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Mental Health
OST - Opioid Substitution Treatment


    • Substance Misuse is defined as use of a substance for a purpose not consistent with legal or medical guidelines, the substance having a negative effect on health or functioning and may take the form of drug dependence.
    • Dependence is defined as:
      • a strong desire to take a substance, or difficulty in controlling its use
      • the presence of a physiological withdrawal state
      • tolerance of the use of the drug
      • neglect of alternative pleasures
      • persistent use of the drug despite harm to self and others
    • Aims:
      • Contribute to improving the health of patients as well as aspects of their personal and social functioning.
      • Focus on improvements to quality of life such as education, employment, relationships with significant others.
      • Reduce the spread of infectious diseases associated with injecting drug use, especially hepatitis B and C and HIV/AIDS.
      • Reduce the mortality and morbidity resulting from the misuse of opioid drugs.
      • Assist individuals to achieve successful withdrawal from opioids.
      • Reduce episodes of illegal and other harmful drug use.
      • Reduce crime associated with opioid use.
    • All aspects of service provision are aimed at reducing harm to the individual, the family/whanau and the community.
    • The Opioid Substitution Treatment offered should:
      • Suppress opioid withdrawal and craving.
      • Not induce sedation or euphoria.
    • Maintenance doses are individualised to assist the patient to achieve their negotiated treatment goals.
    • Any increase/decrease in dose should be based on a clinical assessment.  This clinical assessment might include a serum methadone level.
    • To achieve these aims the service focuses on:
      • Delivering person-centred, services that are both accessible and acceptable to patients.
      • Maintaining a partnership approach with patients.
      • Adopting a motivational rather than confrontational approach.
      • Adopting prescribing practices that are evidence and strengths based.
      • Supporting planned withdrawal from methadone or buprenorphine/naloxone when appropriate.
    • Patient confidentiality and privacy are maintained in accordance with relevant legislation and patient consent is obtained in line with the requirements of the Code of Health and Disability Services Consumer Rights Act 1996.
    • *See Section 1.1 Objectives of OST page 4-5 of " New Zealand Practice Guidelines for Opioid Substitution Treatment 2014"
    • Why transfer to GP Shared care?
    • OST aims to support patients to live as normal a lifestyle as possible within the parameters of treatment. GP shared care has the benefits of;
      • Instigating more comprehensive health care for patients.
      • Allowing services to focus on patients in need for intensive specialist input.
      • Improving social integration by normalizing patients treatment.
    • The phases of treatment provide a patient pathway based on recovery principles. A person may or may not move sequentially through the phases from high intervention to low intervention, but as with any recovery process, may experience periods of higher intervention (re-stabilisation or a return to specialist maintenance) as part of their recovery.
    • Underpinning the practices and policies of BOPAS is local and international research which demonstrates the effectiveness of Opioid Substitution Treatment (OST). Treatment provided by BOPAS is delivered within a framework of sound medical practice, accepted standards, approved guidelines and legal requirements. BOPAS seek to ensure that methadone or buprenorphine/naloxone is prescribed and dispensed in a clinically responsible manner.
    • Roles and responsibilities:
      • The BOPAS lead medical officer as authorising medical officer retains overall responsibility for patients on the GP Shared Care programme.
      • GP authorization is based on a shared care model of service delivery. BOPAS provide specialist support and can always be accessed for advice or assistance. Renewal of authorization is contingent upon prescribing practices remaining consistent with BOPAS policy and regular review with lead clinician. 
      • For roles and responsibilities of the patient, GP and BOPAS, please see documents below:
    • See Section 8 OST in Primary Care page 60-62 of "New Zealand Practice Guidelines for Opioid Substitution Treatment 2014"


  1. Instability Indicators

    • Problematic, harmful or hazardous use of alcohol or other drugs.
    • Engages in or supports criminal activity.
    • Signs of intoxication at clinic or pharmacy.
    • Evidence of intravenous injecting.
    • Irregular dosing.
    • Poor attendance at appointments.
    • Avoidance of urinalysis or blood tests.
    • Behavioural problems such as aggression.
    • Frequently requests changes to dispensing.
    • Requests to replace lost or stolen doses.
    • Any co-existing mental or physical health problems are difficult to treat or are not well managed.
    • *See Section 1.2 Roles of Specialists OST Services page 5 of "New Zealand Practice Guidelines for Opioid Substitution Treatment 2014"
  2. Stability Indicators

