Botulinum A toxins: units versus units

The Immunology of Botulinum Toxin Therapy: A Brief Summary

Like all proteins foreign to the human body, also botulinum toxin (BT) is antigenic and may stimulate an immune response with formulation of antibodies (BT-AB). Affected patients may no longer respond to BT therapy and various degrees of BT-AB related therapy failure (ABF) may result. We want to review the immunological interactions between BT and BT-AB, the prevalence, the time course and the risk factors for BT-AB formation as they are related to the treatment algorithms, the patient's immune system and to exogenic factors. Special emphasis is placed on various features of the BT drugs including the specific biological activity (SBA) as a predictor of their antigenicity. Quantitative detection of BT-AB by the mouse diaphragm assay will be demonstrated. As ABF may have serious consequences for patients affected, careful risk factor analysis is warranted to reduce them wherever possible.

Botulinum Toxin Injections for Treatment of Drooling in Children with Cerebral Palsy: A Systematic Review and Meta-Analysis

Background: We aimed to review and analyse the effectiveness and safety of botulinum toxin type A (BoNT-A) injections for drooling in children with cerebral palsy. Data sources: We searched the EMBASE, MEDLINE, Cochrane Database of Systematic Reviews, and Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library) databases from inception to January 2020. Methods: We included randomized controlled trials and observational studies which (1) involved children with cerebral palsy, (2) used BoNT-A for control of drooling, and (3) provided quantitative evaluations of drooling before and after intervention with BoNT-A. Results: Twenty-one trials met the inclusion criteria. Most studies showed that BoNT-A injections are safe and efficacious as a treatment for drooling in children with cerebral palsy. Four trials had sufficient data to pool the results for the meta-analysis. Both the drooling quotient (p = 0.002) and drooling Ffrequency and severity scale (p = 0.004) supported this conclusion. Conclusion: BoNT-A injections are a safe, reversible, effective treatment for drooling control in children with cerebral palsy that can offer effectiveness for more than 3 months with few side effects. The dosage of BoNT-A should not exceed 4 units/kg. Further studies are required to determine the optimal dosage and target glands.

The Efficacy of Dose Increments of Botulinum Toxin A in the Treatment of Childhood Esotropia

Background

Botulinum toxin is known to have a powerful chemodenervation effect, and it is a well-established alternative to incisional surgery for strabismus. This study aims to investigate the efficacy of dose increments of botulinum toxin A (BTA) for the treatment of specific ranges of angle deviation.

Methods

This was a prospective study that included patients presenting with esotropia to Dhahran Eye Specialist Hospital between 2016 and 2020, who were managed by a single surgeon. Botulinum toxin was given in different dosages (2.5, 5, 7.5, 10 international units (IU)) according to the size of deviation (11–19, 20–29, 30–39, and ≥40 prism diopters (PD)), respectively. A successful outcome was defined as deviation ≤10 PD in the last visit (a minimum of 6 months) following a single injection.

Results

A total of 56 patients with esotropia were included. The mean pre-treatment angle of deviation was 38.6 ± 2.5 PD. BTA injection in a dose of 2.5 IU for the 11–19 PD angle of deviation showed the highest rate of successful outcomes (75%). According to the type of esotropia, partially accommodative esotropia showed the best response to the use of dose increments (59%). The incidence of ptosis post-BTA injection was the least (37.5%) with the smallest dose (2.5 IU).

Conclusion

BTA usage in dose increments is safe, efficient, and might be more cost-effective with less incidence of BTA associated complications. Different esotropia diagnoses have different clinical responses. However, larger studies are necessary to better predict the outcome of using dose increments.

The role of human serum albumin and neurotoxin associated proteins in the formulation of BoNT/A products

Botulinum neurotoxin (BoNT) is synthesized as a progenitor toxin complex (PTC) by Clostridium botulinum. This PTC comprises, in addition to the neurotoxin itself, neurotoxin associated proteins (NAPs) which are composed of three hemagglutinins and one non-toxic, non-hemagglutinin protein. After oral ingestion, these NAPs protect the neurotoxin from the low pH and proteases in the gastrointestinal tract and play a role in the entry via the intestinal barrier. Two of the three therapeutically used botulinum neurotoxin serotype A (BoNT/A) products (onabotulinumtoxinA and abobotulinumtoxinA) contain different amounts of NAPs, while incobotulinumtoxinA, lacks these proteins. In addition, human serum albumin (HSA) that is supposed to stabilize BoNT/A is added at different concentrations. Up to now, the function of the NAPs and HSA after parenteral therapeutic application is not completely understood. To investigate the influence of NAPs and HSA on potency of BoNT/A, we used the ex vivo mouse phrenic nerve hemidiaphragm assay. Increasing doses of HSA resulted dose-dependently in a more pronounced effect of BoNT/A. Though, a plateau was reached with concentrations of 0.8 mg/ml HSA and higher, the accessory addition of NAPs in a relevant amount (4 ng/ml) did not further enhance the effect of BoNT/A. In conclusion, in our ex vivo assay an adequate concentration of HSA prevented BoNT/A from loss of effect and supplementary NAPs did not alter this effect. A confirmation of these data in an in vivo assay is still lacking. However, it might be supposed that even in clinically applied BoNT/A products an increase of HSA accompanied by the avoidance of NAPs could potentially reduce the injected dose and, thus, the risk of unwanted side effects, the treatment costs as well as the risk of a secondary therapy failure due to BoNT/A neutralizing antibodies.

Progress in Applying the Three Rs to the Potency Testing of Botulinum Toxin Type A

Botulinum toxin type A (BTA) is being increasingly used for a range of therapeutic purposes and also for cosmetic reasons. For many years, the potency of BTA has been measured by using an LD50 assay in mice. This assay is a cause for concern due to its unpleasant nature and extreme severity, and the requirement for high numbers of mice to be used. Alternatives to this potency assay are presently reviewed with particular reference to the work at the National Institute for Biological Standards and Control (NIBSC), and to recent work by the UK manufacturer of the substance. An in vivo local paralysis assay with considerably less severity has been developed and is in use at the NIBSC. Alternative, ex vivo functional assays in use include the measurement of BTA-induced paralysis of neurally-stimulated rodent diaphragm or rat intercostal muscle. The latter method has the advantage of allowing more preparations to be derived from one animal. However, these ex vivo methods have not yet been fully validated and accepted by regulatory agencies as potency assays. Endopeptidase assays, although not measuring muscle paralysis directly, may provide a very useful consistency test for batch release and may replace the routine use of the LD50 test for that purpose. These assays measure the cleavage of the SNAP-25 protein (the final stage of BTA action), and have been validated for batch release by the National Control Laboratory (NIBSC), and are in regular use there. ELISA assays, used alongside the endopeptidase assay, also provide useful confirmatory information on the amounts of functional (and non-functional) BTA present. The UK manufacturer is further validating its endopeptidase assay, an ex vivo muscle assay and an ELISA. It is anticipated that their work will lead to a change in the product license, hopefully within the next two years, and will form a critical milestone towards the end of the LD50 potency test.

