INTRODUCTION
Skeletal muscle relaxants (SMRs) are a heterogeneous
group of pharmacologic agents with US Food and
Drug Administration–labeled indications for discomfort
associated with acute, painful musculoskeletal conditions such as low back pain.1 While few data
exist to support the clinical superiority of one SMR
over another for such indications2 and practice guidelines
with respect to optimal dosing and/or duration
schedules for these drugs are lacking,3 they are commonly
prescribed in the United States for low back
and neck pain, often as adjuncts to NSAIDs, acetaminophen,
or opioids.4,5
Unlike other SMRs, concern regarding carisoprodol*
abuse potential has increased over the years.6
Since the 1990s, numerous published case reports of
drug-seeking behavior and utilization in combination
with opioids have suggested this potential.7–12 In addition,
carisoprodol has been reportedly used to enhance
or modify the effects of other drugs, including opioids,
benzodiazepines, cocaine, and ethanol.13 Because carisoprodol
is metabolized to meprobamate6—a controlled
substance with recognized abuse potential—
some states within the United States have enacted legislation
to likewise designate carisoprodol as a controlled
substance, despite the absence of such restriction at the
federal level.14 Despite this, many clinicians remain unaware
of the abuse potential of carisoprodol.15
As in most states, carisoprodol is currently unscheduled
in Idaho; however, recent prior authorization
(PA) criteria were enacted by the Idaho Medicaid
Pharmacy Program, making the drug nonpreferred
and resulting in loss of coverage of carisoprodol for
Idaho Medicaid clients.16 In response to this decision,
we undertook a retrospective review of claims data to
identify and characterize potential indicators of abuse
in long-term users of carisoprodol and to determine
any continued use of the drug by former long-term
users following PA implementation