Allergic conditions

Question 1

Antihistamines: MOA

Answer 1

Blocks H1 receptors, histamine is a major contributor in allergic reactions

Question 2

Antihistamines: drugs (sedating)

Answer 2

• Alimemazine (most sedating)
• Chlorphenamine (QDS)
• Hydroxysine (QT prolongation)
• Promethazine (Most sedating, BD/TDS)

Question 3

Antihistamines: drugs (non-sedating)

Answer 3

• Avrivastine (TDS)
• Cetirizine (OD)
• Fexofenadine (OD, apple + orange juice RED exposure)
• Loratadine (OD)

Question 4

Antihistamines: indication

Answer 4

• Allergies
• Adjunct in anaphylaxis + angioedema
• Nausea + vomiting
• Insomnia

Question 5

Antihistamines: side effect

Answer 5

Sedation
- Label: warning: this medicine makes you sleepy, If you still feel sleepy the next day, do not drive or use tools or machines, do not drink alcohol

QT prolongation (hydroxyzine)
- Low dose + short period - avoid in elderly or half dose
- MHRA: QT prolongation + torsade de pointes

Question 6

Antihistamines: caution

Answer 6

• Prostatic hypertrophy + angle closure glaucoma
• Severe liver impairment (sedating anti-histamines)

Question 7

Allergen immunotherapy

Answer 7

Avoid:
- Beta-blocker - adrenaline may be ineffective
- ACEi - severe anaphylactoid reactions

Question 8

Anaphylaxis (medical emergency): symptoms

Answer 8

• Breathing difficulty
• Angioedema
• Light headed
• Cold clammy skin
• Hives

Question 9

Anaphylaxis (medical emergency): treatment

Answer 9

First line: IM adrenaline

• Adult: 500mcg
• 6-12: 300mcg
• Child 15-30kg: 150mcg

Administer to anterolateral mid third thigh

Second injection after 5-15 min

Call ambulance, lie down + raise legs

MHRA: auto-injectors: quantity: 2, always carry, check expiry, train use

Question 10

Allergic angioedema: Symptoms

Answer 10

• Swollen lips, eyes and tongue
• Hives
• Laryngeal oedema - treated w adrenaline

Question 11

Allergic angioedema: treatment

Answer 11

• IM adrenaline
• Antihistamine + corticosteroid