Opioid Use Disorder (OUD) is a chronic relapsing substance use disorder characterized by compulsive opioid use, impaired control over opioid consumption, continued use despite harmful consequences, and the development of tolerance and withdrawal. The disorder results in clinically significant impairment or distress affecting physical, psychological, social, occupational, or academic functioning.

Epidemiology

• Opioid Use Disorder is a major public health problem worldwide

• It is associated with increased morbidity and mortality due to overdose, infectious diseases, and psychiatric comorbidity

• People who inject opioids are at increased risk of HIV, hepatitis B, hepatitis C, infective endocarditis, and other blood-borne infections

• Early diagnosis and long-term treatment improve survival and reduce complications

Risk Factors

• Previous opioid exposure for chronic pain

• Non-medical use of prescription opioids

• Family history of substance use disorders

• Genetic susceptibility

• Coexisting psychiatric disorders

• Childhood trauma or adverse childhood experiences

• Peer influence

• Poverty and unemployment

• Previous incarceration

• Injection drug use

Pathophysiology

Repeated opioid exposure activates the brain's mesolimbic reward pathway through stimulation of μ-opioid receptors, resulting in increased dopamine release. Chronic opioid use causes neuroadaptation leading to tolerance, physical dependence, craving, and withdrawal. Long-term opioid exposure also alters stress response pathways and executive control, contributing to compulsive drug-seeking behaviour and relapse.

Clinical Presentation

Features of Opioid Use Disorder

• Craving for opioids

• Loss of control over opioid use

• Repeated unsuccessful attempts to stop opioid use

• Continued opioid use despite harmful consequences

• Neglect of work, school, or family responsibilities

• Social and occupational impairment

• Tolerance

• Withdrawal symptoms

• Spending excessive time obtaining, using, or recovering from opioids

Features of Opioid Withdrawal

• Anxiety

• Restlessness

• Yawning

• Lacrimation

• Rhinorrhoea

• Sweating

• Piloerection

• Dilated pupils

• Muscle aches

• Abdominal cramps

• Nausea

• Vomiting

• Diarrhoea

• Insomnia

• Tachycardia

• Hypertension

Diagnostic Criteria (DSM-5)

Diagnosis requires a problematic pattern of opioid use leading to clinically significant impairment or distress, occurring within a 12-month period, with at least two of the following:

• Opioids are often taken in larger amounts or over a longer period than intended

• Persistent desire or unsuccessful efforts to reduce or control opioid use

• A great deal of time is spent obtaining opioids, using opioids, or recovering from their effects

• Craving or a strong desire to use opioids

• Recurrent opioid use resulting in failure to fulfil major obligations at work, school, or home

• Continued opioid use despite persistent or recurrent social or interpersonal problems caused or worsened by opioids

• Important social, occupational, or recreational activities are reduced or abandoned because of opioid use

• Recurrent opioid use in situations where it is physically hazardous

• Continued opioid use despite knowledge of persistent or recurrent physical or psychological problems likely caused or worsened by opioids

• Tolerance, defined by either:

  • Need for markedly increased amounts of opioids to achieve intoxication or desired effect

  • Markedly diminished effect with continued use of the same amount

• Withdrawal, manifested by either:

  • Characteristic opioid withdrawal syndrome

  • Opioids are taken to relieve or avoid withdrawal symptoms

Severity

• Mild: 2–3 criteria

• Moderate: 4–5 criteria

• Severe: 6 or more criteria

Differential Diagnosis

• Opioid withdrawal syndrome

• Opioid intoxication

• Other substance use disorders

• Chronic pain with appropriate opioid therapy

• Major depressive disorder

• Anxiety disorders

• Somatic symptom disorder

Investigations

Investigations are performed to confirm opioid exposure, identify complications, and screen for coexisting medical conditions.

