Safety Profile of Medications for Allergic Rhinitis: A Meta-Epidemiological Analysis of Completed RCTs from ClinicalTrials.gov

Background: Allergic rhinitis (AR) is commonly treated with intranasal and oral pharmacotherapy or allergen immunotherapy (AIT), each associated with distinct safety considerations. This study aimed to systematically evaluate and compare the safety profiles of these therapeutic approaches by analysing adverse events (AEs) reported in completed randomised controlled trials (RCTs). Methods: A meta-epidemiological analysis was conducted using completed RCTs registered in ClinicalTrials.gov up to 20 October 2023. Trials investigating intranasal drugs, oral medications, or AIT for AR were identified using predefined search terms. Adverse events were manually extracted and categorised according to treatment class and dosage. Other adverse events (OAEs) were classified using Common Terminology Criteria for Adverse Events version 5.0 (CTCAE v5.0) and Medical Dictionary for Regulatory Activities (MedDRA) terminology. Meta-analyses compared OAE incidence across treatment groups, including standard-dose, higher-dose, and placebo arms. Results: A total of 216 RCTs were included. Intranasal therapies accounted for 55.56% of trials, predominantly intranasal corticosteroids (INCS) and intranasal antihistamines (INAH). OAE incidence was 16.37% for INCS, 29.43% for INAH, and 8.71% for combination therapy. INAH was associated with higher rates of dysgeusia and nasal discomfort, while higher INCS doses were linked to an increased risk of urinary tract infections. AIT trials comprised 22.69% of studies and demonstrated higher OAE rates, particularly for sublingual immunotherapy (64.96%), followed by subcutaneous (53.98%) and intralymphatic immunotherapy (62.50%). Oropharyngeal AEs were most frequent with sublingual immunotherapy. Oral medications (18.06%) showed the lowest OAE incidence, with upper respiratory tract infections occurring more frequently with oral antihistamines. Conclusions: Among intranasal therapies, INCS demonstrated the most favourable safety profile. Sublingual immunotherapy was associated with a higher frequency of OAEs compared with other AIT modalities. Combination oral antihistamine and leukotriene receptor antagonist therapy appeared to be the safest oral treatment option. Further well-designed studies are needed to refine comparative safety assessments across AR treatments.