Baclofen Toxicity in Kidney Disease

GABAB Receptor: Structure, Biological Functions, and Therapy for Diseases

Gamma-aminobutyric acid (GABA) B receptors (GABABRs) that acts slowly and maintains the inhibitory tone are versatile regulators in the complex nervous behaviors and their involvement in various neuropsychiatric disorders, such as anxiety, epilepsy, pain, drug addiction, and Alzheimer's disease. Additional study advances have implied the crucial roles of GABABRs in regulating feeding-related behaviors, yet their therapeutic potential in addressing the neuropsychiatric disorders, binge eating, and feeding-related disorders remains underutilized. This general review summarized the physiological structure and functions of GABABR, explored the regulation in various psychiatric disorders, feeding behaviors, binge eating, and metabolism disorders, and fully discussed the potential of targeting GABABRs and its regulator-binding sites for the treatment of different psychiatric disorders, binge eating and even obesity. While agonists that directly bind to GABABR1 have some negative side effects, positive allosteric modulators (PAMs) that bind to GABABR2 demonstrate excellent therapeutic efficacy and tolerability and have better safety and therapeutic indexes. Moreover, phosphorylation sites of downstream GABABRs regulators may be novel therapeutic targets for psychiatric disorders, binge eating, and obesity. Further studies, clinical trials in particular, will be essential for confirming the therapeutic value of PAMs and other agents targeting the GABABR pathways in a clinical setting.

Baclofinding solutions: Baclofen-induced encephalopathy in a peritoneal dialysis patient

Baclofen is a gamma-aminobutyric acid agonist that is commonly and widely used for the treatment of muscle spasticity. Given its predominant kidney excretion, patients with reduced kidney function are at particular risk of drug accumulation and toxicity, with neurotoxicity in the form of drowsiness, encephalopathy, seizures, and coma being the most reported clinical features. In addition to the importance of early identification of baclofen toxicity and drug discontinuation, dialysis can effectively accelerate baclofen elimination given its small molecule weight, and the relatively low volume of distribution and weak protein binding. While several cases of baclofen-induced toxicity have been reported in hemodialysis patients, the literature on baclofen toxicity in individuals receiving peritoneal dialysis (PD) is limited. Here, we present a case of baclofen-induced encephalopathy in a PD patient following a single dose of baclofen. In this case, our patient was managed by continuous (24 h) automated PD, with complete recovery of neurological status within three days.

Intrathecal baclofen therapy for spasticity in a person with spinal cord injury and end-stage renal disease dependent on hemodialysis: a case report

INTRODUCTION

Spasticity is one of the most common secondary complications following a spinal cord injury (SCI), which can significantly debilitate a patient irrespective of the severity of the injury. Intrathecal baclofen therapy can effectively reduce global spasticity in bilateral lower extremities at lower doses and allows precise dose titration to manage spasticity optimally. In complex patients with spasticity and multiple medical comorbidities, multidisciplinary teamwork is required to assess ITB safety and deliver timely intervention to prevent secondary complications of spasticity and improve quality of life.

CASE PRESENTATION

A 61-year-old African American male with multiple comorbidities, including end-stage renal disease (ESRD) requiring dialysis sustained non-traumatic SCI due to epidural abscess resulting in paraplegia and severe debilitating spasticity. Spasticity gradually worsened and interfered with his ability to achieve independence with functional activities appropriate for his neurological level of injury. A multidisciplinary team approach in this complex case resulted in a successful ITB trial and subsequent ITB implantation, resulting in reduced spasticity and improved quality of life. To our knowledge, this is the first case report of the administration of intrathecal baclofen pump therapy in a person with SCI and end-stage renal disease (ESRD) dependent on hemodialysis.

DISCUSSION

ITB therapy can be safely delivered in a person with SCI and multiple medical comorbidities, including ESRD, dependent on hemodialysis to manage spasticity. However, a careful evaluation and discussion among the multidisciplinary team managing the patient's morbidities and patient is required to assess the risks and benefits of ITB therapy to allow the patient to make an informed decision.

Baclofen and Tizanidine Adverse Effects Observed Among Community-Dwelling Adults Above the Age of 50 Years: A Systematic Review

OBJECTIVE

This review highlights adverse effects of baclofen and tizanidine in older community-dwelling adults.

DATA SOURCES

A literature search was conducted, including search terms of "adverse effect," "baclofen," "elderly," "falls," "fractures," and "tizanidine." Studies were included if they described community-dwelling adults aged 50 years and older who received oral baclofen or tizanidine. The Federal Drug Administration Adverse Event Reporting System (FAERS) data were compiled for adverse effect incidence.