Botulinum Toxin Treatment for Mild to Moderate Platysma Bands: A Systematic Review of Efficacy, Safety, and Injection Technique

Background

Platysma bands are characteristic of an aging neck. Resection and plication of the platysma muscle is the basis of treatment. However, unfavorable surgical outcomes and improved understanding of platysma band etiology have shifted treatment towards nonsurgical rejuvenation.

Objectives

The aim of this paper was to assess the efficacy, injection techniques, and complications associated with botulinum toxin injection for the treatment of platysma bands.

Methods

A systematic literature search was performed to identify articles reporting botulinum toxin injections for platysma bands in neck rejuvenation. The search included published articles in three electronic databases-Ovid MEDLINE, EMBASE, and the Cochrane Library-between January 1985 and December 2017.

Results

Three studies met the inclusion criteria, with a total of 78 patients undergoing botulinum toxin injection for platysma bands. Incobotulinumtoxin A was used in 62.3% (n = 45/78) of patients, with 38.4% (n = 30/78) receiving abobotulinumtoxin A. Efficacy was assessed using the Merz platysma score scale. A mean score improvement of 2.0 points, with a response rate of 93.7%, was observed after 14 ± 2 days. At 3 months, the mean score improvement was 1.2 points with a response rate of 86%. Patient-reported metrics demonstrated an improvement in 91% (n = 71/78) of subjects. The three studies used a standard injection technique, with a maximum 20 IU of incobotulinumtoxin A and 5 U abobotulinumtoxin A administered per band. Complications were reported in 15.4% (n = 12/78) of patients, with none requiring further intervention.

Conclusions

Botulinum toxin is a highly effective treatment for isolated platysma bands. A safe injection technique is described and recommended for clinical practice.

Level of Evidence 4

Botulinum neurotoxin formulations: overcoming the confusion

Botulinum toxin A is produced by anaerobic spore-forming bacteria and is used for various therapeutic and cosmetic purposes. Botulinum toxin A injections are the most popular nonsurgical procedure worldwide. Despite an increased demand for botulinum toxin A injections, the clinical pharmacology and differences in formulation of commonly available products are poorly understood. The various products available in the market are unique and vary in terms of units, chemical properties, biological activities, and weight, and are therefore not interchangeable. For safe clinical practice and to achieve optimal results, the practitioners need to understand the clinical issues of potency, conversion ratio, and safety issues (toxin spread and immunogenicity). In this paper, the basic clinical pharmacology of botulinum toxin A and differences between onabotulinum toxin A, abobotulinum toxin A, and incobotulinum toxin A are discussed.

Chemodenervation for the Treatment of Facial Dystonia: A Report by the American Academy of Ophthalmology

PURPOSE

To review the medical literature on the outcomes and complications of various Food and Drug Administration-approved botulinum toxins for benign essential blepharospasm (BEB) and hemifacial spasm (HFS).

METHODS

Literature searches were last conducted in February 2017 in PubMed for articles published in English and in the Cochrane Library database without language limitations; studies published before 2000 were excluded. The combined searches yielded 127 citations. Of these, 13 articles were deemed appropriate for inclusion in this assessment, and the panel methodologist assigned ratings to them according to the level of evidence.

RESULTS

A combined total of 1523 patients (1143 with BEB and 380 with HFS) were included in the 13 studies. Five studies provided level I evidence, 2 studies provided level II evidence, and 6 studies provided level III evidence. Pretarsal injections were more efficacious than preseptal injections (96% vs. 86%, respectively). Pretarsal injections also resulted in a higher response rate on clinical scales (P < 0.05) and a longer duration of maximum response for both HFS and BEB. Patients with HFS require lower overall doses of onabotulinumtoxinA than patients with BEB for a similar duration of effect. Adverse events were dose related, and they occurred more frequently in patients who were given more units.

CONCLUSIONS

Level I evidence supports the efficacy of Botox (Allergan Corp., Irvine, CA), Meditoxin, and Xeomin (Merz Pharmaceuticals, Frankfurt am Main, Germany) for the treatment of BEB. Meditoxin and Botox have equivalent effectiveness and incidence of adverse events for BEB and HFS. Dysport (Ipsen Biopharmaceuticals, Inc, Paris, France) seems to have efficacy similar to Botox and Meditoxin for BEB and HFS, but any definitive conclusions from the 2 level II studies in this review are limited by differences in the methodologies used. Higher doses of Botox and Dysport result in more adverse events. Repeated treatments using Botox seem to maintain efficacy for treatment of facial dystonias over a follow-up period of at least 10 years, based on level III evidence.

3,4-diaminopyridine reverses paralysis in botulinum neurotoxin-intoxicated diaphragms through two functionally distinct mechanisms

Botulinum neurotoxins (BoNTs) are exceedingly potent neurological poisons that prevent neurotransmitter release from peripheral nerve terminals by cleaving presynaptic proteins required for synaptic vesicle fusion. The ensuing neuromuscular paralysis causes death by asphyxiation. Although no antidotal treatments exist to block toxin activity within the nerve terminal, aminopyridine antagonists of voltage-gated potassium channels have been proposed as symptomatic treatments for botulism toxemia. However, clinical evaluation of aminopyridines as symptomatic treatments for botulism has been inconclusive, in part because mechanisms responsible for reversal of paralysis in BoNT-poisoned nerve terminals are not understood. Here we measured the effects of 3,4-diaminopyridine (DAP) on phrenic nerve-elicited diaphragm contraction and end-plate potentials at various times after intoxication with BoNT serotypes A, B, or E. We found that DAP-mediated increases in quantal content promote neurotransmission from intoxicated nerve terminals through two functionally distinguishable mechanisms. First, DAP increases the probability of neurotransmission at non-intoxicated release sites. This mechanism is serotype-independent, becomes less effective as nerve terminals become progressively impaired, and remains susceptible to ongoing intoxication. Second, DAP elicits persistent production of toxin-resistant endplate potentials from nerve terminals fully intoxicated by BoNT/A, but not serotypes B or E. Since this effect appears specific to BoNT/A intoxication, we propose that DAP treatment enables BoNT/A-cleaved SNAP-25 to productively engage in fusogenic release by increasing the opportunity for low-efficiency fusion events. These findings have important implications for DAP as a botulism therapeutic by defining conditions under which DAP may be clinically effective in reversing botulism symptoms.

