Mental Health  |  OST Prescribing Pathway - Split Methadone or Buprenorphine/Naloxone dosing

Mental Health

OST Prescribing Pathway - Split Methadone or Buprenorphine/Naloxone dosing

For the vast majority of patients adequate stability can be achieved on a once daily dose of methadone or bup/nal.

Patients in GP shared care are unlikely to require a change to split dosing, unless in exceptional circumstances.

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 (see Pregnancy and OST).


A small number of women become fast metabolizers of methadone or buprenorphine/naloxone in pregnancy. Where this is suspected, obtain trough and peak serum 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.

Split dosing may also be considered for stable patients in the latter part of a planned withdrawal from methadone or buprenorphine/naloxone (usually at doses of 30mg or less) in order to reduce pre-dose withdrawal symptoms and to increase the likelihood of successful completion of withdrawal from methadone or buprenorphine/naloxone.  This needs discussion with and authorisation by the OST service.

Split dosing may be in exceptional circumstances considered for stable patients to better manage physical pain symptoms.

Split dosing (including the proportions of each dose) requires the approval of the BOPAS

*See Section 5.6 Split Methadone Doses page 40 of New Zealand Practice Guidelines for Opioid Substitution Treatment 2014"


Last updated : Thursday, January 09, 2020
Next review date : Friday, January 08,2021

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