Baclofen :: Multiple pharmacies comparison.

ABSTRACT
Intrathecal baclofen (ITB) is a relatively new treatment approach that may be useful for treating spasticity in patients with chronic stroke. In this paper, we examine ITB treatment of spastieity caused by stroke and the implications for physical therapy management. We also present ITB pharmacology, side effects, and the screening procedure.
INTRODUCTION

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In the United States, stroke is the third most common cause of disability and death after heart disease and cancer.1,2 Every year there are approximately 700,000 new cases of stroke and about one-third of patients die from the incident.1,3,4 Stroke is defined as acute neurological dysfunction of vascular origin that lasts more than 24 hours and has signs and symptoms corresponding to the involvement of focal areas of the brain.5 Almost 75% of patients with stroke have motor impairments, resulting in disability, such as impaired transfer, pain, contractures, gait abnormalities, sleep disorders, and the inability to perform activities of daily living, all of which compromise safety.6-12
Spasticity develops in nearly 65% of patients with stroke and while it is a major cause of disability, in some cases it is beneficial in helping the patient stand or ambulate.13,14 Spasticity is assigned different meanings. However, a frequently cited definition proposed by Lance15 describes spasticity as a motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes (muscle tone) with exaggerated tendon jerks, resulting from hyperexcitability of the stretch reflexes. It is one component of the upper motoneuron syndrome and may interfere with voluntary motor function in patients with residual muscle power.15,16
Current management of spasticity includes passive stretching, strengthening, physical modalities, splinting, biofeedback, cold, and electrical stimulation. These treatments have limited results.17,18 Pharmacological management of spasticity includes peripherally acting drugs such as botulinum toxin and dantrolene sodium or centrally acting drugs such as oral baclofen, diazepam, tizanidine, and clonidine.9-11,19,20 When physical, occupational, and medical management of spasticity fails, the patient with stroke may elect surgical management, such as intrathecal baclofen.21,22
Continuous intrathecal baclofen (ITB) was introduced 2 decades ago to treat spasticity, and its beneficial effect has been well documented.23-26 Baclofen is infused via a subcutaneously placed programmable pump.23,27 The pump is implanted in the abdominal wall (Figure 1) with a catheter threaded into the subarachnoid space, at L1-2 and subsequently threaded as high as T-6. Intrathecal baclofen has been reported in the management of spasticity in stroke,28,29 cerebral palsy,30 spinal cord injury,31,32 and amyotrophic lateral sclerosis.33-35 Francisco describes the perfect ITB candidate as one who has had “a stroke with severe, functionally limiting, multijoint spastic hypertonia and predominant involvement of the lower limbs, and one who cannot either tolerate the effects of oral drugs or respond to adequate doses of other therapies.”36
The reminder of this paper will examine ITB treatment of spasticity caused by stroke and the implications for physical therapy management. Spasticity management in spinal cord,37 multiple sclerosis,38 and cerebral palsy3′9 are reviewed elsewhere and are beyond the scope of this review.
BACLOFEN AND ITB PHARMACOLOGY
Baclofen (Lioresal) is an agonist at the gamma-aminobutyric acid (GABA)-B receptor subtype with little or no action at the GABA-A or GABA-C subtypes.40-44 Baclofen acts predominately at the spinal level and attenuates motor output, especially on high frequency, and reflexively mediated muscle activity (ie, spastic motor activity). It inhibits both monosynaptic and polysynaptic reflexes possibly by decreasing excitatory neurotransmitter release from primary afferent terminals, although actions at supraspinal sites may also occur and contribute to its clinical effect.45
One advantage of intrathecal baclofen is that it allows effective cerebrospinal fluid (CSF) concentrations to be achieved with resultant plasma concentrations of 100 times less than those seen with oral administration.23,46 In addition the programmable pump used to deliver the baclofen allows for numerous dose adjustments that are needed during treatment. However, adverse effects of general CNS depression may still appear as indicated by sedation with tolerance, somnolence, ataxia, and respiratory and cardiovascular depression.
Selecting an ITB Candidate and Screening Protocol
According to Meythaler and colleagues,28,29 the ideal candidate is a patient with stroke who presents with severe chronic spasticity in the lower or upper extremities rated at 3 or 4 on the Ashworth47 scale (5-point scale) and an average of at least 2 on the Penn23 Spasm 4-point scale in the affected extremity, as well as having had intolerable CNS side effects with oral antispasticity agents.28,29 Specifically, the patients who use extensor tone to stand and have trunk control in unsupported bench sitting will demonstrate improvement in function with ITB therapy.48 Whereas those patients who move with hip and knee flexion and ankle dorsiflexion will not show the same success. However the appropriateness of the continuous ITB pump has not been established for patients’ with seizures, ventriculoperitoneal shunts, or implantable, programmable medical devices (eg, spinal cord stimulators, pacemakers).