In vitro and ex vivo screening of candidate therapeutics to restore neurotransmission in nerve terminals intoxicated by botulinum neurotoxin serotype A1

Botulinum neurotoxins (BoNTs) are exceedingly potent neurological poisons that block cholinergic release in the peripheral nervous system and cause death by asphyxiation. While post-exposure prophylaxis can effectively eliminate toxin in the bloodstream, there are no clinically effective treatments to prevent or reverse disease once BoNT has entered the neuron. To address the need for post-symptomatic countermeasures, we designed and developed an in vitro assay based on whole-cell, patch-clamp electrophysiological monitoring of miniature excitatory post-synaptic currents in synaptically active murine embryonic stem cell-derived neurons. This synaptic function-based assay was used to assess the efficacy of rationally selected drugs to restore neurotransmission in neurons comprehensively intoxicated by BoNT/A. Based on clinical reports suggesting that elevated Ca²⁺ signaling promotes symptomatic relief from botulism, we identified seven candidate drugs that modulate presynaptic Ca²⁺ signaling and assessed their ability to reverse BoNT/A-induced synaptic blockade. The most effective drugs from the screen were found to phasically agonize voltage-gated calcium channel (VGCC) activity. Lead candidates were then applied to ex vivo studies in BoNT/A-paralyzing mouse phrenic nerve-hemidiaphragm (PND) preparations. Treatment of PNDs with VGCC agonists after paralytic onset transiently potentiated nerve-elicited muscle contraction and delayed progression to neuromuscular failure. Collectively, this study suggests that Ca²⁺-modulating drugs represent a novel symptomatic treatment for neuromuscular paralysis following BoNT/A poisoning.

A Comparison of Botox 100 U/mL and Dysport 100 U/mL Using Dose Conversion Ratio 1: 3 and 1: 1.7 in the Treatment of Cervical Dystonia: A Double-Blind, Randomized, Crossover Trial

OBJECTIVES

Intramuscular injections of botulinum toxin (BTX) are used as symptomatic treatment for cervical dystonia. Botox and Dysport are commercial products containing BTX; however, dosage and concentration of the prepared solution vary considerably among studies. The concentration of BTX in the prepared solution affects clinical outcome. This double-blind, randomized crossover trial compares Botox and Dysport in 2 different dose conversion ratios (1:3 and 1:1.7) when diluted to the same concentration (100 U/mL).

METHODS

Forty-six patients with cervical dystonia received 3 different treatments, Botox in 2 different doses and Dysport as control treatment. The efficacy was evaluated 4 and 12 weeks after treatment using 5 instruments, including Toronto Western Spasmodic Torticollis Rating Scale.

RESULTS AND CONCLUSION

The primary outcome was the estimated median Toronto Western Spasmodic Torticollis Rating Scale total score, which was 1.96 points higher for Botox (1:3) compared with Dysport at week 4, but the difference was not statistically significant (confidence interval, -0.88-4.61; P = 0.0799). No significant differences were seen between Botox (1:1.7) and Dysport. At week 12, a statistically significant difference in effect between Botox (1:3) and Dysport was observed, suggesting a shorter duration of effect for Botox when this ratio (low dose) was used. Furthermore, the patients' assessments showed that the ratio 1:3 resulted in suboptimal efficacy of Botox. These secondary outcome observations indicate that the dose conversion ratio between Dysport 100 U/mL and Botox 100 U/mL may be lower than 1:3, but this must be further validated in a larger patient material.

Conversion Ratio between Botox®, Dysport®, and Xeomin® in Clinical Practice

Botulinum neurotoxin has revolutionized the treatment of spasticity and is now administered worldwide. There are currently three leading botulinum neurotoxin type A products available in the Western Hemisphere: onabotulinum toxin-A (ONA) Botox(®), abobotulinum toxin-A (ABO), Dysport(®), and incobotulinum toxin A (INCO, Xeomin(®)). Although the efficacies are similar, there is an intense debate regarding the comparability of various preparations. Here we will address the clinical issues of potency and conversion ratios, as well as safety issues such as toxin spread and immunogenicity, to provide guidance for BoNT-A use in clinical practice. INCO was shown to be as effective as ONA with a comparable adverse event profile when a clinical conversion ratio of 1:1 was used. The available clinical and preclinical data suggest that a conversion ratio ABO:ONA of 3:1-or even lower-could be appropriate for treating spasticity, cervical dystonia, and blepharospasm or hemifacial spasm. A higher conversion ratio may lead to an overdosing of ABO. While uncommon, distant spread may occur; however, several factors other than the pharmaceutical preparation are thought to affect spread. Finally, whereas the three products have similar efficacy when properly dosed, ABO has a better cost-efficacy profile.

Generation and Characterization of Six Recombinant Botulinum Neurotoxins as Reference Material to Serve in an International Proficiency Test

The detection and identification of botulinum neurotoxins (BoNT) is complex due to the existence of seven serotypes, derived mosaic toxins and more than 40 subtypes. Expert laboratories currently use different technical approaches to detect, identify and quantify BoNT, but due to the lack of (certified) reference materials, analytical results can hardly be compared. In this study, the six BoNT/A1–F1 prototypes were successfully produced by recombinant techniques, facilitating handling, as well as improving purity, yield, reproducibility and biosafety. All six BoNTs were quantitatively nicked into active di-chain toxins linked by a disulfide bridge. The materials were thoroughly characterized with respect to purity, identity, protein concentration, catalytic and biological activities. For BoNT/A₁, B₁ and E₁, serotypes pathogenic to humans, the catalytic activity and the precise protein concentration were determined by Endopep-mass spectrometry and validated amino acid analysis, respectively. In addition, BoNT/A₁, B₁, E₁ and F₁ were successfully detected by immunological assays, unambiguously identified by mass spectrometric-based methods, and their specific activities were assigned by the mouse LD₅₀ bioassay. The potencies of all six BoNT/A1–F1 were quantified by the ex vivo mouse phrenic nerve hemidiaphragm assay, allowing a direct comparison. In conclusion, highly pure recombinant BoNT reference materials were produced, thoroughly characterized and employed as spiking material in a worldwide BoNT proficiency test organized by the EQuATox consortium.

Botulinum Neurotoxins: Qualitative and Quantitative Analysis Using the Mouse Phrenic Nerve Hemidiaphragm Assay (MPN)

The historical method for the detection of botulinum neurotoxin (BoNT) is represented by the mouse bioassay (MBA) measuring the animal survival rate. Since the endpoint of the MBA is the death of the mice due to paralysis of the respiratory muscle, an ex vivo animal replacement method, called mouse phrenic nerve (MPN) assay, employs the isolated N. phrenicus-hemidiaphragm tissue. Here, BoNT causes a dose-dependent characteristic decrease of the contraction amplitude of the indirectly stimulated muscle. Within the EQuATox BoNT proficiency 13 test samples were analysed using the MPN assay by serial dilution to a bath concentration resulting in a paralysis time within the range of calibration curves generated with BoNT/A, B and E standards, respectively. For serotype identification the diluted samples were pre-incubated with polyclonal anti-BoNT/A, B or E antitoxin or a combination of each. All 13 samples were qualitatively correctly identified thereby delivering superior results compared to single in vitro methods like LFA, ELISA and LC-MS/MS. Having characterized the BoNT serotype, the final bath concentrations were calculated using the calibration curves and then multiplied by the respective dilution factor to obtain the sample concentration. Depending on the source of the BoNT standards used, the quantitation of ten BoNT/A containing samples delivered a mean z-score of 7 and of three BoNT/B or BoNT/E containing samples z-scores <2, respectively.

