Population pharmacokinetics of oral baclofen in pediatric patients with cerebral palsy

Postoperative fever following hemispherotomy managed with baclofen: unnoticed treatment

BACKGROUND

There are different types of fever after hemispherotomy; to our knowledge, this is the first time in literature in which baclofen was used to control central fever following hemispherotomy.

CASE PRESENTATION

A 12-year-old female patient who has a history of neonatal hemorrhagic stroke presented with uncontrolled seizures despite receiving three antiepileptic drugs. MRI brain showed marked volume reduction in the left cerebral hemisphere. She underwent a left modified hemispherotomy. Two weeks after surgery, she developed a fever with evidence of infection for which she underwent surgical debridement, the fever subsided gradually and she was discharged after 2 weeks. Then 1 week later, she presented again with a fever and the T-max was 39 °C. After the exclusion of infection and aseptic meningitis, there was a possibility of central fever for which we started baclofen at 5 mg once per day and gradually increased the dose till she reached 20 mg per day at which the fever vanished. The patient remained seizure-free and afebrile for 10 months after surgery.

CONCLUSIONS

Postoperative fever is very common after hemispherectomy or functional hemispherotomy, and the non-infectious etiology is the most encountered. Central fever is a diagnosis of exclusion and its diagnosis leads to avoiding the misuse of antibiotics. We found baclofen safely and successively controlled central fever after hemispherotomy.

Is baclofen the least worst option for spasticity management in children?

Baclofen is often considered a first-line treatment option for spasticity management in children. However, adverse effects, administration, and dosing can be barriers to effectiveness. In my practice, other medications for spasticity management are often used prior to initiating baclofen. In this article, baclofen use for spasticity management in children is briefly reviewed along with discussion of approaches using other medications as first-line treatment options. I will present a rationale for medication selection for spasticity management and discuss the approaches I take in medication selection that incorporate spasticity severity, patient goals, and medication side effect profiles.

Stability Study of Baclofen in an Oral Powder Form Compounded for Pediatric Patients in Japan

Baclofen is used as a skeletal muscle relaxant for multiple sclerosis patients and pediatric patients with cerebral palsy and is prescribed to pediatric patients at 0.3 to 1.0 mg/kg/dose. Baclofen tablets, an oral drug, are usually administered as a powder in pediatric wards after a formulation change by the pharmacist. However, there is no information about stability and assurance of quality for compounded products. The purpose of this study was to design a 10 mg/g oral powder of baclofen and to investigate the stability and changes in the physical properties of this compounded product. A 10 mg/g baclofen powder was prepared by adding extra-fine crystal lactose hydrate to crushed and filtrated baclofen tablets and was stored in a polycarbonate amber bottle with desiccant or in a coated paper laminated with cellophane and polyethylene. The stability of baclofen at 25 ± 2 °C/60 ± 5%RH was tested for 120 days in ‘bottle (closed)’, ‘bottle (in use)’, and ‘laminated’ storage conditions. Baclofen concentrations ranged from 90.0% to 110.0% of the initial concentration under all storage conditions. No crystallographic or dissolution changes were observed after storage. This information can help with the management of baclofen compounded powder in pharmacies.

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.

Assessing a Mass-Based Method for the Preparation of Low-Dosed Paediatric Capsules with Baclofen and Spironolactone

Despite the steadily improving medical care situation in pediatrics, some drugs are still not available in a suitable dose or dosage form and thus need to be prepared extemporaneously. Capsules can be easily compounded at the hospital and public pharmacies, offering an alternative to liquid formulations. This study aims at testing a mass-based approach for the extemporaneous preparation of low-dose pediatric capsules and investigating systematically the API loss during this procedure. A total of 54 capsule batches were prepared with baclofen and spironolactone as pediatric-relevant drugs. The hard capsules were prepared using three different bulking agents consisting of either mannitol, lactose-monohydrate and microcrystalline cellulose mixed with 0.5% colloidal silica. Capsules were tested according to Ph. Eur. method "2.9.40 Content Uniformity" as well as for occurring powder loss and mass uniformity. The results reveal that the mass-based approach, in general, allows the preparation of low-dose pediatric capsules of appropriate quality. However, absolute quality is highly dependent on the homogeneity of the powder mixture and the use of defined parameters for capsule preparation.

