Substance misuse: Cocaine use and its effects

Cocaine is a naturally occurring alkaloid found in the leaves of Erythroxylon coca, a plant native to South America.

Pharmacology

CNS stimulation is the result of cocaine’s activity on three neurotransmitter pathways. Firstly, dopaminergic receptors are blocked, leading to a build-up of dopamine, which is a potent reward signaller. This leads to the feelings of pleasure associated with cocaine use.

Secondly, the serotonin pathways are overstimulated by the selective inhibition of 5-HT3 reuptake, causing a feeling of wellbeing. The synergistic effect on dopamine and serotonin pathways causes euphoria.

Finally, peripheral and central effects on noradrenergic axes lead to vasoconstriction, tachycardia, hypertension and a subjective feeling of increased strength and mental alertness.

Illicit use of cocaine

Powdered cocaine is usually insufflated using a tube to ‘snort’ the drug, but it may also be ‘chased’ (like heroin, smoked off a heated piece of foil) ‘chipped’ into a cigarette to form a ‘joint’ or injected intravenously with or without heroin.

Since the early 1980s, cocaine has been cooked with sodium hydrogencarbonate to remove the hydrochloride ion, making so-called ‘freebase’ or crack cocaine.

The effects of crack are more intense than those of cocaine, but short lived. Smokers and injectors of crack describe having to use it up to 20 times a day so as to avoid the intense ‘crash’ when coming down from a high. Crack may be smoked or injected with heroin, known as ‘snowballing’ or ‘speedballing’.

Use of cocaine has increased in the UK over recent years with the British Crime Survey statistics showing that the prevalence of 16-59 year olds admitting to having used cocaine during their lifetime rising from 3.1% in 1996 to 9.4% in 2008-09.

Symptoms of cocaine use

During the ‘high’, users report feeling increased energy levels and self-confidence with alertness, restlessness and euphoria.

Physical signs include tachycardia, hypertension, pupillary dilation and possibly pyrexia. Such effects may be complicated by tremor, headache, confusion and convulsions at high dosage.

Myocardial infarction and arrhythmias have been associated with cocaine use in younger people and irreversible crack lung results from the chronic smoking of oily freebase leading to pulmonary fibrosis, shortness of breath and chest pain.

There is some evidence that injecting crack into the legs or femoral veins increases the likelihood of deep vein thrombosis.¹

When coming down from a high, users report irritability and anxiety associated with tactile hallucinosis or ‘formication’ – a feeling of insects crawling on the skin. With the over-secretion of dopamine and serotonin, these may be a feeling of despondency lasting until the neurotransmitters are able to ‘reboot’.

Apart from these features, there is no evidence to show that cocaine is physically addictive, but psychological dependence does develop as illustrated by users’ continued usage despite financial implications and loss of relationships through neglect of other interests.

The majority of cocaine use in the UK is occasional and recreational, often in association with alcohol. However, this presents a particular danger as cocaethylene is known to be highly hepatotoxic and the three to five times longer half-life is associated with an 18-25-fold increase in the incidence of sudden cardiac death.²

Cocaine has other adverse effects on the health of users, including an increase in the incidence of autoimmune disorders, including Goodpasture’s syndrome, and on mental health by causing drug-induced psychosis, violence and sexual disinhibition, making users more likely to indulge in high-risk sexual behaviour patterns.

In pregnancy, the rate of miscarriage, placental abruption, intrauterine growth retardation and stillbirth are likely to be due to the vasoconstriction occasioned by cocaine, but the concern about teratogenicity appears to have been overstated.

Taking a history

It is important to ask about recreational drug use, which can be done conveniently when asking about patients’ alcohol consumption. Once reassured that the grounds for asking are health-related, patients are surprisingly honest and open about their drug habits, when the approach is non-judgemental and medical rather than ethical.

Specific discussion of the risks of alcohol and cocaine may be prompted by an AUDIT (Alcohol use disorders identification test) score discussion and this is a good opportunity for a brief intervention along the same lines as the FRAMES model.

Cocaine usage follows three typical patterns, although there may be overlap in any individual patient. The recreational user will usually have no clear pattern of use and will take cocaine infrequently and in the company of others.

A binge user will typically actively seek cocaine and use a large amount over a period of days. Such a patient may experience a significant ‘come down’ and may seek medical attention to deal with the unpleasant feelings. There may be some financial difficulty following a binge.

Finally, the chronic user is likely to use several times every day. The constant search for supplies of drug and funds may lead to acquisitive crime and the isolation from the usual support networks is likely to lead to significant health effects in this time of cocaine user.

Treatment

Drug treatment for cocaine use is problematic. There is no evidence to support the use of psychostimulants in supporting patients in recovery from cocaine use and antidepressants’ effects are no more than would be expected in the general population.⁴

Benzodiazepines have been used in the short-term relief of agitation and insomnia following heavy cocaine use, but some authors express concern that the rebound anxiety and insomnia may do more harm than good. It is therefore a judgement call for a clinician assessing a patient following heavy cocaine use as to whether prescribed medication is indicated or not.

Although there is no effective substitution therapy, it is worth considering referring chronic cocaine users to the local community drug treatment service (CDTS), because psychosocial interventions from trained therapists have been shown to be effective in assisting users to achieve abstinence and recovery. In the chaotic polydrug user, residential rehabilitation may be required.

Prevention of relapse

There is some evidence for the use of naltrexone in the maintenance of abstinence from cocaine use.⁵ For three decades, the idea of vaccination against cocaine has been mooted.

Several promising vaccines have been developed, which sought to prevent cocaine–antibody complexes from crossing the blood-brain barrier, thus preventing the pleasurable effects of cocaine.

A significant drawback might be that users will simply use more drug to obtain the same effects. Preliminary results have been promising since 2004, but there is still no licensed vaccination available.

• Dr Brew is a GP specialising in substance misuse in Leeds

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References

1. Wright N, Martin M, Goff T et al. Cocaine and thrombosis: a narrative systematic review of clinical and in-vivo studies. Subst Abuse Treat Prev Policy 2007; 2: 27.
2. Andrews P. Cocaethylene toxicity. J Addict Dis 1997; 16(3): 75-84.
3. NICE PH24. Alcohol-use disorders: prevention. London: NICE, 2010. Available from: https://www.nice.org.uk/guidance/ph24
4. The RCGP Guide to the Management of Substance Misuse in Primary Care. London: RCGP, 2013. p186-187
5. Schmitz J, Stotts A, Rhoades H, Grabowski J. Naltrexone and relapse prevention treatment for cocaine-dependent patients. Addict Behav 2001; 26(2): 167-80.