Efficacy and Safety of H2 Blockers as an Add-on Therapy to H1 Antihistamines in Allergic Rhinitis: An Open Label Randomised Controlled Trial

Introduction: Allergic Rhinitis (AR), affecting 10-25% of the global population, is commonly treated with antihistamines and corticosteroids. H2-blockers, when combined with H1 antihistamines, enhance treatment efficacy and reduce symptoms. There is a need to conduct studies to establish more evidence around this combination and aid in the informed clinical decision-making process. Aim: To compare the efficacy of Bilastine versus Bilastine combined with Famotidine in the management of AR at days 7 and 14 and also to compare serum IgE levels at days 0 and 14 among both groups. Materials and Mehods: This open-label Randomised Controlled Trial (RCT) was conducted in the Pharmacology and Otorhinolaryngology department of Agartala Government Medical College (AGMC) and Govind Ballabh Pant Hospital (GBPH) between 1st February 2023 and 30th June 2024. The study included 340 newly diagnosed acute AR patients aged 18 years and above from the ENT OPD. Participants were diagnosed by clinicians based on signs and symptoms such as nasal itching, sneezing, a runny nose, and nasal obstruction, with symptoms persisting for more than four consecutive weeks. Randomised participants received either Bilastine 20 mg daily or Bilastine combined with Famotidine 40 mg daily for 14 days. The primary outcomes were nasal and non nasal symptom scores, while secondary outcomes included serum IgE levels. Data were collected in an approved Case Report Form (CRF) and statistically analysed using the Independent t-test, Mann-Whitney U test, Wilcoxon signed-rank test, and Chi-square test. Results: The study included 340 participants aged between 18 and 80 years, comprising 178 (52.4%) males and 253 (74.4%) from urban areas. Rhinorrhea (83 cases, 24.4%) and nasal congestion (79 cases, 23.2%) were the most common symptoms. The combination therapy led to a significantly faster reduction in nasal symptoms (p-value=0.001). Serum IgE levels decreased in both groups (p-value=0.001 in Group A, p-value<0.001 in Group B), with a cut-off for serum IgE being <150 mg/dL. Adverse reactions were minimal, with two cases of nausea and bloating in Group A and two cases of nausea in Group B. Conclusion: AR predominantly affected younger adults (ages 21 25 years). Combination therapy showed no adverse effects and provided faster symptom relief while reducing serum IgE levels.