STUDY SELECTION AND DATA EXTRACTION

The literature search was completed in July 2019 and updated in June 2023. Reviews performed by 2 independent reviewers yielded 15 records. FAERS identified 486 (baclofen) and 305 (tizanidine) adverse effects of interest.

DATA SYNTHESIS

Two retrospective cohort studies evaluating baclofen use in older adults showed increased hospitalizations for encephalopathy in chronic kidney disease (7.2% vs 0.1%) and end-stage renal disease (daily dose 20 mg or more; relative risk [RR] 19.8, 95% CI = [14.0-28.0]). Other articles were case reports; 10 articles reported dyskinesias, encephalopathy or disorientation, and drowsiness associated with baclofen, and 5 articles reported bradycardia and/or hypotension with tizanidine. The FAERS Public Dashboard revealed 12.1% and 28.7% overall incidence of adverse effects of interest, with a 27.8% and 29.2% incidence of falls for baclofen and tizanidine, respectively. Baclofen and tizanidine are associated with concerning adverse effects in older adults. Alternative agents should be considered, but, if necessary, providers should start at lower doses and increase slowly.

CONCLUSIONS

This review highlights the importance of using baclofen and tizanidine with caution in older adults.

Tizanidine: Advances in Pharmacology & Therapeutics and Drug Formulations

Background

Skeletal muscle relaxants (SMRs) are widely used in treating musculoskeletal conditions. All SMRs, with the exception of baclofen and tizanidine, are on the list of 2023 American Geriatrics Society Beers Criteria® for potentially inappropriate medication use in older adults. In our geriatric practice, off-label use of tizanidine as preemptive analgesia drove us to find recent advances in its pharmacology and therapeutics. An update review of tizanidine was thus presented, aiming to bring the latest knowledge to clinicians and promote further research and practical exploration.

Methods

Relevant literature up to December 2023 was identified through searches of PubMed, Web of Science, and Embase.

Results

Tizanidine, a centrally acting alpha-2 adrenoceptor agonist with both antispastic and antispasmodic activity, shows efficacy in the common indications for all SMRs. From the perspective of drug safety, tizanidine has lower incidences of adverse events (injury, delirium, encephalopathy, falls, and opioid overdose) compared to baclofen, no association with risk of Alzheimer's disease as with orphenadrine, no risk of serotonin syndrome like metaxalone when comedicated with serotonergic drugs, no significant pharmacokinetic changes in CYP2C19 poor metabolizers unlike diazepam and carisoprodol, and no physically addictive or abuse properties like carisoprodol and diazepam. From the perspective of new and potential therapeutic uses, tizanidine has additional benefits (eg, gastroprotection that can improve patient tolerance to nonsteroidal anti-inflammatory agents, anti-neuropathic pain, a key component of multimodal analgesia strategy to reduce early postoperative pain, and anti-tumor effects). New delivery systems of tizanidine are developing to improve the pharmacokinetics of oral products, including buccal patches, transdermal delivery systems, nasal spray, and in situ rectal gel.

Conclusion

Tizanidine is an SMR with unique features and may be an optimal initial choice for older adults. There would be more scientific studies, wider therapeutic applications, and new drug formulations in the future.

Pharmacotherapy for Spine-Related Pain in Older Adults

As the population ages, spine-related pain is increasingly common in older adults. While medications play an important role in pain management, their use has limitations in geriatric patients due to reduced liver and renal function, comorbid medical problems, and polypharmacy. This review will assess the evidence basis for medications used for spine-related pain in older adults, with a focus on drug metabolism and adverse drug reactions. A PubMed/OVID search crossing common spine, neck, and back pain terms with key words for older adults and geriatrics was combined with common drug classes and common drug names and limited to clinical trials and age over 65 years. The results were then reviewed with identification of commonly used drugs and drug categories: nonsteroidal anti-inflammatories (NSAIDs), acetaminophen, corticosteroids, gabapentin and pregabalin, antispastic and antispasmodic muscle relaxants, tricyclic antidepressants (TCAs), serotonin-norepinephrine reuptake inhibitors (SNRIs), tramadol, and opioids. Collectively, 138 double-blind, placebo-controlled trials were the focus of the review. The review found a variable contribution of high-quality studies examining the efficacy of medications for spine pain primarily in the geriatric population. There was strong evidence for NSAID use with adjustments for gastrointestinal and renal risk factors. Gabapentin and pregabalin had mixed evidence for neuropathic pain. SNRIs had good evidence for neuropathic pain and a more favorable safety profile than TCAs. Tramadol had some evidence in older patients, but more so in persons aged < 65 years. Rational therapeutic choices based on geriatric spine pain diagnosis are helpful, such as NSAIDs and acetaminophen for arthritic and myofascial-based pain, gabapentinoids or duloxetine for neuropathic and radicular pain, antispastic agents for myofascial-based pain, and combination therapy for mixed etiologies. Tramadol can be well tolerated in older patients, but has risks of cognitive and classic opioid side effects. Otherwise, opioids are typically avoided in the treatment of spine-related pain in older adults due to their morbidity and mortality risk and are reserved for refractory severe pain. Whenever possible, beneficial geriatric spine pain pharmacotherapy should employ the lowest therapeutic doses with consideration of polypharmacy, potentially decreased renal and hepatic metabolism, and co-morbid medical disorders.

