D3.76 - Open-Label Clinical Trial To Evaluate The Effect Of Intranasal Olopatadine/Mometasone And Azelastine/Mometasone On Histamine Reactivity In Skin Prick Tests

Intranasal antihistamines, such as azelastine and olopatadine, are commonly prescribed for the management of allergic rhinitis. Although their clinical efficacy and safety are well established, residual pharmacological activity may influence skin test reactivity for several days after discontinuation. 

There is very limited information addressing the potential influence of topical antihistamines, particularly intranasal formulations such as azelastine and olopatadine, on skin test reactivity. Most available data focus on systemic antihistamines, while studies evaluating the duration and magnitude of suppression associated with topical agents are scarce and heterogeneous

This open-label, prospective pilot study included healthy volunteers treated with intranasal azelastine or olopatadine for seven days. Each dose of intranasal medication was administered after nasal cleansing with Nasa Mist Nasal Saline Solution (NeilMed^®) to ensure optimal mucosal absorption and reduce variability in drug delivery.

Daily histamine skin prick tests (10 mg/mL) were performed to assess wheal diameter and pruritus intensity during a 7-day treatment period with each intranasal antihistamine, followed by a 5-day post-discontinuation phase.

Measurements were recorded in millimeters and analyzed as mean values with 95% confidence intervals. Data were processed using repeated-measures ANOVA with Bonferroni correction for pairwise comparisons versus baseline.

A total of 86 healthy volunteers were included, with a median age of 29 years (range 19–65). Participants received either intranasal azelastine/mometasone (100/50 µg) or olopatadine/mometasone (600/25 µg), two sprays per nostril every 12 hours after nasal cleanising with isotonic saline and sodium bicarbonate solution containing sodium chloride (9 mg/mL) and sodium bicarbonate (0.4–1.0 mg/mL) (Nasa Mist®, NeilMed)

Both azelastine and olopatadine significantly reduced histamine-induced wheal size and pruritus intensity during active treatment (p < 0.001). After drug discontinuation, skin reactivity progressively increased. A statistically significant reduction in skin response was observed after the second dose, returning to baseline approximately four days after treatment withdrawal, while pruritus returned to baseline after three days for both medications.

Intranasal antihistamines exert a measurable suppressive effect on histamine-induced skin and sensory responses that persists beyond the dosing period. A washout interval of approximately five days is recommended before performing skin testing in patients treated with intranasal azelastine or olopatadine