Opioids in chronic non-cancer pain (CNCP)

By Dr Reza Modarres, Specialist Pain Medicine Physician (FFPMANZCA, FRACGP) · Updated October 2026 · For health professionals

Evidence-based opioid prescribing in chronic non-cancer pain (CNCP): oral morphine equivalent daily dose (oMEDD), opioid rotation, buprenorphine and deprescribing, based on the ANZCA Faculty of Pain Medicine (FPM) 2025 position statement and Australian prescribing guidance.

1. What is the role of opioids in chronic non-cancer pain?

Opioids have a well-established role in acute severe pain, cancer-related pain and palliative care. Their role in chronic non-cancer pain is substantially more limited.

Chronic pain is a complex condition involving biological, psychological and social contributors. Pain may involve nociceptive, neuropathic and nociplastic mechanisms, which frequently occur together.

Although opioids can provide short-term analgesia in selected individuals, sustained improvements in physical function, participation and quality of life are not consistently demonstrated with long-term treatment.

Potential harms include tolerance, physical dependence, opioid use disorder, opioid-induced hyperalgesia, constipation, endocrine dysfunction, cognitive impairment, falls, sleep-disordered breathing and potentially fatal respiratory depression.

The primary objective of chronic pain management is improved function and quality of life, rather than pain elimination. Where opioid therapy is appropriate, it should support rehabilitation and participation in a comprehensive multidisciplinary pain management program.

2. What does the FPM position statement recommend?

The Faculty of Pain Medicine’s PS01(PM): Statement regarding the use of opioid analgesics in patients with chronic non-cancer pain (updated October 2025) sets out a framework for opioid prescribing. Opioid treatment should be an individualised, monitored therapeutic trial rather than an indefinite prescription.

The 5As of opioid monitoring

1. Analgesia: is there meaningful pain reduction?
2. Activity: has functional capacity improved?
3. Adverse effects: are there significant medication-related harms?
4. Affect: how are mood, cognition and psychological wellbeing?
5. Aberrant behaviour: are there concerning medication-taking behaviours requiring assessment?

Patients already established on long-term opioids should be reassessed regularly. The decision to continue should be based on sustained benefit and acceptable risk, not simply the duration of prior prescribing.

3. Why should fentanyl patches be avoided in chronic non-cancer pain?

The 2025 FPM position statement states that transdermal fentanyl should not be initiated in CNCP. Reasons for particular caution include:

• High potency and significant risk of respiratory depression.
• Delayed onset and offset, making rapid dose adjustment difficult.
• Continued systemic absorption after patch removal.
• Increased absorption with external heat or fever.
• Risk of errors involving patch strength, replacement and disposal.
• Potential for accidental exposure, particularly in children.

Fentanyl patches should not be used in opioid-naïve patients. They retain specific roles, including selected cancer and palliative care settings.

For patients already using fentanyl patches for CNCP, reassess their response, functional benefit, adverse effects and opportunities for dose reduction or rotation. Do not stop abruptly in a physically dependent patient.

4. Understanding oral morphine equivalent daily dose (oMEDD)

The oMEDD expresses a patient’s total daily opioid exposure as an approximate equivalent oral morphine dose. It is useful for comparing opioid exposure, identifying higher-risk regimens, medication reconciliation and prescribing reviews.

oMEDD (mg/day) = total daily opioid dose × conversion factor

For multiple opioids, calculate the oMEDD of each separately and add the results, including both scheduled and immediate-release doses.

5. What opioid doses correspond to 40 mg oMEDD/day?

These examples show how commonly prescribed opioids compare with the 40 mg oMEDD/day risk threshold.

Example A: tapentadol

The tapentadol dose theoretically equivalent to 40 mg oMEDD is 40 ÷ 0.3 = 133.3 mg/day. So 100 mg/day is about 30 mg oMEDD, and 150 mg/day is about 45 mg oMEDD. No standard twice-daily tablet regimen corresponds exactly to 40 mg oMEDD.

Example B: Targin

Targin combines oxycodone and naloxone. Only the oxycodone component is counted. For Targin 15/7.5 mg twice daily: (15 × 2) × 1.5 = 45 mg oMEDD.