On the translocation of botulinum and tetanus neurotoxins across the membrane of acidic intracellular compartments

Tetanus and botulinum neurotoxins are produced by anaerobic bacteria of the genus Clostridium and are the most poisonous toxins known, with 50% mouse lethal dose comprised within the range of 0.1-few nanograms per Kg, depending on the individual toxin. Botulinum neurotoxins are similarly toxic to humans and can therefore be considered for potential use in bioterrorism. At the same time, their neurospecificity and reversibility of action make them excellent therapeutics for a growing and heterogeneous number of human diseases that are characterized by a hyperactivity of peripheral nerve terminals. The complete crystallographic structure is available for some botulinum toxins, and reveals that they consist of four domains functionally related to the four steps of their mechanism of neuron intoxication: 1) binding to specific receptors of the presynaptic membrane; 2) internalization via endocytic vesicles; 3) translocation across the membrane of endocytic vesicles into the neuronal cytosol; 4) catalytic activity of the enzymatic moiety directed towards the SNARE proteins. Despite the many advances in understanding the structure-mechanism relationship of tetanus and botulinum neurotoxins, the molecular events involved in the translocation step have been only partially elucidated. Here we will review recent advances that have provided relevant insights on the process and discuss possible models that can be experimentally tested. This article is part of a Special Issue entitled: Pore-Forming Toxins edited by Mauro Dalla Serra and Franco Gambale.

Botulinum neurotoxins: genetic, structural and mechanistic insights

Botulinum neurotoxins (BoNTs) are produced by anaerobic bacteria of the genus Clostridium and cause a persistent paralysis of peripheral nerve terminals, which is known as botulism. Neurotoxigenic clostridia belong to six phylogenetically distinct groups and produce more than 40 different BoNT types, which inactivate neurotransmitter release owing to their metalloprotease activity. In this Review, we discuss recent studies that have improved our understanding of the genetics and structure of BoNT complexes. We also describe recent insights into the mechanisms of BoNT entry into the general circulation, neuronal binding, membrane translocation and neuroparalysis.

Botulinum neurotoxin G binds synaptotagmin-II in a mode similar to that of serotype B: tyrosine 1186 and lysine 1191 cause its lower affinity

Botulinum neurotoxins (BoNTs) block neurotransmitter release by proteolyzing SNARE proteins in peripheral nerve terminals. Entry into neurons occurs subsequent to interaction with gangliosides and a synaptic vesicle protein. Isoforms I and II of synaptotagmin were shown to act as protein receptors for two of the seven BoNT serotypes, BoNT/B and BoNT/G, and for mosaic-type BoNT/DC. BoNT/B and BoNT/G exhibit a homologous binding site for synaptotagmin whose interacting part adopts helical structure upon binding to BoNT/B. Whereas the BoNT/B-synaptotagmin-II interaction has been elucidated in molecular detail, corresponding information about BoNT/G is lacking. Here we systematically mutated the synaptotagmin binding site in BoNT/G and performed a comparative binding analysis with mutants of the cell binding subunit of BoNT/B. The results suggest that synaptotagmin takes the same overall orientation in BoNT/B and BoNT/G governed by the strictly conserved central parts of the toxins' binding site. The surrounding nonconserved areas differently contribute to receptor binding. Reciprocal mutations Y1186W and L1191Y increased the level of binding of BoNT/G approximately to the level of BoNT/B affinity, suggesting a similar synaptotagmin-bound state. The effects of the mutations were confirmed by studying the activity of correspondingly mutated full-length BoNTs. On the basis of these data, molecular modeling experiments were employed to reveal an atomistic model of BoNT/G-synaptotagmin recognition. These data suggest a reduced length and/or a bend in the C-terminal part of the synaptotagmin helix that forms upon contact with BoNT/G as compared with BoNT/B and are in agreement with the data of the mutational analyses.

The Use of Botulinum Toxin for the Treatment of Generalized Myoclonus in a DogS

A 13 mo old spayed female mixed-breed dog presented in a nonambulatory state that was attributed to severe myoclonus secondary to distemper. The authors hypothesized that mitigating the myoclonus would help the dog become ambulatory and expedite convalescence. They injected the severely affected muscles with botulinum toxin on two separate occasions over a period of 18 days. Those injections reduced the myoclonus, helping the dog become ambulatory and attaining a comfortable, functional state.

Botulinum toxins: mechanisms of action, antinociception and clinical applications

Botulinum toxin (BoNT) is a potent neurotoxin that is produced by the gram-positive, spore-forming, anaerobic bacterium, Clostridum botulinum. There are 7 known immunologically distinct serotypes of BoNT: types A, B, C1, D, E, F, and G. Clostridum neurotoxins are produced as a single inactive polypeptide chain of 150kDa, which is cleaved by tissue proteinases into an active di-chain molecule: a heavy chain (H) of ∼100 kDa and a light chain (L) of ∼50 kDa held together by a single disulfide bond. Each serotype demonstrates its own varied mechanisms of action and duration of effect. The heavy chain of each BoNT serotype binds to its specific neuronal ecto-acceptor, whereby, membrane translocation and endocytosis by intracellular synaptic vesicles occurs. The light chain acts to cleave SNAP-25, which inhibits synaptic exocytosis, and therefore, disables neural transmission. The action of BoNT to block the release of acetylcholine botulinum toxin at the neuromuscular junction is best understood, however, most experts acknowledge that this effect alone appears inadequate to explain the entirety of the neurotoxin's apparent analgesic activity. Consequently, scientific and clinical evidence has emerged that suggests multiple antinociceptive mechanisms for botulinum toxins in a variety of painful disorders, including: chronic musculoskeletal, neurological, pelvic, perineal, osteoarticular, and some headache conditions.

Immunogenicity of botulinum toxins

Botulinum neurotoxins are formulated biologic pharmaceuticals used therapeutically to treat a wide variety of chronic conditions, with varying governmental approvals by country. Some of these disorders include cervical dystonia, post-stroke spasticity, blepharospasm, migraine, and hyperhidrosis. Botulinum neurotoxins also have varying governmental approvals for cosmetic applications. As botulinum neurotoxin therapy is often continued over many years, some patients may develop detectable antibodies that may or may not affect their biological activity. Although botulinum neurotoxins are considered "lower risk" biologics since antibodies that may develop are not likely to cross react with endogenous proteins, it is possible that patients may lose their therapeutic response. Various factors impact the immunogenicity of botulinum neurotoxins, including product-related factors such as the manufacturing process, the antigenic protein load, and the presence of accessory proteins, as well as treatment-related factors such as the overall toxin dose, booster injections, and prior vaccination or exposure. Detection of antibodies by laboratory tests does not necessarily predict the clinical success or failure of treatment. Overall, botulinum neurotoxin type A products exhibit low clinically detectable levels of antibodies when compared with other approved biologic products. This review provides an overview of all current botulinum neurotoxin products available commercially, with respect to the development of neutralizing antibodies and clinical response.

