The painful truth about lidocaine patches

Pain is one sensation we’ve all shared, yet our experience of it is solitary. As Descartes didn’t say, “I hurt therefore I’m alone”.

Pain was defined in 1979 by the International Association for the Study of Pain as "an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage", and is a common reason for seeing a doctor. Yet when historian Prof Roy Porter (1946-2002) sought medical views on pain down the centuries, he "consulted the pick of the reference books, Roderick McGrew's Encyclopaedia of Medical History (1985). No entry was to be found . . ."

"Pain," concluded Prof Porter in the London Review of Books (November 2nd, 1995), "appears to have become an embarrassment".

Embarrassment or not, pain is prevalent and presents a significant public health problem in Ireland. For example, a study from the Centre for Pain Research at NUI Galway found a 35 per cent prevalence rate of chronic pain among adults. "The cost of chronic pain per patient was €5,665 per year – extrapolated to €5.34 billion or 2.86 per cent of Gross Domestic Product per year."

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Arthritis is the single biggest cause of disability in Ireland, affecting almost one million people and a 2015 report in the European Journal of Public Health stated that the overall prevalence of osteoarthritis (OA) in Ireland was 12.9 per cent (women, 17.3 per cent; men, 9.4 per cent).

According to the Health Service ExecutiveHSE, the medical treatment of OA includes paracetamol; opioids such as codeine; non-steroidal anti-inflammatory drugs; capsaicin cream; and injections into the affected joint(s).

However, one treatment not recommended for OA is the application of topical lidocaine patches (TLPs), with the HSE stating that TLPs are licensed "ONLY in the treatment of neuropathic pain associated with post-herpetic neuralgia (PHN) and should be prescribed ONLY for this indication" and that "patients prescribed lidocaine 5 per cent plaster for unlicensed indications should be reviewed and treatment discontinued".

No clinical evidence

There is no clinical evidence supporting the use of TLPs in the treatment of OA – or any other indication besides PHN. Yet only 5 to 10 per cent of patients on TLPs have PHN; the commonest indication for prescribing TLPs in Ireland is OA; and current national expenditure on TLPs exceeds €30 million annually. These observations are cited by the authors of a recent major study, published in the Irish Journal of Medical Science.

They note that recent changes in national health policy limit the reimbursement of TLPs on the Drug Payment Scheme to the treatment of PHN and in exceptional circumstances, but “this legislation affects only outpatient prescriptions, and there is currently no limitation on inpatient prescribing”.

Senior author Mr James Sproule of Tallaght University Hospital's Department of Orthopaedics helped devise the study, which had two aims. First, to determine how many patients at Tallaght University Hospital received TLP therapy and describe the associated prescribing patterns. Second, "to determine whether inappropriate prescribing practices could be reduced by education sessions delivered by peers".

When 304 inpatients were audited in August 2017, 52 (17 per cent) were on TLPs, mainly for musculoskeletal pain, and – significantly – none had a history of PHN. Following prescriber education to interns – junior doctors – on the proper use of TLPs, a re-audit of 300 inpatients in February 2018 revealed that the number of inpatients on TLPs – most of whom had musculoskeletal pain – had fallen to 18 (6 per cent): “The potential savings between the study periods are therefore €31,418-€93,840 in total and €23,100-€69,000 in musculoskeletal patients.”

So, should all medical grades, including consultants, be educated on the appropriate prescribing of TLPs? The study’s corresponding author Dr Rosie McColgan said: “Most doctors in this country move hospital or department every six months, so delivering regular education on the topic would be a difficult task.”

However, she pointed out that although no clinical evidence supports the use of TLP in osteoarthritis, some pain specialists believe they may have a role in the management of chronic pain conditions: “If the prescription of TLP was limited to anaesthetic and pain consultants only, this should result in a dramatic reduction in inappropriate hospital prescribing and these funds could be redirected to evidence-based interventions for osteoarthritis such as total hip or knee replacements.

“It is not uncommon,” she added, “to place limitations on the prescription of certain medications to specialist departments, eg certain antibiotics need approval from microbiology or infectious diseases.”

‘Unnecessary distress’

Another observation made by the researchers is that those receiving TLPs as inpatients “will be unable to avail of it on the current Drug Payment Scheme upon discharge. The practice of commencing TLP in patients who will be unable to access them in the community causes unnecessary distress to patients.”

Commenting further on this aspect, Dr McColgan said limiting the prescription of TLPs to pain and anaesthetic specialties should reduce the discrepancy between inpatient and outpatient settings: “While recent policy changes limiting the off-label prescription of TLPs in the outpatient setting are a positive measure, these changes should be introduced across the entire healthcare system.”

Dr McColgan reiterated that current evidence does not support the use of TLPs for the management of OA-associated pain: “International evidence-based guidelines such as the UK’s National Institute for Health and Care Excellence, the American Academy of Orthopaedics and the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis do not advocate its use in OA. Expenditure levels on TLP in this country are excessive,” she said.

“These funds, she added, “are being diverted away from tackling important issues in our health system, such as reducing the waiting list for major joint replacement surgery, an intervention that is proven to work.”

With no evidence supporting the use of TLPs to treat OA-associated pain, it seems that this study has exposed a practice that raises serious financial implications for the health service.