Pharmacokinetics VI

Time Course of Drug Plasma Levels
During Irregular Intake
In practice, it proves difficult to achieve
a plasma level that undulates evenly
around the desired effective concentration.
For instance, if two successive doses
are omitted, the plasma level will
drop below the therapeutic range and a
longer period will be required to regain
the desired plasma level. In everyday
life, patients will be apt to neglect drug
intake at the scheduled time. Patient
compliance means strict adherence to
the prescribed regimen. Apart from
poor compliance, the same problem
may occur when the total daily dose is
divided into three individual doses (tid)
and the first dose is taken at breakfast,
the second at lunch, and the third at
supper. Under this condition, the nocturnal
dosing interval will be twice the
diurnal one. Consequently, plasma levels
during the early morning hours may
have fallen far below the desired or,
possibly, urgently needed range.