Prescribing drugs of dependence in general practice

Part C2 - The role of opioids in pain management - Chapter 7

Patient selection for opioid therapy

Last revised: 02 Jun 2020

GPs should be aware that certain patient groups have increased risks of harm in association with opioid use. As part of a patient selection and risk stratification approach, the following patient group attributes should be considered.

Most drugs that are used for pain management cross the placenta. The Australian Drug Evaluation Committee (ADEC) classifies drugs according to fetal risk and notes that there are particular times of concern during pregnancy: weeks 4–10 (organogenesis), and just before delivery. Opioid analgesics taken just before delivery may cause respiratory depression in the newborn, and withdrawal effects may occur in neonates of dependent mothers.

It is always better to avoid drugs during pregnancy. If medication for constant pain relief is required during pregnancy, consultation should occur with a specialist obstetrician or pain physician.

In practice

Prescribers should avoid initiating opioid therapy in pregnant women whenever possible. It is accepted that prescription of ORT for pregnant women with opioid related substance misuse is a harm minimisation strategy.

For pregnant women already on opioids, opioid therapy should be tapered to the lowest effective dose slowly enough to avoid withdrawal symptoms and then discontinued if possible.78 GPs should access appropriate expertise if considering tapering opioids because of possible risk to the woman and to the fetus if withdrawal occurs.8

During breastfeeding, occasional doses of opioids are considered safe, but codeine should be avoided. Use repeated doses with caution, especially if the infant is premature or under four weeks of age. The infant should be monitored for sedation and other adverse effects.157

Patients on workers’ compensation are at risk of being prescribed high-dose opioids, because of higher levels of psychological distress, poorer surgical outcomes and protracted involvement in legal proceedings.406

It is well recognised that patients who are psychologically distressed after a work injury have poorer outcomes.234,407 Therefore, as soon as distress is recognised (even at the first consultation), the patient should be referred to an appropriate health professional (commonly a psychologist) and therapeutic steps undertaken to minimise opioid use.

Evidence also shows that, where possible and appropriate, returning to work has substantial benefits in improving patient morbidity and decreasing mortality.408 When assessing the capacity of the patient to return to work, patient self-assessment of ability is usually reliable, if it matches clinician impression. Activity is not limited to work but includes the usual activities that the patient undertakes in sport, recreation and at home.

For low back pain, patients are most at risk of developing chronic pain syndrome in the period between 8–12 weeks following the date of pain onset.409,410 However, recovery rates are not improved by commencing a new activity program in the first 4–6 weeks after injury.82,411

In practice

Clinicians and patients should be aware of the risks involved with workers’ compensation patients, and focus rehabilitation on increasing function, non-pharmacological approaches and keeping opioid analgesia to a minimum.

The most important treatment modality for musculoskeletal injuries is returning to as much of the patient’s usual activity as soon as possible. For cases of increased complexity multidisciplinary involvement is beneficial, including teamwork with specialists and a physiotherapist with pain management experience.

Opioids can interfere with a complex task such as driving due to sedation; diminished reaction times, reflexes and coordination; reduced peripheral vision due to the persistent miotic effects;412 and decreased ability to concentrate.413

There is little direct evidence that opioid analgesics (eg hydromorphone, morphine or oxycodone) have direct adverse effects on driving behaviour.414 The risk of accidents appears at increased risk in the first weeks of starting opioid therapy or after increasing the dose.413,415 This may be dose dependent.416

There does not appear to be evidence that any one opioid has less impact than another.417 However, stable doses of sustained-release opioids do not appear to impair driving activity.415,418,419

According to Austroads, a person is not fit to hold an unconditional licence if they have an alcohol disorder or other SUD (eg substance dependence, heavy frequent alcohol or other substance use) that is likely to impair safe driving.414,420

The state or territory driver licensing authority may consider a conditional licence. This is subject to periodic review, taking into account the nature of the driving task and information provided by the treating doctor as to whether the following criteria are met:420

  • The person is involved in a treatment program and has been in remission for at least three months.
  • There is an absence of cognitive impairments relevant to driving.
  • There is absence of end-organ effects that impact on driving.