Treatment of Disorders of Tone and Other Considerations in Pediatric Movement Disorders

Pediatric movement disorders (PMDs) consist of a heterogeneous group of signs and symptoms caused by numerous neurological diseases. Different neurological disorders in children also share overlapping movement disorders making a diagnosis of the underlying cause of the movement disorder challenging. The similarity of the symptoms across multiple disease types suggests that there may be a final common motor pathway causing the overlapping movement disorders. There are numerous disorders in children associated with disturbances in tone and involuntary movements. This chapter will focus primarily on those disorders that involve abnormalities of tone and other important considerations of pediatric movement disorders. This chapter will address rating scales and goals for treatment and will include a review of symptomatic treatment and, where possible, the treatment of the underlying disease processes. The chapter will review representative disorders, including an inborn error of metabolism, an autoimmune disorder, and a group of neurodegenerative disorders. These examples demonstrate how the disorder's underlying pathophysiology results in a specific approach to the underlying disease and the associated conditions of tone and involuntary movements. Finally, the multiple treatment options for cerebral palsy and considerations of cerebral palsy mimics will be discussed.

Principles of Medical and Surgical Treatment of Cerebral Palsy

Cerebral palsy is the most common cause of childhood motor disability, affecting 2 to 3/1000 children worldwide. Clinical abnormalities in tone, posture, and movement are the result of brain dysgenesis or injury early in life, and impairment varies in type, distribution, and in severity. The underlying brain disorder may also lead to other associated neurologic and systemic impairments. Variability in functional impairments, which can change during development, necessitates an individualized treatment plan. Treatment options are primarily symptomatic and directed toward optimizing independence, function, and/or ease of care-while limiting side effects. New promising disease-preventing and modifying treatments are emerging.

A Case Report of Baclofen Toxicity in a Pediatric Patient With Normal Kidney Function Successfully Treated With Hemodialysis

Rationale:

Baclofen is a commonly prescribed medication used to decrease spasticity in children with cerebral palsy. Despite its widespread use, this medication has not demonstrated to be consistently effective in clinical studies. Baclofen is also associated with systemic adverse effects due to potent neuronal depression. The management of baclofen toxicity is mainly supportive; however, some studies have shown that hemodialysis may alleviate the symptoms of an overdose and shorten the recovery time.

Presenting concerns:

In this case report, a 6-year-old boy with mild cerebral palsy, neuromyelitis optica, and normal kidney function was found unresponsive at home, with altered mental status, after ingesting 1300 mg of baclofen unobserved. The patient was intubated and mechanically ventilated because of significant neurologic depression with subsequent respiratory failure.

Diagnosis:

The patient was diagnosed with baclofen-induced encephalopathy. An elevated serum baclofen level of 4.00 µg/mL (therapeutic range of 0.08-0.40 µg/mL) was observed 10 hours after he was found unresponsive. The patient’s respiratory status deteriorated; he had high ventilatory requirements and remained comatose.

Intervention:

With the worsening of his clinical condition in the intensive care unit, hemodialysis, administered via a high-efficiency high-flux dialyzer, was initiated approximately 18 hours after he was found unresponsive. The patient underwent 2 hemodialysis runs spaced 9 hours apart, with blood flow rates approaching 250 mL/min.

Outcomes:

Within 3 hours of the first hemodialysis treatment, the patient started to regain consciousness. He was extubated to room air 6 hours after the second hemodialysis treatment.

Novel findings:

Supportive management is the primary treatment of baclofen toxicity in a pediatric patient with normal kidney function. Hemodialysis may be considered in severe cases of baclofen toxicity and worsening clinical status, but further studies are needed to confirm this finding.

Pharmacological Management of Spasticity in Children With Cerebral Palsy

Cerebral palsy (CP), a nonprogressive disease of the central nervous system, is the most common motor disability in childhood. Patients with CP often have a multitude of associated comorbidities, including impact on muscle tone. There are four main types of CP, with spastic as the most commonly diagnosed. Reduction in spasticity is important because it can affect not only the patient's quality of life, functional abilities, and well-being but also the lives of caregivers. The American Academy of Neurology and Child Neurology Society released a practice parameter regarding the pharmacological management of CP-related spasticity in 2010. Since then, data have been published evaluating the safety and efficacy of oral and parenteral medications to manage spasticity. This continuing education review evaluates the available safety and efficacy evidence for oral and parenteral pharmacological agents used to reduce spasticity in children with CP and provides a reference for practitioners managing these patients.

