Phenytoin and chlorpromazine in the treatment of spasticity

Interventions for managing skeletal muscle spasticity following traumatic brain injury

BACKGROUND

Skeletal muscle spasticity is a major physical complication resulting from traumatic brain injury (TBI), which can lead to muscle contracture, joint stiffness, reduced range of movement, broken skin and pain. Treatments for spasticity include a range of pharmacological and non-pharmacological interventions, often used in combination. Management of spasticity following TBI varies from other clinical populations because of the added complexity of behavioural and cognitive issues associated with TBI.

OBJECTIVES

To assess the effects of interventions for managing skeletal muscle spasticity in people with TBI.

SEARCH METHODS

In June 2017, we searched key databases including the Cochrane Injuries Group Specialised Register, CENTRAL, MEDLINE (Ovid), Embase (Ovid) and others, in addition to clinical trials registries and the reference lists of included studies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and cross-over RCTs evaluating any intervention for the management of spasticity in TBI. Only studies where at least 50% of participants had a TBI (or for whom separate data for participants with TBI were available) were included. The primary outcomes were spasticity and adverse effects. Secondary outcome measures were classified according to the World Health Organization International Classification of Functioning, Disability and Health including body functions (sensory, pain, neuromusculoskeletal and movement-related functions) and activities and participation (general tasks and demands; mobility; self-care; domestic life; major life areas; community, social and civic life).

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. Data were synthesised narratively; meta-analysis was precluded due to the paucity and heterogeneity of data.

MAIN RESULTS

We included nine studies in this review which involved 134 participants with TBI. Only five studies reported between-group differences, yielding outcome data for 105 participants with TBI. These five studies assessed the effects of a range of pharmacological (baclofen, botulinum toxin A) and non-pharmacological (casting, physiotherapy, splints, tilt table standing and electrical stimulation) interventions, often in combination. The studies which tested the effect of baclofen and tizanidine did not report their results adequately. Where outcome data were available, spasticity and adverse events were reported, in addition to some secondary outcome measures.Of the five studies with results, three were funded by governments, charities or health services and two were funded by a pharmaceutical or medical technology company. The four studies without useable results were funded by pharmaceutical or medical technology companies.It was difficult to draw conclusions about the effectiveness of these interventions due to poor reporting, small study size and the fact that participants with TBI were usually only a proportion of the overall total. Meta-analysis was not feasible due to the paucity of data and heterogeneity of interventions and comparator groups. Some studies concluded that the intervention they tested had beneficial effects on spasticity, and others found no difference between certain treatments. The most common adverse event was minor skin damage in people who received casting. We believe it would be misleading to provide any further description of study results given the quality of the evidence was very low for all outcomes.

AUTHORS' CONCLUSIONS

The very low quality and limited amount of evidence about the management of spasticity in people with TBI means that we are uncertain about the effectiveness or harms of these interventions. Well-designed and adequately powered studies using functional outcome measures to test the interventions used in clinical practice are needed.

Constitutively active 5-HT2/α1 receptors facilitate muscle spasms after human spinal cord injury

In animals, the recovery of motoneuron excitability in the months following a complete spinal cord injury is mediated, in part, by increases in constitutive serotonin (5-HT2) and norepinephrine (α1) receptor activity, which facilitates the reactivation of calcium-mediated persistent inward currents (CaPICs) without the ligands serotonin and norepinephrine below the injury. In this study we sought evidence for a similar role of constitutive monoamine receptor activity in the development of spasticity in human spinal cord injury. In chronically injured participants with partially preserved sensory and motor function, the serotonin reuptake inhibitor citalopram facilitated long-lasting reflex responses (spasms) previously shown to be mediated by CaPICs, suggesting that in incomplete spinal cord injury, functional descending sources of monoamines are present to activate monoamine receptors below the lesion. However, in participants with motor or motor/sensory complete injuries, the inverse agonist cyproheptadine, which blocks both ligand and constitutive 5-HT2/α1 receptor activity, decreased long-lasting reflexes, whereas the neutral antagonist chlorpromazine, which only blocks ligand activation of these receptors, had no effect. When tested in noninjured control participants having functional descending sources of monoamines, chlorpromazine was effective in reducing CaPIC-mediated motor unit activity. On the basis of these combined results, it appears that in severe spinal cord injury, facilitation of persistent inward currents and muscle spasms is mainly mediated by the activation of constitutive 5-HT2 and α1 receptor activity. Drugs that more selectively block these constitutively active monoamine receptors may provide better oral control of spasticity, especially in motor complete spinal cord injury where reducing motoneuron excitability is the primary goal.

Pharmacological interventions for spasticity following spinal cord injury

BACKGROUND

Spasticity is a major health problem for patients with a spinal cord injury (SCI) that limits patients' mobility and affects independence in activities of daily living and work. Spasticity may also cause pain, loss of range of motion, contractures, sleep disorders and impair ambulation in patients with an incomplete lesion. The effectiveness of available drugs is still uncertain and they may cause adverse effects. Assessing what works in this area is complicated by the lack of valid and reliable measurement tools. The aim of this systematic review is to critically appraise and summarise existing information of the effectiveness of available treatments and to identify areas where further research is needed.

OBJECTIVES

To assess the effectiveness and safety of Baclofen, Dantrolene, Tizanidine and any other drugs for the treatment of long term spasticity in SCI patients as well as the effectiveness and safety of different routes of administration of Baclofen.

SEARCH STRATEGY

We searched the Injuries Group specialised register, the Cochrane Controlled Trials Register, MEDLINE, EMBASE and CINHALH up to 1998. Drug companies and experts active in the area were also contacted.