Transient alteration of consciousness in spinal cord injury secondary to Baclofen use: a case report

INTRODUCTION

Oral baclofen is commonly used for spasticity management, especially with neurogenic bladder in spinal cord injury (SCI). A less common side effect of baclofen is transient alterations of consciousness, which can easily be confused for altered mental status secondary to orthostatic hypotension in SCI.

CASE PRESENTATION

A 43-year-old man with an acute SCI secondary to an aortic dissection was found to have episodes of confusion after titrating oral baclofen from 5 mg three times per day to 10 mg three times per day at an acute rehabilitation facility. Orthostatic hypotension was initially suspected as the cause of transient alterations of consciousness; however, he was never found to be hypotensive during these episodes. His confusion resolved several days after discontinuation of baclofen.

DISCUSSION

Although, confusion and lightheadedness in SCI are commonly caused by orthostatic hypotension, it is important for physicians to be cognizant of baclofen's side effects, which increase in the setting of acute kidney injury (AKI). If an adverse effect is suspected, baclofen should be tapered while remaining observant for signs of baclofen withdrawal, which can be life-threatening. This case report is a reminder for clinicians to be aware of the uncommon adverse effects of baclofen when initiating therapy in SCI, especially in patients with AKI and neurogenic bladders.

A Small Dose Can Cause a Major Problem

Baclofen is a presynaptic gamma-aminobutyric acid agonist, which has been used to treat muscle spasms. Due to its low cost and low addiction potential, baclofen has been the muscle relaxant of choice for many years. This drug is metabolized in the kidneys, posing a threat to patients with underlying renal dysfunction, with complications ranging from drug toxicity to death. We present a case of baclofen toxicity in a patient with renal failure on hemodialysis, who presented with signs and symptoms of baclofen overdose after consuming 10 mg of the medication. The highlight of this case is the detailed history taking, verifying all home medications, and thorough physical examination of the patient.

Low-Dose Baclofen-Induced Encephalopathy in a Healthy Young Adult: Is Baclofen Toxicity Dose-Dependent?

Baclofen is a commonly used medication for managing muscle spasticity with the potential of causing life-threatening adverse effects, including encephalopathy as well as withdrawal symptoms including confusion and hallucinations following abrupt discontinuation. Severe toxicity with baclofen is common in patients with kidney disease, hence the importance of dose reduction and monitoring in patients with renal impairment. This article reports a case of encephalopathy with low-dose baclofen in an otherwise healthy young adult concurrently taking ibuprofen and baclofen and aims to underscore the importance of potential drug interaction and patient education when initiating baclofen.

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.

Management of severe baclofen toxicosis using hemodialysis in conjunction with mechanical ventilation in a cat with chronic kidney disease

Case summary

A 2-year-old castrated male domestic shorthair cat was presented for evaluation of acute and progressive neurologic signs 2-4 h after exposure to baclofen. The suspected ingested dose was 2.1 mg/kg. On admission, the cat was tetraplegic with stuporous mentation, and venous blood gas analysis showed mild hypercapnia (PvCO₂ 43.4 mmHg) raising concern for hypoventilation. Owing to the acute nature of the ingestion, severity of the clinical signs and reported history of chronic kidney disease, hemodialysis was recommended to remove the toxin. A 5 h hemodialysis session was performed using an intermittent platform without hemoperfusion. At the beginning of hemodialysis, worsening hypoventilation and hypercapnia (PvCO₂ 88.6 mmHg) required endotracheal intubation and manual ventilation initially, followed by mechanical ventilation. At the end of the dialysis session, the cat was breathing spontaneously and disconnected from the ventilator. The cat was ambulatory and alert 1 h after the end of dialysis. After an additional 12 h of monitoring, the cat had full return of neurologic function and was discharged from hospital. Serum baclofen concentration measured prior to, during and after hemodialysis showed a 77.7% reduction in baclofen levels immediately after hemodialysis.

