Abstracts of the European Association of Poisons Centres and Clinical Toxicologists XXII International Congress*

Abstract

Henry JA. Imperial College, London, UK. Introduction: Drug taking is increasing dramatically, particularly among young people. One reason for this is that illicit drugs affect brain chemistry to produce a pleasurable experience. With almost all substances, this is due to the effect of dopamine in the nucleus accumbens. In addition, their individual chemical structures determine their toxicodynamics and toxicokinetics, leading to a wide range of wanted and unwanted effects, and. Those involved in clinical toxicology and emergency medicine therefore need to have a basic understanding of the ways in which the different illicit drugs produce their effects. Some examples are given in this abstract, more will be presented. Heroin: Heroin crosses the blood-brain barrier very rapidly, which is why it is the most widely abused opioid. It then breaks down almost immediately to monoacetylmorphine and morphine, which combine with opioid receptors to produce the wanted and unwanted effects. One of the remarkable pharmacological properties of opioids, particularly heroin, is tolerance. Tolerance to heroin is very marked: the initial dose to produce an effect is a few milligrams, and ten milligrams of pure heroin could be fatal by intravenous injection in a drug-naïve individual. However, the average user who seeks help is taking about 750 milligrams of street heroin a day. Overdose can occur from three main causes. The initial dose may be too much, the supply may be of greater purity than usual (though this should not be a problem for the tolerant user), and tolerance may be lost after a few days' abstinence. When this happens, the dose which was taken regularly just a few days beforehand, now becomes potentially lethal. Naloxone acts as an antagonist at opioid receptors, reversing the toxic effects of opioids. Methadone replacement therapy given daily, orally or by injection is used as a way of managing heroin addiction, and has widespread support as it reduces injecting behaviour and criminal activity. However it involves long term use of another opioid, and so is in effect replacing one addiction with another. Cocaine: The effects of cocaine are mainly due to two related pharmacological properties. The first is that it blocks the reuptake of dopamine, which causes the euphoric “high” but which may also lead to confusion, aggression, hallucinations and possibly convulsions. Reuptake of serotonin is also inhibited. The second main property is that it blocks the reuptake of noradrenaline, which causes marked vascular effects, causing a very high blood pressure and possibly chest pain, which is the commonest reason for cocaine users to seek medical advice. Large amounts can also cause hypotension due to sodium channel blockade. Cocaethylene is the ethyl metabolite of cocaine, produced in the liver when alcohol is present. There is no antidote for cocaine toxicity; the main medical treatments include oxygen, diazepam to reduce central and peripheral nervous system activity and lower blood pressure, nitrates to relieve coronary spasm and further control blood pressure, and aspirin for the patient with chest pain. Amphetamine and Methamphetamine: These drugs and related compounds have marked stimulant and sympathomimetic effects, related to their similarity to catecholamines. Euphoria, central nervous system stimulation, appetite suppression, energy, tachycardia and other symptoms occur. Ecstasy: This drug 3,4-methylenedioxymethamphetamine (MDMA: ecstasy) is related to amphetamine. It has acquired a reputation as a dance drug, because of its unique pharmacological effects, which can be summarised as “euphoria, empathy and energy.” It causes the release of large amounts of serotonin in the central nervous system, followed by depletion, and possibly neurotoxicity. Dopamine is also released. It causes secretion of antidiuretic hormone, so that any excess water consumed is not eliminated... [ABSTRACT FROM AUTHOR]