Baclofen in the elderly stroke patient its side-effects and pharmacokinetics

Transcutaneous spinal cord stimulation neuromodulates pre- and postsynaptic inhibition in the control of spinal spasticity

Aside from enabling voluntary control over paralyzed muscles, a key effect of spinal cord stimulation is the alleviation of spasticity. Dysfunction of spinal inhibitory circuits is considered a major cause of spasticity. These circuits are contacted by Ia muscle spindle afferents, which are also the primary targets of transcutaneous lumbar spinal cord stimulation (TSCS). We hypothesize that TSCS controls spasticity by transiently strengthening spinal inhibitory circuit function through their Ia-mediated activation. We show that 30 min of antispasticity TSCS improves activity in post- and presynaptic inhibitory circuits beyond the intervention in ten individuals with traumatic spinal cord injury to normative levels established in 20 neurologically intact individuals. These changes in circuit function correlate with improvements in muscle hypertonia, spasms, and clonus. Our study opens the black box of the carryover effects of antispasticity TSCS and underpins a causal role of deficient post- and presynaptic inhibitory circuits in spinal spasticity.

Pharmacological management of muscle spasticity

Background: Muscle spasticity is a neurologic disorder, which is considered one of the positive signs of upper motor neuron diseases. Spasticity is common after brain or spinal cord injury. Since spasticity results in tendon retraction, muscle weakness, pain, ankylosis, and disability in activities of daily living, treatment is warranted.Current Concepts: Spasticity is usually assessed using the Modified Ashworth Scale or Modified Tardieu Scale. It is treated with various methods, including physical therapy, occupational therapy, orthosis, medication, and surgery. Pharmacological management should be selected according to the location and severity of the symptom and includes oral medications, chemical nerve block, and intrathecal baclofen pump insertion. Oral medications include baclofen, benzodiazepine, dantrolene, and tizanidine. Chemoneurolysis of spasticity is done with botulinum toxin or a mixture of phenol and alcohol.Discussion and Conclusion: Since muscle spasticity affects motor function and activities of daily living, understanding of this symptom and choosing an optimal treatment are necessary. Pharmacologic treatments should be administered with caution especially with the side effects. Optimal treatment of spasticity will bring the best neurological outcome for the patients.

Recommendations from the EXTRIP workgroup on extracorporeal treatment for baclofen poisoning

Baclofen toxicity results from intentional self-poisoning ("acute baclofen poisoning") or accumulation of therapeutic dose in the setting of impaired kidney function. Standard care includes baclofen discontinuation, respiratory support and seizure treatment. Use of extracorporeal treatments (ECTRs) is controversial. To clarify this, a comprehensive review of the literature on the effect of ECTRs in baclofen toxicity was performed and recommendations following EXTRIP methods were formulated based on 43 studies. (1 comparative cohort, 1 aggregate results cohort, 1 pharmacokinetic modeling, and 40 patient reports or series). Toxicokinetic data were available for 20 patients. Baclofen's dialyzability is limited by a high endogenous clearance and a short half-life in patients with normal kidney function. The workgroup assessed baclofen as "Moderately dialyzable" by intermittent hemodialysis for patients with normal kidney function (quality of evidence C) and "Dialyzable" for patients with impaired kidney function (quality of evidence C). Clinical data were available for 25 patients with acute baclofen poisoning and 46 patients with toxicity from therapeutic baclofen in kidney impairment. No deaths or sequelae were reported. Mortality in historical controls was rare. No benefit of ECTR was identified in patients with acute baclofen poisoning. Indirect evidence suggests a benefit of ECTR in reducing the duration of toxic encephalopathy from therapeutic baclofen in kidney impairment. These potential benefits were balanced against added costs and harms related to the insertion of a catheter, the procedure itself, and the potential of baclofen withdrawal. Thus, the EXTRIP workgroup suggests against performing ECTR in addition to standard care for acute baclofen poisoning and suggests performing ECTR in toxicity from therapeutic baclofen in kidney impairment, especially in the presence of coma requiring mechanical ventilation.

Motor-learning based activities may improve functional ability in adults with severe cerebral palsy: A controlled pilot study

BACKGROUND

Cerebral palsy (CP) is a neurodevelopmental disturbance characterized by impaired control of movement. Function often decreases and 15% of adults are classified as severely affected (Gross Motor Function Classification Scale III-V). Little is known about interventions that aim to improve functional abilities in this population.

OBJECTIVE

To evaluate a 12-week intervention based on motor learning principles on functional ability in adults with severe CP.

METHODS

16 adults (36±10 years, GMFCS III-V) were enrolled and divided into an intervention group (Active group) and a standard care group (Control group). Primary outcome measure was Gross Motor Function Measure (GMFM-88). Secondary measures were neurological status. The Active group were measured at baseline, after the intervention and at one-month follow-up. The Control group were measured at baseline and after one month.

RESULTS

Analysis showed statistically significant improvement in GMFM-88 for the Active group from baseline to post assessment compared with the Control group (group difference: 5 points, SE 14.5, p = 0.008, CI: 1.2 to 8.7). Improvements were maintained at follow-up. Results from the neurological screening showed no clear tendencies.

CONCLUSIONS

The study provides support that activities based on motor learning principles may improve gross motor function in adults with severe CP.

A single, clinically relevant dose of the GABAB agonist baclofen impairs visuomotor learning

KEY POINTS

Baclofen is a GABA_B agonist prescribed as a treatment for spasticity in stroke, brain injury and multiple sclerosis patients, who are often undergoing concurrent motor rehabilitation. Decreasing GABAergic inhibition is a key feature of motor learning and so there is a possibility that GABA agonist drugs, such as baclofen, could impair these processes, potentially impacting rehabilitation. Here, we examined the effect of 10 mg of baclofen, in 20 young healthy individuals, and found that the drug impaired retention of visuomotor learning with no significant effect on motor sequence learning. Overall baclofen did not alter transcranial magnetic stimulation-measured GABA_B inhibition, although the change in GABA_B inhibition correlated with aspects of visuomotor learning retention. Further work is needed to investigate whether taking baclofen impacts motor rehabilitation in patients.

