31st January 2024

Management

Opioid overdose

Overdose can be managed with naloxone if needed, for example, for patients presenting with reduced GCS at risk of airway compromise. This should be given in a stepwise approach to avoid precipitating withdrawal, due to the risk of recurrence of dangerous levels of sedation when the naloxone effect subsides (about 30-60 mins). Individuals with heroin dependence should be given overdose awareness training and take-home naloxone alongside opioid substitution therapy to increase safety practices.

Opioid withdrawal

Lofexidine is a non-opioid alpha-adrenergic agonist that can be used to manage symptoms of opioid withdrawal. NICE recommends its use for patients who have declined opioid substitution, wish to detoxify quickly or have only mild or uncertain dependence. Side effects include dry mouth and drowsiness, hypotension and bradycardia.

Opioid substitution

Opioid substitution (via a service referral) should be considered if the following criteria are met:

1. Regular opiate use (often daily).
2. Convincing evidence of current dependence.
3. Ability to comply with the substitution regimen.
4. Not receiving opioid substitution from an alternative source/clinician.

Methadone or buprenorphine can be used as opioid substitution treatment for opioid dependence. Initiation of treatment should be titrated to achieve a dose that avoids intoxication, withdrawal and leads to complete cessation of illicit opioid use. For methadone, this typically takes two to four weeks, but titration of buprenorphine is usually faster. In general, a typical starting dose of methadone would be 10-30mg, and a typical starting dose of buprenorphine would be 4-8 mg. An average maintenance dose of methadone would be between 60 and 120 mg daily, and an average maintenance dose of buprenorphine would be between 12 and 16 mg daily.

Methadone has full agonist properties and is a liquid preparation. Tablet form is available for special circumstances, e.g., to reduce nausea and vomiting. Ultra-long-acting forms like depot aren’t approved for UK use yet. It has a half-life of 13-50 hours, so delayed toxicity can occur; therefore, careful monitoring and dose adjustment are needed during initiation. Buprenorphine is a sublingual tablet with partial agonist and antagonist properties. There is a risk of precipitated withdrawal if the first dose is given when circulating opioids are still present due to the antagonist properties; therefore, the first dose should be given when withdrawal begins (6-12 hours after last opioid use). Both are metabolised by P450 enzymes so prone to drug interactions.

NICE recommends both methadone and buprenorphine. Evidence suggests buprenorphine is associated with lower incidence of fatal overdose during the start of treatment initiation but that more patients remain engaged with treatment when methadone is used. Other factors to consider when choosing which to initiate would include patient preference, any previous treatment failure and existing medication/alcohol interactions. Once established on maintenance treatment, the risk of death by overdose is considerably lower than prior to treatment.

When patients on community opioid substitution are admitted to hospital it is important to independently clarify the patient’s dose and when their last dose was supervised to have been taken (with their key worker and pharmacy). Once this has been confirmed if they have been regularly taking the prescribed medication the same dose can be continued. They should also be given information about drug treatment services, blood-borne virus infections and how to prevent drug overdose. This is termed harm reduction and is an important part of opioid management to consider.