Paracetamol
Although paracetamol is the first-line analgesic, particularly for nociceptive pain, its efficacy is modest. Evidence supporting its long-term use in chronic non-cancer pain is limited, but it remains in multiple guidelines as the first-line drug, especially for older people, given that other options are often contraindicated.19 Regular paracetamol for up to three months provided mean pain relief of 0.3 points (on a 10-point pain scale, 95% confidence interval –0.6 to –0.1 points) in a systematic review of five trials involving 1686 patients with knee or hip osteoarthritis. Its efficacy in other painful conditions is uncertain.20
In view of an increased risk of hepatotoxicity in older adults, sometimes at therapeutic doses,21,22 and emerging evidence of a relative lack of efficacy of paracetamol, the benefits of long-term use need to be re-evaluated. Co-administration of paracetamol with other analgesics is common, however there is a lack of data on the efficacy of combination therapy in chronic non-cancer pain. A Canadian cohort study highlighted the potential additional risk of gastrointestinal bleeding among older people when paracetamol and non-steroidal anti-inflammatory drugs (NSAIDs) are co-administered as compared to NSAIDs alone.23 Prescription of paracetamol for a limited duration is recommended with a review of the response to therapy. Discontinue therapy if there is no response.24,25
Non-steroidal anti-inflammatory drugs
The gastrointestinal, renal and cardiovascular adverse effects of NSAIDs are well known. Upper gastrointestinal complications occur in 1% of older patients treated for 3–6 months and in 2–4% of those treated for one year. This risk continues with longer durations of use.13 The efficacy of NSAIDs for knee osteoarthritis diminished and lost clinical significance by eight weeks of therapy.26 International guideline recommendations do not exclude using NSAIDs in very old people for some musculoskeletal pains with an inflammatory component (e.g. osteoarthritis).27 The harm and benefit of a short course of therapy should be evaluated carefully and discussed with the patient. Co-administration with a proton pump inhibitor is advised for patients at risk of gastrointestinal complications, such as a history of complicated or uncomplicated ulcers, concomitant use of certain drugs (anticoagulants or antiplatelet drugs, including low-dose aspirin), and the presence of Helicobacter pylori infection.28
Topical NSAIDs may be a safer alternative for localised pain. They are the preferred treatment for pain associated with osteoarthritis in the hands and knees.24,25,29 The majority of reports on the safety of topical NSAIDs in older adults are limited by a short period of usage (mostly up to 12 weeks)30,31 and high drop-out rates secondary to lack of efficacy or localised adverse effects.
Adjuvant drugs
In chronic non-cancer pain with a neuropathic component, there is evidence supporting the use of adjuvant drugs, such as gabapentinoids, tricyclic antidepressants and selective serotonin noradrenaline reuptake inhibitors. These drugs have been recommended as first-line therapy based on a meta-analysis of moderate- to high-quality trials in post-herpetic neuralgia and diabetic neuropathy. The number of patients who needed to be treated for one to benefit (NNT) in the general population was 3.6–7.7 over a period of 12 weeks or less.32 However, these trials did not specifically involve older people, so caution is advised when prescribing these drugs in frail older patients, and tricyclic antidepressants are not advisable given the high risk of adverse effects.33
Topical capsaicin and lidocaine (lignocaine) patches can be considered as second-line drugs for localised neuropathic pain, however their efficacy is limited (NNT = 10.6 for capsaicin 8% patch, undetermined for lidocaine (lignocaine) patch).32 The associated cost also prohibits ongoing use in some patients.
Opioids
Current guidelines do not support the long-term use of opioids in chronic non-cancer pain. There is a lack of evidence for long-term efficacy, but significant evidence of harm.10,34 A recent meta-analysis of 30 studies associated opioid use with falls, fall injuries and fractures in older people.35 Opioids are therefore not recommended other than in exceptional circumstances when other treatments have failed and the pain has been shown to be opioid-responsive.10 High doses and co-administration with benzodiazepines should particularly be avoided in frail older people given the additional risk of harm.
Data on the use of newer opioids, such as tapentadol, for chronic non-cancer pain are limited. A Cochrane review of four studies in a general adult population showed tapentadol had a relatively small benefit in treating chronic musculoskeletal pain.36 Data on long-term use in older people are scarce. A sponsored report on the tolerability of sustained-release tapentadol in patients aged 75 years or older showed a more favourable adverse-effect profile than conventional opioids, yet almost a third of patients discontinued by three weeks of usage due to an adverse event, with nausea, constipation, dizziness, and somnolence being the most common.37 Similarly, the efficacy of buprenorphine in treating chronic non-cancer pain is poor.38 It is poorly tolerated due to neurological and psychiatric adverse effects in frail older nursing home patients with dementia, especially those using antidepressants.39 These issues are often not highlighted in clinical trials in which the frail older populations are often excluded.
Deprescribing
Regular review of the drug treatment of chronic non-cancer pain is recommended. Assess the effectiveness of analgesia using the ‘5As’ principle:10
- analgesia
- activity
- affect
- adverse effects
- aberrant behaviours, such as unapproved increase of dose or use of the drug to treat other symptoms, or seeking additional prescriptions from other prescribers.
Consider deprescribing if there has been no meaningful improvement in function or pain, when the risk of harm outweighs benefit, or there are aberrant behaviours.40 Starting a conversation about tapering ineffective drugs with patients can be challenging, especially if they believe the drugs are helpful. Adopt a shared decision-making and tailored approach and involve carers when appropriate.
NPS MedicineWise has developed several resources to assist GPs effectively communicate with patients about managing chronic non-cancer pain.41,42 While these resources were developed around opioid treatment, the same strategy can be used for deprescribing other analgesics. Written information for patients can also aid the discussion of alternative management strategies.43,44
Doses should be reduced slowly in patients who have taken opioids or adjuvant drugs for longer than three months (Table 3).10,45,46 Consider a faster dose reduction, with specialist input, when deprescribing for intolerable adverse effects or opioid misuse.