Baclofen Toxicity in Children With Acute Kidney Injury: Case Reports and Review of the Literature

Baclofen is a medication used for tone management in cerebral palsy. Although it acts mainly at the spinal cord level, it can cause central nervous system adverse reactions at higher doses. Baclofen is mainly eliminated by renal excretion and there have been reports on adverse events when used in adults with renal impairment; however, there are no consensus guidelines as to the dose adjustments required due to renal impairment. The authors describe 2 children with acute kidney injury (AKI) and systemic side effects with initiation of oral baclofen, which was started for treatment of dystonia/spasticity in the recovery phase of their kidney injury. Following the initiation of the drug, they both had decreased level of consciousness and respiratory difficulties, which warranted discontinuation of the drug. These cases highlight the need for reduced initial dose, slow titration, and close monitoring when initiating baclofen treatment in children with AKI.

Medical Updates in Management of Hypertonia

Identifying the subtypes of hypertonia is becoming increasingly important. Treatment strategies, including tone-modulating surgical interventions, medication type and dosing, and chemodenervation, may differ depending on the type of hypertonia present. It is important to delineate how hypertonia interferes with function and quality of life so that the appropriate intervention can be selected at the right time. Outcomes of treatment depend heavily on clear communication of goals. Botulinum toxin should not be used in isolation but as an adjunct to rehabilitation modalities.

Drug deprescription-withdrawal risk, prevention, and treatment

In most cases, a sudden interruption of most medications has no major consequences. There are well-recognized therapies that, when withheld, can either lead to the reappearance of the symptoms they were controlling or to signs or symptoms of withdrawal. In this article, we present a table including medications that when interrupted can produce withdrawal syndromes, the signs and symptoms of the withdrawal syndrome, the time to onset and resolution of the syndrome, information regarding alternative delivery options for the drug/s when the oral route is not possible, as well as prevention and therapy.

Simultaneous Quantitation of S(+)- and R(-)-Baclofen and Its Metabolite in Human Plasma and Cerebrospinal Fluid using LC-APCI-MS/MS: An Application for Clinical Studies

Baclofen is a racemic mixture that is commonly used for the treatment for spasticity. However, the optimal dose and dosing interval to achieve effective cerebral spinal fluid (CSF) concentrations of baclofen are not known. Moreover, it is unclear if there are differences in the ability of R- or S-baclofen to cross the blood–brain barrier and achieve effective CSF concentrations. We have validated a liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method with improved selectivity and sensitivity for the simultaneous quantitation of R- and S-baclofen and metabolites in plasma and CSF. Protein precipitation by acetonitrile was utilized to obtain an acceptable recovery of the analytes. The detection and separation of analytes was achieved on a 48 °C-heated Crownpak CR(+) column (150 mm × 4.0 mm, 5μ) with elution using 0.4% formic acid (FA) in water and 0.4% FA in acetonitrile as the mobile phase running at a flow rate of 1.0 mL/min. Accurate quantitation was assured by using this MS/MS method with atmospheric pressure chemical ionization in multiple reaction monitoring (MRM) mode. Therefore, this method is enantioselective, accurate, precise, sensitive, reliable, and linear from 1 to 1500 ng/mL for baclofen and 2 to 4000 ng/mL for the metabolites. An additional method was developed to separate racemic baclofen 3-(4-chlorophenyl)-4 hydroxybutyric acid metabolites for individual concentration determination. Both validated methods were successfully applied to a clinical pharmacokinetic human plasma and CSF study evaluating the disposition of baclofen and metabolites.

Examining the role of precision medicine with oral baclofen in pediatric patients with cerebral palsy

PURPOSE OF REVIEW

a)Despite its widespread use, oral baclofen requires a critical review of the pharmacology to determine potential precision medicine applications to improve medication administration. Discussing the dose→exposure→response relationship of oral baclofen allows a conceptual framework in which designing clinical trials would become more successful. This paper seeks to examine some of the areas where variability in exposures can exist lead to undesired clinical responses.

RECENT FINDINGS

b)Several factors are at play to implement precision medicine with oral baclofen in the pediatric patient with cerebral palsy. Variations in intestinal absorption, oral baclofen clearance, pharmacogenomic variants, and distribution of this medication into the cerebrospinal fluid cause differences in the amount of baclofen available at the GABA-B receptor site to cause a clinical response.

SUMMARY

c)Oral baclofen has significant variability in disposition and clinical response. Research to determine the causes for this variability and controlling for these factors would allow improvement in clinical outcomes.

