Abstract
Allergic rhinitis (AR) is associated with decreased learning, performance and productivity at work and school, as well as a reduced quality of life. With a staggering annual economic impact between $6 billion and $8 billion, AR affects 20% of the adult population and up to 40% of children. Effective therapy for allergic rhinitis requires understanding the pathophysiology of the disease, as well as the role of various inflammatory mechanisms. As such, various classes of medication are at the physicians' disposal to treat patients with allergic rhinitis. Among these are second-generation antihistamines and anticholinergic agents, intranasal corticosteroids, and mast cell stabilizers. Recently, montelukast, a leukotriene receptor antagonist, has been added to the modes of therapy approved by the US Food and Drug Administration for allergic rhinitis. For patients refractive to standard pharmacologic intervention, immunotherapy has shown some promising results. As newer strategies emerge, treatment regimens for allergic rhinitis should continue to improve not only daytime symptoms, but also nighttime symptoms and sleep with the fewest possible adverse effects.
Allergic rhinitis (AR) is a common ailment, affecting 10% to 25% of the world's population.
1 In the United States, the prevalence of AR has increased during the past three decades; it is currently estimated at 20% in the general adult population and closer to 40% in children.
2,3 Reasons for this increase are not completely understood; however, pollution and indoor exposures—or even in some cases a lack of exposures—may play a role.
4 One theory implicates a major shift in the gene pool, predisposing more individuals to excessive immunoglobulin E (IgE) production and thus, increased expression of AR.
5
Irrespective of its cause, the annual economic impact of this pervasive disease is calculated to be $6.3 billion to $7.9 billion in direct and indirect costs.
6,7 This figure, however, does not account for the detrimental effects of AR on quality of life (QOL), which include fatigue, irritability, memory deficits, excessive daytime somnolence, and depression.
8,9 Quality of life is reduced in this patient population not only because of the disease symptoms (sneezing, nasal pruritus, rhinorrhea, and congestion), but also because its pathophysiology can disrupt normal sleep.
10,11 Therefore, effective therapy for AR must provide symptomatic relief and target the complex underlying inflammatory mechanisms.
This review provides a summary of the pathophysiology of AR, its relationship with asthma, and an analysis of the traditional modes of pharmacotherapy used in its management. This summary is followed by a review of emerging strategies and their rationale use in AR.
Immunotherapy has been shown to be effective in the treatment of seasonal and perennial rhinitis.
89-92 The proposed mechanisms for immunotherapy include blunting of elevations in IgE, decrease in serum neutrophil and eosinophil activity, reduction in the mast cell population as well as associated mediators, and the suppression of allergen-induced T-lymphocyte proliferative responses with an increase in the circulating numbers of allergen-specific CD8
+ T lymphocytes
93-99 (
Figure 4). Some evidence also suggests that these events may be mediated by an effect of immunotherapy on T lymphocytes with an alteration from a predominant “Th2” response to favor an additional “Th1” response, which eventually would lead to the attenuation of tissue eosinophilia and local IgE production.
100
Allergen-specific immunotherapy, administered under controlled conditions with immediate access to resuscitative equipment, has a prominent role in the treatment of severely symptomatic patients with allergic rhinitis who have failed to respond to conventional treatment with antihistamines, topical corticosteroids, or LRTAs, administerd singly or in combination. The advantage of immunotherapy is that the immune system is modified, and this modification may be permanent or at least persist for years after therapy is terminated.