Encyclopedia of Health and Medicine

aging, effects on drug metabolism and drug response 149
DRUGS and MEDICINAL HERBS AND BOTANICALS, should
make sure the prescribing physician and the dispensing
pharmacist know all of them. Numerous
products interact with one another in ways that
alter their effects in the body, increasing the risk
for adverse drug reactions.
Many countries have regulatory requirements
for documenting and reporting adverse drug reactions.
Such requirements help oversight agencies
and health-care professionals monitor issues with
drugs that may not have been apparent during
preapproval testing. In the United States the US
Food and Drug Administration (FDA) oversees
compliance with these requirements and works
with pharmaceutical manufacturers to resolve
issues that arise.
See also ALCOHOL INTERACTIONS WITH MEDICATIONS;
AUTOIMMUNE DISORDERS; CIRRHOSIS; DRUG INTERACTION;
LIVER FAILURE; OFF-LABEL USE; RENAL FAILURE; TOXIC
EPIDERMAL NECROLYSIS.
aging, effects on drug metabolism and drug
response Many drugs have different therapeutic
effects as well as potential adverse DRUG reactions,
depending on a person’s age. The very young and
the very old often have limited LIVER function,
which affects the ways in which the liver metabolizes
drugs, resulting in lower thresholds for toxicity
and unpredictable therapeutic effects. In the infant
and young child, the liver has not yet fully developed
and lacks the structural capacity to metabolize
certain substances. The elderly may lose liver function
due to CIRRHOSIS, fatty deposits accumulating
within the liver (STEATOHEPATITIS), or the normal loss
of cells that occurs with aging. Reduced kidney
function may further affect drug response by slowing
clearance of the drug from the body and thus
maintaining higher than expected concentrations
of the drug in the BLOOD circulation.
Drugs in Children
Two significant issues surround medication therapy
in children. The first is the continually changing
metabolic capability and status of the child’s
body as organ systems grow and mature. The liver
remains relatively unsophisticated in its function
until a child reaches age 10 or 12 years. Not only
does this limit the liver’s ability to metabolize
drugs such as antibiotics and analgesics (pain
relievers), the most common kinds of drugs children
may need, but also it makes the liver vulnerable
to damage from substances that enter the
blood circulation. Incompletely metabolized drugs
increase the risk for damage to other developing
organ systems as well, notably the CENTRAL NERV-
OUS SYSTEM. These factors become of therapeutic
concern when treating serious childhood diseases
for which medications are the primary course of
treatment, such as SEIZURE DISORDERS, CONGENITAL
HEART DISEASE, and cancer.
The second issue in regard to medication therapy
in children is that many drugs do not undergo
testing or evaluation for their effectiveness or
safety in pediatric use because children make up a
very small percentage of the drug’s intended
patient population or because the potential risks of
involving children in clinical research studies are
too high. The consequence is that doctors rely on
best practices standards and OFF-LABEL USE of drugs
in prescribing medications, which are safe and
effective in adults but untested in children, to
treat health conditions in children.
Drugs in the Elderly
The body undergoes significant metabolic and
functional changes by the seventh and eighth
decades of life, a blend of the normal processes of
aging and the cumulative effect of health conditions.
The liver and KIDNEYS become less efficient,
which affects the amount of a drug that enters the
blood circulation and how long the drug remains
in the body. Health conditions such as ATHEROSCLE-
ROSIS (fatty deposits in the walls of the arteries)
may alter the flow of blood through the body.
Changes in NERVOUS SYSTEM function may alter the
release of neurotransmitters. These kinds of
changes in the body influence how, and how well,
drugs work.
Often the very reasons elderly people need to
take therapeutic drugs (such as to treat CARDIOVAS-
CULAR DISEASE [CVD], DIABETES, kidney disease) have
significant effects on the ways in which the body
can handle the drugs and how those drugs affect
the body. As well, older people are more likely to
have complex or multiple health conditions and
take multiple medications, increasing the risk for
ADVERSE DRUG REACTION, DRUG INTERACTION, and
OVERDOSE.