next DOSEof the drug. The trough level helps the
doctor determine if the dosage is appropriate to
achieve the desired therapeutic effect and is useful
information primarily at the onset of treatment.
The goal of most medication therapy is a steady
state of the drug’s concentration in the body, at
which there is little difference between the drug’s
PEAK LEVEL(highest concentration in the blood cir-
culation) and trough level.
Trough level is an especially important measure
for NARROW THERAPEUTIC INDEX(NTI) drugs (drugs for
which the margin between therapeutic and toxic
is very close) such as theophylline (to treat
ASTHMA), certain ANTIBIOTIC MEDICATIONS,
cyclosporine for IMMUNOSUPPRESSIVE THERAPY, some
antiseizure medications, and many antiarrhythmia
medications.
See also HALF-LIFE; THERAPEUTIC LEVEL.trough level 173