Histamine and Serotonin (pharmacology) Flashcards

1
Q

What is histamine?

A

It is a biogenic monoamine autacoids, which is found in non-neural tissues and functions as a neurotransmitter.

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2
Q

What are the major histamine-producing cells? (4)

A

Mast cells, basophils, ECL cells and histaminergic neuron.

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3
Q

What activates the release of histamine? (4)

A

-IgE crosslinking
-allergy inducing drugs
-somatostatin
-dopamine d2

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4
Q

From which amino acid is histamine derived from?

A

Histidine

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5
Q

What type of amino acid is histidine?

A

Essentially amino acid

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6
Q

Which enzyme catalyzes the formation of histamine from histidine?

A

Histamine decarboxylase enzyme

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7
Q

What are the characteristics of H1 receptor (histamine receotor)

A

LOCATION-Throughout the body, skin, CNS, heart, nerve cells.
TYPE OF RECEPTOR- G-protein coupled receptor, activates phospholipase C.
EFFECTS- Increases vascular permeability.
TREATMENT- Nausea, allergies, sleep disorder.

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8
Q

What are the characteristics of H2 receptor?

A

LOCATION-Throughout the body, gastric mucosa parietal cells, heart.
TYPE OF RECEPTOR- G-protein coupled receptor, it activates adenyl cyclase.
EFFECTS- Increases secretion of gastric acid.
TREATMENT- Stomach ulcers

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9
Q

Clinical relevance of antihistamines (4)

A

Relief from allergies and immune reactions.
Relief from gastric distress
Relief from certain nausea and vomiting conditions
Used to treat insomnia

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10
Q

Side effects of 1st generation H1 antihistamines (4)

A

Anticholinergic, antiadrenergic and antiserotonin.
-They can cross the BBB and causes sedation.
-Increased appetite
-Cognitive impairment

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11
Q

What are the H1 antihistamines correctly called?

A

H1 receptor inverse agonists

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12
Q

What are the differences between first generation and second generation H1 antihistamines? (8)

A

First genaration
-Lipophilic
-Crosses BBB easily
-Less selective for H1 receptor
-Anticholinergic, antiadrenergic, antisorotonergic and antidopaminergic.

Second generation
-Lipophobic
-Does not cross BBB easily, affects CNS less.
-More selective for H1 receptor
-Less effect on other receptors

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13
Q

Name two first generation antihistamines, what they are used for as well as a special note regarding them (6)

A

Promethazine
-Used as sedative anti-emetic
-Special note:It is sedative and has anti-emetic effect due to CNS effects.

Cyproheptadine
-Eroxigenic (appetite stimulant)
-Special note: It has eroxigenic effects due to antiserotonergic activity.

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14
Q

Name two second generation antihistamines, what they are used for and a special note about them.

A

Desloratadine
-Allergies
-Active metabolite of loratadine.

Terfenadine
-Allergies
-Withdrawn due to cardiotoxicity.

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15
Q

Name three receptors that histamine can bind in and the effects it causes.

A

Alpha 1- smooth muscle contraction
Alpha 2-Smooth muscle relaxation
-Inhibition of transmitter release

Beta -Smooth muscle relaxation
-Heart muscle contraction
-Glycogenolysis

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16
Q

What are the side effects for antihistamines?

A

CNS effects-Causes sedation, drowsiness and loss of coordination.
Anticholinergic effects- causes tachycardia, dry mouth and urinary retention.
Anti-alpha-adrenergic effects- hypotension leading to dizziness.
Antiserotonergic effects- causes orexigenesis which can lead to weight gain.

17
Q

Name the two mast cell stabilisers that are used for asthma

A

Cromoglicic acid
Nedocromil

18
Q

Name the four H2 receptor antagonists, what they are used as and special notes regarding them

A

Cimetidine- they have severe side effects.
Nizatidine
Ranitidine
Famotidine
The last three are more potent that cimetidine.
-They are all used as antacid in gastric distress

19
Q

What are the clinical indications for H2 receptor blockers? (5)

A

-Duodenal and gastric ulcer disease.
-Stress ulcer and gastritis
-Ellison syndrome
-Gastroesophageal reflux disease (GERD)
-Prophylaxis of aspiration pneumonia

20
Q

What are some of the side effects of H2 receptor antagonists? (4)

A

GIT upset
Dizziness
Repetitive use causes low efficacy
Confusion

21
Q

What is anaphylaxis?

A

Acute and severe hypersensitivity reaction

22
Q

Symptoms of anaphylaxis

A

Immune reactions-rashes, oedema
Respiratory distress-Bronchospasms
Cardiovascular distress-hypotension, arrhythmias

23
Q

What is the 1st line of treatment for anaphylaxis?

A

Adrenaline

24
Q

What are other pharmacological treatments for anaphylaxis

A

-Bronchodilators
-Adrenocorticosteroids
-Antihistamines

25
Q

Where do we find serotonin?

A

-Throughout the body
-Gastrointestinal wall
-Blood
-CNS

26
Q

How do we get serotonin in the CNS?

A

-Serotonin cannot cross the BBB, but Tryptophan which forms serotonin can cross the BBB.

27
Q

Which enzyme degrades serotonin?

A

Monoamine oxidase A

28
Q

What are the biological effects of serotonin? (4)

A

-Nausea and vomiting
-Smooth muscle contraction
-Vasodilation and vasoconstriction blood vessels.
-Inhibition of neurotransmitter release

29
Q

What do high levels of serotonin cause? (5)

A

-Migraine
-Diarrhoea
-Seizures
-Fever
-Unconsciousness

30
Q

What are the treatments for serotonin syndrome?

A

Cyproheptadine
Anticonvulsants
Muscle relaxants