Immunogenicity of botulinum toxins

Botulinum neurotoxins are formulated biologic pharmaceuticals used therapeutically to treat a wide variety of chronic conditions, with varying governmental approvals by country. Some of these disorders include cervical dystonia, post-stroke spasticity, blepharospasm, migraine, and hyperhidrosis. Botulinum neurotoxins also have varying governmental approvals for cosmetic applications. As botulinum neurotoxin therapy is often continued over many years, some patients may develop detectable antibodies that may or may not affect their biological activity. Although botulinum neurotoxins are considered "lower risk" biologics since antibodies that may develop are not likely to cross react with endogenous proteins, it is possible that patients may lose their therapeutic response. Various factors impact the immunogenicity of botulinum neurotoxins, including product-related factors such as the manufacturing process, the antigenic protein load, and the presence of accessory proteins, as well as treatment-related factors such as the overall toxin dose, booster injections, and prior vaccination or exposure. Detection of antibodies by laboratory tests does not necessarily predict the clinical success or failure of treatment. Overall, botulinum neurotoxin type A products exhibit low clinically detectable levels of antibodies when compared with other approved biologic products. This review provides an overview of all current botulinum neurotoxin products available commercially, with respect to the development of neutralizing antibodies and clinical response.

Immunogenicity of botulinum toxins

Botulinum neurotoxins are formulated biologic pharmaceuticals used therapeutically to treat a wide variety of chronic conditions, with varying governmental approvals by country. Some of these disorders include cervical dystonia, post-stroke spasticity, blepharospasm, migraine, and hyperhidrosis. Botulinum neurotoxins also have varying governmental approvals for cosmetic applications. As botulinum neurotoxin therapy is often continued over many years, some patients may develop detectable antibodies that may or may not affect their biological activity. Although botulinum neurotoxins are considered "lower risk" biologics since antibodies that may develop are not likely to cross react with endogenous proteins, it is possible that patients may lose their therapeutic response. Various factors impact the immunogenicity of botulinum neurotoxins, including product-related factors such as the manufacturing process, the antigenic protein load, and the presence of accessory proteins, as well as treatment-related factors such as the overall toxin dose, booster injections, and prior vaccination or exposure. Detection of antibodies by laboratory tests does not necessarily predict the clinical success or failure of treatment. Overall, botulinum neurotoxin type A products exhibit low clinically detectable levels of antibodies when compared with other approved biologic products. This review provides an overview of all current botulinum neurotoxin products available commercially, with respect to the development of neutralizing antibodies and clinical response.

Prospective randomised controlled trial comparing trigone-sparing versus trigone-including intradetrusor injection of abobotulinumtoxinA for refractory idiopathic detrusor overactivity

BACKGROUND

Botulinum toxin A is effective for treatment of idiopathic detrusor overactivity (IDO). The trigone is generally spared because of the theoretical risk of vesicoureteric reflux (VUR), although studies assessing injection sites are lacking.

OBJECTIVE

Evaluate efficacy and safety of trigone-including versus trigone-sparing intradetrusor injections of abobotulinumtoxinA in patients with IDO.

DESIGN, SETTING, AND PARTICIPANTS

Twenty-two patients from one centre were randomised to trigone-including or trigone-sparing injections.

INTERVENTION

Injection of 500 U abobotulinumtoxinA diluted to 20ml into 20 trigone-including or trigone-sparing sites.

MEASUREMENTS

The primary outcome measure was total overactive bladder symptom score (OABSS) at 6 wk. The OABSS questionnaire was completed at 0, 6, 12, and 26 wk. Baseline and postinjection urodynamic studies and micturating cystourethrograms were performed. Baseline values and subsequent time points were compared by t test. A mixed-effect model was used for repeated measures in time.

RESULTS AND LIMITATIONS

For symptom scores at baseline compared with scores at 6 wk postinjection, the mean total OABSS improved from 22.4 to 8.7 (p<0.001) in the trigone-including group compared with 22.7 to 13.4 (p<0.03) in the trigone-sparing group. The difference in mean change from baseline was 4.4 points in favour of the trigone-including group (p=0.03). The total OABSS at 12 and 26 wk and the urgency subscale scores at 6, 12, and 26 wk showed significant improvement in favour of the trigone-including group. Mean postvoid residual volumes and clean intermittent self-catheterisation rates between the two groups were similar. No patients developed VUR. Performing injections under general anaesthetic was a limitation, as tolerability under local anaesthetic was not assessed. A further limitation is the lack of a trigone-only arm.

CONCLUSIONS

Trigone-including injections are superior to trigone-sparing injections for the treatment of refractory IDO and did not cause VUR in this study.

Retrospective evaluation of the dose equivalence of Botox(®) and Dysport (®) in the management of blepharospasm and hemifacial spasm: a novel paradigm for a never ending story

Botox(®) and Dysport(®) are the preparations of botulinum neurotoxin most widely used for therapeutic purposes. Several studies have addressed the topic of the equivalency ratio (D/B ratio) to be used in clinical practice and whether a reliable value exists is still a matter of debate. To this purpose, we ideated a novel paradigm by retrospectively examining the patients affected by hemifacial spasm and blepharospasm. We compared the pairs of treatments with a switch from one brand to the other undergone by the same patient in consecutive sessions with overlapping clinical outcome. Out of 2006 treatments, we found 51 treatment pairs. D/B ratio was extremely variable (range 1.2-13.3) and in most cases (65%) it was between 1:3 and 1:5. In conclusion, even if the 1:4 ratio might be reliable for clinical purpose, a true bioequivalence between Dysport(®) and Botox(®) might not exist due to the intrinsic difference in their pharmacokinetic properties.

The biological activity of botulinum neurotoxin type C is dependent upon novel types of ganglioside binding sites

The seven botulinum neurotoxins (BoNT) cause muscle paralysis by selectively cleaving core components of the vesicular fusion machinery. Their extraordinary activity primarily relies on highly specific entry into neurons. Data on BoNT/A, B, E, F and G suggest that entry follows a dual receptor interaction with complex gangliosides via an established ganglioside binding region and a synaptic vesicle protein. Here, we report high resolution crystal structures of the BoNT/C cell binding fragment alone and in complex with sialic acid. The WY-motif characteristic of the established ganglioside binding region was located on an exposed loop. Sialic acid was co-ordinated at a novel position neighbouring the binding pocket for synaptotagmin in BoNT/B and G and the sialic acid binding site in BoNT/D and TeNT respectively. Employing synaptosomes and immobilized gangliosides binding studies with BoNT/C mutants showed that the ganglioside binding WY-loop, the newly identified sialic acid-co-ordinating pocket and the area corresponding to the established ganglioside binding region of other BoNTs are involved in ganglioside interaction. Phrenic nerve hemidiaphragm activity tests employing ganglioside deficient mice furthermore evidenced that the biological activity of BoNT/C depends on ganglioside interaction with at least two binding sites. These data suggest a unique cell binding and entry mechanism for BoNT/C among clostridial neurotoxins.