Laboratory Investigations

• Urine drug screening

• HIV testing with appropriate counselling and consent

• Hepatitis B screening

• Hepatitis C screening

• Syphilis screening where indicated

• Full blood count

• Liver function tests

• Renal function tests

• Blood glucose

• Pregnancy test in women of reproductive age where appropriate

Additional Investigations

• Electrocardiogram before and during methadone therapy where indicated due to the risk of QT interval prolongation

• Chest radiograph if pulmonary infection is suspected

• Blood cultures when infective endocarditis is suspected

Management

Treatment Goals

• Achieve sustained abstinence from illicit opioids

• Prevent opioid withdrawal

• Reduce opioid craving

• Prevent overdose

• Reduce HIV and viral hepatitis transmission

• Improve physical, psychological, and social functioning

Non-Pharmacological Management

• Assess readiness to change using motivational interviewing

• Provide psychoeducation regarding opioid dependence and relapse prevention

• Offer therapeutic group therapy in a structured treatment environment

• Educate patients on the risks of HIV, hepatitis B, and hepatitis C transmission associated with sharing needles

• Promote needle and syringe harm reduction programmes where available

• Provide counselling for safer injection practices

• Encourage family involvement where appropriate

• Treat coexisting psychiatric disorders

• Facilitate vocational and social rehabilitation

Pharmacological Management

Opioid Substitution Therapy

Methadone 10–30 mg orally as an initial dose based on clinical assessment and urine drug screening results. Increase the dose by 5–10 mg every 3–5 days until opioid withdrawal symptoms and craving are adequately controlled. Once clinical stability has been been achieved, maintenance treatment should continue for a minimum of two years. Dose adjustments should be individualized according to clinical response. Patients receiving methadone should be monitored for sedation, respiratory depression, drug interactions, and QT interval prolongation. For comprehensive management, refer to the National Guidelines for Comprehensive Management of Opioid Use Disorder.

OR

Buprenorphine 8–32 mg sublingually. The dose should be titrated according to control of opioid withdrawal symptoms and craving. Buprenorphine should be initiated after objective signs of opioid withdrawal have developed to reduce the risk of precipitated withdrawal. Ongoing maintenance therapy should be individualized according to treatment response and clinical stability.

Treatment Principles

• Medication-assisted treatment should always be combined with psychosocial interventions

• Treatment adherence should be monitored regularly

• Urine drug screening may be used to assess treatment progress

• Long-term maintenance therapy is associated with lower relapse and mortality rates

• Abrupt discontinuation should be avoided because of the high risk of relapse

Referral Criteria

Refer to the next level of care if:

• Severe opioid withdrawal requiring inpatient management

• Opioid overdose

• Failure to respond to opioid substitution therapy

• Significant psychiatric comorbidity

• Suicidal ideation or self-harm risk

• Pregnancy

• Severe medical complications

• HIV or viral hepatitis requiring specialist management

• Diagnostic uncertainty

Complications

• Opioid overdose

• Respiratory depression

• Death

• HIV infection

• Hepatitis B and hepatitis C

• Infective endocarditis

• Skin and soft tissue infections

• Chronic constipation

• Depression

• Anxiety disorders

• Social and occupational dysfunction

• Criminal justice involvement

Prevention

• Rational prescribing of opioid medicines

• Early identification of opioid misuse

• Public education regarding opioid dependence

• Harm reduction programmes

• Needle and syringe exchange programmes

• HIV and hepatitis prevention programmes

• Access to medication-assisted treatment

• Long-term psychosocial support

Prognosis

Opioid Use Disorder is a chronic relapsing condition. Long-term medication-assisted treatment combined with psychosocial interventions significantly reduces opioid use, overdose, HIV transmission, criminal activity, and mortality. Treatment adherence and continued follow-up are essential for sustained recovery.

Patient Education

• Opioid dependence is a treatable chronic medical condition

• Long-term treatment is usually required

• Do not stop methadone or buprenorphine without medical advice

• Avoid sharing needles or injection equipment

• Attend all scheduled clinic visits and counselling sessions

• Take medicines exactly as prescribed

• Seek immediate medical care for overdose symptoms, severe breathing difficulty, or loss of consciousness

• Family support improves treatment success