ABSTRACT

The GABA_B agonist baclofen is taken daily as a treatment for spasticity by millions of stroke, brain injury and multiple sclerosis patients, many of whom are also undergoing motor rehabilitation. However, decreases in GABA are suggested to be a key feature of human motor learning, which raises questions about whether drugs increasing GABAergic activity may impair motor learning and rehabilitation. In this double-blind, placebo-controlled study, we investigated whether a single 10 mg dose of the GABA_B agonist baclofen impaired motor sequence learning and visuomotor learning in 20 young healthy participants of both sexes. Participants trained on visuomotor and sequence learning tasks using their right hand. Transcranial magnetic stimulation (TMS) measures of corticospinal excitability, GABA_A (short-interval intracortical inhibition_, 2.5 ms) and GABA_B (long-interval intracortical inhibition_, 150 ms) receptor activation were recorded from left M1. Behaviourally, baclofen caused a significant reduction of visuomotor aftereffect (F_1,137.8  = 6.133, P = 0.014) and retention (F_1,130.7  = 4.138, P = 0.044), with no significant changes to sequence learning. There were no overall changes to TMS measured GABAergic inhibition with this low dose of baclofen. This result confirms the causal importance of GABA_B inhibition in mediating visuomotor learning and suggests that chronic baclofen use could negatively impact aspects of motor rehabilitation.

A Novel Quantitative Spasticity Evaluation Method Based on Surface Electromyogram Signals and Adaptive Neuro Fuzzy Inference System

Stroke patients often suffer from spasticity. Before treatment of spasticity, there are often practical demands for objective and quantitative assessment of muscle spasticity. However, the common quantitative spasticity assessment method, the tonic stretch reflex threshold (TSRT), is time-consuming and complicated to implement due to the requirement of multiple passive stretches. To evaluate spasticity conveniently, a novel spasticity evaluation method based on surface electromyogram (sEMG) signals and adaptive neuro fuzzy inference system (i.e., the sEMG-ANFIS method) was presented in this paper. Eleven stroke patients with spasticity and four healthy subjects were recruited to participate in the experiment. During the experiment, the Modified Ashworth scale (MAS) scores of each subject was obtained and sEMG signals from four elbow flexors or extensors were collected from several times (4–5) repetitions of passive stretching. Four time-domain features (root mean square, the zero-cross rate, the wavelength and a 4th-order autoregressive model coefficient) and one frequency-domain feature (the mean power frequency) were extracted from the collected sEMG signals to reflect the spasticity information. Using the ANFIS classifier, excellent regression performance was achieved [mean accuracy = 0.96, mean root-mean-square error (RMSE) = 0.13], outperforming the classical TSRT method (accuracy = 0.88, RMSE = 0.28). The results showed that the sEMG-ANFIS method not only has higher accuracy but also is convenient to implement by requiring fewer repetitions (4–5) of passive stretches. The sEMG-ANFIS method can help stroke patients develop proper rehabilitation training programs and can potentially be used to provide therapeutic feedback for some new spasticity interventions, such as shockwave therapy and repetitive transcranial magnetic stimulation.

Recovery cycles of posterior root-muscle reflexes evoked by transcutaneous spinal cord stimulation and of the H reflex in individuals with intact and injured spinal cord

Posterior root-muscle (PRM) reflexes are short-latency spinal reflexes evoked by epidural or transcutaneous spinal cord stimulation (SCS) in clinical and physiological studies. PRM reflexes share key physiological characteristics with the H reflex elicited by electrical stimulation of large-diameter muscle spindle afferents in the tibial nerve. Here, we compared the H reflex and the PRM reflex of soleus in response to transcutaneous stimulation by studying their recovery cycles in ten neurologically intact volunteers and ten individuals with traumatic, chronic spinal cord injury (SCI). The recovery cycles of the reflexes, i.e., the time course of their excitability changes, were assessed by paired pulses with conditioning-test intervals of 20–5000 ms. Between the subject groups, no statistical difference was found for the recovery cycles of the H reflexes, yet those of the PRM reflexes differed significantly, with a striking suppression in the intact group. When comparing the reflex types, they did not differ in the SCI group, while the PRM reflexes were more strongly depressed in the intact group for durations characteristic for presynaptic inhibition. These differences may arise from the concomitant stimulation of several posterior roots containing afferent fibers of various lower extremity nerves by transcutaneous SCS, producing multi-source heteronymous presynaptic inhibition, and the collective dysfunction of inhibitory mechanisms after SCI contributing to spasticity. PRM-reflex recovery cycles additionally obtained for bilateral rectus femoris, biceps femoris, tibialis anterior, and soleus all demonstrated a stronger suppression in the intact group. Within both subject groups, the thigh muscles showed a stronger recovery than the lower leg muscles, which may reflect a characteristic difference in motor control of diverse muscles. Based on the substantial difference between intact and SCI individuals, PRM-reflex depression tested with paired pulses could become a sensitive measure for spasticity and motor recovery.