Dosing, efficacy and safety plus the use of computerized photography for botulinum toxins type A for upper facial lines

INTRODUCTION

Several studies confirm that botulinum toxins type A (BTX-A) are effective for reducing facial lines caused by hyperactive muscles. Two different commercial types of BTX-A currently available are BTX-A-1 (Botox) and BTX-A-2 (Dysport). This paper reports further comparison of dosing, efficacy and safety.

METHODS

Sites treated: glabellar, horizontal forehead lines and crow's feet. Different dilutions and dosages were studied with BTX-A-1 and BTX-A-2. The reduction of facial lines was evaluated by investigators and patients. Computerized photographic numerical assessment was also studied in determining the efficacy of BTX-A for crow's feet lines.

RESULTS

Study 1: Injecting glabellar lines at doses of BTX-A-1 (30 units) and BTX-A-2 (75 units) (2.5:1 ratio BTX-A2:BTX-A1) showed similar efficacy. Study 2: BTX-A-2 (256 units total) was significantly more effective than BTX-A-1 (64 units total) (i.e. a dose ratio of 4:1) for upper face lines. No differences in the side-effect profiles between the two toxins were observed in either study. Study 3: A computerized photographic numerical assay was an objective assessment of crow's feet severity. Using a dose ratio of BTX-A-2 to BTX-A-1 of 3:1 showed a trend towards BTX-A-2 superiority.

CONCLUSION

Two different botulinum toxins type A were shown to be effective and safe for hyperfunctional facial lines. The choice of dose, dilution and placement is critical for each individual toxin. Computerized photography gave numerical severity scores of crow's feet severity.

Neutralizing antibodies and secondary therapy failure after treatment with botulinum toxin type A: much ado about nothing?

OBJECTIVES

As the indications and duration of treatment of botulinum toxin type A (BoNT-A) increase, so do reports of patients who fail therapy after initially responding well. Although a loss of efficacy is commonly thought to be associated with neutralizing antibodies (NAbs), this relationship is not strongly correlated, and other factors may play a significant role. To explore this issue, we evaluated levels of NAbs in a large selected cohort of secondary nonresponders to BoNT-A using the highly sensitive mouse phrenic nerve-hemidiaphragm assay.

METHODS

Serum samples from 503 patients treated with BoNT-A who had a variety of diagnoses were tested for the presence of NAbs.

RESULTS

Fewer than half of the patients (n = 224, 44.5%) were found to be NAb-positive, indicating that in more than half of the secondary nonresponders, lack of efficacy is not due to NAb formation. The proportion of secondary nonresponders with NAbs was greater for higher dose indications (focal spasticity and spasmodic torticollis) than for lower dose indications (blepharospasm and hemifacial spasm) and increased with shorter injection intervals. Neutralizing antibody development was independent of the commercial preparation used.

CONCLUSIONS

Our results indicate that although NAb formation does play a role in secondary treatment failure with BoNT-A, this is not the cause in all patients, and the influence of other factors needs to be investigated. Gaining a better understanding of the underlying mechanisms for secondary treatment failure may help in the prediction, diagnosis, management, and prevention of this problem.

Measurement of botulinum types A, B and E neurotoxicity using the phrenic nerve-hemidiaphragm: improved precision with in-bred mice

Botulinum neurotoxins induce a prolonged muscle paralysis by specifically blocking the release of neuronal transmitters from peripheral nerve junctions. The current method for assessing the potency of botulinum toxin and antitoxins is the mouse LD50 assay. The mouse phrenic nerve-diaphragm assay is an in vitro assay that closely mimics in vivo respiratory paralysis. In this study, we have further improved the assay by using gelatin as a non-frothing alternative to albumin and investigated the effects of botulinum toxin serotypes A, B and E on phrenic nerve-hemidiaphragms from out-bred MF1 and in-bred Balb/c mice. Improved reproducibility was found with in-bred mice. Balb/c mice were also found to be much less sensitive to type B toxin perhaps indicating differences in the expression of receptor components. Hemidiaphragm preparations from Balb/c mice were approximately 7 times more sensitive to type A toxin and 7-12 times more sensitive to type E toxin relative to type B toxin. These findings indicate that when fully optimised the mouse nerve-diaphragm preparation can provide a functional in vitro model for accurate and reproducible assessment of toxin activity.

[Different botulinum toxins and their specifications]

Botulinum neurotoxin A was the first developed for therapeutic and then esthetic uses, Botox first and then Dysport. These two products differ on a few points, explaining their nonequivalence of units: American and British tests of the mouse LD50 units based on solutions that were not identical and 500microg vs 150microg serum albumin dose in the excipient. The neurotoxin- accessory protein complexes were also different: 900 kDa homogeneous for Botox, 500 kDa heterogeneous for Dysport, giving greater diffusion for Dysport, but this is under debate and could result from an excessive conversion ratio. Clinical comparative studies, often with weak methodology, have defined an ideal ratio between these two products, guaranteeing efficacy, but without an overly pronounced diffusion. In the first publications for neurological and ophthalmological indications, the conversion ratio between Dysport and Botox was high, 4:1, and sometimes higher. However, today, particularly for cosmetic indications, the trend is toward a much lower ratio, 2.5:1, or perhaps less for dyshidrosis. This lower ratio has an economic incidence: Dysport is less expensive and therefore more competitive. The price of Dysport's cosmetic product, Azzalure, compared to the price of Vistabel, which is Botox's cosmetic presentation, has not yet been defined in France. The other A toxins, Xeomin, and the Asian toxins, MyoBloc (botulinum toxin type B), tested compared to Botox, have a slightly lower efficacy.

Outcome predictors, efficacy and safety of Botox and Dysport in the long-term treatment of hemifacial spasm

BACKGROUND AND PURPOSE

To review the clinical characteristics and the long-term outcome of patients with hemifacial spasm (HFS) who received botulinum neurotoxin (BoNT) over the past 10 years.

RESULTS

A total of 108 patients received 665 treatments. Mean latency of clinical effect was 5.4 +/- 5.3 days for Botox and 4.9 +/- 4.6 days for Dysport (P > 0.05). Mean duration of clinical improvement was higher after the injection of Dysport than Botox: 105.9 +/- 54.2 and 85.4 +/- 41.6 days respectively (P < 0.01). The percentage of treatment failures was 6.5% for Botox and 4.6% for Dysport (P > 0.05). The doses of Botox significantly increased over time (beta = 0.35, P < 0. 001) whilst Dysport dose remained unchanged (beta = 0.16, n.s.). The duration of clinical benefit slightly increased with Botox (beta = 0.12; P < 0.01), but remained constant for Dysport. Side effects occurred in 17.4% of treatments: 16.7% of patients who had received Botox, and in 19.7% who had received Dysport (P > 0.05). The most common side effects were palpebral ptosis and lacrimation; ptosis and lagophtalmos was more common in Dysport treatments (P < 0.005).

