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Wise et al.

Page 90

However, due to the low cost of these medications, clinical situations may arise that would justify their use.

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All but 1 of the RCTs investigating the efficacy of H 2 antihistamines are within the context of pretreatment of a subject prior to a nasal allergen challenge. Wood-Baker et al. 1193 compared oral cetirizine to oral ranitidine. Objective measures of nasal airway resistance showed greater improvement with ranitidine, yet cetirizine decreased objective measures of nasal secretion more than ranitidine. Taylor-Clark et al. 1194 found similar improvement in nasal airway resistance between cetirizine and ranitidine, but a significant improvement with the use of combination therapy. Combination therapy was also shown to improve nasal airflow when cimetidine was added to cetirizine. 1195 Two studies did not find improvement in nasal airflow with the addition of an H 2 antihistamine. 1196,1197 The clinical significance of these objective findings is unclear, and the studies that employed PROMs did not demonstrate subjective improvement in nasal obstruction. Four studies investigated the impact of H 2 antagonism on symptoms; however, these studies did not utilize standardized outcome measures as they pre-dated the development of such tools. Subjects were asked to report some combination of congestion, blockage, itching, drainage, sneezing, eye symptoms, and asthma with a categorical severity measure. Three of the 4 studies examined symptoms after nasal allergen challenge, and none demonstrated efficacy of H 2 antihistamines, either alone or in conjunction with an H 1 antihistamine in diminishing allergic symptoms. 1195-1198 One study of 23 subjects 1198 did investigate the impact of cimetidine in conjunction with chlorpheniramine in a real-world setting. Subjects with known late-summer AR were randomized during this season to receive alternating 2 week courses of either chlorpheniramine plus placebo, or chlorpheniramine plus cimetidine, and symptom scores were recorded twice daily along with adjuvant medical therapies (specifically, oral corticosteroids). Patients receiving both H 1 and H 2 antihistamines reported decreased medication usage (28 corticosteroid days vs 44 corticosteroid days, p < 0.02) and decreased symptoms scores during 1 of the 8 weeks when weed pollen counts were high. A caveat of this study is its utilization of a first-generation antihistamine that is no longer recommended as a first-line treatment of AR. The data existing on the use of H 2 antihistamines in AR are limited in scope and quality. The objective findings of improved nasal airway resistance suggest that the H 2 histamine receptor does modulate nasal tissue response to histamine. 1193-1195 However, the clinical significance of this mechanism is not clear, particularly in the context of modern treatment algorithms. 1195-1198 The relatively manageable side effect profile and costs of H 2 antihistamines, does offer patients with otherwise recalcitrant AR symptoms an additional treatment option. • Aggregate Grade of Evidence: B (Level 1b: 6 studies; Table IX.B.1.b). • Benefit: Decreased objective nasal resistance, and improved symptom control in 1 study when used in combination with H 1 antagonists. • Harm: Drug-drug interaction (P450 inhibition, inhibited gastric secretion and absorption),

Int Forum Allergy Rhinol . Author manuscript; available in PMC 2020 June 10.