Successful Treatment of Stiff Person Syndrome with Intrathecal Baclofen

Intrathecal baclofen therapy is a recognized treatment for severe spasticity. We report here a case of stiff person syndrome in Australia, treated with intrathecal baclofen followed by a rehabilitation programme with substantial clinical and functional improvements. A 59-year-old woman diagnosed with stiff person syndrome had become hoist-dependent and required full care due to severe spasticity over the past 12 years. Treatment with oral benzodiazepines and botulinum toxin injections to the affected muscles had no therapeutic response. After a test dose of 100 pg intrathecal baclofen resulted in a substantial improvement in her physical function, a decision was made to insert an intrathecal baclofen delivery device. This case report supports the use of intrathecal baclofen therapy and a formal inpatient rehabilitation programme for spasticity related to stiff person syndrome.

Pharmacologic Treatment Tools: Systemic Medications and Toxins, Opportunities, and Pitfalls

Treatment of pathologic muscle overactivity associated with upper motor neuron syndrome can be multifaceted. One of the initial decisions to be made when formulating an overarching treatment plan is selecting a combination of strategies that is most applicable. Strategies may include physical interventions, such as stretching or splinting modalities, or surgery, whereas pharmacotherapeutic strategies encompass oral/systemic medications as well as agents, such as toxins and alcohols, used for focal chemodenervation. This article reviews the oral/systemic therapies as well as toxins that are used focally. Although medication can also be administered via intrathecal pumps, this treatment approach is discussed elsewhere.

Intrathecal Therapies

Intrathecal baclofen therapy is a well-established technique for spasticity management. This article briefly reviews the pharmacology of intrathecal baclofen as well as customary approach for utilization of this targeted drug delivery concept. Following these descriptions, four unusual presentations will be described, including the need for initial trialing, patient-directed boluses during chronic intrathecal baclofen therapy, use of medications other than baclofen for intrathecal therapy in spastic patients, and intraventricular baclofen delivery. These hypothetical cases are provided in an effort to expand the use of targeted drug delivery to larger population of spastic patients.

Using Baclofen to Explore GABA-B Receptor Function in Alcohol Dependence: Insights From Pharmacokinetic and Pharmacodynamic Measures

Background: The role of GABA-B neurotransmission in addiction has recently received increased attention, with clinical trials indicating that baclofen, a GABA-B receptor agonist, may reduce alcohol consumption, craving and promote abstinence. However, the optimal dose to treat alcohol dependence is unclear with patients requesting and tolerating much higher doses of baclofen, compared with other clinical uses. We assessed the pharmacokinetics and pharmacodynamics (PK/PD) of baclofen to provide insight into GABA-B sensitivity in this patient group, relative to controls. Methods: Male healthy volunteers (controls, n = 12) and abstinent alcohol dependent individuals (AD, n = 8) received single oral doses of baclofen or placebo in a 3-way crossover design. Controls received placebo/10 mg/60 mg baclofen in a randomized, double-blind design, AD received placebo/60 mg/90 mg baclofen in a single-blind design. PK/PD measures were recorded at baseline and multiple time-points up to 6 h post-dosing, including plasma baclofen, plasma growth hormone (GH), Subjective High Assessment Scale (SHAS) and biphasic alcohol effects scale (BAES). Repeated measures ANOVA analysis explored "change from baseline" dose, time, group, and interaction effects, t-tests compared peak effects. Results: Dose-dependent effects of baclofen on PK and PD measures were observed in both control and AD groups. Whilst there were no significant group differences in any baclofen PK parameters (t _1/2, t _max , C _max , AUC), marked differences in PD effects were clearly evident. In controls, 60 mg baclofen significantly increased total SHAS and BAES scores, and significantly increased plasma GH levels compared with placebo, with peak effects at 60-120 min, in line with its PK profile. In AD, 60 mg baclofen had limited effects on these parameters; SHAS scores, BAES scores and plasma GH levels were significantly blunted compared with controls (significant group^*time interactions P = 0.0014, 0.0015 and P < 0.0001, respectively). Conclusions: Our study shows blunted sensitivity to baclofen in AD relative to controls, with no difference in PK suggesting a lower GABA-B receptor sensitivity. This may explain why higher baclofen doses are requested and tolerated in the treatment of alcohol dependence. Our data has implications for choice of dose in future clinical trials in AD and possibly other substances of dependence.

Central Hyperthermia Treated with Bromocriptine

Introduction. Central hyperthermia is common in patients with brain injury. It typically has a rapid onset with high temperatures and marked fluctuations and responds poorly to antibiotics and antipyretics. It is also associated with worse outcomes in the brain injured patient. Recognizing this, it is important to aggressively manage it. Case Report. We report a 34-year-old male with a right thalamic hemorrhage extending to the midbrain and into the ventricles. During his admission, he developed intractable fevers with core temperatures as high as 39.3°C. Infectious workup was unremarkable. The fever persisted despite empiric antibiotics, antipyretics, and cooling wraps. Bromocriptine was started resulting in control of the central hyperthermia. The fever spikes were reduced to minor fluctuations that significantly worsened with any attempt to wean off the bromocriptine. Conclusion. Diagnosing and managing central hyperthermia can be challenging. The use of bromocriptine can be beneficial as we have reported.

Safety and efficacy of incobotulinumtoxinA as a potential treatment for poststroke spasticity

Spasticity is a common disabling symptom for several neurological conditions. Botulinum toxin type A injection represents the gold standard treatment for focal spasticity after stroke showing efficacy, reversibility, and low prevalence of complications. In recent years, incobotulinumtoxinA, a new Botulinum toxin type A free of complexing proteins, has been used for treating several movement disorders with safety and efficacy. IncobotulinumtoxinA is currently approved for treating spasticity of the upper limb in stroke survivors, even if several studies described the use also in lower limb muscles. In the present review article, we examine the safety and effectiveness of incobotulinumtoxinA for the treatment of spasticity after stroke.