    • Defined and progressing towards treatment goals.
    • No problematic, harmful or hazardous use of alcohol or drugs.
    • No evidence of criminal activity.
    • Responsible management of takeaways.
    • Schedules and attends appointments.
    • Rarely requests changes to dispensing.
    • Social stability as evidenced by relationships with others, stable and healthy housing, employment/occupation.
    • Any co-existing mental or physical health problems are well managed.
    • Participates in primary health care.
    • Complies with programme requirements.
  3. Recommended Reviews

    • Appointments:
      • Initially the patient will see his/her GP every 28 days when a new script is needed. This is recommended to occur for at least 3 months when the patient is new to your practice. Where there is an established relationship with the patient or there are other indications for less frequent appointments this can be negotiated between the GP, patient and Addiction Liaison Clinician (from the BOPAS service).
      • After this initial time the patient must be seen by the GP once every 3 months for a review. The patient usually collects their script from the GP, practice nurse or receptionist at their review and in the two months between the three monthly appointments.
    • Three monthly review
    • Not attending appointments
      • If a patient consistently does not attend appointments, the GP may refrain from writing any further scripts until the patient is seen or may write a short-term interim prescription until a new appointment can be scheduled. The GP should also contact the case manager and or the Addiction Liaison Clinician.
    • GP - Six Monthly Information Forms
      • The Addiction Liaison Clinician will contact your practice at least every six months to update information. Please provide any additional information you may wish to raise at this time or any time between contacts. It is essential for BOPAS to have current information for continued GP prescribing authorisation.


  1. Visit the drug or drug-related issues pathway or prescribing issues pathway

  2. Contact details:

    Bay of Plenty Addiction Service (BOPAS)
    Kowhai House, Tauranga Hospital, Cameron Road
    Private Bag 12024, Tauranga 3143

    • Opening Hours: Mon-Fri 8.30am-5.00pm             
    Area Phone Fax

    BOPAS, reception

    (07) 579 8391

    (07) 5718095

    MHS Crisis team

    (after hours)

