamine
  • Platelet activating factor (PAF)
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5
Q

Which 4 mediators cause exudation (fluid filtering from circulatory system into the surrounding tissue)?

A

Plasma proteins:

  • Complement
  • Coagulation system
  • Fibrinolytic system
  • Kinin system
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6
Q

What are the 7 principle mediators/autocoids/local hormones of inflammation and allergy?

A
  • Histamine
  • Platelet Activating Factor
  • Bradykinin
  • Nitric Oxide
  • Cytokines (interleukins, interferons, chemokines, colony stimulating factors)
  • Eicosanoids (prostagladins, thromboxanes, leukotrienes)
  • Plasma proteins (kinins, complement, coagulation and fibrinolytic factors)
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7
Q

When are these mediators released?

A

From cells upon stimulation

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8
Q

How is histamine synthesised?

A

Decarboxylation of histamine by L-histadine decarboxylase

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9
Q

Which 2 enzymes rapidly metabolises histamine?

n.b. they produce two different products

A

Histamine-N-methyltransferase

or

Diamine oxidase/histaminase

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10
Q

How many different types of histamine receptor subtypes have been discovered?

A

4

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11
Q

Which two types of celLs contain histamine contained in granules?

A
  • Mast cells
  • Basophils
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12
Q

Which cells in the gastric glands in the gastric mucosa are also found to contain histamine?

A

Enterochromaffin-like cells (ECL)

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13
Q

In which organs of the body can the highest levels of histamines be found?

A

Lung

Skin

Brain

GI tract

n.b. they are found throughout the body too!!

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14
Q

Where are mast cells produced?

A

Bone marrow

(released as immature cell and matures in the tissue)

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15
Q

Which antibody does the FCERI receptor have a high affinity for?

A

IgE

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16
Q

What are the 4 stages of mast cell degradation?

A
  1. Priming of mast cells (body produced IgE = bind mast cells = chemical mediator release)
  2. 2nd exposure to allergen = IgE bind to mast cell surface
  3. Activates mast cell (granule movement and fusion to membrane due to increased Ca)
  4. Degranulation (release of chemical mediators)
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17
Q

Which two other factors can activate mast cells?

A

Complement components:

C3a

C5a

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18
Q

Which process gets the complement & phagocytes present mainly in the blood to the site of tissue invasion?

A

Inflammatory response

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19
Q

What 2 things can cause histamine release?

A
  • Some neuropeptides (e.g. substance p)
  • certain basic drugs (e.g. morphine & tubocurarine)

n.b. some basic drugs e.g. morphine and other opioids can displace histamine from mast cells without activating cell surface receptors

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20
Q

What inhibits histamine release?

A

An increase in cAMP

e.g. by beta adrenoreceptor agonists

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21
Q

What are the 3 physiological roles of histamine?

A
  • local immune response (tissue repair, inflammation, control of local blood flow, allergies & anaphylaxis)
  • regulates physiological function in the gut (increased gastric acid secretion = H2)
  • Neurotransmitter in CNS
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22
Q

Why is the reaction to histamine location dependant?

A
  • different histamine receptors

(all GPCRs) = H1, H2, H3 & H4

(located in different tissues & couple different G proteins)

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23
Q

What type of receptor is the H1 receptor?

And where is it found?

A

GPCR - Gq

= activates PLC & PIP2

Found in smooth m, endothelium & CNS tissue

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24
Q

Activation of the H1 receptor causes (8):

A
  • Bronchial smooth muscle contraction
  • vasodilation
  • separation of endothelial cells
  • increased vascular permeability
  • pain and itching
  • motion sickness
  • allergic rhinitis
  • sleep and appetite suppression
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25
Q

What are H1 receptor antagonists used for?

A
  • Treat allergy (hay fever, urticaria)
  • Treat nausea and vomiting
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26
Q

How H1 receptor antagonists drugs taken?

Where are they metabolised?

A

Orally

Hepatic metabolism

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27
Q

Name 3 1st generation H1 receptor antagonists?

A
  • Mepyramine
  • Promethazine
  • Diphenhydramine
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28
Q

What is the average duration of effect for H1 receptor antagonists?

A

Approx 4-6 hours

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29
Q

What is promethazine used for (4)?

A
  • Allergic disorders
  • Nausea and vomiting
  • Insomnia
  • Sedation
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30
Q

What is Diphenhydramine used for (4)?

A

Antihistamine with:

  • Anticholinergic
  • Antitussive (prevents coughing)
  • Antiemetic (prevents nausea)
  • Sedative
31
Q

What are the 2 benefits of 2nd generation over 1st generation H1 receptor antagonists?

A
  • less CNS depression (non-drowsy)
  • Last longer (12-24 hours)
32
Q

What are the 4 different 2nd generation H1 receptor antagonists?

A
    • Fexofendine
    • Cetirizine
    • Loritadine
    • Cinnarizine
33
Q

What is fexofendine used to treat (1)?

A

Seasonal allergic rhinitis

34
Q

What is ceterizine used to treat (4)?

A

Hay fever

Allergies

Angioedema = swelling of deeper layers of skin

Urticaria (hives)

35
Q

What is Loratadine used to treat (1)?

A

Allergies

36
Q

What is Ciinnarizine used to treat (2)?