Effect of oral baclofen on spasticity poststroke: responders versus non-responders

Objective To assess quantitatively the efficacy of oral baclofen for spasticity poststroke. Methods The participants were 29 persons poststroke with increased resistance to passive ankle dorsiflexion and ankle clonus on clinical assessment. Baclofen was administered at 20 mg/day for 1 week. The ankle joint was passively dorsiflexed at either 5°/s (slow stretch) or 90°/s (fast stretch) by a custom-built device. The ankle joint angle and resistive torque were measured during the ramp-and-hold stretch, with gastrocnemius electromyogram. The main outcome measures were the numbers of ankle clonus during hold, and the torques at 10° of ankle dorsiflexion in slow stretch (T-slow) and fast stretch (T-fast). Moreover, the velocity-dependent torque (ΔT = T-fast - T-slow) was compared between before and after oral baclofen. Results The numbers of ankle clonus, T-slow, T-fast, and ΔT for all participants did not exhibit significant differences between before and after baclofen administration. However, reduction in the number of ankle clonus of five or more was accompanied with a reduction in ΔT (4.0 ± 1.8 Nm) in three participants (the responders). Conclusion Although the responder rate was low, some participants responded to oral baclofen. Thus, a short-term trial of oral baclofen, and quantitative and electrophysiological assessments of muscle tone and ankle clonus are recommended.

Pharmacological and neurosurgical interventions for managing dystonia in cerebral palsy: a systematic review

AIM

To systematically review evidence for pharmacological/neurosurgical interventions for managing dystonia in individuals with cerebral palsy (CP) to inform a care pathway.

METHOD

Searches included studies with a minimum of five participants with dystonia in CP receiving oral baclofen, benzodiazepines (clonazepam, diazepam, lorazepam), clonidine, gabapentin, levodopa, trihexyphenidyl, botulinum toxin, intrathecal baclofen (ITB), or deep brain stimulation (DBS). Evidence was classified according to American Academy of Neurology guidelines.

RESULTS

Twenty-eight articles underwent data extraction: one levodopa, five trihexyphenidyl, three botulinum toxin, six ITB, and 13 DBS studies. No articles for oral baclofen, benzodiazepines, clonidine, or gabapentin met the inclusion criteria. Evidence for reducing dystonia was level C (possibly effective) for ITB and DBS; level C (possibly ineffective) for trihexyphenidyl; and level U (inadequate data) for botulinum toxin.

INTERPRETATION

For dystonia reduction, ITB and DBS are possibly effective, whereas trihexyphenidyl was possibly ineffective. There is insufficient evidence to support oral medications or botulinum toxin to reduce dystonia. There is insufficient evidence for pharmacological and neurosurgical interventions to improve motor function, decrease pain, and ease caregiving. The majority of the pharmacological and neurosurgical management of dystonia in CP is based on clinical expert opinion.

WHAT THIS PAPER ADDS

Intrathecal baclofen and deep brain stimulation are possibly effective in reducing dystonia. Current evidence does not support effectiveness of oral medications or botulinum toxin to reduce dystonia. Evidence is inadequate for pharmacological/neurosurgical interventions impact on improving motor function, pain/comfort, and easing caregiving. The majority of the care pathway rests on expert opinion.

Multivariate Analysis and Machine Learning in Cerebral Palsy Research

Cerebral palsy (CP), a common pediatric movement disorder, causes the most severe physical disability in children. Early diagnosis in high-risk infants is critical for early intervention and possible early recovery. In recent years, multivariate analytic and machine learning (ML) approaches have been increasingly used in CP research. This paper aims to identify such multivariate studies and provide an overview of this relatively young field. Studies reviewed in this paper have demonstrated that multivariate analytic methods are useful in identification of risk factors, detection of CP, movement assessment for CP prediction, and outcome assessment, and ML approaches have made it possible to automatically identify movement impairments in high-risk infants. In addition, outcome predictors for surgical treatments have been identified by multivariate outcome studies. To make the multivariate and ML approaches useful in clinical settings, further research with large samples is needed to verify and improve these multivariate methods in risk factor identification, CP detection, movement assessment, and outcome evaluation or prediction. As multivariate analysis, ML and data processing technologies advance in the era of Big Data of this century, it is expected that multivariate analysis and ML will play a bigger role in improving the diagnosis and treatment of CP to reduce mortality and morbidity rates, and enhance patient care for children with CP.

