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Three Part Question

In [patients with chronic lower back pain] is [topical lidocaine patch better than placebo] at [reducing pain and improving functionality]?

Clinical Scenario

A 56yr old man with a chronic history of intermittent low back pain presents to your ED. It hasn’t been right since a motorcycle injury ten years ago and when his pain is exacerbated, as it has been this time for three weeks now, it affects his gait and daily functioning, with stiffness, difficulty standing from sitting, pain on movement, worse on rising. No red flags in history or exam. He is on co-codamol and difene as per his GP, and has tried agents for neuropathic pain previously but felt they were ineffective. No red flags in history or exam. Your consultant advises you to give him a prescription for a lidocaine patch and to get him out the door. You know that the patch is only licensed for post-herpetic neuralgia and wonder if you are just wasting the patient’s time and money with this measure.

Search Strategy

Ovid Medline 1990 to week 1 Feb 2015:
exp Low Back Pain/ or exp Back Injuries/ or exp Back/ or exp Back Pain/ or exp Back Muscles/ or back pain$.mp
AND
lidocaine$.mp. or exp Lidocaine/
AND
exp Administration, Topical/ or topical$.mp. OR patch$.mp. or exp Transdermal Patch/
limit: English language

Search Outcome

29 papers found – 5 relevant for critical appraisal.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Galer et al Nov 2004 USA	Adults in 8 centres with non-radicular LBP* rated mod-severe on the NPS* - on standard pain regimes. Number of patients enrolled not given – 71 included in analyses	6-week prospective, multicentre, open-label, nonrandomized CEBM Level 2b	Neuropathic pain scale change from baseline at week 2 and 6.	6 weeks of treatment with lidocaine patch 5% significantly improved all 4 NPS composite measures at both Week 2 and Week 6 ( p < 0.001). 6 patients discontinued due to AEs*	No calculation for sample size offered. Recruitment methods not elaborated. No control group. No placebo group. No blinding of statistical assessment. Risk of Hawthorne effect.
Argoff et al Nov 2004 USA	77 adults recruited at 7 sites with a mix of post-herpetic neuralgia, chronic low back pain (n=28), and diabetic neuropathy with a daily pain scale of at least 4 already on a treatment regime including gabapentin. Excluded – recent steroid/LA/botox injections.	2-week prospective, multicentre, open-label, nonrandomized CEBM Level 2b	NPS change from baseline at week 2	3 patients discontinued due to AEs. Intervention significantly improved all composite measures for LBP (p ≤ 0.005)	Only 28 patients in LBP group. No control, placebo, randomisation, blinding of statistical assessment.
Baliki et al Oct 2008 USA	19 patients, 11 with chronic back pain (CBP)	Very small cohort study without clear selection criteria, CEBM 4	Change in visual analogue scale, short-form McGill Pain Questionnaire	Data only on 13 patients (8 with CBP). CBP patients exhibited a significant decrease in pain after 2 weeks of topical Lidocaine treatment as measured by VAS (p < 0.01) and average pain during scan (p<0.05)	Very small study. Manner of recruitment and rationale for sample size not given. Pain scores taken in MRI scanner, as primary outcome sought is correlation of scores with fMRI – not generalisable.
Hashmi et al April 2012 USA	38 chronic back pain(CBP) patients recruited via newspaper ads – 1 dropout for technical data failure, 7 ’unspecified’ drop-outs 15 patients in control group. The 30 analysed study patients were on no other analgesics during the study	Small RCT, double-blind, placebo-controlled CEBM 2b (see weaknesses)	McGill pain questionnaire (MPQ), neuropathic pain scale (NPS), Beck depression inventory (BDI) and Beck anxiety inventory (BAI)	50% patients in both the Lidocaine and placebo arms reported a greater than 50% decrease in pain. However the other half showed a negligible decrease – strong inter-individual variability. Significant decrease in back pain magnitude with treatment duration (F 2,89=7.8, p<0.001) B-E). The effects of Lidocaine patch on CBP pain could not be distinguished from that of placebo either by pain scores or brain activity on fMRI.	Underpowered – authors acknowledge that 536 subjects would need to be recruited according to calculations. Only 30 patients and 7 ‘unspecified’ dropouts. Authors acknowledge that placebo effect may be enhanced by the setting, e.g., being enrolled in an attentive pain trial with fMRI. Strong self-selection with patients having being recruited via newspaper advertisements. The fact that these patients were on no other analgesics during the study infers that they are not the typical pain clinic patients recruited in previous studies on this topic.
White et al Dec 2003 USA	107 adults (mean 56yo – LBP group mean 51yo) with a mix of post-herpetic neuralgia, chronic low back pain (n=47, 44%), and diabetic neuropathy with a daily pain scale of at least 4 already on a treatment regime including gabapentin. Excluded – recent steroid/LA/botox injections, additional chronic pain issues, change in exercise regime, patients with possible secondary gain (social security benefits, litigation)	2-week prospective, multicentre, open-label, nonrandomized pilot study CEBM Level 2b	Brief pain inventory(BPI) – change in pain at baseline over 2 week period, and also change in general activity, mood, walking ability, normal work, relationships with others, sleep, and enjoyment of life	5 patients discontinued due to AEs from patch. BPI scores significantly lower at Week 2 compared with baseline for all groups combined (P < 0.0001) Statistically significant improvement from baseline observed at week 2 for each BPI measure of QOL for all patients combined	No placebo group, control group, or blinding for statistical assessment. Short duration. No rationale/ calculation for sample size. Risk of Hawthorne effect. Although it is assumed the patients were recruited from tertiary centres this is not stated in the paper.