CONCLUSIONS

Both brands are effective and safe in treating HFS; efficacy is long-lasting. The differences in outcome and side effects confirm that, albeit the active drug is the same, Botox and Dysport should be considered as two different drugs.

Dose equivalence of two commercial preparations of botulinum neurotoxin type A: time for a reassessment?

BACKGROUND

The units of different preparations of botulinum neurotoxin type A (BoNT-A) have different potencies, and dosing recommendations for each product are not interchangeable. Historically, there has been debate concerning the dose-equivalence ratio that should be used in clinical practice.

METHODS

Published evidence was considered to establish an appropriate dose-conversion ratio for the two main commercially available preparations of BoNT-A--Dysport (Dp) and Botox (Bx).

RESULTS

Four key areas of evidence were identified: nonclinical and preclinical studies; studies exploring the diffusion characteristics and effects of complexing proteins; comparative experimental data from human studies; and clinical studies. Nonclinical data indicate that the principal reasons for differences in unit potency between the two products are dilution artefacts in the mouse assay. Use of saline as a diluent, at high dilutions, results in significant loss of potency in the Bx assay, whereas use of gelatin phosphate buffer in the Dp assay procedure protects the toxin during dilution. The published data on mouse assays show a Dp : Bx unit ratio range of 2.3-2.5 : 1 in saline and 1.8-3.2 : 1 in gelatin phosphate buffer. Data indicate that complexing proteins or size of the complex, which is highly pH sensitive, play no role in toxin diffusion and that Dp and Bx have similar diffusion characteristics when used at comparable doses. Randomized, controlled clinical studies indicate that 3 : 1 is more appropriate than 4 : 1, but the two products are not equivalent at this ratio. Comparative human experimental studies using the extensor digitorum brevis test, facial lines and anhidrotic action halo tests support dose-conversion ratios less than 3 : 1.

LIMITATIONS

Data comparing dose equivalence ratios from the non-clinical setting should be extrapolated into the clinical setting with some caution.

CONCLUSIONS

Dose-conversion ratios between Dp and Bx of 4 : 1 and greater are not supported by the recent literature.

Prevalence of neutralising antibodies in patients treated with botulinum toxin type A for spasticity

Botulinum toxin (BT) has been used with great success to treat various muscle hyperactivity disorders. Occasionally, antibodies against BT (BT-AB) can be formed. When they are directed against the neurotoxin component of the BT drug, they are called neutralising antibodies. They can reduce the therapeutic effect partially or completely. We have measured neutralising BT-AB by use of the mouse diaphragm assay (MDA) in 42 adult patients with spasticity in the order of their appearance in the clinic. The patients had been treated for at least 2 years with BT type A (BT-A) and received on an average 14.2 +/- 6.1 BT-A injection series. BT-A was applied as Botox only, Dysport only or by sequential application of both preparations. The mean cumulative doses were 4,610 +/- 1,936 units Botox and 14,033 +/- 7,566 units Dysport, respectively. The mean treatment time was 4.5 +/- 1.8 (2-8) years. All patients were initially responsive to BT-A therapy. MDA detected BT-AB in 12% (5/42) of patients. However, in three patients the BT-AB titre was very low (<0.3 mIU/ml), in one it was intermediate (0.6 mIU/ml) and in one patient it was high (>1.0 mIU/ml). All BT-AB negative patients and also two of the patients with low BT-AB titre remained clinically responsive to BT therapy throughout the study. In conclusion, prevalence of BT-AB formation with clinical relevance (6%, 3/42) in adult patients with spasticity is not higher than that of BT-treated patients with cervical dystonia and much lower than that of BT-treated patients with infantile cerebral palsy.

Is botulinum toxin useful in treating headache? No

The discrepancy between the widespread use of botulinum neurotoxin (BoNT) in managing headache and the supporting clinical evidence is unprecedented. No substance seems to have inspired more physicians and patients to undertake spirited treatment attempts. Tremendous treatment success in small, uncontrolled clinical trials has been repeatedly reported, but no substance that has been studied to an equal extent has so utterly failed to provide proof of effect in controlled clinical trials. Nevertheless, even though most randomized, controlled clinical trials have not met their defined primary outcome criterion, BoNT is still considered a promising treatment alternative for primary headache disorders. Experimental approaches to the pathophysiologic impact of BoNT on the perception of pain have been equally unsuccessful. Although most studies have been unable to find a direct antinociceptive effect in humans, some researchers continue to seek specific injection sites or injection techniques that may promise more successful results. Others look for a positive effect by narrowing the indications for BoNT to more homogenous symptoms or special patient subgroups. The results of randomized, controlled studies involving a total of 3552 patients indicate that BoNT injection is probably ineffective for patients with migraine and chronic tension-type headache regardless of injection site, dosage, or injection regimen, and there is insufficient evidence to draw a conclusion about its effectiveness for the treatment of chronic daily headache or subforms. The lack of direct experimental or clinical trial evidence that BoNT has a direct antinociceptive effect in humans must be addressed before more trials are conducted, involving even more patients. Additional pathophysiologically oriented research is also needed to unravel the mechanisms of action of BoNT in human pain perception or, alternatively, to bring it all down to the placebo effect.

Botulinum neurotoxin — from laboratory to bedside

Botulinum neurotoxin (BoNT) has been used clinically since 1980, with an ever-increasing range of clinical applications. This has coincided with a period of massively expanded interest in the underlying biology of the neurotoxin. Tremendous advances have taken place in the scientific understanding of neurotoxin structure and function since the description of their endopeptidase activity in 1992. These developments have led to an increased understanding of the mechanisms underpinning the clinical use of the neurotoxins and also in the technologies available to support their clinical use. The expanding range of clinical applications, and use in increasing doses, has also generated challenges for the clinicians and manufacturers of BoNT preparations to ensure continuing efficacy and safety margins for these new clinical settings. To date the increased clinical use of BoNTs has occurred largely empirically, and not by application of the recent insights into neurotoxin structure and function. With the increased knowledge regarding the biology of the neurotoxins, however, there is the opportunity to select preferred forms of the toxin for particular clinical applications and even to consider engineering the neurotoxins to produce modified products more suited to specific clinical applications. These developments and opportunities that have arisen, particularly over the last decade, emphasise the increasing need to maintain an active two way dialogue between clinicians and basic scientists to ensure that the advances in the laboratory are translated into clinical benefit and that the clinical developments in use of neurotoxin are supported by the scientific research activity. This article is based upon presentations given in a workshop at the 5th International Conference on Basic and Therapeutic Aspects of Botulinum and Tetanus Toxin in Denver in June, 2005 seeking to address issues relating to the laboratory/clinic interface.

