Optimal Antihistamines for Allergic Rhinitis and Urticaria
Rhinitis is a common condition, which affects 25% of the population in Singapore. It has considerable effect on the quality of life, sleep and work/school performance and socio-economic impact due to health care utilization, treatment cost and loss of work/school days.
Rhinitis has been classified, based on the time and type of exposure and symptoms, into seasonal allergic rhinitis (SAR; most often caused by outdoor allergens, such as pollens or molds), perennial allergic rhinitis (PAR; most frequently, although not necessarily, caused by indoor allergens such as house dust mites, molds, cockroaches, and animal dander), and occupational allergic rhinitis. Meanwhile, urticaria is classifed as “spontaneous” (acute spontaneous [spontaneous wheals < 6 weeks] or chronic spontaneous [spontaneous wheals > 6 weeks]), and “physical” according (EAACI/GA(2)LEN/EDF/WAO) guidelines.
The recommended workup of a clinical diagnosis of allergic rhinitis is a test for sensitisation to inhalant allergens prevalent to that specific climate. In a local Singapore study looking at 6600 children presence of allergen sensitization, typically house dust mites and occasional cockroach and cat/dog sensitization, documented by skin prick testing. Presence of allergen sensitization identifies a subset of patients whose nasal and ocular symptoms are more persistent, with significantly increased asthma exacerbations and hospitalization.
Management of Rhinitis and Urticaria
H1 antihistamines interfere with histamine action and downregulate allergic inflammation. They are the first-line treatment options for both persistent allergic rhinitis and chronic urticaria, as recommended by the ARIA and EAACI/GA(2)LEN/EDF/WAO guidelines. Second-generation antihistamines are recommended over the first-generation antihistamines, due to pharmacokinetics, and lack of anticholinergic and sedative side effects. Factors for consideration include efficacy, safety, cost-effectiveness, patient preference (eg tablet size, syrup), goals of treatment, anticipated adherence to treatment, disease severity and control, and presence of ocular symptoms or asthma.
Therapeutics for Chronic Urticaria
Despite the algorithms available for management of chronic urticaria as shown in Table 1, compliance and adherence to these management guidelines have been sub-optimal in practice around the world. There has been little guidance to the antihistamines dosing for children with chronic urticaria as their weighs varies greatly for children ranging from 6 months old to 12 years old. Recent publication for this have shown that in children, stepwise dosing of 1-2 times of the standard dose, denoted as step 1 and step 2 dose for cetirizine in Table 1 was adequate for management of chronic urticaria in a cohort of Singaporean children. The inclusion of other second generation antihistamines in the table based on a weight based stepwise titration of antihistamines for chronic urticaria control.
Therapeutics for Rhinitis
There has been some revisions in guidelines for the ARIA guidelines for 2016. In PAR, it is recommended that the maintenance of intranasal corticosteroids alone or in combination with an non-sedating 2nd generation antihistamines can be consider if itchy nose, sneezing or rhinorrhoea predominates. In the advent of intranasal corticosteroids with intranasal antihistamines, a combination is recommended for patients with recurring symptoms all congestions associated with itchy, runny nose and sneezing symptoms. In PAR, the guidelines advise intranasal corticosteroids in favour of leukotriene receptor antagonist.
In SAR, it has been suggested that the use of oral antihistamines or intranasal antihistamines be administered alongside the intranasal corticosteroids. In patient with concomitant asthma, especially exercise-induced and/or aspirin-exacerbated respiratory diseases, the addition of leukotriene antagonist maybe more beneficial than the oral antihistamines.
Lastly, in this group of patients whose SAR rhinitis remains sub-optimally controlled on the above medications, the consideration of sublingual immunotherapy for grasses. In Singapore, the option of sublingual immunotherapy for house dust mite related allergic rhinitis is shown to decrease symptoms and decrease medication scores.
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A Specialist’s Point of View – Written by Dr Chiang Wen Chin
Dr Chiang Wen Chin
is a Paediatric Allergist currently working in Mount Elizabeth Hospital Medical Centre. She is presently a visiting consultant of the Department of Paediatric Medicine. She is also an Adjunct Associate Professor of Duke NUS Graduate Medical School Singapore KK Woman’s and Children’s Hospital.
Dr Chiang underwent advanced training in Paediatric Allergy and Clinical Immunology at Duke University, USA.
Her subspeciality interest includes management of children with food allergies, asthma, allergic rhinitis, eczema, drug allergies, sublingual immunotherapy and immunodeficiency. She has set up the sublingual Immunotherapy program and food and drug provocation programs in KK Woman’s and Children’s Hospital.