Relevance and novel information

This is the first report of baclofen toxicity in a cat successfully treated with hemodialysis and mechanical ventilation simultaneously. Treatment with hemodialysis therapy and mechanical ventilation could be considered in cases of acute baclofen toxicosis to improve outcome and reduce the length of the hospital stay.

Less is More: Deprescribing Medications in Older Adults with Kidney Disease: A Review

Due to age and impaired kidney function, older adults with kidney disease are at increased risk of medication-related problems and related hospitalizations. One proa ctive approach to minimize this risk is deprescribing. Deprescribing refers to the systematic process of reducing or stopping a medication. Aside from preventing harm, deprescribing can potentially optimize patients' quality of life by aligning medications with their goals of care. For some patients, deprescribing could involve less aggressive management of their diabetes and/or hypertension. In other instances, deprescribing targets may include potentially inappropriate medications that carry greater risk of harm than benefit in older adults, medications that have questionable efficacy, including medications that have varying efficacy by degree of kidney function, and that increase medication regimen complexity. We include a guide for clinicians to utilize in deprescribing, the List, Evaluate, Shared Decision-Making, Support (LESS) framework. The LESS framework provides key considerations at each step of the deprescribing process that can be tailored for the medications and context of individu al patients. Patient characteristics or clinical events that warrant consideration of deprescribing include limited life expectancy, cognitive impairment, and health status changes, such as dialysis initiation or recent hospitalization. We acknowledge patient-, clinician-, and system-level challenges to the depre scribing process. These include patient hesitancy and challenges to discussing goals of care, clinician time constraints and a lack of evidence-based guidelines, and system-level challenges of interoperable electronic health records and limited incentives for deprescribing. However, novel evidence-based tools designed to facilitate deprescribing and future evidence on effectiveness of deprescribing could help mitigate these barriers. This review provides foundational knowledge on deprescribing as an emerging component of clinical practice and research within nephrology.

Nonsteroidal anti-inflammatory drugs in end-stage kidney disease: dangerous or underutilized?

Introduction: Nonsteroidal anti-inflammatory drugs (NSAIDs) are a popular class of analgesic and anti-inflammatory medications, but their use is often avoided in end-stage kidney disease (ESKD) patients due to their reputation for nephrotoxic side effects. This removes a useful agent from the analgesic arsenal, even as ESKD patients suffer from proportionally more severe chronic pain than the general population as well as from a large reliance on opioid medications. Areas Covered: This paper reviews the current literature to comprehensively define the pharmacologic mechanisms and adverse effects of NSAIDs and reassesses the viability of their use in ESKD patients. Expert opinion: The evidence directly examining the impact of NSAIDs on long-term outcomes in ESKD is limited. Further study quantifying the risk of NSAID use - especially in dialysis-dependent patients - is warranted. Given the difficulty in achieving adequate pain control in ESKD patients, limited use of NSAIDs in these patients may yet be justified.

Synthesis and biological analysis of anti-addiction effect and hepatotoxicity of tow baclofen analogues complexed with β-Cyclodextrin

AIM AND OBJECTIVE

The excessive consumption of alcohol and the installation of a dependence is, in most cases, facilitated by favorable psychological factors which trigger and maintain the behavior of consumption. Examples more frequently encountered in individuals having difficulty with alcohol are in particular: one or more anxiety disorders, deficits in the capacities to manage stress and anxiety. The main objective of this work was study in vivo the anti-addiction effect and hepatotoxicity of tow baclofen analogues complexed with β-Cyclodextrin (βCD) on an alcohol-dependent rat model.

MATERIALS AND METHODS

The synthesis of two analogues ABF1 and ABF2 close to baclofen was reported. The structural determination of the two compounds was confirmed by NMR and IR analysis. The complexation of analogues with βCyclodextrin (βCD) was performed in water at room temperature (25 °C). The interactions of ABF with β-Cyclodextrin, and the stability constant (Ka) of the inclusion complex formed between them were investigated by using UV-visible spectroscopy. The biological effects of baclofen and the two analogues on alcohol dependence were studied in wistar rats. The anti-addiction effect of the analogues was tested by measuring the alcohol intake and the variation of the animal behaviour. The toxicity of the compounds was also analysed on liver injury markers.