Validated Method for the Quantification of Baclofen in Human Plasma Using Solid-Phase Extraction and Liquid Chromatography-Tandem Mass Spectrometry

A highly sensitive and fully validated method was developed for the quantification of baclofen in human plasma. After adjusting the pH of the plasma samples using a phosphate buffer solution (pH 4), baclofen was purified using mixed mode (C8/cation exchange) solid-phase extraction (SPE) cartridges. Endogenous water-soluble compounds and lipids were removed from the cartridges before the samples were eluted and concentrated. The samples were analyzed using triple-quadrupole liquid chromatography-tandem mass spectrometry (LC-MS-MS) with triggered dynamic multiple reaction monitoring mode for simultaneous quantification and confirmation. The assay was linear from 25 to 1,000 ng/mL (r(2) > 0.999; n = 6). Intraday (n = 6) and interday (n = 15) imprecisions (% relative standard deviation) were <5%, and the average recovery was 30%. The limit of detection of the method was 5 ng/mL, and the limit of quantification was 25 ng/mL. Plasma samples from healthy male volunteers (n = 9, median age: 22) given two single oral doses of baclofen (10 and 60 mg) on nonconsecutive days were analyzed to demonstrate method applicability.

Effectively managing intractable central hyperthermia in a stroke patient by bromocriptine: a case report

Central hyperthermia is characterized by a rapid onset, high temperature, marked temperature fluctuation, and poor response to antipyretics and antibiotics. Although poststroke central hyperthermia is common, prolonged instances are rare. We report a case of prolonged central fever after an intracranial hemorrhage. Before the accurate diagnosis and management of central fever, the patient underwent long-term antibiotic use that led to pseudomembranous colitis. Bromocriptine was used to treat the prolonged central hyperthermia, after which the fever did not exceed 39°C. A week later, the body temperature baseline was reduced to 37°C and a low-grade fever with minor temperature fluctuation occurred only a few times. No fever occurred in the month following the treatment. After the fever subsided, the patient could undergo an aggressive rehabilitation program.

A Review of Spasticity Treatments: Pharmacological and Interventional Approaches

Spasticity is a velocity-dependent increase in muscle tone and uncontrolled, repetitive, involuntary contractions of skeletal muscles. Spasticity presents as upper motor neuron symptoms in patients with central nervous system pathology such as stroke, spinal cord injury, brain injury, or multiple sclerosis. As a result, a patient can have significant pain and limited mobility, which can lead to decreased quality of life and difficulty maintaining personal care. In this article we discuss mechanisms, indications, efficacy, and side effects of the most accepted current treatments. Currently available treatment options include oral medications and interventional procedures. Oral medications comprise centrally acting agents, such as baclofen, clonidine, and tizanidine, as well as anticonvulsants such as benzodiazepines and gabapentin and peripherally acting dantrolene. Interventional procedures include focal injections of botulinum toxin, phenol or alcohol, and an intrathecal baclofen pump. Surgical treatments include selective dorsal rhizotomy and neurectomy. We found that there are several treatments available with data to support their use, but many still need further research to prove their efficacy and develop optimal utilization.

The use of intrathecal baclofen in pain management

SUMMARY Intrathecal therapy involves the subarachnoid delivery of medications where the administered agents have enhanced potency and diminished systemic exposure compared with oral administration. Baclofen exerts its therapeutic action by enhancing the inhibition produced by the endogenous neurotransmitter GABA. While well-established within the armamentarium of tools for spasticity management, the role of intrathecal baclofen for the management of chronic pain is less certain. The purpose of this review is to describe the pharmacology of intrathecal baclofen, relate the role of intrathecal baclofen in neurologic and non-neurologic conditions, and report upon the potential utility of coadministering baclofen with other agents via the intrathecal route of delivery.

Metabolic and Pharmacokinetic Differentiation of STX209 and Racemic Baclofen in Humans

STX209 is an exploratory drug comprising the single, active R-enantiomer of baclofen which is in later stage clinical trials for the treatment of fragile x syndrome (FXS) and autism spectrum disorders (ASD). New clinical data in this article on the metabolism and pharmacokinetics of the R- and S-enantiomers of baclofen presents scientific evidence for stereoselective metabolism of only S-baclofen to an abundant oxidative deamination metabolite that is sterically resolved as the S-enantiomeric configuration. This metabolite undergoes some further metabolism by glucuronide conjugation. Consequences of this metabolic difference are a lower C_max and lower early plasma exposure of S-baclofen compared to R-baclofen and marginally lower urinary excretion of S-baclofen after racemic baclofen administration. These differences introduce compound-related exposure variances in humans in which subjects dosed with racemic baclofen are exposed to a prominent metabolite of baclofen whilst subjects dosed with STX209 are not. For potential clinical use, our findings suggest that STX209 has the advantage of being a biologically defined and active enantiomer.

Differential effects of sodium oxybate and baclofen on EEG, sleep, neurobehavioral performance, and memory

STUDY OBJECTIVES

Sodium oxybate (SO) is a GABAβ agonist used to treat the sleep disorder narcolepsy. SO was shown to increase slow wave sleep (SWS) and EEG delta power (0.75-4.5 Hz), both indexes of NREM sleep (NREMS) intensity and depth, suggesting that SO enhances recuperative function of NREM. We investigated whether SO induces physiological deep sleep.

DESIGN

SO was administered before an afternoon nap or before the subsequent experimental night in 13 healthy volunteers. The effects of SO were compared to baclofen (BAC), another GABAβ receptor agonist, to assess the role of GABAβ receptors in the SO response.