In practice

Each patient should be considered individually and it is ultimately the prescriber’s judgement that determines opioid prescription.421–424 Where there are concerns about a patient’s ability to drive (eg high doses of opioids or opioids plus other sedative medication), a formal driving assessment may be considered.

When starting opioid therapy, patients should be advised that they are likely to be impaired and should not drive until a stable regime has been obtained for at least two weeks.

There is moderate, generally consistent evidence that driving performance of patients on long-term opioids for chronic pain may not be negatively affected by their medication.413,425 Driving at night may be a problem due to the persistent miotic effects of opioid drugs reducing peripheral vision.412

Sleep-disordered breathing describes a spectrum of disorders, including obstructive sleep apnoea (OSA). One in 15 adults has moderate or more severe OSA, experiencing partial or complete cessation of breathing many times during sleep, and around 80% of those who could benefit from treatment remain undiagnosed.426

Compared to people without OSA, people with OSA are at higher risk of increased sensitivity to opioid analgesia and decreased sensitivity to pain.427 Administration of opioids may also exacerbate OSA.428,429

Experts in this area recommend non-opioid analgesics, and other pain management techniques should be used as either an alternative to opioids or to help limit the amount of opioid required.430–432

In practice

If opioids are prescribed for patients with mild sleep-disordered breathing, careful monitoring and cautious dose titration should be used. Prescribing opioids to patients with moderate or severe sleep-disordered breathing should be avoided whenever possible to minimise risks for opioid overdose.8,433

The use of opioids in patients with severe untreated sleep apnoea is not recommended.101

As the population ages the challenge of safe and appropriate pain management increases. Management challenges include age-related changes in physiology, increased risk of falls,434,435 pharmacodynamics and pharmacokinetics, higher prevalence of comorbidities and concurrent medications, altered responses to pain, and difficulties with assessment of pain severity and response to treatment, including problems related to cognitive impairment.

Consider the use of non-drug strategies such as movement, exercise, physiotherapy and psychological therapies as alternatives to, or in combination with, medication.436 Where opioids are used, consider risk assessment for falls and interventions to mitigate common risks of opioid therapy such as constipation. Also, monitor older patients for the presence of cognitive impairment.8,436

Despite the higher incidence of side effects with drug therapy in older people, analgesics may still be safely and effectively used if tailored for the individual patient and comorbidity and other medications are considered.436 However, analgesics should be:436

  • initiated one at a time using a low dose
  • monitored regularly and adjusted as needed to improve efficacy and limit adverse events
  • titrated slowly according to response
  • used in combination where synergistic effects provide improved pain relief with fewer side effects than higher doses of a single drug.

When prescribing opioids to older adults, it is important to provide education about risky medication-related behaviours such as obtaining controlled medications from multiple prescribers and saving or stockpiling unused medications.8

Analgesics for older patients

In general, there is limited evidence about the use of analgesic medications in older patients. Older patients are often specifically excluded from clinical trials because of their age, comorbidities or concurrent medications.

For all patient groups, timing of medication administration and duration of action is important. Severe, episodic pain requires treatment with medicines with a rapid onset of action and short duration. However, if a patient is experiencing continuous pain, regular analgesia is the most effective, possibly using modified-release formulations.436


Paracetamol

Paracetamol is recommended as a first-line therapy in older adults for mild to moderate pain. There is no evidence to support a need for dosage reduction of paracetamol in this group. Although there is emerging evidence of ineffectiveness of paracetamol in low back pain and some osteoarthritis conditions,295 these findings are disputed.


Non-steroidal anti-inflammatories

The use of non-selective NSAIDs is relatively contraindicated in older patients due to increased risk of gastric and renal side effects, as well as cardiovascular and cerebrovascular effects.437 However, individual circumstance and context may make these drugs an appropriate choice. A large 2010 study of patients with arthritis (mean age 80 years) found that overall, patients on NSAIDs appear to fare better than those taking opioids: the opioid cohort showed higher rates of fracture, hospital admission and all-cause mortality with similar or higher rates of cardiovascular, renal and gastrointestinal adverse effects.438

Judicious use is advised particularly in older patients;439 support with protective proton pump therapy is advised.440


Adjuvant therapies – Anticonvulsants

An increase in adverse effects with pregabalin appears to be dose related rather than associated with patient age. However, the initial doses of anticonvulsant drugs should be low and increases in dose should occur slowly. The reduction in renal function that occurs with increasing age means that the elimination of gabapentin and pregabalin may be reduced and lower doses required.

