Lidocaine patch useful for knee OA and low back pain?

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Rheumawire

May 12, 2004

Lidocaine patch useful for knee OA and low back pain?

Vancouver, BC - Two open-label studies have suggested that the lidocaine

patch (Lidoderm®, Endo Pharmaceuticals) may be useful in the treatment

of knee osteoarthritis (OA) and chronic low back pain [1,2]. Both

studies were sponsored by the manufacturer and have led to further

trials with the product in both new indications, this time with placebo

controls. The patch (containing 5% lidocaine) is currently approved in

the US only for the relief of pain associated with postherpetic

neuralgia (PHN).

Results from the open-label studies were presented here last week at the

joint meeting of the American Pain Society and the Canadian Pain

Society. Principal investigator of the osteoarthritis study, Dr Chris

Codding (Health Research Institute, Oklahoma City, OK), says the data

suggest that the lidocaine patch " may reduce common pain qualities

associated with osteoarthritis " and that it could be a useful treatment

for this patient population. Codding tells rheumawire that she has

already started to use the product off-label in some of her

osteoarthritis patients, specifically those who cannot tolerate oral

therapies such as nonsteroidal anti-inflammatory drugs (NSAIDs).

One of the investigators involved in the low-back-pain study, Dr ph

Gimbel (Arizona Research Center, Phoenix), describes the lidocaine patch

as an " innovative treatment for postherpetic neuralgia " and says he is

" encouraged " by the new studies. " We are constantly looking for new and

innovative ways to help patients relieve chronic pain, " he adds.

The OA study involved 100 patients with moderate to severe

osteoarthritis who were already using some medication. Patients who were

taking drugs regularly (eg, NSAIDs daily) were asked to continue with

their usual regime and use the patch as an add-on therapy (n=88), but

those who were taking medication on an " as-needed " basis were asked to

refrain and use the lidocaine patch as monotherapy (n=12).

Participants were issued lidocaine patches once every 24 hoursthey could

take several patches to cover the whole painful area but had to be

consistent in how many patches they used each day. The study lasted for

2 weeks, and efficacy was assessed by patient questionnaires using the

Neuropathic Pain Scale (NPS). This assessment tool measures 10 distinct

components of pain (including sharp, deep, dull, and surface pain as

well as overall intensity and overall unpleasantness).

All of the patients, whether using the lidocaine patch as monotherapy or

as add-on therapy, reported a significant improvement in all 10

individual pain qualities (p<0.05), Codding and colleagues told the

meeting. The patches were well tolerated, they said. There were no

reports of treatment-related adverse events in the monotherapy group,

and all the treatment-related adverse effects in the add-on group were

rated as mild to moderate (the events included headache, dermatitis,

nausea, and elevated blood pressure).

" Although further placebo-controlled studies need to confirm this

preliminary data, the lidocaine patch may be a useful treatment for this

population, " says Codding. " Since the product has a low risk of systemic

side effects, it may also be better tolerated than many oral therapies. "

The low-back-pain study lasted for 6 weeks and involved 71 patients with

back pain, who were stratified into 3 groups depending on the duration

of their back pain: <3 months (n=11), between 3 and 12 months (n=17),

and >12 months (n=43). Again, patients applied the lidocaine patches

every 24 hours, up to a maximum of 4 patches.

At 6 weeks, the total patient population also showed a significant

improvement in all 4 NPS composite measures (p<0.001). Patients in all

the groups reported a significant improvement in many of the individual

pain qualities on the NPS (p<0.001), except for the qualities of cold,

sensitive, and itchy, which were rated as mild at baseline. However, the

pain qualities that were affected most differed between the 3 groups:

patients with a short duration of back pain noted significant

improvements in sharp, dull, deep, and surface pain as well as overall

intensity and unpleasantness, whereas those with the longest duration of

back pain noted significant improvement in all the qualities of pain,

except for cold. This suggests that the characteristics of a patient's

pain qualities may change over time in low back pain, the researchers

suggested.

The most commonly reported adverse events were dermal in natureeg,

dermatitis, papules, and pruritis (n=6, 8.5% overall). Other events

included dizziness (n=3) and nausea (n=2) and were generally moderate.

Slight edema occurred in 1 patient, and well-defined erythema developed

in 3 patients. In total, 6 of the 71 patients (8.5%) discontinued

because of adverse events.

Zosia Chustecka

Sources

1. Gammaitoni A, F. Burch F, Codding C, et al. Presentation: Lidocaine

patch 5% effectively treats pain qualities in osteoarthritis: results of

a 2-week, prospective, open-label trial. Vancouver, BC: American Pain

Society and the Canadian Pain Society: 2nd joint scientific meeting; May

6-9, 2004:Poster 897.

2. Gammaitoni A, Gimbel J, Hale M, et al. Presentation: Lidocaine patch

5% effectively treats neuropathic pain qualities in low-back pain:

results of a 6-week, prospective, open-label trial. Vancouver, BC:

American Pain Society and the Canadian Pain Society: 2nd joint

scientific meeting; May 6-9, 2004:Poster 896.

I'll tell you where to go!

Mayo Clinic in Rochester

http://www.mayoclinic.org/rochester

s Hopkins Medicine

http://www.hopkinsmedicine.org