Spinal cord injury sequelae alter drug pharmacokinetics: an overview

Prevalence of opioid use in adults with spinal cord injury: A systematic review and meta-analysis

OBJECTIVE

To determine the prevalence, reported harms and factors associated with opioid use among adults with spinal cord injury (SCI) living in the community.

STUDY DESIGN

Systematic review and meta-analysis.

METHODS

Comprehensive literature searches were conducted in PubMed (MEDLINE), EMBASE, CINAHL, Web of Science and Scopus for articles published between 2000 and 2023. Risk of bias was assessed using a prevalence-specific tool. Random-effects meta-analyses were conducted to pool prevalence data for any context of opioids. Sensitivity and subgroup analyses were also performed. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed, and the study protocol was registered via Prospero (CRD42022350768).

RESULTS

Of the 4969 potential studies, 38 were included in the review. Fifty-three percent of studies had a low risk of bias, with a high risk of bias in 5% of studies. The pooled prevalence for the 38 studies included in the meta-analysis (total cohort size of 50,473) across any opioid context was 39% (95% confidence interval [CI], 32-47). High heterogeneity was evident, with a prediction interval twice as wide as the 95% CI (prediction interval, 7-84%). Mean or median opioid dose was unreported in 95% of studies. Opioid dose and factors related to opioids were also rarely explored in the SCI populations.

CONCLUSIONS

Results should be interpreted with caution based on the high heterogeneity and imprecise pooled prevalence of opioids. Contextual details including pain, cohort-specific injury characteristics and opioid dosage were inconsistently reported, indicating a clear need for additional studies in a population at greater risk of experiencing opioid-related adverse effects.

Safety and Efficacy of Riluzole in Traumatic Spinal Cord Injury: A Systematic Review With Meta-Analyses

Traumatic spinal cord injury (SCI) is a cause of significant morbidity, often resulting in long-term disability. We aimed to compare outcomes after riluzole versus patients who received placebo or standard of care with no specific intervention. MEDLINE, Embase, Scopus, and Cochrane Library database searches yielded 92 records, and five met the study inclusion criteria. Fixed-effect and random-effects models were used to establish odds ratios (ORs) and mean difference (MD) with 95% confidence intervals (CIs) for each outcome. The results of the pooled analysis showed that in patients with acute traumatic SCI, riluzole resulted in increased American Spinal Injury Association (ASIA) motor scores at 3 months (MD 0.26, 95% CI [-0.10,0.61], I2 = 0%; p = 0.157) and 6 months (MD 0.21, 95% CI [-0.17,0.60], I2 = 0%; p = 0.280) and change in ASIA Impairment Scale (AIS) at 3 months (OR 0.59, 95% CI [-0.12,1.30], I2 = 0%, p = 0.101) and 6 months (OR 0.28, 95% CI [-0.50,1.06], I2 = 0%, p = 0.479) in comparison to the control groups, though not to a level of statistical significance. Riluzole resulted in fewer adverse events than the control groups (OR -0.12, 95% CI [-1.59,1.35], I2 = 0%, p = 0.874) and lower mortality (OR -0.20, 95% CI [-1.03,0.63], I2 = 0%, p = 0.640), though also not to a level of statistical significance. These meta-analyses suggest that riluzole for the treatment of traumatic SCI is safe and results in improved neurological outcomes when compared to controls, though not to a level of statistical significance. More robust prospective, randomized studies are necessary to help inform the safety and efficacy of riluzole for traumatic SCI.

Catalytic antioxidant nanoparticles mitigate secondary injury progression and promote functional recovery in spinal cord injury model

Traumatic spinal cord injury exacerbates disability with time due to secondary injury cascade triggered largely by overproduction of reactive oxygen species (ROS) at the lesion site, causing oxidative stress. This study explored nanoparticles containing antioxidant enzymes (antioxidant NPs) to neutralize excess ROS at the lesion site and its impact. When tested in a rat contusion model of spinal cord injury, a single dose of antioxidant NPs, administered intravenously three hours after injury, effectively restored the redox balance at the lesion site, interrupting the secondary injury progression. This led to reduced spinal cord tissue inflammation, apoptosis, cavitation, and inhibition of syringomyelia. Moreover, the treatment reduced scar tissue forming collagen at the lesion site, protected axons from demyelination, and stimulated lesion healing, with further analysis indicating the formation of immature neurons. The ultimate effect of the treatment was improved motor and sensory functions and rapid post-injury weight loss recovery. Histological analysis revealed activated microglia in the spinal cord displaying rod-shaped anti-inflammatory and regenerative phenotype in treated animals, contrasting with amoeboid inflammatory and degenerative phenotype in untreated control. Overall data suggest that restoring redox balance at the lesion site shifts the dynamics in the injured spinal cord microenvironment from degenerative to regenerative, potentially by promoting endogenous repair mechanisms. Antioxidant NPs show promise to be developed as an early therapeutic intervention in stabilizing injured spinal cord for enhanced recovery.

