This Page Intentionally Left Blank - Int Medical

264 Neck and back pain – mechanical strain
extrapolated from their effectiveness in managing the closely related syndrome
of refractory back pain. 5
Muscle relaxants are often prescribed for sprains and strains of the neck
and back. Although agents in this class have sedative properties, they provide
no direct skeletal muscle relaxation at the doses commonly used for MSSP. 6
In fact, the sedative effects of skeletal muscle relaxants are probably responsible
for their efficacy (compared with placebo) as monotherapy for improving
MSSP pain. 7,8 Clinicians who use muscle relaxants to treat MSSP should
be aware that the likely mediator of symptom relief is not muscular at all, but
rather the drugs’ sedative actions.
Despite anecdotal suggestions of efficacy, and prevalent use in everyday
acute care practice, the dual-therapy approach combining muscle relaxants
and NSAIDs lacks robust evidentiary support. If widely held beliefs in this
regimen’s utility are indeed accurate, efficacy could be a placebo effect or a
salutary combination of sedation with analgesia. There are no RCT data
finding benefit of dual therapy over single-agent use of either NSAIDs or
muscle relaxants. 9,10
Commonly used muscle relaxants include cyclobenzaprine (5–10 mg
PO TID), orphenadrine (100 mg PO BID), metaxolone (800 mg PO
TID–QID), methocarbamol (1000 mg PO QID), carisoprodol (350 mg PO
TID–QID), and chlorzoxazone (250–500 mg PO TID–QID). While there are
no data comparing effectiveness of muscle relaxants for MSSP, these agents
differ with respect to chemical class, pharmacology, and relative propensity
to cause certain adverse effects. 11 For example, cyclobenzaprine and orphenadrine
are associated with anticholinergic side effects; chlorzoxazone
(rarely) causes hepatic toxicity, and carisoprodol has abuse potential. 12,13 As
one of the more commonly prescribed skeletal muscle relaxants, cyclobenzaprine
has the advantage of familiarity and is probably as good as any other
muscle relaxant; its sedative effects can be minimized by using a lower dose
(5 mg PO TID). 3
Potential for side effects (e.g. sedation) and lack of evidence of improved
pain relief over that attained with NSAID monotherapy relegates muscle
relaxants to second-line use. These agents are recommended only for
patients in whom they have been effective in the past, or in those who fail