allergy and anaphylaxis

Question 1

antihistamine imp points

Answer 1

used in allergies

1st gen - sedating
- alimemazine, promethazine, chlorphenamine, cyclizine
- alimemazine + promethazine more sedating than chlorphenamine + cyclizine

2nd gen - less sedating
- acrivastine, cetirizine, loratidine, desloratidine, fexofenadine
- fexofenadine 120mg available as OTC now

can also be used in n&v, migraines and insomina - S.Es of antihistamines
- n&v - cinnarizine, cyclizine, promethazine
- migraine - bucclizine (migraleve)
- occasional insomnia - prometh (sominex)

Question 2

allergen immunotherapy imp points

Answer 2

immunotherapy using allergen vaccines can reduce symptoms of asthma and allergic rhinoconjunctivitis
- contain house dust mite, pollen etc.

vaccines containing bee/wasp venom extract - reduce risk of severe anaphylaxis

omalizumab - monoclonal antibody that binds to igE -
- s.e. - churg strauss syndrome, hypersensitivity reaction

Question 3

anaphylaxis imp points

Answer 3

severe life threatening hypersensitivity reaction - rapid developing airway constriction/circulation problems
- immediate hypotension
- usually caused by allergen - food, drug, venom, latex

how to deal with anaphylaxis:
1) use auto-injector immediately (IM adrenaline/epinephrine)

2) call 999 state anaphylaxis - administer CPR if needed

3) lie them down and raise legs
- want blood to go back up body as its gone down to bottom of body

4) remove trigger causing reaction if possible

5) repeat after 5 mins

Question 4

treatment given to anaphylactic patients

Answer 4

high flow oxygen given as soon as possible - when paramedics arrive

IV fluids given if pt hypotension/shock

after stabilisation - non sedating antihistamine - cetirizine given or IM/IV chlorphenamine if oral not possible

bronchodilator - salbutamol to open airways and/or ipratropium can be given if pt has persistent respiratory problems

Question 5

adrenaline/epinephrine doses and MHRA warning

Answer 5

child upto 6 months - 100 to 150mcg

child 6 months to 5 years - 150mcg

child 6-11 - 300mcg

over 12 - 500mcg

MHRA warning - 2 autoinjectors should be prescribed + carried at ALL times