MEASUREMENTS AND RESULTS

As expected, a nap significantly decreased sleep need and intensity the subsequent night. Both drugs reversed this nap effect on the subsequent night by decreasing sleep latency and increasing total sleep time, SWS during the first NREMS episode, and EEG delta and theta (0.75-7.25 Hz) power during NREMS. The SO-induced increase in EEG delta and theta power was, however, not specific to NREMS and was also observed during REM sleep (REMS) and wakefulness. Moreover, the high levels of delta power during a nap following SO administration did not affect delta power the following night. SO and BAC taken before the nap did not improve subsequent psychomotor performance and subjective alertness, or memory consolidation. Finally, SO and BAC strongly promoted the appearance of sleep onset REM periods.

CONCLUSIONS

The SO-induced EEG slow waves seem not to be functionally similar to physiological slow waves. Our findings also suggest a role for GABAβ receptors in REMS generation.

Baclofen toxicity in patients with advanced nephropathy: proposal for new labeling

BACKGROUND

Despite several reports in the literature of baclofen toxicity in patients with renal dysfunction, the drug is being used for many patients.

METHODS

Herein we report a case of baclofen-induced encephalopathy in a patient with pre-end-stage renal disease and review the literature regarding the magnitude of baclofen toxicity in patients with renal insufficiency. A Medline search for studies in English was performed. Twenty-one case reports involving 41 patients (including our patient) were identified.

RESULTS

The majority of patients were elderly (62.5% above 60 years) males (56.3%) on dialysis (62.9%). Neurotoxicities were almost always present at presentation. Manifestations of baclofen toxicity usually started 2-3 days after starting baclofen; however, periods as long as 16 weeks have been reported. The daily dose of baclofen ranged from 5 to 60 mg with a mean dose of 20 mg. Hemodialysis (HD) was the most common treatment modality used for drug elimination (65.7%). The recovery time ranged from 2 h in patients who received HD, to 8 days with conservative treatment.

CONCLUSION

The literature does not mention a clear recommendation about baclofen safety and dose adjustment, or a minimum level of kidney function below which the drug should not be used.

Differential effects of GABAB receptor subtypes, {gamma}-hydroxybutyric Acid, and Baclofen on EEG activity and sleep regulation

The role of GABA(B) receptors in sleep is still poorly understood. GHB (γ-hydroxybutyric acid) targets these receptors and is the only drug approved to treat the sleep disorder narcolepsy. GABA(B) receptors are obligate dimers comprised of the GABA(B2) subunit and either one of the two GABA(B1) subunit isoforms, GABA(B1a) and GABA(B1b). To better understand the role of GABA(B) receptors in sleep regulation, we performed electroencephalogram (EEG) recordings in mice devoid of functional GABA(B) receptors (1(-/-) and 2(-/-)) or lacking one of the subunit 1 isoforms (1a(-/-) and 1b(-/-)). The distribution of sleep over the day was profoundly altered in 1(-/-) and 2(-/-) mice, suggesting a role for GABA(B) receptors in the circadian organization of sleep. Several other sleep and EEG phenotypes pointed to a more prominent role for GABA(B1a) compared with the GABA(B1b) isoform. Moreover, we found that GABA(B1a) protects against the spontaneous seizure activity observed in 1(-/-) and 2(-/-) mice. We also evaluated the effects of the GHB-prodrug GBL (γ-butyrolactone) and of baclofen (BAC), a high-affinity GABA(B) receptor agonist. Both drugs induced a state distinct from physiological sleep that was not observed in 1(-/-) and 2(-/-) mice. Subsequent sleep was not affected by GBL whereas BAC was followed by a delayed hypersomnia even in 1(-/-) and 2(-/-) mice. The differential effects of GBL and BAC might be attributed to differences in GABA(B)-receptor affinity. These results also indicate that all GBL effects are mediated through GABA(B) receptors, although these receptors do not seem to be involved in mediating the BAC-induced hypersomnia.

Consensus on the appropriate use of intrathecal baclofen (ITB) therapy in paediatric spasticity

Among features of motor disorders in children, spasticity is associated with considerable morbidity and problems in care, particularly in severely affected patients. Intrathecal baclofen (ITB) has been increasingly used as a relatively specific treatment modality for spasticity. To date, most of the evidence for its use in paediatric patients has come from retrospective and uncontrolled studies, although randomised, controlled trials of screening ITB and ITB therapy itself have recently been published. This consensus statement on the use of ITB in paediatric patients with spasticity was developed on the basis of currently available evidence, with the aim of providing information for clinicians, promoting an expert opinion and a consistent approach to the management of these patients and emphasising the need for further prospective, large-scale studies.

Role of oral medications in spasticity management

Oral medications are frequently used to manage spasticity. Some clinicians may believe that oral medications are a more conservative or "first-line" strategy to treat this condition. However, their use may lead to significant adverse events. Additionally, efficacy has not been well-established, in particular the ability of these medications to enhance functional outcome. The decision regarding the use of oral medications is further complicated by the fact that a number of different agents have been used for many different diagnoses. The relative dearth of well-controlled studies makes the choice of medications for a given clinical condition even more difficult. This article reviews the mechanisms of action of some of the medications that are more commonly used to treat spasticity and identifies some studies that may suggest efficacy, or lack thereof, for certain diagnoses. Because questions remain regarding the benefit of oral medications, potential side effects also are emphasized to help the reader consider both potential risks and benefits. The article is intended as a broad overview, rather than comprehensive review of the literature.

Prolonged unconsciousness in a patient on automated peritoneal dialysis

A 79-year-old man with end-stage renal disease treated by automated peritoneal dialysis was referred to the emergency department for altered consciousness. The first investigations, including toxicology screening, failed to reveal the precise etiology. The patient was treated for a possible seizure. After the progression of central nervous system depression with bradypnea, the patient was intubated and mechanically ventilated. It appeared later on that he had ingested by mistake one of his wife's medications, baclofen. Baclofen was detected in the blood sampled on admission at a level above the therapeutic range. Baclofen is mainly excreted by the kidney. A short-term administration of low-dose of baclofen is not effectively removed by peritoneal dialysis and may result in prolonged but reversible coma.