The naloxone component mainly reduces opioid-induced constipation through local gastrointestinal opioid receptor antagonism. It does not remove systemic opioid risks, including respiratory depression, dependence or overdose.

Clinical interpretation: the 40 mg threshold is not a treatment target or a safe maximum. Opioid-related harm can occur at any dose, and risk rises with dose, comorbidities and concurrent sedative medicines.

6. Opioid rotation: when and why should we switch opioids?

Opioid rotation means changing from one opioid to another to improve tolerability, simplify treatment or achieve a better balance between analgesia and adverse effects. It may be considered when there is:

• Partial analgesic benefit but unacceptable adverse effects.
• Significant constipation, sedation or cognitive impairment.
• A clinical reason to change the route of administration.
• Difficulty with adherence or a complex opioid regimen.
• A need to rationalise long-term opioid prescribing.

Rotation is not a substitute for deprescribing. Where the patient has no meaningful functional benefit from opioids, gradual dose reduction and cessation may be more appropriate than switching to another opioid.

Incomplete cross-tolerance

Tolerance to one opioid does not necessarily mean equivalent tolerance to another. Prescribing the full calculated equianalgesic dose of a replacement opioid may cause over-sedation, respiratory depression or overdose; the FPM table itself cautions about this.

For many conventional rotations, an initial 25–50% reduction from the calculated equianalgesic dose is commonly recommended, followed by individualised titration and monitoring. This is a general principle, not a universal formula. Methadone, transdermal fentanyl and buprenorphine need drug-specific conversion guidance.

Worked example: oxycodone to tapentadol

A patient takes modified-release oxycodone 20 mg twice daily.

1. Current oMEDD: oxycodone 40 mg/day × 1.5 = 60 mg oMEDD.
2. Theoretical tapentadol equivalent: 60 ÷ 0.3 = 200 mg tapentadol/day.
3. Allow for incomplete cross-tolerance: a 25–50% reduction gives a theoretical range of 100–150 mg tapentadol/day.
4. Individualise: choose an available formulation, consider patient-specific risks and review closely for benefit, withdrawal and adverse effects.

These calculations illustrate the principle only and are not an automatic prescription. Tapentadol combines μ-opioid agonism with noradrenaline reuptake inhibition, so its effects cannot be predicted perfectly from oMEDD equivalence.

7. Why consider buprenorphine?

Buprenorphine is a partial μ-opioid receptor agonist with high receptor affinity and slow dissociation. It also has antagonist activity at κ-opioid receptors. These properties may offer some advantages over full μ-agonists in selected patients.

However, buprenorphine is still an opioid. It can cause dependence, withdrawal, sedation, constipation, falls and potentially life-threatening respiratory depression. Concurrent benzodiazepines, gabapentinoids, alcohol and other CNS depressants increase risk.

Since the 2020 TGA opioid reforms, modified-release opioids, including buprenorphine patches, are not indicated for chronic non-cancer pain other than in exceptional circumstances. A potentially better respiratory safety profile does not make buprenorphine routine first-line treatment for chronic pain.

8. How to rotate from an oral opioid to transdermal buprenorphine

Rotation to transdermal buprenorphine needs more than matching oMEDD values. Although the FPM table equates a 20 micrograms/hour patch with about 40 mg oMEDD/day, this does not mean every patient taking 40 mg oral morphine daily can safely switch directly to that strength. The FPM calculator is intended for calculating opioid exposure, not for determining replacement doses, and the eviQ calculator does not provide direct conversion to transdermal buprenorphine because conversion evidence is limited.

Requires individualised clinical assessment. The steps below are a general approach, not a fixed switching protocol.

