innovator and generic drugs. Generic drugs may
also have trade names, which manufacturers often
use to establish brand recognition and brand loy-
alty for marketing purposes. For example, Elavil
and Endep are trade names for amitriptyline, a
commonly prescribed tricyclic antidepressant. The
manufacturer of an innovator drug may also pro-
duce and market generic versions of the drug
when the innovator drug’s patent expires.
In nearly all circumstances a person may take
any manufacturer’s product, generic or innovator
drug, and experience the same therapeutic effects.
The only exception is with NARROW THERAPEUTIC
INDEX(NTI) DRUGS, in which the margin between
the therapeutic dose and the toxic dose is exceed-
ingly small. People who take NTI drugs should
always take the same product, whether the inno-
vator drug or a generic drug. Variations in the
drug’s inactive ingredients can affect how the
body absorbs the drug, which can have therapeu-
tic significance with NTI drugs.
In its electronic document THEORANGEBOOK,the
FDA maintains a list of newly approved generic
drugs, updated each month, and a list of all
generic drugs available in the United States. The
Orange Book is available at the FDA’s Web site
(www.fda.gov/cder/ob).
See also INVESTIGATIONAL NEW DRUG(IND); LEGEND
DRUGS; OFF-LABEL USE; SCHEDULED DRUG.
half-life The length of time it takes for the body
to metabolize or eliminate from the body 50 per-
cent of the amount of a DRUGa person takes or
receives. Drug half-life is an important factor in
determining appropriate DOSAGEand for treating
OVERDOSE. Drug half-life also helps the doctor
know when to expect to begin to see the effects of
the drug. The calculation of drug half-life is loga-
rithmic. Drug informational literature, packaged
with prescription drugs, provides general informa-
tion about the drug’s half-life that is generally
adequate for most clinical circumstances. A doctor
may conduct BLOODtests to measure the levels of a
drug in an individual’s blood circulation over a
period of time as a means of indirectly assessing
half-life, though this is seldom therapeutically
necessary.
See also BIOAVAILABILITY; CYTOCHROME P 450
(CYP 450 ) ENZYMES; EFFICACY; METABOLISM; PEAK LEVEL;
THERAPEUTIC LEVEL; THERAPEUTIC WINDOW; TROUGH
LEVEL.imported drug A DRUGor pharmaceutical prod-
uct not manufactured in the country of purchase.
Countries may have differing requirements for
testing and product safety for the manufacture
and distribution of drugs within their borders. In
the United States the Food and Drug Administra-
tion (FDA) has regulatory authority over drug
production and distribution and establishes the
standards for bringing drugs into the country.
The Internet has dramatically broadened access
to foreign markets for drugs. Many Americans are
drawn to Internet purchasing because of the ease
and convenience and because imported drugs are
often less expensive than the same drugs pur-
chased in the United States. However, health
experts caution that drugs purchased through
locations in other countries, either by mail order
or via the Internet, may not meet US quality stan-
dards for purity, potency, and safety and may not
be legal to bring into the country.
The FDA supports the National Association of
Boards of Pharmacy’s Verified Internet Pharmacies
Web site, http://www.nabp.net. This system provides
another way for consumers to verify the legiti-
macy of online pharmacies.
See also GENERIC DRUG; INVESTIGATIONAL NEW DRUG
(IND).innovator drug The first DRUGcontaining its spe-
cific active ingredients to receive approval for use
from the US Food and Drug Administration
(FDA). An innovator drug’s patent protects the
drug from market competition, giving its manu-
facturer exclusive right to produce and sell the
drug. The innovator drug’s manufacturer gener-
ally has invested significant time and money in
the drug’s development, testing, and approval
process. Only when the patent expires may com-
peting pharmaceutical manufacturers produce and
market a generic version of the innovator drug.
See also GENERIC DRUG; INVESTIGATIONAL NEW DRUG
(IND).investigational new drug (IND) A new DRUGin
the final phases of development for which the US
Food and Drug Administration (FDA) grantsinvestigational new drug (IND) 159