RESULTS

The amino-3-phenylbutanoic acid (ABF1) and 3,4,5-trihydroxy-N-(methyl-2-acetate) benzamide (ABF2) were synthesized. The complexation of both analogues of baclofen (BF) with β-cyclodextrin (βCD) (ABF- βCD) was realized and confirmed by the stability constant of the inclusion complex (Ka) and Job's method. The evaluation of anti-addiction activity in vivo showed that ABF1-βCD inhibits the consumption of alcohol at the doses equivalent to those of baclofen. Both baclofen analogues have shown an anxiolytic effect. Regarding the toxicity of the two compounds, our results showed that ABF1-βCD has less toxic effect than baclofen, it reduces the activity of ALT and AST enzymes. Histologically ABF1-βCD has no effect on structure of the liver in addition and has a protective effect against lesions alcohol-induced liver disease.

CONCLUSION

Therefore, it can be suggested that ABF1 analogue combined with β-Cyclodextrin can be used as a treatment for alcohol dependence. Further clinical works are needed to confirm its effectiveness.

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.

Classics in Chemical Neuroscience: Baclofen

Baclofen, β-(4-chlorophenyl)-γ-aminobutyric acid, holds a unique position in neuroscience, remaining the only U.S. Food and Drug Administration (FDA) approved GABA_B agonist. While intended to be a more brain penetrant, i.e, ability to cross the blood-brain barrier (BBB), version of GABA (γ-aminobutyric acid) for the potential treatment of epilepsy, baclofen's highly efficacious muscle relaxant properties led to its approval, as a racemate, for the treatment of spasticity. Interestingly, baclofen received FDA approval before its receptor, GABA_B, was discovered and its exact mechanism of action was known. In recent times, baclofen has a myriad of off-label uses, with the treatment for alcohol abuse and drug addiction garnering a great deal of attention. This Review aims to capture the >60 year legacy of baclofen by walking through the history, pharmacology, synthesis, drug metabolism, routes of administration, and societal impact of this Classic in chemical neuroscience.

The case for cautious consumption: NSAIDs in chronic kidney disease

PURPOSE OF REVIEW

Strong epidemiological and pathologic evidence associates NSAIDs with kidney disease, both acute and chronic. Hence, the usage of NSAIDs has decreased in patients with, or at risk for, chronic kidney disease (CKD). Coupled with this has been a rise in use of opioids and other non-NSAID alternatives, which do come with significant, and underrecognized, risk of nonrenal adverse events. We review the literature to understand if this shift is appropriate or deleterious.

RECENT FINDINGS

NSAIDs do have a low but tangible risk in causing acute kidney injury, electrolyte imbalances, and increasing blood pressure. However, their role in causing progressive kidney disease is due to long-term usage in high cumulative dosages, and the use of NSAIDs in combination with other agents. Alternatives such as opioids, tramadol, gabapentin and baclofen have weak evidence to support their use and strong evidence to show their harm in patients with CKD.

SUMMARY

Tradeoffs are inherent in using active pharmaceuticals, and NSAIDs are no exception. Balancing potential benefits with possible adverse effects around pain management should be a part of every conversation for patients with kidney disease.

Pharmacokinetics and toxicity of high-dose baclofen in ICU patients

BACKGROUND

High-dose baclofen could prove beneficial in patients with unhealthy alcohol use in intensive care units (ICU). However, the pharmacokinetic properties of baclofen are unknown in this population. Our objectives were to investigate the pharmacokinetics of baclofen and the relationship between baclofen exposure and its toxicity in the ICU.

MATERIALS AND METHODS

As part of a healthcare quality improvement project, we conducted a prospective, single-center study in a surgical intensive care unit at Nantes University Hospital in order to assess our local protocol of sedation in patients with consumption of alcohol above the recommended limits by the National Institute on Alcohol Abuse and Alcoholism (NIAAA). Baclofen pharmacokinetics were investigated by a non-compartment analysis and a population approach in 20 patients under mechanical ventilation. After a baclofen loading dose on day 1, daily doses were divided into 3 intakes adapted to glomerular filtration rate (GFR) and blood samples were withdrawn on day 3 for pharmacokinetic analysis. Baclofen was administered until extubation or tracheostomy and agitation-related events as well as the potential side effects of baclofen were noted.

