Heroin
Street-level heroin (diamorphine, diacetylmorphine, Fig. 1A) is normally encountered in the laboratory in paper or plastic packs that typically contain 100 to 200 mg of brown (or sometimes white) powder (Fig. 2A). The street-level purity varies depending on availability and other factors, but values of 40–60% are common in the UK. Bulk shipments of heroin may be packaged as rectangular blocks or in other configurations (Fig. 2B) Cutting agents for heroin include sugars, paracetamol (acetaminophen) and caffeine.
Production of heroin The raw material for the production of heroin is opium, a naturally occurring product of the plant Papaver somniferum L. (opium poppy). The green seed heads are cut to release a milky latex which contains morphine. This latex dries on the seed head to form a gum, which is then collected and bulked as raw opium. The raw opium is treated to extract the morphine (Fig. 1B) and the extract is then acetylated with acetic anhydride to produce diamorphine. Opium contains other alkaloids and natural substances which can be carried through to the final product. Sometimes known as ‘Chinese heroin’, heroin from South East Asia is a white powder that consists of diamorphine hydrochloride and minor amounts of other opium alkaloids, but adulterants are unusual. This material is ideally suited to injection. Heroin from South West Asia is a much cruder product. Typically seen as a brown powder that contains diamorphine base, it has variable amounts of other opium derived alkaloids (e.g. monoacetylmorphine, noscapine, papaverine and acetyl codeine) as well as adulterants such as caffeine and paracetamol. It is believed that these cutting agents are added to heroin either at the time of manufacture or during transit. ‘Profiling’ of heroin is carried out to provide intelligence information. This typically involves identifying and quantifying the various alkaloids together with the active drug and the adulterants. The action of heroin is via interaction with G protein-coupled opioid receptors in the brain, the brainstem and the spinal chord. Heroin is rapidly metabolised to morphine. Like morphine, heroin is an agonist primarily for the mu (μ) opioid receptor but with some agonist action against kappa (k) and delta (∆) receptors. Binding to the receptor closes Ca2+ channels on presynaptic nerve terminals, thereby reducing neurotransmitter release. It also opens K channels inhibiting postsynaptic neurons. Effects include analgesia, euphoria, reduction in anxiety, constipation, respiratory depression and pin point pupils. Heroin is a highly addictive drug. Prolonged use also gives rise to drug tolerance, resulting in higher levels of drug intake required to gain the same pleasurable effects.
Figure 1 (A) Diacetylmorphine (heroin); (B) morphine.
Figure 2 Heroin. (A) Examples of heroin powder showing the variety of colour of the material. (B) Compressed form typically used for importation (the blocks shown are wrapped in plastic and overwrapped with tape). (Photograph: US Drug Enforcement Administration.)
