Pruritis

Question 1

Which substances can induce mast cell degranulation?

Answer 1

1. Substance P
2. IgE
3. Allergen
4. C5a
5. Opiates

Question 2

What are the four causes of itch?

Answer 2

1. Pruritoceptive causes
2. Neurogenic causes
3. Neuropathic causes
4. Psychogenic causes

Question 3

Which class of drug is ondansetron?

Answer 3

Opiate antagonist

(for serotonin)

Question 4

What are three classes of itch mediators?

Answer 4

1. Chemical mediators in the skin - histamine, acetylcholine, substance P etc
2. Nerve transmission - Unmyelinated C fibres
3. Central nervous system mediators - Opiates

Question 5

In nerve fibres are exposed (unmyelinated), yet not damaged, which cause of itch is involved?

Answer 5

Pruritoceptive

Question 6

Which cause of itch is associated with damage to central or peripheral nerves?

Answer 6

Neuropathic

Question 7

How can neurogenic itch be described?

Answer 7

Itch which originates in the CNS yet there is no evident damage

Question 8

Insect bite reaction involves which type of itch?

Answer 8

Pruritoceptive

Question 9

What is doxepin?

Answer 9

Antidepressant

Question 10

Which type of antihistamines must be used to treat itch?

Answer 10

Sedative antihistamines (usually first generation)

Question 11

Which anti-histamine is commonly used to treat itch?

Answer 11

Chlorophenamine maleate

Question 12

Pruritoceptive itch can be defined in which way?

Answer 12

Something usually associated with inflammation or dryness in the skin which triggers itch

(e.g. insect bite)

Question 13

Name 3 pre-formed mediators from mast cells

Answer 13

1. Proteases
2. Histamine
3. Heparin
4. Cytokines

Question 14

Name mediators which are synthesised post-degranulation in mast cells

Answer 14

1. Prostaglandin D2
2. Leukotrienes C4, D4 and E4
3. Platelet activating factor
4. Cytokines