Allergic Rhinitis and its Impact on Asthma - ARIA

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ALLERGIC RHINITIS AND ITS IMPACT ON ASTHMA GUIDELINES ● 2010 – V. 9/8/2010 Question 10 Should immediate <strong>and</strong> total cessation of exposure to an occupational agent or exposure control be used in patients with occupational rhinitis <strong>and</strong> asthma? Summary of findings One systematic review from the British Occupational Health Research Foundation (106) <strong>and</strong> one health technology assessment (123) assessed methods aimed at reducing occupational agent exposure for treatment of occupational asthma. The report by Beach <strong>and</strong> colleagues (123) was more extensive <strong>and</strong> provided more detailed information <strong>and</strong> we used it to inform this recommendation. Moreover, the findings of both reviews were consistent. Beach <strong>and</strong> colleagues found two small r<strong>and</strong>omised trials (one employed respiratory devices in 26 farmers <strong>and</strong> the other compared reactions to various types of gloves in eight healthcare workers) <strong>and</strong> 52 cohort studies that investigated the effect of reducing exposure on asthma outcomes in workers with occupational asthma. Outcomes in workers with continued exposure was assessed in 14 studies, <strong>and</strong> reduced exposure in 18. Eight studies investigated the effectiveness of personal protection equipment. Most studies had methodological limitations <strong>and</strong> there was some uncertainty about the directness of the interventions due to confounding. Benef<strong>its</strong> Studies that assessed forced expiratory volume in one second (FEV1) found that it improved over time in a minority of workers who were either removed from exposure or had reduced the exposure. In most studies symptoms either remained stable or deteriorated with continued exposure at work. On the other h<strong>and</strong>, the majority of studies that examined workers removed from exposure or whose exposure had been reduced reported improvement in asthma symptoms. Respiratory protective equipment reduced the severity, but did not eliminate symptoms. Only two studies measured quality of life <strong>and</strong> found that it did not differ among workers removed from exposure compared to those whose exposure had been reduced. Harms Seven studies examined socioeconomic outcomes among workers with occupational asthma <strong>and</strong> found that both workers removed from the workplace <strong>and</strong> those who continued the exposure suffered a loss in income. Two studies reported that a significant proportion of workers who were removed from exposure remained unemployed or took an early retirement (25% <strong>and</strong> 70% in each of the studies). The United Kingdom’s Surveillance of Work-related <strong>and</strong> Occupational Respiratory Disease program found that 30% of people reported to have occupational asthma were unemployed when contacted later (124). Conclusions <strong>and</strong> research needs Specific measures reducing occupational agent exposure may be of net clinical benefit, but this likely depends on the type of causative agent. The overall quality of evidence supporting the reduction of exposure was very low. Further research on cessation or reduction of occupational agent exposure is needed to inform this recommendation. PAGE 42 OF 153
ALLERGIC RHINITIS AND ITS IMPACT ON ASTHMA GUIDELINES ● 2010 – V. 9/8/2010 Recommendation In patients with occupational asthma, we recommend immediate <strong>and</strong> total cessation of exposure to occupational allergen (strong recommendation | very low quality evidence). When total cessation of exposure is not possible, we suggest specific strategies aimed at minimizing occupational allergen exposure (conditional recommendation | very low quality evidence). Underlying values <strong>and</strong> preferences: The recommendation to immediately <strong>and</strong> totally cease the exposure to occupational allergen places a relatively high value on reducing the symptoms of asthma <strong>and</strong> deterioration of lung function, <strong>and</strong> a relatively low value on the potential socioeconomic downsides (e.g. unemployment). Pharmacological treatment of allergic rhinitis Question 11 Should oral H1-antihistamines be used for the treatment of allergic rhinitis? Questions 11 <strong>and</strong> 12 should be considered as complimentary <strong>and</strong> indivisible. We begin this section with a note on classification of H1-antihistamines. Then we evaluate whether oral H1-antihistamines should be used at all (Question 11). We consider old <strong>and</strong> new generation oral H1-antihistamines separately. Following these recommendations we compare old to new generation oral H1-antihistamines (Question 12). Note on classification <strong>and</strong> terminology H1-antihistamines are a class of agents that share some mechanisms of action – they are antagonists of histamine at H1 receptor sites or they act as inverse agonists. However, in addition to antagonising the effect of histamine, they have other actions that may contribute to the difference in their effectiveness or safety. There are many classifications of H1-antihistamines according to their chemical structure (e.g. alkylamines, piperazines, piperidines, etc.), time when they reached the market (e.g. first generation versus second generation), or their adverse effects (e.g. sedating versus non-sedating, interacting with cytochrome P450 versus non-interacting, cardiotoxic versus noncardiotoxic, interacting with food versus non-interacting etc.). All the above properties, except for chemical structure, are not dichotomous but rather a continuum with any threshold being arbitrary. Furthermore, the magnitude of these effects should be estimated with a systematic review of literature which is not yet available. As a result there is no consensus which H1-antihistamine belongs to which group <strong>and</strong> this causes confusion for clinicians <strong>and</strong> patients. In this document we use terms ―old generation‖ or ―new generation‖ as corresponding to the terms ―older‖, ―first generation‖ or ―sedating‖ <strong>and</strong> ―newer‖, ―second generation‖ or ―non-sedating‖ H1antihistamines. We chose not to use any functional designation, e.g. ―sedating‖ or ―non-sedating‖, acknowledging that the degree of sedation is a continuum without a definite <strong>and</strong> reliable cut-off value <strong>and</strong> that this terminology does not take into account other potential adverse effects (e.g. cardiotoxicity or anticholinergic effect). We also did not rely on the commonly used definition of first <strong>and</strong> second generation based on the date threshold of 1980 when a particular medication reached the market (125). PAGE 43 OF 153
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