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3.4 Antihistamines, hyposensitisation

3.4.1    Antihistamines

Non-sedative antihistamines
Cetirizine tablets, liquid
Loratadine Tablets


Although drowsiness is rare with these agents, patients should still be advised that it may occur and could affect skilled tasks such as driving.

Sedative antihistamines
Chlorphenamine tablets, syrup, injection
Hydroxyzine tablets - see note 
Promethazine tablets, liquid, injection


Hydroxyzine should not be given to patients with a prolonged QT interval (or with risk factors). The maximum adult daily dose is now 100mg. See MHRA DSU April 2015


3.4.2 Allergen Immunotherapy

Acarizax sublingual tablet - Hospital-only. Specialist Paediatric and Adult Allergy Clinics only
Grass and Tree Pollen (Pollinex) extracts
Grass pollen extract (Grazax) tablet - freeze dried. Administered sublingually. Hospital-only. Specialist Paediatric and Adult Allergy Clinics only; RED drug

For Referral Guideline for SubLingual ImmunoTherapy (SLIT) with Grazax in children with allergic rhinitis and allergy to grass pollen – click here

Omalizumab Injection - see NICE TA 278 and NICE TA 339
Oralvac Compact sublingual drops (unlicensed product) - Adult allergy clinic only; RED drug
Mepolizumab – see NICE TA 431 


3.4.3 Allergic emergencies

Epinephrine (Adrenaline) 1 in 1,000, 1 in 10,000 injection (EpiPen/Jext).

For guidance on use and patient information, including advice to all always carry TWO auto injectors at all times – see MHRA Drug Safety Update May 2014

C1-esterase inhibitor 500 units


For BNF section link: 3.4 Antihistamines, hyposensitisation, and allergic emergencies