Monitoring of side effects is important, particularly for somnolence and dizziness with pregabalin, but the lack of hepatic metabolism and low drug interactions makes gabapentin and pregabalin useful in older patients.


Adjuvant therapies – Antidepressants

Caution should be exercised with TCAs as their clearance may decrease in older patients. Confusion and hypotension are more likely in this group due to increasing anticholinergic load. Lower initial doses are recommended with careful monitoring for side effects. Contraindications to TCAs include prostatic hypertrophy, narrow angle glaucoma, cardiovascular disease and impaired liver function.

Other antidepressants may be more appropriate: SNRIs (duloxetine) have shown to be effective and safe in older patients though care should be taken with poor renal function.


Opioid therapy

Appropriate precautions must be taken when considering opioid therapy for older patients.102 These precautions include lower starting doses, slower titration, longer dosing intervals, more frequent monitoring and tapering of benzodiazepines.78,102 There is an increased risk of adverse effects including cognitive impairment, sedation, respiratory depression and falls.441,442 The risk of respiratory depression is minimised by monitoring the patient for sedation and reducing the dose of opioid if this occurs.441

While there are large individual differences, older patients are more sensitive to opioids and dose requirement decreases progressively with age, often reduced by 50% or more. There may be fewer pharmacokinetic differences between older and younger patients with fentanyl requirements.445,446 In patients older than 75 years, the elimination half-life of tramadol is slightly prolonged447 and lower daily doses have been suggested.448


In practice

Older patients require less opioid medication than younger patients to achieve the same degree of pain relief; harms can also occur at lower doses than they occur in younger patients.445,446,449 However, inter-patient variability exists in all age groups and doses must be titrated to effect in all patients.

Patients with chronic renal disease frequently report pain450 and patients with cancer often develop severe renal impairment.451

Analgesics for patients with renal disease

Pain adjuvants

Pain adjuvants gabapentin and pregabalin require dose adjustments dependent on creatinine clearance.452

There is limited data on TCAs. Metabolite accumulation may occur and increase the risk of adverse effects but there is little evidence to indicate need for dose reduction. Duloxetine is avoided in patients with creatinine clearance <30 mL/min.453


Opioids

Prescribers should use additional caution and increased monitoring to minimise risks of opioid therapy in patients with renal insufficiency.8 While all patients on opioids should be monitored for adverse effects, there are particular opioids (or their metabolites) that are more likely to cause toxicity in patients with renal impairment.454 These include morphine, diamorphine and codeine derivatives.454

Hydromorphone, methadone, morphine and tramadol have been used in patients with renal disease but with dose adjustments depending on the degree of impairment.337 Tapentadol is not recommended for use with creatinine clearance <30 mL/min. Alternates to pethidine and dextropropoxyphene are recommended.455,456


In practice

The safest analgesics for patients with renal impairment are buprenorphine, fentanyl and paracetamol.337 These analgesics are not associated with high active metabolite load or significantly prolonged clearance. Oxycodone can usually be used without any dose adjustment as its metabolites do not appear to contribute to any clinical effect.337 Hydromorphone is used for patients undergoing dialysis.

Liver disease does not always equate with hepatic dysfunction, and there is no accurate measure of liver disease severity that can be used to guide dose adjustment.457

Analgesics for patients with liver disease

Paracetamol

Paracetamol is safe in patients with chronic liver disease, but a reduced dose of 2–3 g daily is recommended for long-term use.457


Pain adjuvants

Adjuvant analgesics such as TCAs and anticonvulsants may be used cautiously for cirrhotic patients with neuropathic pain.458 Gabapentin or pregabalin may be better tolerated in cirrhosis because of non-hepatic metabolism and a lack of anticholinergic side effects.458


Opioids

Prescribers should use additional caution and increased monitoring to minimise risks of opioids in patients with hepatic insufficiency.8 In these patients, opioids are well known to cause sedation, constipation and precipitate encephalopathy. There is an increased risk for patients with hypoalbuminaemia, and immediate-release as opposed to controlled-release formulations are advised.458

Mild pain not controlled with paracetamol may be best managed with either low-dose tramadol or oxycodone (not slow-release formulation) with an increase in laxatives.458 Fentanyl and buprenorphine are also considered relatively safe. However, combined preparations of slow-release oxycodone and naloxone are not recommended.