Fifteen-year experience in treating blepharospasm with Botox or Dysport: same toxin, two drugs

OBJECTIVES

To compare the clinical characteristics and the long-term outcome of a large series of patients with blepharospasm (BS) treated with the two most used brands of BoNT-A over the last 15 years.

METHODS

We have reviewed the clinical charts of 128 patients with BS who received botulinum neurotoxin (BoNT) in 1341 treatments (Botox in 1009, Dysport in 332) over the last 15 years.

RESULTS

Mean dose per session was 34U +/- 15 for Botox and 152U +/- 54 for Dysport. Mean latency of clinical effect was 4.5 +/- 4.6 days for Botox and 5.0 +/- 5.7 days for Dysport (P > 0.05). Mean duration of clinical improvement was higher for Dysport than Botox: 80.1 +/- 36.3 and 66.2 +/- 39.8 days, respectively (P < 0.01). In a six-point scale (0: no efficacy, 6: remission of BS), the mean efficacy of both treatments was 3.60 +/- 1.3; 3.51 +/- 1.4 (Botox) and 3.85 +/- 1.2 (Dysport), P < 0.01. The doses of Botox (beta = 0.40) and Dysport (beta = 0.16) were significantly increased over time. Side effects occurred in 325 out of 1341 treatments (24.2%): 21.8% of the patients who had received Botox, and in 31.6% of those who had received Dysport (P < 0.01).

CONCLUSIONS

Both brands are effective and safe in treating blepharospasm; efficacy is long lasting. The differences in outcome and side effects suggest that, albeit the active drug is the same, Botox and Dysport should be considered as two different drugs.

Biological activity of two botulinum toxin type A complexes (Dysport and Botox) in volunteers: a double-blind, randomized, dose-ranging study

Despite extensive clinical experience and published data regarding botulinum toxin, questions remain about the clinical substitution of one botulinum toxin formulation for another. In the case of Dysport and Botox, dose-equivalence ratios ranging from 1:1 to 6:1 (Dysport:Botox) have been advocated. This dose-ranging, electroneurographic study investigated the dose equivalence, diffusion characteristics (spread) and safety of these two type-A toxins in 79 volunteers. Dysport and Botox caused significant and similar reductions in compound muscle action potential (CMAP) amplitude in the target muscle (extensor digitorum brevis, EDB) 2 weeks after injection, with effects persisting to the 12-week timepoint. For both products, the reduction in amplitude was increased with increasing doses and with increasing concentration. The effects of toxin on neighbouring muscles were much smaller and of a shorter duration than those on the target muscle, implying a modest spread of toxin. Unlike the target muscle, the effects were greater with the higher volume, suggesting this volume led to greater diffusion from the EDB. No adverse events were reported. Statistical modelling with CMAP amplitude data from the target muscle gave a bioequivalence of 1.57 units of Dysport:1 unit of Botox (95 % CI: 0.77-3.20 units). The data indicate that a dose-equivalence ratio of 3:1 was within the statistical error limits, but ratios over 3:1 are too high.

The use of botulinum toxin A for treatment of possible essential blepharospasm in a dog

A 3-year-old Great Dane with bilateral possible essential blepharospasm resulting in ocular complications is described. Conservative treatment was not successful and the disease was treated with local injections of botulinum toxin A into the orbicularis oculi muscle. Blepharospasm disappeared completely 5 to 6 days after injection and did not reappear until 3 to 4 months later, at which time the injection was repeated. After several treatments over a period of more than 3 years no side effects have occured. Botulinum toxin A appeared to be effective in the treatment of essential blepharospasm in this dog.

Evidence based medicine on the use of botulinum toxin for headache disorders

Botulinum toxin blocks the release of acetylcholine from motor nerve terminals and other cholinergic synapses. In animal studies botulinum toxin also reduces the release of neuropeptides involved in pain perception. The implications of these observations are not clear. Based on the personal experiences of headache therapists, botulinum toxin injections have been studied in patients with primary headaches, namely tension-type headache (TTH), chronic migraine (CM) and chronic daily headache (CDH). So far, the results of randomized, double-blind, placebo controlled trials on botulinum toxin in a total of 1117 patients with CDH, 1495 patients with CM, and 533 patients with TTH have been published. Botulinum toxin and placebo injections have been equally effective in these studies. In some of the studies, the magnitude of this effect was similar to that of established oral pharmacotherapy. This finding may help to explain the enthusiasm that followed the first open-label use of botulinum toxin in patients with headache. However, research is continuing to determine the efficacy of botulinum toxin in certain subgroups of patients with CM or CDH.

Treatment of habitual snoring with botulinum toxin: a pilot study

The objective of this study was to investigate whether injections of botulinum toxin into the soft palate reduce snoring in a subgroup of patients that present an active process causing habitual snoring. The study was conducted in eight patients with habitual snoring but without evidence of obstructive sleep apnea. Polysomnography was performed for diagnostic purposes and to monitor sleep quality before and after treatment. The patients and their partners completed a questionnaire before and after treatment. Recordings of snoring noise before and after treatment were evaluated on a visual analog scale by a blinded assessor. Doses of 20 U of botulinum toxin type A (Dysport) were injected unilaterally into the muscles of the soft palate. Snoring was reduced in eight cases. The patients reported no major adverse effects. These results justify further studies of botulinum toxin therapy in patients with habitual snoring. The scheme presented for injections of botulinum toxin into the levator veli palatini muscle provides a rational basis for the design of such studies. Therapy with botulinum toxin for habitual snoring is safe, non-invasive, easy to perform, fully reversible, and thus warrants investigation under placebo-controlled, double-blind conditions. This treatment is appropriate for a disorder that is of paramount social importance but does not pose a medical threat to the individuals affected.

Decreased muscle loading delays maturation of the tendon enthesis during postnatal development

Physical environment influences the development and maintenance of musculoskeletal tissues. The current study uses an animal model to explore the role of the physical environment on the postnatal development of the supraspinatus tendon enthesis. A supraspinatus intramuscular injection of botulinum toxin A was used to paralyze the left shoulders of mice at birth. The supraspinatus muscles of right shoulders were injected with saline to serve as contralateral controls. The supraspinatus enthesis was examined after 14, 21, 28, and 56 days of postnatal development. Histologic assays were used to examine fibrocartilage morphology and percentage osteoclast surface. Micro-computed tomography was used to examine muscle geometry and bone architecture. At 14 days there were no differences between groups in fibrocartilage formation, muscle geometry, bone architecture, or osteoclast surface. When comparing groups at 21, 28, and 56 days, muscle volume was decreased, fibrocartilage development was delayed, mineralized bone was decreased, and osteoclast surface was higher at each timepoint in the botulinum group compared to the contralateral saline control group. Our results indicate that the development of the tendon enthesis is sensitive to its mechanical environment. A reduction in muscle loading delayed the development of the tendon-to-bone insertion site by impeding the accumulation of mineralized bone. Physical factors did not play a significant role in enthesis maturation in the first 14 days postnatally, implying that biologic factors may drive early postnatal development.