    (07) 579 8329

    0800 800 508

  3. Concurrent Issues

    • Pain Management
        • Mild to moderate acute pain can usually be effectively managed with simple analgesics (including mild opioid medications) and/or other appropriate medications.
        • Opioid maintenance patients with acute severe pain usually require higher doses of opioid agonists than non-opioid tolerant patients in order to achieve adequate pain relief. (Many receive inadequate analgesia for acute severe pain).
        • In the event an OST patient is hospitalised their GP prescriber will need to liaise with the hospital staff to ensure continuation of methadone or buprenorphine/naloxone in hospital, cancellation of the prescription at the community pharmacy and the resumption of prescribing at the community pharmacy on discharge. BOPAS can assist as required.
        • Chronic pain in Opioid maintenance patients should be managed in the same way as it is for other patients.
        • Methadone or buprenorphine/naloxone as prescribed for maintenance treatment may provide partial relief for some chronic pain.
        • BOPAS advises consultation with a specialist pain management service or BOPAS medical officer before considering the regular prescribing of opioid medication for the management of chronic pain.
        • Note: Long term methadone treatment can saturate and dull opioid receptors leading to increased patient pain levels as the body tries to compensate for inhibited pain recognition (hyper-analgesia; increased sensitivity to pain secondary to long-term blockade of opiate-based pain receptors)
        • *See Section 6.6; 6.6.1; 6.6.2 Management of Acute and Chronic Pain page 49 of "New Zealand Practice Guidelines for Opioid Substitution Treatment 2014"
        • There are several health problems during pregnancy that should be discussed including:
          • General nutrition.
          • Risks of anaemia.
          • Alcohol and nicotine consumption.
          • Oral hygiene and dental health.
          • Complications from chronic infection related to injection practice.
          • Antenatal and postnatal mental health problems.
        • Advice should be given regarding potential complications of pregnancy associated with drug use:
          • Premature delivery.
          • Low birth weight.
          • Placental abruption.
          • Neonatal abstinence syndrome.
        • Opioid Detoxification in pregnant women:
          • Should be undertaken with caution; and
          • In the second trimester with small frequent reductions − however, expert opinion suggests that a patient should be free to choose to initiate detoxification at any stage of pregnancy, provided her circumstances and her ability to cope are taken into consideration.
        • Partial splitting of the dose may also be considered for stable pregnant patients in the latter half of pregnancy in order to avoid the necessity for increase in the dose, especially for those on doses below 60mg. A single daily dose should be reinstituted following delivery.
        • Note: A small number of women become fast metabolizers of methadone or buprenorphine/naloxone in pregnancy. Where this is suspected, obtain trough and peak serum methadone levels and discuss with the BOPAS before instituting split dosing. These women are at greater risk of destabilization in pregnancy and timely assessment and management can prevent this.
        • In general, it is safe to breastfeed while a mother is taking methadone as long as there are no other factors that would make breastfeeding unsafe, such as using illegal drugs or using certain prescription medications. Methadone is found in breast milk, but only a small amount gets passed along to the baby.
        • There are many benefits to breastfeeding for both the mother and her baby.
          • Breast milk has important nutrients that will help baby grow and may help prevent infection
          • Babies who are breastfed are generally more healthy and don't have to visit the doctor as often as babies who are fed formula
          • Breastfeeding helps the mother and her baby bond
          • Breastfeeding may help baby cope with withdrawal symptoms
        • Although there is no official statement saying that mothers cannot breastfeed if they are taking methadone, it would be wise to discuss this with the specialist service to learn more about it.
        • *See Section 6.7 Management of Pregnant and Breastfeeding Women page 52-56 of "New Zealand Practice Guidelines for Opioid Substitution Treatment 2014"
  4. Concurrent Medical Conditions

      • Issues for the GP managing a patient on Opioid Substitution Treatment (OST) are:
        • Testing for HIV, Hepatitis A, B and C (including Hep C PCR RNA test).
        • Preventing infection/transmission.
        • Monitoring LFTs in those with chronic Hepatitis B & C.
        • Offering treatment for hep C, or refer for specialist treatment where required.
        • Offering Hepatitis A & B vaccination to those who are HAV & HBV antibody negative.
      • Patients with chronic liver disease on long-term opioid maintenance usually do not require alterations in their dose. However, if there is an abrupt change in liver function they may require dose adjustment. The development of jaundice is also a sign that the liver may not be able to metabolize methadone or buprenorphine/naloxone at the normal rate.
      • Where there is significant impairment it is suggested that the methadone serum level is checked every 2 to 3 months to ensure that it is not rising due to impaired metabolism of methadone. Seek the advice of BOPAS or a specialist gastroenterologist if there are concerns.
      • Methadone or buprenorphine/naloxone is a respiratory depressant and care should be taken in prescribing methadone or buprenorphine/naloxone to patients with these disorders.
      • Note that carbamazepine, phenytoin and phenobarbitone interact with methadone (see methadone or buprenorphine/naloxone interactions section).
      • Note that antidepressant and antipsychotic medications may interact with methadone or buprenorphine/naloxone (see methadone or buprenorphine/naloxone interactions).


Disclaimer: These pathways, for the care and management of patients within Bay of Plenty, have been developed jointly by primary and secondary care clinicians. They provide guidance for General Practice teams to diagnose and manage patients suffering from a number of different conditions, and contain patient information resources. The pathways are maps of publicly-funded services accessed by referral from the community, and are strongly evidence based, but are not full clinical guidelines. As the pathways are suggested guidance only, while using them you must exercise your own clinical judgement and pertinent clinical data when treating your patient. This site is intended to be flexible and frequently updated. While every effort has been made to ensure accuracy, all information should be verified.