Baclofen Toxicity in Kidney Disease

Baclofen, a commonly prescribed muscle relaxant, is primarily excreted via the kidneys; toxicity is a potentially serious adverse outcome in patients with decreased kidney function. We describe a patient with end-stage kidney disease receiving hemodialysis who developed neurotoxicity and hemodynamic instability after receiving baclofen for muscle spasms. In this case, prompt recognition of baclofen toxicity and urgent hemodialysis were effective in reversing this toxicity. This case is used to examine the pharmacokinetics and pathophysiology of baclofen toxicity and discuss appropriate diagnosis and management of baclofen toxicity. We recommend reducing the baclofen dose in patients who have moderately reduced kidney function (estimated glomerular filtration rate, 30-60mL/min/1.73m²) and avoiding use in patients with severely reduced kidney function (estimated glomerular filtration rate < 30mL/min/1.73m²) or on renal replacement therapy.

Pharmacogenomic Variability of Oral Baclofen Clearance and Clinical Response in Children With Cerebral Palsy

BACKGROUND

Pharmacogenomic variability can contribute to differences in pharmacokinetics and clinical responses. Pediatric patients with cerebral palsy with genetic variations have not been studied for these potential differences.

OBJECTIVE

To determine the genetic sources of variation in oral baclofen clearance and clinical responses.

DESIGN

Pharmacogenomic add-on study to determine variability in oral baclofen clearance and clinical responses.

SETTING

Multicenter study based in academic pediatric cerebral palsy clinics.

PARTICIPANTS

A total of 49 patients with cerebral palsy who had participated in an oral baclofen pharmacokinetic/pharmacodynamic study.

METHODS OR INTERVENTIONS

Of 53 participants in a pharmacokinetic/pharmacodynamic trial, 49 underwent genetic analysis of 307 key genes and 4535 single-nucleotide polymorphisms involved in drug absorption, distribution, metabolism, and excretion. Associations between genotypes and phenotypes of baclofen disposition (weight-corrected and allometrically scaled clearance) and clinical endpoints (improvement from baseline in mean hamstring Modified Tardieu Scale scores from baseline for improvement of R1 spastic catch) were determined by univariate analysis with correction for multiple testing by false discovery rate.

MAIN OUTCOME MEASUREMENTS

Primary outcome measures were the genotypic and phenotypic variability of oral baclofen in allometrically scaled clearance and change in the Modified Tardieu Scale angle compared to baseline.

RESULTS

After univariate analysis of the data, the SNP of ABCC9 (rs11046232, heterozygous AT versus the reference TT genotype) was associated with a 2-fold increase in oral baclofen clearance (mean 0.51 ± standard deviation 0.05 L/h/kg for the AT genotype versus 0.25 ± 0.07 L/h/kg for the TT genotype, adjusted P < .001). Clinical responses were associated with decreased spasticity by Modified Tardieu Scale in allelic variants with SNPs ABCC12, SLC28A1, and PPARD.

CONCLUSIONS

Genetic variation in ABCC9 affecting oral baclofen clearance highlights the need for continued studies of genetic polymorphisms to better characterize variable drug response in children with cerebral palsy. Single-nucleotide polymorphisms in ABCC12, SLC28A1, and PPARD were associated with varied responses, which warrants further investigation to determine their effect on spasticity.

LEVEL OF EVIDENCE

II.

Baclofen Toxicity Responsive to Hemodialysis in a Pediatric Patient with Acute Kidney Injury

Background Baclofen (para-chlorophenyl-gamma-aminobutyric acid) is widely used for its therapeutic effect of providing muscle relaxation from the persistent muscle spasms and posturing often related to spinal and central nervous system injuries. However, baclofen is also a potent neuronal depressant which is most evident in cases of toxicity. In severe toxicity, respiratory failure and obtundation may occur. Case-diagnosis/treatment We present the case of a neurologically devastated 16-year-old on chronic baclofen therapy for bilateral spastic cerebral palsy (Gross Motor Function Classification System level V) who presented with fever, leukocytosis, and hypotension. Initial management with fluid resuscitation and antimicrobials for presumed infection did initially improve the patient's mental status; however, he subsequently became comatose later during the same hospitalization. Comprehensive diagnostic studies and infectious work-up did not reveal an etiology. Upon further examination of history, acute kidney injury from chronic nonsteroidal use and complicated by vancomycin toxicity was suspected to cause acute baclofen toxicity. The patient underwent a single run of hemodialysis with resultant neurologic improvement and later laboratory-confirmed toxic baclofen levels. Conclusion Clinicians should consider possible acute baclofen toxicity in patients with impaired renal function who present with neurologic depression. Respiratory failure and mechanical ventilation, with its associated intensive care costs and complications, may be avoided with prompt treatment using hemodialysis.