Pharmacological management of acute spinal cord injury: a longitudinal multi-cohort observational study

Multiple types and classes of medications are administered in the acute management of traumatic spinal cord injury. Prior clinical studies and evidence from animal models suggest that several of these medications could modify (i.e., enhance or impede) neurological recovery. We aimed to systematically determine the types of medications commonly administered, alone or in combination, in the transition from acute to subacute spinal cord injury. For that purpose, type, class, dosage, timing, and reason for administration were extracted from two large spinal cord injury datasets. Descriptive statistics were used to describe the medications administered within the first 60 days after spinal cord injury. Across 2040 individuals with spinal cord injury, 775 unique medications were administered within the two months after injury. On average, patients enrolled in a clinical trial were administered 9.9 ± 4.9 (range 0-34), 14.3 ± 6.3 (range 1-40), 18.6 ± 8.2 (range 0-58), and 21.5 ± 9.7 (range 0-59) medications within the first 7, 14, 30, and 60 days post-injury, respectively. Those enrolled in an observational study were administered on average 1.7 ± 1.7 (range 0-11), 3.7 ± 3.7 (range 0-24), 8.5 ± 6.3 (range 0-42), and 13.5 ± 8.3 (range 0-52) medications within the first 7, 14, 30, and 60 days post-injury, respectively. Polypharmacy was commonplace (up to 43 medications per day per patient). Approximately 10% of medications were administered acutely as prophylaxis (e.g., against the development of pain or infections). To our knowledge, this was the first time acute pharmacological practices have been comprehensively examined after spinal cord injury. Our study revealed a high degree of polypharmacy in the acute stages of spinal cord injury, raising the potential to impact neurological recovery. All results can be interactively explored on the R_XSCI web site ( https://jutzelec.shinyapps.io/RxSCI/ ) and GitHub repository ( https://github.com/jutzca/Acute-Pharmacological-Treatment-in-SCI/ ).

Potentially harmful drug-drug interactions in the therapeutic regimens of persons with spinal cord injury

OBJECTIVES

Individuals with spinal cord injury deal with multiple health complications that require them to use many medications. The purpose of this paper was to find the most common potentially harmful drug-drug interactions (DDIs) in therapeutic regimens of persons with spinal cord injury, and the risk factors associated with it. We further highlight the relevance of each of the DDIs specific to spinal cord injury population.

DESIGN

Observational design and cross-sectional analysis.

SETTING

Community; Canada.

PARTICIPANTS

Individuals with spinal cord injury (n = 108).

MAIN OUTCOME MEASURES/ANALYSIS

The main outcome was the presence of one or more potential DDIs that can lead to an adverse outcome. All the reported drugs were classified as per the World Health Organization's Anatomical Therapeutic Chemical Classification system. Twenty potential DDIs were selected for the analysis based on the most common medications prescribed to people with spinal cord injury and severity of clinical consequences. The medication lists of study participants were analyzed for selected DDIs.

RESULTS

Among the 20 potential DDIs analyzed in our sample, the top 3 prevalent DDIs were Opioids + Skeletal Muscle Relaxants, Opioids + Gabapentinoids, and Benzodiazepines + ≥ 2 other central nervous system (CNS)-active drugs. Of the total sample of 108 respondents, 31 participants (29%) were identified with having at least one potential DDI. The risk of having a potential DDI was highly associated with polypharmacy, though no associations were found between the presence of a drug interaction and age, sex, level of injury, time since injury, or cause of injury among the study sample.

CONCLUSION

Almost three out of ten individuals with spinal cord injury were at risk of having a potentially harmful drug interaction. Clinical and communication tools are needed that facilitate identification and elimination of harmful drug combinations in the therapeutic regimens of patients with spinal cord injury.