1. Assess the indication and current therapy. Confirm meaningful opioid responsiveness, current oMEDD, duration of therapy, withdrawal risk, hepatic function, concurrent sedatives and the reason for switching.
2. Decide whether a patch is appropriate. The patient should need continuous analgesia, be suitable for transdermal delivery and meet the product indication.
3. Choose a conservative starting strength. Australian product information advises starting patients previously on oral opioids at a low patch strength, with individualised titration. The lowest strength is 5 micrograms/hour.
4. Plan the transition. Allow for the delayed onset of the patch and the offset of the previous opioid. Carefully planned short-acting rescue medication may be needed. Avoid unstructured continuation of the previous full-agonist regimen.
5. Monitor and titrate. Monitor sedation, respiratory status, withdrawal, pain interference and function. Steady state is reached by about day 3; do not increase the dose at less than 3-day intervals, and follow product-specific guidance.

What about micro-overlap or microinduction?

In selected opioid-tolerant patients, specialist-supervised low-dose buprenorphine initiation while temporarily continuing a full agonist may allow a gradual transition with less withdrawal. Protocols vary considerably between oral, sublingual and transdermal formulations, evidence remains limited (particularly in CNCP), and the approach is not interchangeable with standard patch initiation.

Complex conversions, higher-dose regimens, suspected opioid use disorder and transitions involving fentanyl or methadone warrant pain medicine or addiction medicine input.

9. Opioid dose reduction and deprescribing

For patients without sustained functional benefit, or where harms outweigh benefits, gradual deprescribing should be considered. The FPM 2025 statement gives examples of reduction strategies:

These are examples, not fixed schedules. A patient-centred approach considers duration of exposure, psychological distress, comorbidities and withdrawal risk. Sudden cessation is generally inappropriate in physically dependent patients unless an immediate safety concern requires urgent management. Where opioid dependence rather than pain becomes the main problem, FPM recommends involving an Addiction Medicine service.

10. Safer opioid prescribing in general practice

Before initiating, continuing or rotating opioids, review the diagnosis, measurable functional goals, medication risks and opportunities for non-opioid treatment.

Important considerations include sleep apnoea, respiratory impairment, renal and hepatic dysfunction, frailty, psychiatric comorbidities, alcohol use, concurrent sedatives, adherence and driving safety.

In Queensland, prescribers must check QScript real-time prescription monitoring and comply with Schedule 8 prescribing requirements.

Consider take-home naloxone for all outpatients prescribed opioids, based on risk. FPM specifically recommends naloxone and education when oMEDD exceeds 40 mg/day, adjusted for individual circumstances. Monitoring should focus on daily activity and participation, not only numerical pain scores.

11. When should a GP refer to a pain medicine specialist?

Consider specialist assessment for patients:

• On escalating opioid doses without meaningful functional improvement.
• Requiring more than 60 mg oMEDD/day to establish opioid responsiveness.
• With significant opioid-related adverse effects.
• Needing complex opioid rotation or consideration of buprenorphine transition.
• With suspected opioid-induced hyperalgesia or unsuccessful opioid reduction.
• With concurrent high-risk sedative prescribing or a complex biopsychosocial presentation.

A pain medicine assessment can help with opioid optimisation, medication rationalisation, structured deprescribing and integration of psychological, physical and interventional pain management where appropriate. Referral information.

Clinical resources and references

1. Faculty of Pain Medicine, ANZCA. PS01(PM) Statement regarding the use of opioid analgesics in patients with chronic non-cancer pain. Updated October 2025. PDF
2. Faculty of Pain Medicine, ANZCA. PS01(PM) Appendix 2: Opioid dose equivalence calculation table. October 2025. PDF
3. Faculty of Pain Medicine, ANZCA. FPM Opioid Calculator. anzca.edu.au
4. Therapeutic Goods Administration. Prescription opioid regulatory reforms, 2020. Summary for GPs: RACGP newsGP
5. Cancer Institute NSW. eviQ Opioid Conversion Calculator. eviq.org.au
6. NSW Agency for Clinical Innovation. 5As opioid therapy monitoring tool. safetyandquality.gov.au
7. Australian product information: buprenorphine transdermal patch (Norspan). Check the current PI on the TGA website.
8. Webster L, Gudin J, Raffa RB, et al. Understanding buprenorphine for use in chronic pain: expert opinion. Pain Med. 2020;21(4):714-723. PMC7139205
9. Queensland Health. Regulating QScript. health.qld.gov.au

Updated October 2026. Reviewed against FPM PS01(PM), October 2025.

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