Heroin diacetylmorphine also known as diamorphine, is a semi-synthetic opioid drug synthesized from morphine, a derivative of the opium poppy. Heroin was made from the opium poppy which up to this point was used prior to the 19th century as a recreational drug in Mesopotamia. Opium's pharmaceutical properties were discovered later to consist of both morphine and codeine. Both of these has been used for a long time and even today as a pain killer. However, later in the 19th century it was experimented to find a variation of morphine and codeine. Heroin was first made by C. R. Alder Wright in 1874 where he noticed that the dogs he injected with the substance behavior begin to change immediately. Their behavior and physiology were similar to what you would have seen in Ewan McGregor in Trainspotting: fear, great prostration, sleepy, and loss of coordinated muscle movements (and possibly constipation). This research was largely forgotten until diamorphine was synthesized by a German chemist at Bayer. The same guys that gave aspirin were also the guys that distributed heroin as a non-addictive morphine substitute and cough suppressant! Heroin was possibly more addictive than its natural father.
So why is heroin so great and why am I talking about it? The answer lies in its absorption properties and its pharmokinetics. These can be understood by the putting the drug in water and understanding its properties at the interface mapping its true surface area. This property investigates whether a drug can get into and through a membrane like the blood brain barrier (BBB), intestine or possibly the skin.
So doctors and drug addicts both know that heroin can get to the brain faster than morphine because of the acyl groups on it. Heroin is the most fast-acting of all the opiates. When injected, it reaches the brain in 15-30 seconds; smoked heroin reaches the brain in around 7 seconds. The peak experience via this route lasts at most a few minutes. This makes heroin is one hell of a drug and usually the best drugs especially the drugs that affect the mind are sadly abused recreationally and also this drug by our society. Also like many psychoactive or nervous system drugs heroin is highly addictive. However, what makes a drug good enough to get into the brain? As I mentioned briefly when talking about Anne Peniette's paper a good drug to affect the brain needs to have the correct physiochemical properties and likely the correct shape to enter through the BBB. Replacing the two hydrogen-bonding -OH groups with -OCOCH3 (see below with the two groups on the left) makes heroin much less soluble in water than morphine, but more soluble in non-polar solvents, like oils and fats!!
Heroin is injected directly into the bloodstream, but once there it can pass rapidly through the blood-brain barrier which normally prevents the passage of water-soluble and large molecules. As a result it is much more potent than morphine, but its effect does not last as long. Again, once the heroin molecule is absorbed into the body, the acetyl groups are removed, reforming morphine.
