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Substance use problems: Pharmacotherapy

Alcohol

Alcohol dependence

Pharmacotherapy for alcohol dependence can easily be prescribed by the primary care physician (see Table 6.2: Pharmacotherapy for alcohol dependence ). It should always be paired with at least brief counselling or, if available, a structured treatment program.

Acute withdrawal

The severity of withdrawal varies depending on the individual, so the amount of medication used to treat a person in acute withdrawal from alcohol should be flexible. The evidence suggests that all benzodiazepines are equally efficacious. However, diazepam is commonly used because of its long half-life (40 hours) that results in a pharmacokinetic self-taper after loading, which means a smoother withdrawal and fewer rebound symptoms. 

Clinical Institue Withdrawal Assessment for Alcohol (CIWA-AR)

Alcohol withdrawal symptoms are assessed using the Clinical Institute Withdrawal Assessment for Alcohol (CIWA-Ar). For patients with a CIWA-Ar score of 10 or more, or who are experiencing disorientation or hallucinosis, benzodiazepines should be used.

A typical CIWA-Ar protocol is to give 20 mg po every hour until symptoms ameliorate. The patient should be assessed before each dose. Diazepam loading via symptoms scores is safe and can be done on an outpatient basis. Suggest that the patient should stop drinking alcohol the evening before and come to the office in the morning. Up to 60 mg (three doses) of a benzodiazepine can be given over three hours.

Consider inpatient management if the patient experiences the following:

  • need for further benzodiazepines
  • delirium tremens
  • fever over 38 degrees Celsius
  • medical illness needing treatment
  • Wernicke's encephalopathy
  • other drug dependence such as barbiturates and benzodiazepines

Generally, if there is a history of withdrawal seizures, 20 mg of diazepam should be given every hour for three consecutive doses. For those with severe asthma, respiratory failure or liver disease, a shorter-acting benzodiazepine (oxazepam or lorazepam) is recommended.

Opioids

Methadone

Methadone is well supported by large cohort studies for the treatment of opioid dependence. In Canada, exemption from the Controlled Drugs and Substances Act (1996) is needed to prescribe methadone. Local provincial regulators set guidelines and regulations.

Treatment is often long-term (months to years). Methadone has a narrow therapeutic window with risk of overdose, especially in non-tolerant individuals.

Buprenorphine

Buprenorphine, an opioid receptor partial agonist, is available in Canada as a buprenorphine/naloxone combination.

While training and education are strongly encouraged before prescribing buprenorphine, physicians are not required to seek an exemption from Health Canada as they are if they decide to prescribe methadone.

Compared with methadone, buprenorphine:

  • is less likely to cause an overdose due to the so-called "ceiling effect"
  • allows more rapid titration
  • involves milder withdrawal during tapering

Tobacco

Pharmacotherapy doubles the chances of quitting tobacco use per given quit attempt. Pharmacotherapy for smoking cessation (See Table 6.3: Pharmacotherapy for smoking cessation) shows first-line treatments following U.S. guidelines and summarizes Cochrane reviews giving the level of evidence and official indication for the treatment of tobacco dependence.

Evidence shows that pharmacotherapy works with people who smoke 10 or more cigarettes per day and those interested in stopping smoking. Treatment lasts eight to 12 weeks and success is defined as not smoking at the six-month or more follow-up date from the quit attempt or at least three months after the medication is stopped. The actual duration of treatment should be individualized.