Facts on File Encyclopedia of Health and Medicine

substitution maintains therapeutically acceptable
consistency for potency and EFFICACY.
The current standard of practice calls for close
monitoring of blood concentrations until the drug
reaches the desired therapeutic level, with routine
blood tests to monitor blood concentration over
time, when the person begins taking a new drug,
and when there is a change in the person’s health
status (including significant change in body
weight). Once the blood concentration of the drug
reaches a steady state with the drug at a therapeu-
tic level the NTI becomes less of a concern.

COMMONLY PRESCRIBED

NARROW THERAPEUTIC INDEX (NTI) DRUGS

aminophylline carbamazepine clindamycin

clozapine cyclosporin digoxin

disopyramide isoproterenol levothyroxine

lithium metaproterenol phenytoin

prazosin primidone procainamide

quinidine valproic acid warfarin

See also BIOAVAILABILITY; BIOEQUIVALENCE; ORANGE

BOOK, THE;PEAK LEVEL; THERAPEUTIC LEVEL; THERAPEU-

TIC WINDOW; TROUGH LEVEL.

162 Drugs