Improvements in healthcare and cost benefits associated with botulinum toxin treatment of spasticity and muscle overactivity

Spasticity is a widespread, disabling form of muscle overactivity affecting patients with central nervous system damage resulting in upper motor neurone syndrome. There is a range of effective therapies for the treatment of spasticity (e.g. physical, anaesthetic, chemodenervation and neurolytic injections, systemic medication and surgery), but all therapies must be based on an individualized, multidisciplinary programme targeted to achieve patient goals. Appropriate therapy should be based on the extent and severity of spasticity, but spasticity and its consequences, regardless of presentation or cause, are commonly treated with systemic agents. This may be ill-advised as systemic treatment is associated with many undesirable effects. In particular, elderly patients with post-stroke spasticity are at risk from the central adverse effects of systemic medication (e.g. sedation and gait disturbance), which make them more susceptible to falling, with an associated increased risk of fracture. The rising costs of fracture care and its sequelae are fast becoming an international problem contributing to high healthcare expenditure. Botulinum toxin type-A (BoNT-A) treatment is highly effective for some of the more common forms of spasticity and muscle overactivity, and has a favourable profile when compared with systemic agents and other focal treatments. Therefore, the clinical benefits of BoNT-A treatment outweigh the apparent high costs of this intervention, showing it to be a cost-effective treatment.

Pooled analysis of the safety of botulinum toxin type A in the treatment of poststroke spasticity

OBJECTIVE

To examine the safety of botulinum toxin type A (BTX-A).

DESIGN

Analysis of pooled data of 9 double-blind, placebo-controlled studies of patients with spasticity after stroke.

SETTING

University hospitals and specialty rehabilitation centers in the United States.

PARTICIPANTS

A total of 482 patients with upper-limb spasticity and 310 with lower-limb spasticity (overall mean age, 58y; 60% men).

INTERVENTION

Treatment with BTX-A (n=534; 1-3 treatments; mean dose, 231U) or placebo (n=258).

MAIN OUTCOME MEASURE

Adverse events.

RESULTS

Most patients (69%) received only 1 treatment with BTX-A. Patients were followed for a mean of 17.8 weeks (range, 0.1-44.7wk) after each treatment. A total of 352 (65.9%) patients in the BTX-A group and 163 (63.2%) in the placebo group reported at least 1 adverse event (P=.475). The most frequent adverse events reported by patients (>5% but <10% in either group) were respiratory infection, seizures, incoordination, and injection site pain, none of which occurred at a significantly higher rate in the BTX-A group (all P>.05). The majority of adverse events were rated as mild or moderate in severity. Only nausea was reported at a significantly higher rate in the BTX-A group (12/534 [2.2%]) than the placebo group (0/258) (P=.011); in contrast, injection site pain, chest pain, and allergic reaction were reported significantly more frequently in the placebo group.

CONCLUSIONS

BTX-A has an acceptable safety profile for treatment of patients with focal spasticity following stroke, a population in which adverse events and comorbidities are common.

A randomized, double-blind, placebo-controlled study of the efficacy and safety of tolperisone in spasticity following cerebral stroke

To study the efficacy and safety of tolperisone - a centrally acting muscle relaxant with membrane stabilizing activity - in the treatment of stroke-related spasticity. This was a randomized, double-blind, placebo-controlled, multicenter study with parallel groups. Treatment lasted 12 weeks and was started with a titration period of variable length (dose range 300-900 mg tolperisone daily). The degree of spasticity determined on the Ashworth Scale in the most severely affected joint area was defined as primary target parameter. Hundred and twenty patients (43 females, 77 males) in a mean age of 63.3 +/- 10.6 years were recruited and received treatment. In the majority of patients both limbs of each side (right: n = 59; left: n = 56) were affected by the spasticity which on average had been present for 3.3 +/- 4.4 years. A 62% of the patients were treated with a daily dose >/=600 mg tolperisone. Tolperisone reduced the mean Ashworth Score by a mean of 1.03 +/- 0.71 compared with a mean reduction of 0.47 +/- 0.54 in the placebo group (P < 0.0001). A 78.3% of the patients on tolperisone versus 45% of the placebo patients experienced a reduction by at least 1 point on the Ashworth Scale (P < 0.0001). Functional and overall assessments of efficacy confirmed superior efficacy of tolperisone. Adverse events occurred less often on active treatment (n = 19) than on placebo (n = 26) and were mostly of mild-to-moderate intensity. No withdrawals caused by adverse events were reported in the tolperisone group. The findings of the present study demonstrate the efficacy and excellent tolerance of tolperisone in the treatment of spastic hypertonia following cerebral stroke. Study data further suggest that an individual dose titration which may exceed the recommended maximum dose of 450 mg daily results in optimized therapeutic benefit.

