Opiate abuse and dependence

Opiate abuse and dependence

Definition

Opiate dependence or addiction is defined as the continued use of opiates, despite these causing significant problems, which may be physical, neuropsychiatric and social.

Opiates are all drugs derived from opium, i.e. the milk of the opium poppy. Opium contains morphine and codeine. Natural and synthetic derivatives of these drugs are useful, effective analgesics, but opiates also have the potential to become drugs of abuse.

Heroin (a derivative of morphine) is a popular opiate of abuse, but other drugs including morphine, pethidine, codeine and dihydrocodeine are also commonly abused. In its pure form, heroin is a white powder, but on the streets it is bought as an off-white or brown powder, and is known by many street names including ‘H, gear, smack, junk, skag, white stuff, sugar’. Health care professionals with access to opiates may abuse drugs like fentanyl.

Incidence/prevalence

Heroin abuse fell during the late 1990s, but rose again rapidly in 2000 and 2001. A fall in use since then has been attributed to the fall in supply after the Taliban banned production in Afghanistan. Despite the fall in numbers of users, the number of heroin-induced deaths has remained static. Heroin and morphine account for ∼40% of drug-abuse-related deaths in the United Kingdom.

Pathophysiology

Opiates have central nervous system depressant effects, and they act as analgesics and cause euphoria. Abusers repeatedly take the drug to achieve the euphoric effect; however, this results in opiate tolerance, i.e. increased doses are required to achieve the same effect. Withdrawal symptoms also occur, and so further doses are taken to avoid the withdrawal.

Heroin can be smoked (‘chasing the dragon’), snorted, or injected into a vein (‘shooting up’ or ‘mainlining’), or subcutaneously (‘skin popping’) or intramuscularly. It acts rapidly, within 10–20 seconds, if injected, and within 20–30 seconds, if snorted. Snorting is the most common method of use, as it does not require any special preparation. The effects last 4–6 hours.

Clinical features

Following use of heroin, side effects include nausea and vomiting (usually only on first few uses), drowsiness, sedation, constricted pupils and dry, itchy skin.

Long-term users generally have constipation, features of selfneglect, weight loss, there may be needle-tracks and evidence of complications.

A history should be taken of recent and previous heroin use, including methods of administration, use of other drugs such as benzodiazepines, alcohol intake, previous attempted rehabilitation and any previous heroin-related problems. A close social history should be taken, as well as a medical history and examination.

Complications

The most serious complications are associated with intravenous use. Use of non-sterile equipment and water used to mix the powder lead to cellulitis, throm-bophlebitis, skin and organ (e.g. cerebral) abscesses and infective endocarditis. Sharing of needles means that hepatitis B and C, and HIV can be transmitted. Deep vein thromboses and pulmonary emboli occur. Other problems include acute pulmonary oedema, anaphylaxis and aspiration pneumonia.

With excessive doses, coma and death from respiratory failure occur. The variability in the purity of street heroin means that with every use there is a risk of accidental overdose, especially after a break from use when tolerance is reduced, or if other drugs or alcohol increase the sedative effect.

Withdrawal leads to nausea, vomiting, abdominal cramps, diarrhoea, watery eyes and nose and muscle twitching. Seizures may occur.

Social problems include loss of job, deterioration in relationships and criminal activities to obtain money to buy drugs, including stealing, prostitution and drug dealing.

Investigations

These depend on the presentation of the individual. Investigations may be needed for possible complications such as infective endocarditis, HIV, hepatitis and DVT, depending on the history and clinical diagnosis.

Management

Heroin intoxication is treated by ensuring airway protection, and giving the opiate antagonist naloxone. This rapidly reverses the opiate action, but is shortacting, so the patient requires further monitoring for 24 hours and may need a naloxone infusion.

Heroin abusers should be referred to a drug rehabilitation counsellor or centre, and considered for rehabilitation. Methadone, a long-acting opiate, which does not cause euphoria, is used as a method of programmed withdrawal, to ameliorate the withdrawal symptoms. Supportive therapy is needed to prevent the patient from seeking increased doses (either of heroin, other drugs or even methadone) elsewhere, and relapse is common. In some cases, patients stay on long-term methadone at a low maintenance dose. Although they remain dependant on methadone, they are less likely to relapse, less likely to have an overdose, and are not at risk from HIV infection.