Roflumilast is rapidly and almost
completely absorbed after oral administration,
with 79% absolute
bioavailability.10 Peak plasma roflumilast
concentrations are reached in
about one hour, while steady state is
achieved in about three to four days
with once-daily dosing. Roflumilast
exhibits a linear and predictable
pharmacokinetic profile over doses
ranging from 250 to 1000 μg.5
Roflumilast is rapidly metabolized
to an active metabolite, roflumilast
N-oxide, via cytochrome P-450
(CYP) isoenzymes 3A4 and 1A2. Roflumilast
N-oxide exhibits potency
and specificity similar to those of the
parent compound and is estimated
to contribute 90% of the total PDE-4
inhibitory activity of roflumilast.
Peak plasma concentrations of the
active metabolite are reached in eight
hours, and steady-state plasma concentrations
are reached within six
days.5 Approximately 70% of roflumilast
is excreted in the urine.6
Coadministration with food can
reduce the maximum plasma concentration
(Cmax) of roflumilast by
40% and the time to maximum
plasma concentration (tmax) by one
hour (relative to fasting-state values)
without affecting the Cmax and tmax
of the active metabolite.11 As the
N-oxide component is primarily
responsible for roflumilast’s pharmacologic
activity, the medication can
be taken with or without food.6 Additional
pharmacokinetic features of
roflumilast and roflumilast N-oxide
are summarized in Table 2.