RESULTS

In this population, pharmacokinetic parameters [absorption latency time = 0.37 h, absorption constant rate = 2.2 h^-1, apparent volume of distribution = 105 L, apparent clearance (l/h) = 13.5 × (GFR/103)^0.839] were characterized by modified absorption and the influence of renal function: renal failure significantly increased baclofen exposure (p = .007) and significantly decreased baclofen clearance (p = .007) compared with patients without renal failure. When comparing patients with or without possible signs of baclofen toxicity, no difference was found regarding baclofen exposure (p = .34) and plasma peak concentration (p = .26).

CONCLUSIONS

The a priori planned algorithm for dose adaptation according to renal clearance appeared to be suitable in our population. Daily administration of 150 mg of baclofen in ICU patients with preserved renal function did not lead to toxic concentrations in the plasma. A dose reduction of approximately 40%, 60% and 70% in patients with mild, moderate and severe renal failure could be suggested.

Muscle Relaxant Use Among Hemodialysis Patients: Prevalence, Clinical Indications, and Adverse Outcomes

RATIONALE & OBJECTIVE

Muscle relaxants are often used to treat musculoskeletal pain or cramping, which are commonly experienced by hemodialysis patients. However, the extent to which muscle relaxants are prescribed in this population and the risks associated with their use have not been characterized.

STUDY DESIGN

Observational cohort study.

SETTING & PARTICIPANTS

140,899 Medicare-covered adults receiving hemodialysis in 2011, identified in the US Renal Data System.

EXPOSURE

Time-varying muscle relaxant exposure.

OUTCOMES

Primary outcomes were time to first emergency department visit or hospitalization for altered mental status, fall, or fracture. Secondary outcomes were death and composites of death with each of the primary outcomes.

ANALYTICAL APPROACH

Multivariable Cox regression analysis.

RESULTS

10% of patients received muscle relaxants in 2011. 11%, 6%, 3%, and 13% had an episode of altered mental status, fall, fracture, and death, respectively. Muscle relaxant use was associated with higher risk for altered mental status (HR, 1.39; 95% CI, 1.29-1.51) and fall (HR, 1.18; 95% CI, 1.05-1.33) compared to no use. Muscle relaxant use was not statistically significantly associated with higher risk for fracture (HR, 1.17; 95% CI, 0.98-1.39). Muscle relaxant use was associated with lower hazard of death (HR, 0.85; 95% CI, 0.76-0.94). However, hazards were higher for altered mental status or death (HR, 1.17; 95% CI, 1.10-1.25), fall or death (HR, 1.14; 95% CI, 1.06-1.22), and fracture or death (HR, 1.10; 95% CI, 1.01-1.20).

LIMITATIONS

A causal association between muscle relaxant use and outcomes cannot be inferred, and residual confounding cannot be excluded. Exposure and outcomes were ascertained using administrative claims.

CONCLUSIONS

Muscle relaxant use was common in hemodialysis patients and associated with altered mental status and falls. We could not rule out a clinically meaningful association between muscle relaxant use and fracture. The lower risk for death with muscle relaxants may have been the result of residual confounding. Future research to define the appropriate use of muscle relaxants in this population is warranted.

Pharmacokinetic Studies of Baclofen Are Not Sufficient to Establish an Optimized Dosage for Management of Alcohol Disorder

Several clinical randomized trials have evaluated the interest of baclofen in patients with alcohol use disorder. Depending on the study design and the inclusion criteria, the results vary from enthusiastic to pessimistic. However, all researchers and practitioners agree that they observe a wide variability in the therapeutic responses. If some patients exhibit a clinical response at low doses, ~40 mg daily, others require doses higher than 300 mg. Before multiplying new other clinical trials, it is required to better understand the reason of this variability. Several mechanisms may be responsible for providing different effects with an identical daily dose. Especially, each pharmacokinetic step, absorption, distribution, metabolism, and elimination may lead to a different exposure after an identical dose. Absorption may imply a saturation process limiting the bioavailability (F) of baclofen in some patients. In such a situation, food, or drug-drug interaction can change the absorption rate of the drug modifying the maximum concentration (Cmax) and area under the curve (AUC). Distribution and brain penetration across the blood-brain barrier may depend of a specific transporter. These transporters are subject to genetic polymorphism and drug-drug interaction. Finally, elimination may be increased by a specific secretion pathway. This review describes all available pharmacokinetic data on these different pharmacokinetics steps aiming to identify the source of variability of baclofen in patients with alcohol use disorder.