Efficacy and Safety of Single Botulinum Toxin Type A
(Botox®) Injection for Relief of Upper Trapezius
Myofascial Trigger Point: A Randomized,
Double-Blind, Placebo-Controlled Study
Photsawee Kwanchuay MD, MSc, MBA*, Thavatchai Petchnumsin MD*,
Pichet Yiemsiri MD*, Nakkamol Pasuk MA*,
Wannarat Srikanok RN, EdD**, Chanasak Hathaiareerug MD*
Affiliation :
* Department of Physical Medicine and Rehabilitation, Pramongkutklao Hospital and College of Medicine, Bangkok, Thailand
** The Royal Thai Army Nursing College, Bangkok, Thailand
Objective : Botulinum toxin injection has been applied for pain relief in various chronic pain syndromes. Recently, systematic
review studies reported inconclusive effects of Botulinum toxin in myofascial pain management. The present study aimed
to demonstrate the efficacy and safety of Botulinum toxin type A (BTxA) (Botox®) injection for pain reduction in myofascial
trigger point (MTrP) of the upper trapezius muscle.
Material and Method: Thirty-three patients with 48 MTrP on the upper trapezius muscles over three months with moderate
to severe pain intensity diagnosed at physical medicine and rehabilitation outpatient department were recruited between
December 2011 and March 2012. Eligible patients were blinded and randomly injected with single 0.2 ml (20 IU) of BTxA
for 24 MTrP and 0.2 ml of 0.9% NaCl solution for 24 MTrP at the most tender trigger point on the upper trapezius muscle.
All patients were advised for stretching exercise and ergonomic adaptation throughout the study. At 3- and 6-week after
injections, visual analogue scale (VAS), the pressure pain threshold (PPT), and reported adverse effects were measured.
Results : Both BTxA and control groups demonstrated statistically significant differences in VAS reduction and increased
PPT after 3 weeks and 6 weeks compared with before treatment. There were no statistically significant differences in VAS
reduction from baseline between the two groups at 3- and 6-week after treatment. A statistically significant difference in
improvement of PPT from baseline and 6-week after BTxA injection compared with 0.9% NaCl group was shown (1.00.9
and 0.50.7, p = 0.036). There was mild degree side-effects that spontaneous resolved within one week in both groups
without significant difference in percentage. No severe adverse effects were reported during the study.
Conclusion : The efficacy in VAS reduction of a single 20 IU of Botulinum toxin type A (Botox®) injection was not different
from 0.9% NaCl for myofascial trigger point at the upper trapezius muscle. However, Botulinum toxin type A (Botox®)
showed statistically significant more increased in pressure pain threshold at 6-week after injection without severe adverse
effects.
Keywords : Myofascial trigger point, Botulinum toxin, Upper trapezius muscle
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