I was listening to a radio interview this past weekend with an author who was once addicted to heroin for a period of 20 years. He is now clean, having overcome his addiction, and has written about his experience.
During the course of the discussion, he observed: ?Some really great scientists must have designed the opiates. There is no doubt in my mind that they were perfectly designed for the human mind.?
The interviewer didn?t comment on this observation but it stuck in my mind because it is wrong. The opiates were not ?designed? for human beings. They are simply the naturally occurring secondary metabolites of the poppy plant, Papaver somniferum.
Most plants produce a wide variety of compounds as part of their normal metabolism. Indeed, a single cell of any plant could easily contain upwards of 100,000 different chemical species.
Everything from the blatantly obvious such as water and DNA to complex secondary metabolites such as morphine or thebaine might be present in a plant cell. There are many compounds that we have yet to even identify in every plant.
Considering the number of species of plants and the local variations within those species, the number of chemical compounds pervading our environment because of plants alone is quite prodigious. Plants are chemical factories and they are extraordinarily good at what they do.
Much of synthetic organic chemistry over the past 200 years has been spent trying to make compounds obtained from plants. It can take years and in some cases decades for chemists in the laboratory to recreate what plants do without any thought and minimal effort.
A case in point is the opiates. Yes, we can make these compounds in the laboratory but the process is long, tedious, and expensive and the overall yield is low, so why would we? Much easier to grow the plants and just extract the compounds that we need!
This is exactly what happened in the early 1800s with morphine.
The medicinal properties of P. somniferum have been known for around 5,000 years. There is evidence that the resin or latex from poppies was used to ease pain and induce sleep in ancient Sumer. Certainly the name for the poppy has the same root as ?somnolence? or a state of near-sleep.
The Greeks appear to have used opium both medicinally and recreationally. There is reference to it in the Odyssey by Homer. Hippocrates prescribed the juice of the white poppy mixed with the seed of nettle for various ailments.
Opium is the latex or sticky juice that can be extracted from unripe seed pods of the poppy plant. It is collected as a white substance that turns to a dirty brown after exposure to air. It typically contains between 5 and 20 per cent morphine as the principal pharmaceutical ingredient. Although other secondary metabolites such as codeine, noscapine, papaverine, and thebaine are present, it is morphine that dominates and provides the maximum pharmaceutical effect.
In 1805, F. W. A. Sertrner, a German pharmacy assistant, isolated morphine as a colourless crystalline powder. This greatly increased its efficacy as a pain reliever. The pure compound is also free of the unwanted side effects from the consumption of all the remaining chemical species found in raw opium.
It was pure morphine that was adopted by physicians during the American civil war as an analgesic during surgery. The introduction of the hypodermic syringe 10 years prior allowed doctors to directly deliver the drug into the blood stream both increasing the effectiveness of morphine and enhancing the speed with which the drug took hold. Morphine became the standard treatment for the management of pain.
Of course, the use of morphine comes at a cost. Soldiers returning home after the American Civil War were often described as suffering from ?the Soldier?s disease?. Morphine withdrawal can be a painful and sometimes fatal process.
It was in 1898 that diacetylated morphine was introduced under the trade name ?Heroin?. The idea was that it would not have the addictive side effects of morphine itself and would be better tolerated by humans. Unfortunately, these early doctors were wrong and heroin - which was once sold in cough syrup for children - was banned in 1914.
But the real question is why do these compounds have such a profound effect on the human mind? The answer is that the drugs have a structure that mimics naturally occurring chemical compounds called endorphins.
These natural peptide compounds have specific receptors in the brain that allow them to control the sensation of pain and reward. It just so happens that the opiates have a similar shape and can act as a skeleton key turning on those same neural pathways.
The opiates aren?t designed for the human brain. It is just an accident that they fit. But it is an accident that has allowed their use for pain control for much of human history.