Comparative efficacy and safety of skeletal muscle relaxants for spasticity and musculoskeletal conditions: a systematic review

Skeletal muscle relaxants are a heterogeneous group of medications used to treat two different types of underlying conditions: spasticity from upper motor neuron syndromes and muscular pain or spasms from peripheral musculoskeletal conditions. Although widely used for these indications, there appear to be gaps in our understanding of the comparative efficacy and safety of different skeletal muscle relaxants. This systematic review summarizes and assesses the evidence for the comparative efficacy and safety of skeletal muscle relaxants for spasticity and musculoskeletal conditions. Randomized trials (for comparative efficacy and adverse events) and observational studies (for adverse events only) that included oral medications classified as skeletal muscle relaxants by the FDA were sought using electronic databases, reference lists, and pharmaceutical company submissions. Searches were performed through January 2003. The validity of each included study was assessed using a data abstraction form and predefined criteria. An overall grade was allocated for the body of evidence for each key question. A total of 101 randomized trials were included in this review. No randomized trial was rated good quality, and there was little evidence of rigorous adverse event assessment in included trials or observational studies. There is fair evidence that baclofen, tizanidine, and dantrolene are effective compared to placebo in patients with spasticity (primarily multiple sclerosis). There is fair evidence that baclofen and tizanidine are roughly equivalent for efficacy in patients with spasticity, but insufficient evidence to determine the efficacy of dantrolene compared to baclofen or tizanidine. There is fair evidence that although the overall rate of adverse effects between tizanidine and baclofen is similar, tizanidine is associated with more dry mouth and baclofen with more weakness. There is fair evidence that cyclobenzaprine, carisoprodol, orphenadrine, and tizanidine are effective compared to placebo in patients with musculoskeletal conditions (primarily acute back or neck pain). Cyclobenzaprine has been evaluated in the most clinical trials and has consistently been found to be effective. There is very limited or inconsistent data regarding the effectiveness of metaxalone, methocarbamol, chlorzoxazone, baclofen, or dantrolene compared to placebo in patients with musculoskeletal conditions. There is insufficient evidence to determine the relative efficacy or safety of cyclobenzaprine, carisoprodol, orphenadrine, tizanidine, metaxalone, methocarbamol, and chlorzoxazone. Dantrolene, and to a lesser degree chlorzoxazone, have been associated with rare serious hepatotoxicity.

Baclofen neurotoxicity in uremic patients: is continuous ambulatory peritoneal dialysis less effective than intermittent hemodialysis?

OBJECTIVES

To compare the efficacy between continuous ambulatory peritoneal dialysis (CAPD) and intermittent hemodialysis in the treatment of baclofen-associated neurotoxicity.

METHODS

Three uremic patients suffering baclofen-associated neurotoxicity were treated by CAPD at our hospital. We obtain 12 cases with detailed clinical course of baclofen-associated neurotoxicity treated by hemodialysis from a literature review using the Medline and Science Citation Index, six of these patients were treated by early hemodialysis which was defined as hemodialysis intervention within 48 h of the onset of clinical toxicity.

RESULTS

Our cases regain full consciousness within 2-3 days after the onset of neurotoxicity. Clinical characteristics of our cases including age, dialysis time, preexisting central nervous system (CNS) lesion, concomitant use of CNS depressant, total baclofen dose, onset of neurotoxicity, and duration of neurotoxicity are not significantly different from reported cases that treated by either early or routine hemodialysis.

CONCLUSIONS

Baclofen should be avoided in uremic patients. When consciousness disturbance occurs in uremic patients, baclofen-associated neurotoxicity should be included in the list of differential diagnosis. According to experiences of our patients, we conclude that neither early nor routine hemodialysis is more effective than CAPD in shortening the recovery time of baclofen-associated neurotoxicity.

Inappropriate medication prescribing in residential care/assisted living facilities

OBJECTIVES

To identify the extent to which inappropriately prescribed medications (IPMs) are administered to older patients in residential care/assisted living (RC/AL) facilities and to describe facility and resident factors associated with receipt of one or more IPMs.

DESIGN

Cross-sectional study of a stratified, representative sample of 193 facilities in four states.

SETTING

We identified representative geographic regions within Florida, New Jersey, North Carolina, and Maryland and drew from within them a stratified random sample of 193 RC/AL facilities. Three subtypes of facilities were included in the sample: small homes (<16 beds), larger "new-model" homes, and larger "traditional" homes.

PARTICIPANTS

Within each larger home, a random sample of residents aged 65 and older was approached for consent; in smaller homes all residents were approached. The overall enrollment rate was 92%; 2,078 residents were enrolled.

MEASUREMENTS

Questionnaires and on-site observations were used to gather data on facility administration and staffing and resident characteristics. All prescription and nonprescription medications taken at least 4 of the 7 days before data collection were taken from medication administration records and coded for analysis. IPM designation was based on modification of a list developed by Beers et al. and currently used by nursing home surveyors.

RESULTS

The majority of RC/AL patients were taking five or more medications; 16.0% of these patients were receiving IPMs. The most common IPMs were oxybutynin, propoxyphene, diphenhydramine, ticlopidine, doxepin, and dipyridamole. In multivariate analyses, using generalized estimating equations, IPM use was associated with the number of medications received, smaller facility bed size, moderate licensed practical nurse turnover, absence of dementia, low monthly fees, and absence of weekly physician visits.

CONCLUSIONS

IPMs remain a problem in long-term care, but rates in these RC/AL settings compare favorably with those reported for other frail older populations, suggesting that use of medications with severe adverse effects may be waning. Regular physician facility visits may improve prescribing, as will attention to high-risk groups such as individuals on multiple medications.

Baclofen toxicity in patients with severely impaired renal function

OBJECTIVE

To report the toxic effects of baclofen in patients with severely impaired renal function.

DATA SOURCES

From 1991 to 1995, nine patients with severely impaired renal function (2 not receiving dialysis, 1 undergoing continuous ambulatory peritoneal dialysis [CAPD], and 6 receiving maintenance hemodialysis), who exhibited clinical toxicity after baclofen therapy at our hospital were included for analysis. Another seven cases from the literature obtained by computerized (MEDLINE) and manual (Index Medicus) search methods published between 1980 and 1995 were also reviewed.

INTERVENTION

Among our nine patients, the six undergoing chronic hemodialysis and one not undergoing dialysis received early (< 48 h) hemodialysis after toxic symptoms developed. The patient undergoing CAPD received late hemodialysis (> 72 h), and the other patient who had not undergone dialysis received only supportive care.

