Sometimes it seems like there are more medicines than there are
diseases, and it can be hard to keep them straight. Some
medications can be bought over the counter at pharmacies or
other stores. Others require a doctor's prescription. A few
medicines are available only in hospitals. What Are Medicines?
Medicines are chemicals or compounds used to cure, halt, or
prevent disease; ease symptoms; or help in the diagnosis of
certain illnesses. Advances in medications have enabled doctors
to cure many diseases and save lives. These days, medicines come
from a variety of sources. Many were developed from substances
found in nature, and even today many are extracted from plants.
For example, one medicine that is used to treat certain cancers
comes from the Pacific yew tree. Some medicines are produced in
a laboratory by mixing together a number of chemicals. Others,
like penicillin, are byproducts of organisms such as fungus. And
a few medicines are even biologically engineered by inserting
genes into bacteria that m