SELECTION CRITERIA

All parallel and crossover RCTs including spinal cord injury patients complaining of "severe spasticity". Studies where less than 50% of patients had a spinal cord injury were excluded.

DATA COLLECTION AND ANALYSIS

Methodological quality of studies (allocation concealment, blinding, patients characteristics, inclusion and exclusion criteria; interventions; outcomes; lost to follow up) was independently assessed by two investigators. The heterogeneity among studies did not allow quantitative combination of results.

MAIN RESULTS

Nine out of 53 studies met the inclusion criteria. Study design was: 8 cross over, 1 parallel-group trial. Two studies (14 SCI patients), showed a significant effect of intrathecal baclofen in reducing spasticity (Ashworth Score and ADL performances), compared to placebo, without any side effect. The study comparing tizanidine to placebo (118 SCI patients) showed a significant effect of tizanidine in improving Ashworth Score but not in ADL performances. Tizanidine group reported significant rates of adverse effects (drowsiness, xerostomia). For the other drugs (Gabapentine, Clonidine, Diazepam, Amytal and oral Baclofen ) the results do not provide evidence for a clinical significant effectiveness.

REVIEWER'S CONCLUSIONS

There is insufficient evidence to assist clinicians in a rational approach to antispastic treatment for SCI. Further research is urgently needed to improve the scientific basis of patient care.

Anti-spasticity agents for multiple sclerosis

BACKGROUND

Spasticity is a common problem in MS patients causing pain, spasms, loss of function and difficulties in nursing care. A variety of oral and parenteral medications are available.

OBJECTIVES

To assess the absolute and comparative efficacy and tolerability of anti-spasticity agents in multiple sclerosis (MS) patients.

SEARCH STRATEGY

Randomised controlled trials (RCTs) of anti-spasticity agents were identified using MEDLINE, EMBASE, bibliographies of relevant articles, personal communication, manual searches of relevant journals and information from drug companies.

SELECTION CRITERIA

Double-blind, randomised controlled trials (either placebo-controlled or comparative studies) of at least seven days duration.

DATA COLLECTION AND ANALYSIS

Two independent reviewers extracted data and the findings of the trials were summarised. Missing data were collected by correspondence with principal investigators. A meta-analysis was not performed due to the inadequacy of outcome measures and methodological problems with the studies reviewed.

MAIN RESULTS

Twenty-three placebo-controlled studies (using baclofen, dantrolene, tizanidine, botulinum toxin, vigabatrin, prazepam and threonine) and thirteen comparative studies met the selection criteria. Only thirteen of these studies used the Ashworth scale, of which only three of the six placebo-controlled trials and none of the seven comparative studies showed a statistically significant difference between test drugs. Spasms, other symptoms and overall impressions were only assessed using unvalidated scores and results of functional assessments were inconclusive.

REVIEWER'S CONCLUSIONS

The absolute and comparative efficacy and tolerability of anti-spasticity agents in multiple sclerosis is poorly documented and no recommendations can be made to guide prescribing. The rationale for treating features of the upper motor neurone syndrome must be better understood and sensitive, validated spasticity measures need to be developed.

Spasticity and drug therapy

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

Antispasticity drugs: mechanisms of action

Several different drugs are now used, or are potentially useful, to treat patients with spasticity. Although these compounds vary in their actions on spinal neurons and reflex arcs, it is possible to formulate reasonable hypotheses regarding their modes of action. The benzodiazepines bind to specific benzodiazepine receptors linked to classic gamma-aminobutyric acid (GABA) receptors located on the terminals of primary afferent fibers. This binding results in an increased affinity of the GABA receptor for the amino acid, an augmented flux of chloride ions across the terminal membrane, and an increase in the amount of presynaptic inhibition. Baclofen activates GABAB receptors putatively located on the same terminals. Activation of these receptors retards the influx of calcium ions into the terminals, thereby reducing the evoked release of excitatory amino acids and possibly other transmitters. Progabide and its metabolites act on both classic and GABAB receptors. Glycine works on specific inhibitory receptors located on spinal interneurons and motoneurons. The phenothiazines act on the brainstem to alter the function of fusimotor fibers. Phenytoin and carbamazepine reduce the afferent output of muscle spindles. Dantrolene diminishes the activation of the contractile process in muscle fibers by reducing the release of calcium ions from the sarcoplasmic reticulum. This review summarizes the data supporting these concepts.

Prevention of reserpine rigidity by alpha-2 adrenergic antagonists

Since alpha adrenergic antagonists are known to protect rats from the extrapyramidal effects of reserpine, the purpose of this study was to examine the relative contribution of alpha-2 receptors in modifying the reserpine-induced syndrome. Rats were pretreated with either clonidine, yohimbine, phentolamine, methysergide or SKF-7265. Thirty minutes later they were given reserpine (20 mg/kg) and evaluated using eleven categories of behavioral responses for three hours. Yohimbine, an alpha-2 antagonist, was the most effective agent in protecting against the reserpine effects. Phentolamine and SKF-7265, which block both alpha-1 and alpha-2 receptors, were also effective. Clonidine, an alpha-2 agonist, and methysergide a serotonin antagonist, were not. In all cases the alpha blocking drugs prevented the motor responses but did not alter the autonomic responses induced by reserpine. The results show not only the efficacy of alpha adrenergic antagonists in protecting against reserpine rigidity but more importantly that the blockade of alpha-2 receptors may be the functionally important action. These results are consistent with the view that some descending motor pathways are controlled by an adrenergic mechanism and suggest that alpha-2 receptors are an important component.