Street pharmacy

Medical students will come across illegal drugs at every stage of their career. Beth Chapman guides you through their names, actions, uses, and misuses

SAKKI/REX

Cannabis

Otherwise known as black, blast, blow, Bob Hope, dope, draw, ganja, gear, grass, hash, hashish, hemp, herb, marijuana, pot, puff, northern lights, resin, skunk, smoke, spliff, wacky backy, and weed.

How does it work?

Cannabis contains hundreds of active constituents. Pharmacologically, the most important is tetrahydrocannabinoid (THC). This mimics naturally occurring (endogenous) cannabinoids within the body and acts on specific receptors located within the central nervous system and peripherally.^{1 2} When stimulated these receptors interact with other neurochemical pathways and are largely responsible for the psychobehavioural and physiological effects of the drug (box 1).

Use

Cannabis was first used as a medicine sometime before 100 ad in ancient China and could still be legally prescribed in the United Kingdom until 1973. However, laws relating to cannabis use vary from country to country.

A growing body of research has identified the actions of cannabis in the body and investigated its value for many diseases. There are practical problems with giving the drug (box 2), but a constructive debate over the therapeutic role of cannabis is often hindered by a blurring of the separate issues of medical and recreational use.

• Pain-Cannabinoids help to block nociceptors, which signal the presence of tissue damage. They also act on the brain's pain modulating centre to reduce sensitivity to pain. Most research is examining the effects of these actions on neuropathic and chronic pain^{1 3}
• Nausea-Cannabinoid receptors have been identified in the area of the brain involved with emesis control, and cannabinoids have been shown to be effective in controlling nausea and vomiting associated with chemotherapy^{4 5}
• Muscle spasticity and tremor-Cannabinoid receptors are distributed in the areas of the brain involved with controlling movement (specifically the basal ganglia). Their signals are mostly inhibitory, suggesting cannabinoids could have an effect in disorders such as Parkinson's disease, Tourette's syndrome, and multiple sclerosis.^{6 7} Evidence also indicates that cannabinoids may interfere with the immune processes behind multiple sclerosis.^8-10 A recent UK study found that patients with multiple sclerosis treated with cannabis or tetrahydrocannabinoid reported improvement with some symptoms but not with others¹¹
• AIDS-The cannabinoid profile of appetite stimulation and relief from pain, nausea, and anxiety is of particular interest in the treatment of the effects of AIDS⁵
• Gastrointestinal disorders-Activation of cannabinoid receptors in the gut reduces gastric acid secretion and motility. The therapeutic implications of this are yet to be established.^{12 13}

Misuse

Cannabis has been used recreationally for as long as it has been used medically, but such use was banned in the United Kingdom in 1928, when it was thought to cause madness. Although withdrawal symptoms are not always clear, many users feel that they are addicted and want help in stopping (box 3).

Amphetamine and related substances

Otherwise known as base, billy whizz, speed, sulphate, uppers, whites, whiz, methylphenidate (Ritalin), dexamphetamine (Dexedrine), methamphetamine, ice, methylamphetamine, meth, and Nazi crank.

How do they work?

Amphetamines increase the release of noradrenaline in nerve endings centrally and peripherally. This has a number of stimulatory effects including delaying the onset of fatigue (box 4).

Use

In the past, amphetamines have been used to help with weight loss and to treat low blood pressure, asthma, migraines, depression, and epilepsy. Medical use is now limited due to problems with tolerance and dependence.

• Narcolepsy-Dexamphetamine sulphate helps to delay the onset of rapid eye movement sleep and is beneficial in treating narcolepsy (uncontrolled sudden attacks of sleep)¹⁴
• Attention deficit hyperactivity disorder-Methylphenidate is related to amphetamine and is used to improve the attention span of children with this condition
• US Air Force pilots-Pilots in the United States can choose to take dexamphetamine sulphate for any mission lasting longer than eight hours. Its use has been implicated in some of the "friendly fire" fatalities in the recent war with Iraq.¹⁵¹⁶

Misuse

The recreational use of amphetamine has changed from providing light relief for bored housewives in the 1950s to being a popular energy booster on the dance and rave scenes.

Ecstasy

Otherwise known as 3,4-methyleneioxymethamphetamine (MDMA), Adam (MDA), brownie, doves, E, Edward, elephants, essence, M&Ms, MDMA powder, Mitsi(bushie)s, pills, rhubarb and custard, shamrocks, sweeties, tenamphetamine, white burger, white dove, and X.

How does it work?

