Background: Rupatadine is a histamine receptor type 1 antagonist that has been used to treat allergic rhinitis and urticaria.
Objective: The aim of this study was to compare the effect of 2 rupatadine tablet formulations on the inhibition of histamine-induced wheal-and-flare cutaneous responses.
Methods: In this single-blind, single oral dose, crossover study, healthy male volunteers were randomized to receive 10 mg of either a rupatadine reference or test formulation after an overnight fast. After a 10-day washout period, the subjects were crossed over to receive the other formulation. Subjects were asked to sit with their arm resting on the table while histamine was injected intradermally. The skin prick test was performed on the upper half of the volunteers' forearms before administration and at 1, 2, 4, 6, 12, and 24 hours after study drug administration. Fifteen minutes after each skin prick test, the wheal-and-flare responses were visualized under a bright lamp. AUC0-24 was the primary end point.The 90% CI of least squares mean ratio (%) of the test: reference formulations for maximum inhibition of histamine-induced wheal-and-flare response (Imax%), Tmax, AUC0-24 mm(2)/h, and AUC0-24%/hr were expected to be within 80% to 125% of untransformed data and 80% to 120% of log-transformed data for the 2 formulations to be considered pharmacodynamically equivalent. Subjects were monitored for any spontaneously reported adverse event (AE) throughout the study. In addition, they were specifically asked about the occurrence of any AEs on a checklist (ie, drowsiness, dizziness, dryness of mouth, itching sensation, headache, nausea) throughout the study.
Results: Of the 15 subjects assessed for inclusion, 12 healthy male volunteers (mean [SD] age, 30 [5] years; height, 162 [6] cm; weight, 58 [6] kg) participated in the study. Administration of reference and test formulations of rupatadine significantly inhibited the histamine-induced cutaneous responses in all subjects (P <0.001). Wheal Imax% with the reference and test formulations was 67.97% (11.57%) and 66.76% (9.40%), respectively. Flare Imax% was 59.06% (11.95%) and 56.92% (16.31%), respectively. None of the subjects withdrew from the study due to AEs. Both formulations were well tolerated except for an itching sensation on injection of histamine in all patients; no subject complained of any adverse drug reaction.
Conclusion: In this small study of healthy adult males, the test formulation of the rupatadine tablet was found to be pharmacodynamically equivalent to the reference formulation, as measured by inhibition of histamine-induced cutaneous wheal-and-flare responses.
Keywords: healthy subjects; histamine-induced cutaneous response; pharmacodynamic equivalence; rupatadine.