Clinical Decision Support for Precision Dosing: Opportunities for Enhanced Equity and Inclusion in Health Care

Precision dosing aims to tailor doses to individual patients with the goal of improving treatment efficacy and avoiding toxicity. Clinical decision support software (CDSS) plays a crucial role in mediating this process, translating knowledge derived from clinical trials and real-world data (RWD) into actionable insights for clinicians to use at the point of care. However, not all patient populations are proportionally represented in clinical trials and other data sources that inform CDSS tools, limiting the applicability of these tools for underrepresented populations. Here, we review some of the limitations of existing CDSS tools and discuss methods for overcoming these gaps. We discuss considerations for study design and modeling to create more inclusive CDSS, particularly with an eye toward better incorporation of biological indicators in place of race, ethnicity, or sex. We also review inclusive practices for collection of these demographic data, during both study design and in software user interface design. Because of the role CDSS plays in both recording routine clinical care data and disseminating knowledge derived from data, CDSS presents a promising opportunity to continuously improve precision dosing algorithms using RWD to better reflect the diversity of patient populations.

Longitudinal Impact of Acute Spinal Cord Injury on Clinical Pharmacokinetics of Riluzole, a Potential Neuroprotective Agent

Riluzole, a benzothiazole sodium channel blocker that received US Food and Drug Administration approval to attenuate neurodegeneration in amyotrophic lateral sclerosis in 1995, was found to be safe and potentially efficacious in a spinal cord injury (SCI) population, as evident in a phase I clinical trial. The acute and progressive nature of traumatic SCI and the complexity of secondary injury processes can alter the pharmacokinetics of therapeutics. A 1-compartment with first-order elimination population pharmacokinetic model for riluzole incorporating time-dependent clearance and volume of distribution was developed from combined data of the phase 1 and the ongoing phase 2/3 trials. This change in therapeutic exposure may lead to a biased estimate of the exposure-response relationship when evaluating therapeutic effects. With the developed model, a rational, optimal dosing scheme can be designed with time-dependent modification that preserves the required therapeutic exposure of riluzole.

Impact of gastrointestinal tract variability on oral drug absorption and pharmacokinetics: An UNGAP review

The absorption of oral drugs is frequently plagued by significant variability with potentially serious therapeutic consequences. The source of variability can be traced back to interindividual variability in physiology, differences in special populations (age- and disease-dependent), drug and formulation properties, or food-drug interactions. Clinical evidence for the impact of some of these factors on drug pharmacokinetic variability is mounting: e.g. gastric pH and emptying time, small intestinal fluid properties, differences in pediatrics and the elderly, and surgical changes in gastrointestinal anatomy. However, the link of colonic factors variability (transit time, fluid composition, microbiome), sex differences (male vs. female) and gut-related diseases (chronic constipation, anorexia and cachexia) to drug absorption variability has not been firmly established yet. At the same time, a way to decrease oral drug pharmacokinetic variability is provided by the pharmaceutical industry: clinical evidence suggests that formulation approaches employed during drug development can decrease the variability in oral exposure. This review outlines the main drivers of oral drug exposure variability and potential approaches to overcome them, while highlighting existing knowledge gaps and guiding future studies in this area.

Hepatic dysfunction after spinal cord injury: A vicious cycle of central and peripheral pathology?

The liver is essential for numerous physiological processes, including filtering blood from the intestines, metabolizing fats, proteins, carbohydrates and drugs, and regulating iron storage and release. The liver is also an important immune organ and plays a critical role in response to infection and injury throughout the body. Liver functions are regulated by autonomic parasympathetic innervation from the brainstem and sympathetic innervation from the thoracic spinal cord. Thus, spinal cord injury (SCI) at or above thoracic levels disrupts major regulatory mechanisms for hepatic functions. Work in rodents and humans shows that SCI induces liver pathology, including hepatic inflammation and fat accumulation characteristic of a serious form of non-alcoholic fatty liver disease (NAFLD) called non-alcoholic steatohepatitis (NASH). This hepatic pathology is associated with and likely contributes to indices of metabolic dysfunction often noted in SCI individuals, such as insulin resistance and hyperlipidemia. These occur at greater rates in the SCI population and can negatively impact health and quality of life. In this review, we will: 1) Discuss acute and chronic changes in human and rodent liver pathology and function after SCI; 2) Describe how these hepatic changes affect systemic inflammation, iron regulation and metabolic dysfunction after SCI; 3) Describe how disruption of the hepatic autonomic nervous system may be a key culprit in post-injury chronic liver pathology; and 4) Preview ongoing and future research that aims to elucidate mechanisms driving liver and metabolic dysfunction after SCI.