A

Motion sickness & vertigo

(also contains Ca T-type channel blocker)

37
Q

In which neurones are high concentrations of histamine and histamine decarboxylase found?

A

Hypothalamus

38
Q

What are the effects of Histamine as a neurotransmitter?

A

Arousal (alertness)

Sleep (quality)

Circadian Rhythm

39
Q

From which nucleus of the hypothalamus is histamine released?

A

Tubermammillary nucleus

40
Q

What causes motion sickness?

A

The disagreement between visual perceived movement and the movement detected by the vestibular system

  • Same effect from neurotoxins= stimulates H1 receptors in the nucleus solitary tract = vomitting
41
Q

How to antihistmaine (H1) drugs work?

A

Atropine like action

= blocks muscarinic ACh receptors = depression in CNS = depresses vestibular reflex centre = alleviates nausea

42
Q

What type of receptors are H2 receptors?

A

GPCR - Gs

= increased cAMP & PKA activation

43
Q

Where are H2 receptors found?

A

= vascular smooth muscle and parietal (gut) cells

44
Q

What are H2 anti-histamine drugs used to treat (2)?

A

Gastric ulcers

Excess acid secretion

45
Q

What does activation of the H2 histamine receptors cause (6)?

A
  • Vasodilation
  • Smooth muscle relaxation
  • Gastric acid secretion
  • Inhibits antibody synthesis
  • Inhibits T cell proliferation
  • Inhibits Cytokine producation
46
Q

Which histamine receptors are involved in gastric acid secretion?

A

H2

47
Q

On which cells are the histamine receptors involved in gastric acid secretion located?

A

Parietal cells

48
Q

When histamine binds to the H2 receptor on parietal cells what happens that causes gastric acid secretion?

A

= increased cAMP = activates proton pump = gastric acid secretion

49
Q

Which two drugs are used to decrease gastric acid secretion?

A

Cimetidine

Ranitidine

50
Q

What are the side effects of drugs used to decrease gastric acid secretion?

A

Diarrhoea

Headaches (imbalance in gastric system)

Dizziness

Skin rashes

Tiredess

n.b. these are pretty minor so they are still commonly used

51
Q

What is cimetidine used to treat?

A

Heartburn and peptic ulcers(decrease gastric acid secretion)

52
Q

What is Ranitidine used to treat?

A

Peptic ulcers and gastroesophageal reflux disease & urticaria (hives)

53
Q

What type of receptors are H3 receptors?

A

GPCR - Gi (inhibits cAMP)

54
Q

Where are H3 receptors mostly found?

A

Mostly in the CNS (cortex and sub cortex)

55
Q

Which channels do the activated G protein interact with?

A

N-type voltage gated Ca receptors

56
Q

What happens when the H3 receptor is activated?

A
  • Feedback inhibition of synthesis and release of histamine
  • inhibits release of neurotransmitters
57
Q

What are H3 receptors currently used to research?

A

sleep disorders, neuropathic pain, obesity, potentially movement disorders. schizophrenia and ADHD

58
Q

What type of receptors are H4 receptors?

A

GPCR -> Gi

inhibits cAMP production

59
Q

Where are H4 receptors found?

A

Basophils & bone marrow

Thymus

Smooth intestine

Spleen

Colon

60
Q

What are H4 receptors used for?

A

Research tool

61
Q

What happens when H4 receptors are activates?

A

Regulates neutrophil release from bone marrow

Mediates eosinophil shape change

Mast cell chemotaxis

Beta & Gamma subunits act as PLC (phospholipase C)

62
Q

What is anaphylaxis?

A

Whole body reaction of a previously sensitised animal to the sensitising allergen

63
Q

What are the immediate effects of anaphylaxis?

A
  • smooth muscle contraction
  • vasodilation
  • increased vascular permeability
  • nausea
  • abdominal pain
  • palpitation
  • urticaria (hives)
  • hypotension (inadequate circulation) = SHOCK
64
Q

What is the drug treatment for anaphylaxis?

A
  • immediate adrenaline subcutaneously
  • IV maintain volume and supply additional medication
65
Q

Which other drugs are administered in anaphylaxis?

A
  • H1 receptor antagonists = chlorphenamine & promethazine
  • glucocorticoids
66
Q

What do glucocorticoids do in anaphylaxis?

A

suppress slow onset urticaria (hives), bronchospasm, laryngeal oedema and hypotension

67
Q

Which histamine receptor antagonists often have the side effect of sedation?

A

H1

68
Q

How do H1 receptor antagonists cause sedation?

A

They have an atropine like action on ACh receptor = CNS depression = drowsiness (useful for treating terminally ill patients or those experiencing insomnia due to allergic reactions)

69
Q

Which antihistamines can be used as sedatives for short or long dental procedures?

A

Diphenhydramine

Hydroxyzine

Promethazine

70
Q

How long before an appointment are the antihistamines used as sedatives for short or long dental procedures given?

A

1 hour

71
Q

Which side effect may H1 antihistamines give?

A

Anticholinergic effect e.g. dry mouth

72
Q

How can Gastrooesophageal reflux affect the mouth?

A

Damage to teeth and buccal mucosa

Glossitis

Burning mouth

Ulceration

73
Q

What effect can prolonged use of antihistamine syrups have on primary enamel?

A

Erosive(can be reversed by using fluoride toothpastes)

** Pharmacology - CF (4 decks)

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