Examiner les données scientifiques concernant l’identification et la prise en charge de l’usage abusif d’opiacés et de la dépendance à leur endroit chez des patients en soins de première ligne souffrant de douleur chronique.

Une recension a été effectuée dans MEDLINE à l’aide des expressions en anglais «usage abusif d’opiacés» et «toxicomanie». Les quelques études sur la prévalence de la dépendance aux opiacés dans les populations de première ligne se fondaient sur une étude rétrospective de dossiers médicaux (preuves de niveau II). La plupart des recommandations portant sur l’identification et la prise en charge de l’usage abusif d’opiacés reposaient sur l’opinion d’experts (preuves de niveau III).

Les médecins devraient demander à tous les patients traités aux opiacés s’ils ont actuellement ou s’ils ont eu un problème de dépendance, ou s’il y a des antécédents familiaux de ce problème. Les médecins devraient prendre des «précautions universelles», notamment prescrire avec prudence et surveiller constamment les signes d’usage abusif. S’ils soupçonnent un usage abusif d’opiacés chez leur patient, ils peuvent faire l’essai d’une thérapie structurée aux opiacés pour une période de temps limitée, si le patient n’obtient pas d’opiacés d’autres sources. L’essai devrait comporter une administration passant d’une fois par jour à une fois par semaine, des analyses d’urine régulières et la diminution des doses d’opiacés. Si l’essai échoue ou n’est pas indiqué, un traitement à la méthadone ou au buprénorphine devrait être recommandé.

Il est possible, dans les soins de première ligne, d’identifier et de prendre en charge avec succès l’usage abusif d’opiacés et la dépendance à leur endroit.

Physicians’ concerns about patients’ becoming dependent on opioids, however, are legitimate. The prevalence of opioid misuse is increasing, and untreated dependence can result in loss of productivity, family disruption, depression, overdose, and suicide.^3-5 Family physicians must be able to prescribe opioids safely and effectively, and at the same time must identify and manage opioid misuse and dependence in their practices.

MEDLINE was searched using such terms as “opioid misuse” and “addiction.” The few studies on the prevalence of opioid dependence in primary care populations were based on retrospective chart reviews (level II evidence). Observational studies have documented a high prevalence of opioid misuse in certain primary care patient populations, although the population prevalence is unknown. Most recommendations regarding identification and management of opioid misuse in primary care are based on expert opinion (level III evidence). Screening instruments for detecting opioid dependence have not yet been fully validated in primary care. Level I evidence indicates that primary care physicians can manage opioid dependence safely and effectively with methadone or buprenorphine therapy.

Physical symptoms of withdrawal include myalgia, and cramps and diarrhea. Psychological symptoms include anxiety, craving, and insomnia. Objective signs include lacrimation, acute rhinitis, yawning, sweating, chills, and piloerection. These signs are most evident several days after high doses of opioids are discontinued. Withdrawal peaks 2 to 3 days after last use, and physical symptoms largely resolve by 5 to 10 days after last use, although insomnia and dysphoria can last for months afterward. Opioid withdrawal does not have medical complications except during pregnancy when it can induce spontaneous abortion, premature labour, and neonatal withdrawal.

The reported prevalence of opioid dependence among chronic pain patients varies among clinical settings. A review of studies conducted in tertiary care pain clinics found that prevalence ranged from 3% to 19% or more.^13,14 Other studies, generally of older patients attending specialty clinics, found rates of 1% to 3%.¹⁵ In 3 retrospective chart reviews in primary care clinics, 7% to 31% of charts documented opioid misuse,^16,17 and drug abuse was diagnosed in 6% of these patients.¹⁸ The true prevalence of prescribed opioid misuse is unknown. In the Health Care for Communities Study in the United States, which involved 14000 patients,¹⁹ those taking prescription opioids had 4 times the risk of problems with use of prescribed and illicit drugs and of mood and anxiety disorders the other participants had. These studies must be interpreted with caution because opioid misuse is not synonymous with opioid dependence. A detailed diagnostic assessment of opioid users found that non-addicted patients frequently misuse opioids.²⁰

The prevalence of prescription opioid misuse appears to be increasing. The Drug Abuse Warning Network in the United States reported a 7-fold increase in oxycodone-related emergency department visits from 1996 to 2002.^10,11 A national surveillance system involving addiction experts confirmed that opioid abuse increased in the United States from 2002 to 2004, with oxycodone showing the greatest increase.²¹