Spinal cord injury pharmacotherapy: Current research & development and competitive commercial landscape as of 2015

CONTEXT

Current treatment of spinal cord injury (SCI) focuses on cord stabilization to prevent further injury, rehabilitation, management of non-motor symptoms, and prevention of complications. Currently, no approved treatments are available, and limited treatment options exist for symptoms and complications associated with chronic SCI. This review describes the pharmacotherapy landscape in SCI from both commercial and research and development (R&D) standpoints through March 2015.

METHODS

Information about specific compounds has been obtained through drug pipeline monographs in the Pharmaprojects® (Citeline, Inc., New York, New York, USA) drug database (current as of a search on May 30, 2014), websites of individual companies with compounds in development for SCI (current as of March 24, 2015), and a literature search of published R&D studies to validate the Pharmaprojects® source for selected compounds (current as of March 24, 2015).

RESULTS

Types of studies conducted and outcomes measured in earlier phases of development are described for compounds in clinical development Currently four primary mechanisms are under investigation and may yield promising therapeutic targets: 1) neuronal regeneration; 2) neuroprotection (including anti-inflammation); 3) axonal reconnection; and 4) neuromodulation and signal enhancement. Many other compounds are no longer under investigation for SCI are mentioned; however, in most cases, the reason for terminating their development is not clear.

CONCLUSION

There is urgent need to develop disease-modifying therapy for SCI, yet the commercial landscape remains small and highly fragmented with a paucity of novel late-stage compounds in R&D.

Systemic administration of epothilone D improves functional recovery of walking after rat spinal cord contusion injury

Central nervous system (CNS) injuries cause permanent impairments of sensorimotor functions as mature neurons fail to regenerate their severed axons. The poor intrinsic growth capacity of adult CNS neurons and the formation of an inhibitory lesion scar are key impediments to axon regeneration. Systemic administration of the microtubule stabilizing agent epothilone B promotes axon regeneration and recovery of motor function by activating the intrinsic axonal growth machinery and by reducing the inhibitory fibrotic lesion scar. Thus, epothilones hold clinical promise as potential therapeutics for spinal cord injury. Here we tested the efficacy of epothilone D, an epothilone B analog with a superior safety profile. By using liquid chromatography and mass spectrometry (LC/MS), we found adequate CNS penetration and distribution of epothilone D after systemic administration, confirming the suitability of the drug for non-invasive CNS treatment. Systemic administration of epothilone D reduced inhibitory fibrotic scarring, promoted regrowth of injured raphespinal fibers and improved walking function after mid-thoracic spinal cord contusion injury in adult rats. These results confirm that systemic administration of epothilones is a valuable therapeutic strategy for CNS regeneration and repair after injury and provides a further advance for potential clinical translation.

Prescription drug claims following a traumatic spinal cord injury for older adults: a retrospective population-based study in Ontario, Canada

Study design

Retrospective cohort study.

Objectives

The objectives for this study were to examine the prevalence of polypharmacy for people with traumatic spinal cord injury (SCI) following injury and to determine risk factors.

Setting

Ontario, Canada

Methods

We used provincial-level administrative health services data of publicly funded healthcare encounters housed at the Institute for Clinical Evaluative Sciences, Toronto, Ontario. We examined prescription medications dispensed over a 1 year period post injury for persons 66+ years with an index traumatic SCI between 2004 and 2014. Polypharmacy was defined as being on 10 or more drug classes. Descriptive and analytical statistics were conducted. Relative risks and 95% confidence limits for factors related to polypharmacy were calculated using a robust Poisson multivariate regression model.

Results

We identified 418 cases of persons with traumatic SCI during the observation window. A total of 233 patients (56%) were taking at least 10 drug classes in the year following discharge from care for traumatic SCI. The mean number of drug classes taken post injury was 11 (SD = 6). Continuity of care was significantly associated with polypharmacy, with a higher continuity of care (having at least 75% of visits with the same doctor) reducing the risk of polypharmacy. The most common drugs prescribed were laxatives, opioids and cardiovascular-related drugs.

