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Nitroglycerin patches for shoulder pain

Continuing the shoulder pain theme, Bandolier came across an interesting RCT from a group in Santander [1] (though see the one-report reflex in Bandolier 27 ). They assembled some biologically plausible evidence for nitroglycerin being effective in inflammation and vasodilatation though a nitric oxide mechanism. They claim to have shown that nitroglycerin patches (NTG) were effective in thrombophlebitis syndrome.

Study

Patients had shoulder pain of less than 7 days duration, with tenderness in the supraspinatus region and limited motion on movement. Randomisation was between a 5 mg NTG transdermal patch and an identical placebo applied in the most painful area. A new patch was applied for each of three days.

Outcomes

At the start, and after 24 and 48 hours, pain intensity was measured on a 10-point scale, together with the duration of pain in the previous 24 hours and restriction of joint movement.

Results

By 48 hours there were significant (and large) improvements in pain, its duration, and improvement in shoulder movement.

At 48 hours, pain intensity was 2 or less (out of 10) in 9/10 patients given NTG compared with 0/10 given placebo. There was no reduction in pain intensity in placebo patients. The NNT for pain intensity of 2 or less for NTG compared with placebo was 1.1 (0.9 - 1.4).

At 48 hours, duration of pain was 1 hour or less per day in 9/10 patients given NTG compared with 0/10 given placebo. In placebo patients the duration of pain was between 1 and 12 hours. The NNT for pain duration of 1 hour or less per day for NTG compared with placebo was 1.1 (0.9 - 1.4).

At 48 hours, joint motion was unrestricted in 8/10 patients given NTG compared with 0/10 given placebo. In placebo patients joint motion was restricted by 25%-50%. The NNT for unrestricted joint motion for NTG compared with placebo was 1.3 (1.0 - 1.8).

Comment (credibility strain)

These results look great, don't they. Yes, it was a randomised trial, with double blinding. But it was only 10 patients per group, and the random play of chance may be bigger than we think with these small numbers. Statistical significance does not transfer directly into clinical practice.

Given that there is a sort of Bayesian drift here, with some biological foundation and clinically plausible results, what is needed is a larger, pragmatic trial in primary care.

Reference:

  1. JR Berrazueta, A Losada, J Poveda et al. Successful treatment of shoulder pain syndrome due to supraspinatus tendinitis with transdermal nitroglycerin. A double blind study. Pain 1996 66: 63-7.



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