Ecstasy is structurally related to lysergic acid diethylamide (LSD) and amphetamine and so is a stimulant and a mild hallucinogenic. It stimulates central and peripheral a and b adrenoceptors and so has a mixture of effects including increased heart rate and blood pressure, sweating, jaw clenching, and nausea, which are exacerbated by dehydration, heat, and physical exertion.¹⁷ A surge of serotonin release in the brain is responsible for the sense of well being felt by the user.¹⁸

Use

Ecstasy cannot be prescribed by doctors in the United Kingdom.

• Post traumatic stress disorder-The feeling of empathy and "at one-ness" with each other has been used by some therapists, particularly marriage guidance counsellors, and ecstasy is still prescribed by some in Switzerland. A group of scientists in the United States are about to start a controversial trial to test whether ecstasy can help people with post traumatic stress disorder to release their experiences¹⁹
• Parkinson's disease-People with Parkinson's disease have abnormal levels of the neurotransmitters dopamine and serotonin. Some find that ecstasy provides relief from both the symptoms of the disease and from those of the dopamine treatment (dyskinesia), probably by increasing serotonin concentrations.²⁰²¹²² Further research is underway.

Misuse

Ecstasy is strongly linked with the all night dance scene. With its wide street availability and low cost, it is often more popular than alcohol among clubbers. Long term use can lead to psychological addiction, but the exact consequences for the brain are not clear.

Cocaine

Otherwise known as coke, charlie, C, white, Percy, snow, and toot.

SAM TINSON/REX

Magic mushrooms

How does it work?

Cocaine is an alkaloid found in leaves of the South American coca shrub. It blocks uptake of adrenaline, noradrenaline, and dopamine into nerve endings increasing their concentration at receptor sites. The central effects are similar to but briefer than those of amphetamine.²³

Use

In the 1860s, cocaine was considered to be the elixir of life, making the user confident, energetic, and free of pain. It was available over the counter in the United Kingdom until 1916.

• Local anaesthetic-This is the only legitimate use for cocaine. It is a vasoconstrictor which slows down absorption and gives it an advantage over other topical anaesthetics, but the potential for systemic effects limits its use.

Misuse

Cocaine use is increasing in the United Kingdom and is gaining popularity among young professionals. Psychological dependence on the coke rush is more likely than a physiological addiction, but the effects of long term use are not clear.

Heroin (diamorphine)

Otherwise known as boy, brown, china white, dragon, gear, H, horse, junk, skag, and smack.

How does it work?

Morphine is derived from opium and belongs to a group of drugs called opioids or opiates. Heroin (diamorphine) is derived from morphine, but the ease with which it crosses the blood-brain barrier makes it more powerful and faster acting.

Heroin affects the body by acting on the same receptors as endogenous opioids. It depresses the nervous system centrally reducing the respiratory rate and anxiety, but it is also a stimulant and induces vomiting, pupil constriction and feelings of euphoria. In the cardiovascular system, veins and arterioles dilate, which can result in a drop in blood pressure.²⁴

Use

When morphine was first synthesised at the beginning of the 19th century it was promoted as a cure for opium dependence. Then diamorphine came along as a substitute for morphine addicts. As our ancestors developed a new habit, doctors became wiser and its medical use became increasingly restricted. The most common indication for diamorphine use is pain relief although weaker opioids are used to treat diarrhoea and dry coughs.

• Pain-Diamorphine acts on pain pathways in the brain, spinal cord and peripheral tissue.^{25 26} It is most effective in moderate to severe acute pain (such as in a heart attack) and in chronic pain. The combination of its sedative, analgesic, and anxiolytic properties make it a useful treatment for patients who need palliative care
• Acute pulmonary oedema-Diamorphine can help with fluid on the lungs caused by acute left ventricular failure. It counteracts the panic associated with shortness of breath and reduces both preload (venous dilatation) and afterload (arteriolar dilatation).²⁴

Tolerance

Tolerance to the effects of diamorphine occurs quickly and may be due to disruption of the signalling response from the opioid receptors. This occurs after relatively low level exposure to the drug and necessitates increasingly high doses to achieve the same effect.²⁷

An exogenous supply of opioids-that is, diamorphine-also decreases the endogenous production creating physical dependence on the external source. If this is stopped suddenly, then withdrawal can occur producing the "cold turkey" symptoms of sweating, chills, vomiting and diarrhoea, muscular cramps, and weakness.²⁴

Misuse

Recreational use of opiates was banned in the United Kingdom after the first world war. Morphine and diamorphine provide the user with a feeling of warmth and emotional and physical numbness, and an addiction to the drug is notoriously difficult to beat.