Among the remedies which it has pleased almighty God
to give to man to relieve his sufferings, none is so universal and
efficacious as opium.
Sir Thomas Sydenham, 1680
Opium is a heterogeneous drug derived from the milky exudate
of the opium poppy, Papaver somniferum. The word opium is derived
from the Greek word for juice. This natural product, which contains
over 20 different alkaloids, has been used to control human discomfort
for over five millennia. Opium was used clinically in the early
days of European medicine, but it fell into disfavor because of
toxic outcomes from nonstandardized drugs that were not used with
necessary care. Paracelsus repopularized the use of opium in the
16th century, and by the second half of that century, clinical use
of opium was understood and adopted by physicians throughout the
The French pharmacist Jean-François Derosne isolated
a crystalline precipitate from opium in 1803, but that material
was a mixture of morphine and narcotine. It was not until 3 years
later that the German pharmacist Friedrich Wilhelm Sertürner
isolated the alkaloid morphine from opium. He named this powerful
drug after Morpheus, the Greek god of dreams. Other opium alkaloids including
papaverine and codeine were soon isolated, and within a few decades,
the purified alkaloids began to replace crude opium in clinical
Narcotic—a term derived from the Greek word meaning
benumbing—was originally used to describe opium derivatives.
Today, narcotic has become a legal term that includes a broad range of
sedating and potentially abused drugs, many of which are not at
all related to opium. Because the word narcotic has such negative
connotations, clinicians should not use it when talking with patients.
Opioid is the preferred term in both clinical and scientific dialogue.
Opioids are literally opium-like substances. In the recent past,
opioid was used primarily to describe endogenous opium-like substances,
and the term opiate was used to describe drugs that are opium derivatives. The
differences between exogenous opioids, such as morphine, and endogenous
opioids, such as β-endorphin, do not justify differing terminology.
Opioid accurately describes both types of compounds and is generally
considered the preferred term today.
It is not logical that the human body should contain specific
receptors for alkaloids derived from a plant. The presence of endogenous
opioids was postulated to explain the presence of opioid receptors
before the endogenous substances were isolated. Three distinct families
of endogenous human opioid peptides, the endorphins, enkephalins,
and dynorphins, have been isolated. These peptides are found within
the central nervous system (CNS), adrenal medulla, nerve plexi,
gastric exocrine glands, and intestines. These peptides appear to
have multiple roles including modulation of pain, neurohumoral transmission,
and neurohormonal effects.
Opioids remain the most effective analgesics available. They
are clinically useful in treating diarrhea and gastrointestinal
hypermotility because activation of opioid receptors in the intestines slows
peristalsis. Opioids decrease respiratory ...