Comment(s)

Chronic back pain is both common and refractory to treatment, with patients at risk of significant side-effect and polypharmacy from chronic use of paracetamol, NSAIDs, opioids and neuropathic agents. Although only licensed as 3rd line therapy for post-herpetic neuralgia, Versatis 5% lidocaine patch has a low side effect profile and is frequently prescribed off label in EDs as an adjunct in chronic low back pain, based on multiple open label trials showing a significant reduction in pain scores. These papers are non-randomised, not blinded, and all have a strong risk of providing the patients the additional comforts of being involved in trials that give highly attentive care and the psychological reminder via the constant sensation of the patch that they are being ‘treated’, inflating the analgesic effect. The one small-scale RCT performed to date found a significant effect in some patients from both lidocaine and placebo. However, there is strong inter-individual variability with some patients getting relief from neither. No difference could be appreciated between placebo and active ingredient and as such it is implied that the success seen in the open-label trials could be equally achieved with placebo. Of note these patients were recruited via newspaper advertisements; such a strong self-selection bias could indicate susceptibility to placebo; further these patients were not on other analgesics during the study, in stark contrast to the other studies available, where lidocaine patch was used as adjunct.

Clinical Bottom Line

Although Lidocaine 5% patch in chronic lower back pain appears to give significant relief to a substantial proportion of individuals, there is evidence to suggest that any analgesic effects reported are equivalent to placebo, with no trials to prove superiority. Larger RCTs with a statistically acceptable power are needed to establish any effect and justify the current costs associated with use.

References

1. Galer, B., et al. Use of the lidocaine patch 5% in reducing intensity of various pain qualities reported by patients with low-back pain. Current Medical Research and Opinion. Vol. 20, Supp. 2, 2004, S5–S12
2. Argoff et al. Effectiveness of the lidocaine patch 5% on pain qualities in three chronic pain states: assessment with the Neuropathic Pain Scale. Current Medical Research and Opinion. Vol. 20, Supp. 2, 2004, S21–S28
3. Baliki et al A preliminary fMRI study of analgesic treatment in chronic back pain and knee osteoarthritis. Molecular Pain Vol. 4 No. 1
4. Hashmi, J, et al Lidocaine patch (5%) is no more potent than placebo in treating Chronic back pain when tested in a randomised double blind placebo controlled brain imaging study. Molecular Pain Vol 8. No. 29
5. White, W., et al Lidocaine Patch 5% With Systemic Analgesics Such as Gabapentin: A Rational Polypharmacy Approach for the Treatment of Chronic Pain. Pain Medicine Vol. 4, No. 4