In practice

Co-prescription of laxatives is mandatory to avoid constipation and encephalopathy in patients with hepatic insufficiency.

Culturally responsive care

Culture, language and religious convictions have an impact on pain sensitivities, assessment and management. There are significant cultural differences in self-care when managing pain, which affect pain relief seeking behaviour.459,460

Given the large inter-individual differences in pain behaviours and analgesic requirements in any patient group, pain should be assessed and managed on an individual basis rather than expectations associated with any cultural or ethnic group.461,462

There are genetic differences (refer to Prescribing drugs of dependence in general practice, Part C1: Opioids – Section 3.1.2 Metabolism and duration of activity) in the metabolism of opioids,349,463,464 which also need to be considered.

Prescribing opioids to Aboriginal and Torres Strait Islander peoples

High-quality literature to inform acute pain management and opioid use in Aboriginal and Torres Strait Islander peoples is limited or conflicting.465–468

As with all patients, comorbidities need to be considered when selecting analgesics. Higher levels of medical comorbidities such as renal failure have been identified within the Aboriginal and Torres Strait Islander population.469

In practice

Non-Indigenous GPs should consider seeking the assistance of an Aboriginal health worker or an interpreter to assist in communication and cross-cultural understandings (as needed).470,471

Many people experiencing long-term pain may have a range of chronic health conditions, including mental health issues.472 For example, the AIHW (2016) reports that three in 10 people living with back pain are living with mental health issues, which is twice the rate of the general population.473

Depression is the most common mental health comorbidity with long-term pain. It is associated with poorer quality of life and increased functional impairment.474 Diagnosis may be challenging as there are indistinct symptom boundaries between chronic pain, distress and depression.475

Chronic pain is associated with a range of other psychological problems including anxiety, somatisation, fear of pain, anger and hostility.476 Around one-third (31.8%) of people with a psychotic disorder in Australia are also experiencing chronic pain.477

Patients may present with pain as a manifestation of mental health problems. However, opioids should be reserved for well-defined somatic or neuropathic pain conditions.411

Patients with a mental health disorder, including SUDs, are at greater risk of adverse effects from opioid treatment. Prescribers should use additional caution and increased monitoring: titrate more slowly and seek consultant advice where feasible.8,78

Before prescribing opioids, a thorough evaluation for contraindications to opioids is recommended.101 Treatment of anxiety and depression should be optimised prior to initiation of opioids.8 The concomitant use of benzodiazepines should be avoided;101 tapering of benzodiazepines or referral is suggested before starting opioid therapy.90

GPs should review patients’ histories of controlled substance prescriptions using PDMP data to determine whether they are receiving opioid dosages or dangerous combinations that put them at high risk for overdose.

In practice

Prescribers should use additional caution and increased monitoring: titrate more slowly and seek appropriate advice. Referral to mental health and/or pain medicine specialist is recommended for patients with:101

  • mental and behavioural health disorders
  • SUDs
  • uncontrolled or severe psychiatric disorders
  • suicidal ideation or actions
  • significant medical comorbidities
  • adverse behavioural or cognitive effects.

There is an issue with accessibility to services in many areas, but this should not be a reason for lack of consultation.

Multidisciplinary care and maximal use of non-pharmacological and non-opioid therapies to address analgesia should be undertaken. Optimise therapies to address mental health conditions. Consider low ceiling doses for opioids and naloxone therapy.

Stratification of patients into high-risk, medium-risk, and low-risk categories is important prior to consideration of initiation and maintenance of opioid therapy. Risk stratification is justified in all patients who are likely to undergo long-term opioid therapy due to the significant proportion of potential harm, misuse and abuse.

In practice

Risk stratification should be considered as part of a clinical evaluation for opioid therapy. Stratifications aids in decisions regarding risk modification therapies (eg naloxone) and referral.

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