Conclusion

Findings suggest that polypharmacy is extensive among older adults with traumatic SCI. Persons with better continuity of care are less likely to have polypharmacy compared to those with less continuity.

Sponsorship

This project was funded by a Connaught New Investigator Award (University of Toronto), and the Craig H. Neilsen Foundation Psychosocial Research Pilot Grant (Grant #441259).

Spinal Cord Injury Level Influences Acute Plasma Caffeine Responses

PURPOSE

This study aimed to investigate the absorption curve and acute effects of caffeine at rest in individuals with no spinal cord injury (SCI), paraplegia (PARA), and tetraplegia (TETRA).

METHODS

Twenty-four healthy males (eight able-bodied [AB], eight PARA, and eight TETRA) consumed 3 mg·kg caffeine anhydrous (CAF) in a fasted state. Plasma caffeine [CAF], glucose, lactate, free fatty acid, and catecholamine concentrations were measured during a 150-min rest period.

RESULTS

Peak [CAF] was greater in TETRA (21.5 μM) compared with AB (12.2 μM) and PARA (15.1 μM), and mean peak [CAF] occurred at 70, 80, and 80 min, respectively. Moderate and large effect sizes were revealed for TETRA compared with PARA and AB (-0.55 and -1.14, respectively) for the total area under the [CAF] versus time curve. Large interindividual responses were apparent in SCI groups. The change in plasma catecholamine concentrations after CAF did not reach significance (P > 0.05); however, both adrenaline and noradrenaline concentrations were lowest in TETRA. Significant increases in free fatty acid were seen over time (P < 0.0005), but there was no significant influence of SCI level. Blood lactate concentration reduced over time (P = 0.022), whereas blood glucose concentration decreased modestly (P = 0.695), and no difference between groups was seen (P > 0.05).

CONCLUSION

The level of SCI influenced the caffeine absorption curve, and there was large interindividual variation within and between groups. Individual curves should be considered when using caffeine as an ergogenic aid in athletes with an SCI. The results indicate TETRA should trial low doses in training and PARA may consider consuming caffeine greater than 60 min before exercise performance. The study also supports caffeine's direct effect on adipose tissue, which is not secondary to catecholamine release.

The risks of polypharmacy following spinal cord injury

OBJECTIVE

The purpose of this study was to examine the overall prevalence of polypharmacy within the spinal cord injury (SCI) population, the level of polypharmacy with respect to seven classes of high-risk drugs commonly used to treat secondary conditions in the SCI population, and the overall risks for drug-related problems (DRP) related to polypharmacy.

DESIGN

A retrospective case-control design.

SETTING

A commercially available claims dataset that included patient cases from 4800 hospitals in the USA between 2007 and 2009.

PARTICIPANTS

Individuals with tetraplegia, paraplegia, and those with SCI but not specified as either tetraplegia or paraplegia as well as a control population of randomly selected, age- and sex-matched individuals without a diagnosis of SCI.

OUTCOME MEASURES

The overall prevalence of polypharmacy, the prevalence of commonly prescribed high-risk medications, and the prevalence of reported DRPs.

RESULTS

Overall, the patients in the SCI population were prescribed significantly more medications than their control counterparts. There was a higher rate of individuals being prescribed medications from multiple high-risk classes (e.g. analgesic-narcotics, anticonvulsant, antidepressant, and skeletal muscle relaxer), as well as multiple medications within each class (e.g. multiple analgesic-narcotics). The SCI group had a higher incidence of DRPs.

CONCLUSION

Our results are some of the first to demonstrate the extent of polypharmacy in individuals with SCI, including commonly prescribed high-risk medications, leading to a higher rate of DPRs. The higher rate of polypharmacy and DRPs can impact rehabilitation goals and community integration following neurologic injury.

