Antihistamines

Question 1

How is histamine formed?

Answer 1

Decarboxylation of histidine by histadine carboxylase

Question 2

What cells generally release histamine?

Answer 2

mast cells and basophils

Question 3

Which organs have the highest number of mast cells?

Answer 3

lungs, gastrointestinal tract and skin

Question 4

What does stimulation of H1 receptors cause? (2)

Answer 4

Smooth muscle contraction, vasodilation

Question 5

What do sedating antihistamines do?

Answer 5

Block/inhibit the actions of histamine at H1 receptor

Question 6

How do sedating antihistamines sedate?

Answer 6

The cross the blood brain barrier and block H1 receptors leading to drowsiness and sedation

Question 7

What is another effect that sedating antihistamines can have on other receptors?

Answer 7

they can inhibit acetylcholine at antimuscarinic receptors

Question 8

What are 3 adverse effects you may have if a sedating h1 antihistamine attaches to a h1 receptor?

Answer 8

CNS neuro-transmission reduction, sedation, appetite increase and cognitive and neuro-psychomotor performance reduction.

Question 8

What are three other uses for sedating antihistamines?

Answer 8

Motion sickness, insomnia and secretion drying

Question 9

What is the duration of action of antihistamines?

Answer 9

8-30 hours

Question 10

What is 1 adverse effect you may have if a sedating h1 antihistamine attaches to a muscarinic receptor?

Answer 10

Xerostoma (or dry mouth), urinary retention or sinustodial tachycardia

Question 11

What is 1 adverse effect you may have if a sedating h1 antihistamine attaches to an alpha adrenergic receptor?

Answer 11

Hypotension, dizziness or reflex tachycardia

Question 12

What type of receptors do non-sedative antihistamines target?

Answer 12

H1 receptors

Question 13

What happens when you stimulate H2 receptors by histamine?

Answer 13

secretion of gastric acid in the stomach and increased HR and CO

Question 14

What happens when you stimulate H3 receptors by histamine?

Answer 14

Decreases histamine release from histaminergic neurones and decreases acquisition and storage of long and short term memories

Question 15

What are the three elements of the histamine triple response?

Answer 15

Reddening of the skin, surrounding flare and weal (red swollen mark)

Question 16

What causes the histamine triple response?

Answer 16

Stimulation of the H1 receptors

Question 17

What causes type 1 IgE allergic reactions?

Answer 17

Continuous exposure to an allergen in the environment leading to the formation of IgE antibodies and increasing sensitisation from lack of tolerance.

Question 18

What are the symptoms of hay fever? (5)

Answer 18

vasodilation
increased capillary permeability
itchy and swollen red eyes
itchy runny nose or nasal stuffiness
sneezing

Question 19

What are the symptoms of hives? (3)

Answer 19

vasodilation
increased capillary permeability
skin rashes
weals
itch

Question 20

What does FAST stand for in allergies and what is one thing you look for in each letter?

Answer 20

Face- rash, hives, swelling of lips, tongues and eyes
Airway- difficulty breathing, swallowing and speaking
Stomach- ab pain, vomiting and diarrhoea
Total body- Rash, swelling, weakness, paleness, loss of consciousness

Question 21

What does H3 stimulation cause?

Answer 21

lower histamine release from the histaminergic neurones and lower acquisition of short and long term memories

Question 22

what does antidromic mean?

Answer 22

back against a normal signal

Question 23

What does T helper 2 cells produce and what do they do?

Answer 23

they make cytokines promoting allergen sensitising pathways

Question 24

`What is the name of the high affinity IGE receptor IGE binds to?

Answer 24

FCER1

Question 25

How many receptors do IGE bind to to activate the intracellular cascade?

Answer 25

2

Question 26

what are 2 side effects of morphine?

Answer 26

asthma symptoms and respiratory depression

Question 27

what type of agonist is a H1 receptor blocking agent

Answer 27

inverse agonists

Question 28

What activates B cells and leads to sensitisation?

Answer 28

Cytokines produced by TH2