- For other uses see Opiate (disambiguation), or for the class of drugs see
Opioid.
In medicine, the term opiate describes any of the narcotic alkaloids found in opium.
Overview
The main opiates derived from opium are morphine, codeine,
thebaine, and Papaverine, Noscapine, narceine and approximately 25 other alkaloids are also present, but have essentially little to no
effect on the central nervous system, and are not usually considered to be
opiates.
The alkaloids
Morphine
Morphine is by far the most prevalent alkaloid in opium,
making up anywhere from 10% to 16% of the total mass, and is responsible for many of its potentially harmful effects, such as
pulmonary edema, respiratory depression, coma, cardiac and/or respiratory failure, with a normal lethal dose of 120 to 250
mg.[1] (approximately two grams of opium.[2]) However the occurrence of pulmonary edema is uncommon. The
most frequently reported occurrences of opiate/opioid induced pulmonary edema are among recreational heroin users.[3][4] Although uncommon, reports of morphine induced pulmonary edema are not unheard of.[5] The primary difference being the more careful supervision of morphine
administration compared to the lack of supervision and medical expertise among illicit heroin users. Conversely, morphine may
also be used in the treatment of pulmonary edema.[6][7] Despite morphine being the
most medically significant alkaloid, larger quantities of the milder codeine—most of it manufactured from morphine—are consumed
medically.
The expression of the morphine content of opium as a percentage depends in part on the moisture content. When the government
purchases the opium as soon as practicable after it is collected, the moisture content is then usually about 30%. Commercial
opium usually has around 10 to 15% moisture. Opium apparently dried at ordinary temperatures still retains considerable
moisture—usually about six percent—which can be driven off at about 103 degrees Celsius.
The quantity of morphine produced by poppy plants in the form of opium depends on two factors: the percentage of morphine in
the opium, and the quantity of opium produced. The latter factor in turn depends in part on whether each capsule is bled several
times, or just once. In Turkey, Bulgaria, Greece and the Balkans, each capsule is bled only once, but in most other
opium-producing countries, like Iran, India, and Afghanistan, the capsules are incised repeatedly, often four or five times on different days, until they
will yield no more latex. The quantity of latex falls off rapidly with later incisions, and so does the morphine content.[8] Usually, all the opium obtained is mixed together. This is
probably the chief reason for the often lower morphine content of Iranian and Indian opiums as compared with Turkish and Balkan
opiums, although it must also be recognized that there are low-yielding and high-yielding strains of the poppy, one or the other
of which may predominate in a given region.
Samples of opium assaying some 15% morphine from Japan, Indochina and Afghanistan, as well as from Turkey, Greece and the Balkans have been examined by the
Secretariat. Afghanistan at one time exported two grades of opium, one
of about 15% morphine and the other about 10%. The morphine content of dry capsule-chaff is about 0.25% to 0.5%, when not washed
out by rain. Here again there are low-yielding and high-yielding varieties, but proper agricultural selection of poppies for
morphine production means taking into account not only the percentage yield of morphine, but also the total weight of
capsule-chaff produced per hectare, the poppy seed production per hectare, and other factors.
Most of the licit morphine is used to manufacture codeine through O-methylation. Morphine is also used to manufacture other drugs, such as heroin, dihydromorphine, hydromorphone and many others. Of these, the conversion of morphine to heroin is particularly noteworthy
due to heroin's unusual pharmacological properties. The acetylation of morphine's two hydroxyl groups results in a chemically
different drug, but nearly identical pharmacological properties, the principal difference being lipid solubility. This increase
in lipid solubility allows heroin to enter the brain more rapidly than morphine.[1] As heroin is not pharmacologically active it must first be metabolized. The
active metabolites of heroin are morphine and 3-monoacetylmorphine.
Codeine
The codeine content of opium is related inversely to the morphine content but only in a general way. Codeine yield is closely
related to the type of opium produced in a given district or even in some cases in an entire country. The opiums of the principal
exporting countries have approximately the following percentages of codeine: Balkans 1.25%; Turkey 1.25%; Iran 3.4%; India
3.0%.
The highest percentages of codeine obtained by the Secretariat (averaging about 4.3%) were found in opium samples which came
from north-eastern Asia (Korea, northern China).
The manufacturers’ statistics do not ordinarily show all the codeine obtained from opium. Some of it co-precipitates with the
morphine, and there is no necessity of purifying the morphine completely of its codeine content, especially if it is to be used
to manufacture more codeine.
Codeine is used to manufacture dihydrocodeine, hydrocodone, and others. It may also be used to manufacture the drugs ordinarily made by conversion of
thebaine.[2]
Thebaine and Papaverine
The United Nations Secretariat is currently engaged in a survey, the most
extensive ever attempted in this field, of opium samples from different regions for their thebaine and papaverine percentages. As
yet, it is premature for general conclusions. However, the highest thebaine percentages found (nearly 5%) were in some samples
from Indochina, which at the same time had virtually no papaverine. Both thebaine and papaverine have been high in most Iranian
samples run. Papaverine is low in some Afghan and Indian opiums.
Thebaine is the most poisonous opium alkaloid and is scarcely used medically. It is even omitted from some of the preparations
of mixed opium alkaloids which are used as soluble substitutes for opium. However, it is converted
into several other narcotics which have medical use: hydrocodone, acetyldihydrocodeine, oxycodone, and the highly potent and
powerful narcotic, oxymorphone.
Papaverine has a considerable medical use, so much so that supplies available from opium have sometimes run short. It is then
manufactured synthetically.[3]
Terminology
Opiate has traditionally referred to not only the alkaloids in opium, but also natural and semi-synthetic derivatives
of morphine (itself an opiate). The term is often incorrectly used to refer to all drugs with
opium- or morphine-like pharmacological action, which are more properly classified under
the broader term opioid.
References
- ^ Mallinckrodt MSDS.
- ^ Anil Aggrawal. Narcotic Drugs.
- ^ Sporer KA, Dorn E.. Heroin-related noncardiogenic pulmonary edema : a case series..
- ^ Steensen P, Jørgensen HS, Juhl B.. Heroin-induced pulmonary edema.
- ^ Lethal Acute Pulmonary Edema Following Intravenous Naloxone in A Patient Received Unrelated Bone
Marrow Transplantation.
- ^ Effectiveness of morphine in non-cardiogenic pulmonary edema due to chlorine gas
inhalation..
- ^ Mattu A, Martinez JP, Kelly BS.. Modern management of cardiogenic pulmonary edema..
- ^ Annett, Harold Edward, "Factors Influencing Alkaloidal Content and Yield of
Latex in the Opium Poppy (Papaver somniferum)". Biochemical Journal, 14, 618–36 (1920).
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