Riluzole as a neuroprotective drug for spinal cord injury: from bench to bedside

Spinal cord injury (SCI) is a devastating event resulting in permanent loss of neurological function. To date, effective therapies for SCI have not been established. With recent progress in neurobiology, however, there is hope that drug administration could improve outcomes after SCI. Riluzole is a benzothiazole anticonvulsant with neuroprotective effects. It has been approved by the U.S. Food and Drug Administration as a safe and well-tolerated treatment for patients with amyotrophic lateral sclerosis. The mechanism of action of riluzole involves the inhibition of pathologic glutamatergic transmission in synapses of neurons via sodium channel blockade. There is convincing evidence that riluzole diminishes neurological tissue destruction and promotes functional recovery in animal SCI models. Based on these results, a phase I/IIa clinical trial with riluzole was conducted for patients with SCI between 2010 and 2011. This trial demonstrated significant improvement in neurological outcomes and showed it to be a safe drug with no serious adverse effects. Currently, an international, multi-center clinical trial (Riluzole in Acute Spinal Cord Injury Study: RISCIS) in phase II/III is in progress with riluzole for patients with SCI (clinicaltrials.gov, registration number NCT01597518). This article reviews the pharmacology and neuroprotective mechanisms of riluzole, and focuses on existing preclinical evidence, and emerging clinical data in the treatment of SCI.

A prospective, multicenter, phase I matched-comparison group trial of safety, pharmacokinetics, and preliminary efficacy of riluzole in patients with traumatic spinal cord injury

A prospective, multicenter phase I trial was undertaken by the North American Clinical Trials Network (NACTN) to investigate the pharmacokinetics and safety of, as well as obtain pilot data on, the effects of riluzole on neurological outcome in acute spinal cord injury (SCI). Thirty-six patients, with ASIA impairment grades A-C (28 cervical and 8 thoracic) were enrolled at 6 NACTN sites between April 2010 and June 2011. Patients received 50 mg of riluzole PO/NG twice-daily, within 12 h of SCI, for 14 days. Peak and trough plasma concentrations were quantified on days 3 and 14. Peak plasma concentration (Cmax) and systemic exposure to riluzole varied significantly between patients. On the same dose basis, Cmax did not reach levels comparable to those in patients with amyotrophic lateral sclerosis. Riluzole plasma levels were significantly higher on day 3 than on day 14, resulting from a lower clearance and a smaller volume of distribution on day 3. Rates of medical complications, adverse events, and progression of neurological status were evaluated by comparison with matched patients in the NACTN SCI Registry. Medical complications in riluzole-treated patients occurred with incidences similar to those in patients in the comparison group. Mild-to-moderate increase in liver enzyme and bilirubin levels were found in 14-70% of patients for different enzymes. Three patients had borderline severe elevations of enzymes. No patient had elevated bilirubin on day 14 of administration of riluzole. There were no serious adverse events related to riluzole and no deaths. The mean motor score of 24 cervical injury riluzole-treated patients gained 31.2 points from admission to 90 days, compared to 15.7 points for 26 registry patients, a 15.5-point difference (p=0.021). Patients with cervical injuries treated with riluzole had more-robust conversions of impairment grades to higher grades than the comparison group.

Pharmacology of riluzole in acute spinal cord injury

OBJECT

The aim of this paper was to characterize individual and population pharmacokinetics of enterally administered riluzole in a Phase 1 clinical trial of riluzole as a neuroprotective agent in adults 18-70 years old with acute spinal cord injury (SCI).

METHODS

Thirty-five individuals with acute SCI, American Spinal Injury Association Impairment Scale Grades A-C, neurological levels from C-4 to T-12, who were enrolled in the Phase 1 clinical trial sponsored by the North American Clinical Trials Network for Treatment of Spinal Cord Injury, received 50 mg riluzole twice daily for 28 doses. The first dose was administered at a mean of 8.7 ± 2.2 hours postinjury. Trough plasma samples were collected within 1 hour predose, and peak plasma samples were collected 2 hours postdose on Days 3 and 14 of treatment. Riluzole concentrations were quantified by high-performance liquid chromatography assay. The data were analyzed for individual and population pharmacokinetics using basic structural and covariate models. The pharmacokinetic measures studied were the peak concentration (C(max)), trough concentration (C(min)), systemic exposure (AUC(0-12)), clearance (CL/F), and volume of distribution (V_F) normalized by the bioavailability (F).

RESULTS

The C(max) and AUC(0-12) achieved in SCI patients were lower than those in ALS patients on the same dose basis, due to a higher CL and larger V. The pharmacokinetics of riluzole (C(max), C(min), AUC(0-12), CL, and V) changed during the acute and subacute phases of SCI during the 14 days of therapy. It was consistently observed in patients at all clinical sites that C(max), C(min), and AUC(0-12) (128.9 ng/ml, 45.6 ng/ml, and 982.0 ng × hr/ml, respectively) were significantly higher on Day 3 than on Day 14 (76.5 ng/ml, 19.1 ng/ml, and 521.0 ng × hr/ml, respectively). These changes resulted from lower CL (49.5 vs 106.2 L/hour) and smaller V (557.1 vs 1297.9/L) on Day 3. No fluid imbalance or cytochrome P 1A2 induction due to concomitant medications was identified during the treatment course to account for such increases in V and CL, respectively. Possible mechanisms underlying these changes are discussed.