Risk factors for opioid dependence include youth; current, past, or family history of substance abuse; concurrent psychiatric disorders; and a childhood history of sexual abuse. Studies of the positive or negative predictive value of these risk factors have had inconsistent results.^12,22,23

Table 1 Opioid Risk Tool

Table 2 CAGE test

Table 3 Behaviour suggesting opioid dependence

Table 4 Additional clinical features of opioid dependence

Table 5 Clinical features of pain patients with and without addictions

Opioid misuse can be grouped into several categories: unsanctioned use (running out early, bingeing); altering the route of delivery (injecting, crushing tablets); accessing opioids from other sources (friends, the street, other doctors); drug-seeking behaviour (anger, harassing office staff for fit-in appointments); and reluctance to use other methods of pain management. This behaviour stems from opioid-dependent patients’ need to overcome opioid tolerance, achieve desired psychoactive effects, and relieve withdrawal symptoms.

If asked, opioid-dependent patients might say that they experience withdrawal symptoms at the end of a dosing interval. They might even acknowledge that, although they use the drug for pain, they are also addicted to it. They typically experience depression, anxiety, and social isolation and often have a current, past, or strong family history of addiction.

It is sometimes difficult to distinguish patients with opioid dependence from patients with pain disorder, also known as chronic pain syndrome. Patients with pain disorder often describe their pain in dramatic terms, are prescribed high doses of opioids, focus on medications, and are depressed and socially isolated. They differ from opioid-dependent patients in that they are not usually seeking a psychoactive effect from their opioids, do not have a strong personal or family history of addiction, and generally comply with their medication schedules.

Table 6 Urine testing for drugs

Table 7 Interpretation of urine drug-screening results among patients receiving oxycodone

Physicians should manage opioid dependence as they would any other medical condition, without defensiveness, avoidance, or anger (Table 8). Physicians can anticipate varying degrees of resistance from patients and must be comfortable with setting boundaries and saying “no.”

Table 8 Management of suspected opioid misuse or dependence

Management strategies described below allow patients with chronic pain to receive opioids under controlled conditions based on their level of risk of addiction. The category “suspected opioid misuse or dependence” recognizes the difficulty in diagnosing opioid dependence in patients who will not disclose their true symptoms or behaviour.

Patients suspected of abusing a specific opioid should, in general, be switched to a different opioid. Oxycodone and hydromorphone should be used with caution. Tapering is indicated if the opioid dose is well above 300 mg/d of morphine. Tapering can improve patients’ mood and pain³⁵ because the cycle of intoxication and withdrawal is less extreme once they have been stabilized at a lower dose. Tapering should be done with scheduled doses of controlled-release opioids, if possible. A suggested tapering schedule involves reductions of 10% every 2 to 4 weeks, slowing to reductions of 5% once a dose of one third of the initial dose is reached.³⁶ The end point of successful tapering is either abstinence or a moderate scheduled dose that provides effective analgesia with minimal withdrawal symptoms. Patients who remain noncompliant with the trial after 1 to 3 months should be referred for opioid agonist treatment.

Opioid agonist treatment consists of daily supervised dosing, gradual introduction of take-home doses, frequent urine tests, and medical follow up and counseling. Methadone is an oral opioid with a slow onset and long duration of action. In appropriate doses it relieves symptoms of withdrawal and cravings for 24 hours without inducing sedation or euphoria. Methadone maintenance is highly effective in reducing drug use and its consequences (level I evidence).^37-41 Buprenorphine, soon to be available in Canada as Subutex^® and Suboxone^®, is a sublingual partial opioid agonist. Buprenorphine has level I evidence of effectiveness^42,43 and can be prescribed safely and effectively by primary care physicians.^44-47 While buprenorphine might be less effective than high doses of methadone, it can be titrated more quickly and has a lower risk of overdose.^48,49

Opioid misuse and dependence can be detected through careful assessment of patients, vigilance for opioid misuse, and urine testing. If opioid misuse or dependence is suspected, physicians could consider a trial of structured opioid therapy provided patients are not injecting opioids, crushing opioid tablets, or acquiring opioids from other sources. If the trial fails or is not indicated, patients should be referred for opioid agonist treatment with methadone or buprenorphine.