Bioequivalence assessment of tulobuterol transdermal delivery system in healthy subjects

Objective: The purpose of this study was to evaluate the bioequivalence in the pharmacokinetics of two 2-mg tulobuterol transdermal delivery systems (TDSs) in healthy subjects. Materials and methods: The pharmacokinetic (PK) analysis was performed using data from a randomized, openlabel, single-dose, two-way, two-period, crossover study. Eligible subjects received either the Bretol® patch (test drug) or Hokunalin ® patch (reference drug) in sequence according to their allocated group. Serial blood samples for PK analyses were collected for up to 48 hours after tulobuterol TDS application. The PK parameters, including the maximum concentration (C_max) and area under the curve from time zero to the last quantifiable concentration time (AUC_last), were estimated by using noncompartmental analysis. The geometric mean ratios (GMRs) of the C_max and AUC_last and their 90% confidence intervals (CIs) were estimated. Results: A total of 27 subjects completed the study as planned. The concentration-time profiles of tulobuterol were similar in both formulations. The GMRs (90% CIs) of Cmax and AUC_last were 0.9443 (0.8790 - 1.0144) and 0.9600 (0.8660 - 1.0642), respectively. Conclusion: The PK profiles of both tulobuterol TDSs were comparable. In addition, the 90% CIs of the GMR were within the bioequivalence criteria of 0.800 - 1.250. Therefore, the Bretol® patch can be used as an alternative to the Hokunalin® patch for the treatment of patients with asthma and chronic obstructive pulmonary disease.