Histamine and Serotonin (pharmacology)

Question 1

What is histamine?

Answer 1

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

Question 2

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

Answer 2

Mast cells, basophils, ECL cells and histaminergic neuron.

Question 3

What activates the release of histamine? (4)

Answer 3

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

Question 4

From which amino acid is histamine derived from?

Answer 4

Histidine

Question 5

What type of amino acid is histidine?

Answer 5

Essentially amino acid

Question 6

Which enzyme catalyzes the formation of histamine from histidine?

Answer 6

Histamine decarboxylase enzyme

Question 7

What are the characteristics of H1 receptor (histamine receotor)

Answer 7

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.

Question 8

What are the characteristics of H2 receptor?

Answer 8

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

Question 9

Clinical relevance of antihistamines (4)

Answer 9

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

Question 10

Side effects of 1st generation H1 antihistamines (4)

Answer 10

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

Question 11

What are the H1 antihistamines correctly called?

Answer 11

H1 receptor inverse agonists

Question 12

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

Answer 12

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

Question 13

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

Answer 13

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.

Question 14

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

Answer 14

Desloratadine
-Allergies
-Active metabolite of loratadine.

Terfenadine
-Allergies
-Withdrawn due to cardiotoxicity.

Question 15

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

Answer 15

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

Beta -Smooth muscle relaxation
-Heart muscle contraction
-Glycogenolysis

Question 16

What are the side effects for antihistamines?

Answer 16

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.

Question 17

Name the two mast cell stabilisers that are used for asthma

Answer 17

Cromoglicic acid
Nedocromil

Question 18

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

Answer 18

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

Question 19

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

Answer 19

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

Question 20

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

Answer 20

GIT upset
Dizziness
Repetitive use causes low efficacy
Confusion

Question 21

What is anaphylaxis?

Answer 21

Acute and severe hypersensitivity reaction

Question 22

Symptoms of anaphylaxis

Answer 22

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

Question 23

What is the 1st line of treatment for anaphylaxis?

Answer 23

Adrenaline

Question 24

What are other pharmacological treatments for anaphylaxis

Answer 24

-Bronchodilators
-Adrenocorticosteroids
-Antihistamines

Question 25

Where do we find serotonin?

Answer 25

-Throughout the body
-Gastrointestinal wall
-Blood
-CNS

Question 26

How do we get serotonin in the CNS?

Answer 26

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

Question 27

Which enzyme degrades serotonin?

Answer 27

Monoamine oxidase A

Question 28

What are the biological effects of serotonin? (4)

Answer 28

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

Question 29

What do high levels of serotonin cause? (5)

Answer 29

-Migraine
-Diarrhoea
-Seizures
-Fever
-Unconsciousness

Question 30

What are the treatments for serotonin syndrome?

Answer 30

Cyproheptadine
Anticonvulsants
Muscle relaxants