RESULTS

A review of these 16 cases revealed that most patients received only small doses and very short-term baclofen therapy. Altered consciousness was the major presenting feature. Severe acute complications, such as seizures and respiratory depression, were relatively uncommon among patients with severely impaired renal function. However, abdominal pain, which has previously rarely been reported, was noted in five of our nine patients. Most patients showed clinical improvement after hemodialysis. An analysis of these nine patients revealed that those who received early hemodialysis had a shorter recovery time than the patient who received only supportive care (2.71 +/- 0.42, respectively, vs. 9 d; p < 0.01). A lag of several hours between the end of the hemodialysis session and an improvement in the level of consciousness was noted.

DISCUSSION

As most patients with severely impaired renal function developed toxic symptoms soon after initiating a low-dose baclofen regimen, the accumulated dosage was small and severe complications were less common. Abdominal pain may have occurred as a result of the gamma-aminobutyric acid-mediated cholinergic effect exerted by baclofen. The delay in conscious recovery after hemodialysis may be due to a delay in the clearance of baclofen from the central nervous system.

CONCLUSIONS

Patients with severely impaired renal function generally develop baclofen intoxication soon after the initiation of low-dose therapy. Thus, the administration of baclofen, regardless of the dosage, in these patients is not appropriate. Abdominal pain, in addition to altered consciousness, is a common presenting feature in patients with renal failure who have baclofen intoxication. Hemodialysis is effective in alleviating the clinical symptoms and shortening the recovery time for such patients.

Hepatic drug metabolism and aging

Although there is considerable variation in the effect of age on drug biotransformation, the metabolism of many drugs is impaired in the elderly. Age-related physiological changes, such as a reduction in liver mass, hepatic metabolising enzyme activity, liver blood flow and alterations in plasma drug binding may account for the decreased elimination of some metabolised drugs in the elderly. It is difficult, however, to separate an effect of aging from a background of marked variation in the rate of metabolism due to factors such as individual metabolic phenotype, environmental influences, concomitant disease states and drug intake. The prevailing data suggest that initial doses of metabolised drugs should be reduced in older patients and then modified according to the clinical response. In most studies the elderly appear as responsive as young individuals to the effects of compounds which induce or inhibit the activity of cytochrome P450 isozymes. Concurrent use of other agents, which induce or inhibit drug metabolism, mandates dose adjustment as in younger patients. Many questions remain unanswered. For instance, limitations of in vitro studies prevent any firm conclusion about changes in hepatic drug metabolising enzyme activity in the elderly. With aging, some pathways of drug metabolism may be selectively affected, but this has not been adequately scrutinised. The possibility that metabolism of stereoisomers may be altered in the elderly has not been adequately tested. The effect of aging on the distribution of polymorphic drug metabolism phenotypes is still not established, despite potential implications for disease susceptibility and survival advantage.

Pharmacokinetics of baclofen in spastic patients receiving multiple oral doses

The pharmacokinetics of racemic baclofen as determined from plasma and urine data in six spastic patients treated with individualized oral doses, 30-80 mg daily, are presented. Peak plasma concentrations were achieved 1.9 h (+/- 0.7) after a dose. The fluctuation in the plasma concentration was great, ranging from 188 to 439%. The total body clearance averaged 175 ml.min-1 (+/- 44), plasma protein binding 35% (+/- 6). Baclofen was for the greater part excreted unchanged by the kidney, 65% (+/- 16). Its apparent renal equalled the creatinine clearance. The contribution of the renal clearance to the total body clearance can explain the previously described toxicity when renal impairment is present. The results agree with earlier reports on single doses in healthy subjects.

Plasma and urinary excretion kinetics of oral baclofen in healthy subjects

Baclofen, a centrally acting muscle relaxant, is used in the treatment of spasticity. Its pharmacokinetics has been derived from plasma and urine data in four healthy subjects, whose renal function was simultaneously measured. After oral administration of a single 40 mg dose, baclofen was mainly excreted unchanged by the kidney, 69 (14)%. The half-life, calculated from extended least squares modelling (ELSMOS) both of plasma and urine data was 6.80 (0.68) h, which is longer than reported in most studies based solely on plasma data. The renal excretion rate constant had the high mean value of 0.35 (0.24) h-1, and the apparent renal clearance of baclofen equalled the creatinine clearance. Passive tubular reabsorption is relatively unimportant, since no dependence was observed on variables urine flow or pH. Although active tubular secretion may contribute to its renal clearance, as shown by the effect of co-administration of probenecid, glomerular filtration appears to be the dominant transport mechanism.

Spasticity and drug therapy

An overview is presented of pathophysiology, classification and measurement of spasticity and of its treatment, especially with dantrolene and baclofen. In spasticity, the balance between excitatory and inhibitory neurotransmitters in the central nervous system is impaired by mechanisms that are for the greater part unknown. Spasticity includes various disorders of motor control, and classification is needed for a meaningful evaluation of antispastic therapy. Cerebral palsy is a specific disorder, sometimes also called spasticity. Measurement of spasticity is complicated and should include signs characteristic of spasticity and parameters for clinical improvement. Dantrolene and baclofen have established their place in the treatment of spastic disorders, but a preference for either drug is hard to give. For tizanidine it is still too early to determine its place in therapy. Dantrolene is a direct acting muscle relaxant which should be avoided in patients with pre-existing liver damage. Its mechanism of metabolism and excretion is for the greater part unknown. The GABAB agonist baclofen is a centrally acting muscle relaxant. In patients with impaired renal function the dose should be reduced. Abrupt withdrawal carries the risk of unwanted reactions. The R(-)-enantiomer has proved to be the active isomer. This means that human trials need reappraisal, especially those relating to the pharmacokinetics of the racemate.