Allergic Conditions Flashcards
How do the antihistamines work?
Binds to H1 receptor site to block the action of histamine
What are the sedating antihistamines?
Promethazine
Chlorphenamine
Hydroxyzine (QT prolongation)
Ketotifen
What are the non-sedating antihistamines?
Acrivastine
Cetirizine
Loratadine
Fexofenadine
What are antihistamines used for?
Nasal - hayfever Skin - urticaria Nausea and vomiting Insomnia Adjunct in emergency anaphylaxis and angioedema
What antihistamines are used for nausea and vomiting?
Cinnarizine Cyclizine Promethazine hydrochloride Promethazine teoclate Buclizine (migraines only OTC)
What are the antihistamines used for insomnia?
Promethazine hydrochloride
Diphenhydramine
What are the side effects of the antihistamines?
Old - more sedating + antimuscarinic
New - less sedation + less psychomotor impairment
Avoid alcohol
Driving may be impaired
What are the cautions with antihistamines?
BPH
Glaucoma
Severe liver impairment
Dementia with sleeping tablets - can affect memory
What is the MHRA for hydroxyzine?
QT prolongation + torsades de pointes
Is hydroxyzine used for a short period or long period?
Short
Max dose 100mg
What are the contraindications for hydroxyzine?
Drugs that prolong QT interval CVD Family history of sudden death Hypokalaemia Hypomagnesaemia Bradycardia
What are the uses for allergen immunotherapy?
Reduce allergic asthma symptoms
Allergic rhinoconjunctivitis
Reduce severe anaphylaxis in hypersensitivity to wasp and bee stings
What are the desensitising vaccines used for?
Hay fever unresponsive to other anti allergy drugs
Hypersensitivity to wasp and bee venom
Who do the allergen vaccines need to be avoided in?
Asthma Pregnant women Children under 5 years Beta blockers ACEi
What is the omalizumab injection used for?
As an add on treatment for
Severe persistent allergic asthma 6+
Chronic spontaneous urticaria 12+
What are the side effects of the omalizumab injection?
Churg Strauss syndrome and hypersensitivity reactions
How do you treat anaphylaxis?
Secure airways and restore blood pressure
Raise legs and lay flat
If sick or unconscious place in recovery position
Adrenaline Repeat every 5 mins if necessary < 6 - 150mcg 6-12 - 300 mcg 12+ - 500 mcg
Can adrenaline be given to patients on beta blockers?
Yes but IV salbutamol may be better
What are the adjuncts used in anaphylaxis?
High flow oxygen and IV fluids
Chlorphenamine injection
Hydrocortisone injection
What is the MHRA advice for auto injectors?
Prescribe 2 auto injectors. Carry at all times
Patient/carer trained on how to use
Check expiry dates
What is angioedema?
Swelling of the skin often caused by allergic reactions
How do you treat laryngeal oedema?
Adrenaline
Antihistamine
Corticosteroid