Pharmacokinetics of Roflumilast and Its Active Metabolite Roflumilast N-Oxide in Healthy Chinese Subjects After Single and Multiple Oral Doses

Background and Objectives Roflumilast is a selective, oral phosphodiesterase 4 inhibitor approved for the treatment of severe chronic obstructive pulmonary disease. The aim of this study was to evaluate the pharmacokinetics of roflumilast and roflumilast N-oxide in healthy Chinese subjects, and the effects of gender and food on their respective pharmacokinetic profiles. Methods 36 healthy Chinese subjects were recruited in a randomized, single-center, open-label, parallel group study and assigned to 0.25-, 0.375-, and 0.5-mg dose groups. The single-dose pharmacokinetic studies in fasting condition were carried out in all groups. Moreover, the food effect study and multiple-dose study were conducted in 0.375-mg dose group. Serial blood samples were collected over 168 h after dosing, and plasma concentrations of roflumilast and roflumilast N-oxide were determined using a validated LC-MS/MS method. Results After oral administration of single doses of 0.25, 0.375 and 0.5 mg of roflumilast under fasting condition, the mean AUC(0-72h) for roflumilast was 21.7 +/- 8.3, 29.8 +/- 8.3 and 54.2 +/- 21.3 ng center dot h/mL, respectively. Meanwhile the mean AUC(0-168h) for roflumilast N-oxide was 290 +/- 103, 385 +/- 107 and 673 +/- 245 ng center dot h/mL, respectively. In the steady state after the multi-dose administration, the exposure to roflumilast in the subjects increased 20-40 %, and the exposure to roflumilast N-oxide increased about 169 %, compared to the single-dose administration. No statistically significant effect of gender on the disposition of roflumilast and roflumilast N-oxide was observed. Food had no effect on systemic exposure to roflumilast and roflumilast N-oxide in the subjects, but delayed the T (max) of roflumilast by 0.9 h and reduced the C-max of roflumilast by approximately 20 %. Conclusion Based upon between-study comparison, peak and systemic exposure of roflumilast and roflumilast N-oxide were higher in Chinese than that in Caucasian subjects after oral administration of the same dose (i.e., 0.25 and 0.5 mg). It implies that the therapeutic dose for Chinese patients may be different from that for Caucasians, warranting further investigation.