CONCLUSIONS

This is the first report of clinical pharmacokinetics of riluzole in patients with SCI. The C(max) and AUC(0-12) achieved in SCI patients were lower than those in ALS patients on the same dose basis, due to a higher clearance and larger volume of distribution in SCI patients. The finding in SCI patients of an increase in the clearance and distribution of riluzole between the 3rd and 14th days after SCI, with a lower plasma concentration of riluzole on the 14th day, stresses the importance of monitoring changes in drug metabolism after SCI in interpreting the safety and efficacy of therapeutic drugs that are used in clinical trials in SCI. Clinical trial registration no.: NCT00876889.

Polypharmacy and the role of physical medicine and rehabilitation

Polypharmacy and inappropriate prescribing practices lead to higher rates of mortality and morbidity, particularly in vulnerable populations, such as the elderly and those with complex medical conditions. Physical medicine and physiatrists face particular challenges given the array of symptoms treated across a spectrum of conditions. This clinical review focuses on polypharmacy and the associated issue of potentially inappropriate prescribing. The article begins with a review of polypharmacy along with relevant aspects of pharmacokinetics and pharmacodynamics in the elderly. The adverse effects and potential hazards of selected medications commonly initiated and managed by rehabilitation specialists are then discussed with specific attention to pain medications, neurostimulants, antipsychotics, antidepressants, antispasmodics, sleep medications, and antiepileptics. Of particular concern is the notion that an adverse effect of one medication can mimic an indication for another and lead to a prescribing cascade and further adverse medication events. Appropriate prescribing practices mandate an accurate, current medication list, yet errors and inaccuracies often plague such lists. The evidence to support explicit (medications to avoid) and implicit (how to evaluate) criteria is presented along with the role of physicians and patients in prescribing medications. A brief discussion of "medication debridement" or de-prescribing strategies follows. In the last section, we draw on the essence of physiatry as a team-based endeavor to discuss the potential benefits of collaboration. In working to optimize medication prescribing, efforts should be made to collaborate not only with pharmacists and other medical specialties but with members of inpatient rehabilitation teams as well.

Thiopental dose requirements for induction of anaesthesia and subsequent endotracheal intubation in patients with complete spinal cord injuries

BACKGROUND

Dose requirements of thiopental depend on patient characteristics and infusion rate. We determined thiopental dose requirements for induction of anaesthesia, and the effects of remifentanil on cardiovascular and bispectral index (BIS) responses to tracheal intubation in spinal cord-injured (SCI) patients undergoing general anaesthesia.

METHODS

Twenty patients with traumatic complete SCI undergoing elective surgery were enrolled. Twenty patients without SCI served as control. Anaesthesia was induced with thiopental, followed by remifentanil 1 μg/kg and rocuronium 0.8 mg/kg, and maintained with 2% sevoflurane and 50% nitrous oxide in oxygen after tracheal intubation. Thiopental was administered at a rate of 50 mg/15 s until abolition of the eyelash reflex. Thiopental doses, BIS values, systolic arterial blood pressure (SAP), heart rate (HR) and plasma catecholamine concentrations were measured.

RESULTS

Total thiopental dose required to abolish the eyelash reflex based on total body weight (BW) (5.26 ± 0.87 vs. 3.91 ± 1.07 mg/kg, P < 0.001) or lean BW (6.56 ± 1.37 vs. 5.24 ± 1.36 mg/kg, P < 0.01) were significantly smaller in the SCI group than in the control. SAP was decreased by induction of anaesthesia with thiopental and remifentanil, and increased by tracheal intubation in both groups. However, the peak SAP after intubation was smaller in the SCI patients. HR increased significantly above baseline values following intubation in both groups with no significant intergroup differences. Hypertension was more frequent in the control group. Norepinephrine concentrations remained unaltered following intubation in both groups.

CONCLUSIONS

These results suggest that the dose requirements of thiopental for induction of general anaesthesia and subsequent tracheal intubation are reduced in the SCI patients.