OnabotulinumtoxinA as a promising treatment for primary trochlear headache: A retrospective case series.

OBJECTIVES: To report the efficacy of onabotulinumtoxinA (BoNTA) injections in relieving pain in patients with primary trochlear headache (PRTH). METHODS: Examination of medical records for patients diagnosed with PRTH according to the International Classification of Headache Disorders, 3rd edition criteria and treated with BoNTA. Data were collected for variables related to pain relief, duration of effectiveness, and adverse effects. RESULTS: Six patients were included in the study. All had previously undergone standard care interventions, including infiltrations or oral treatments, yet experienced treatment failure or symptom recurrence. All patients received 20 units of BoNTA, administered in the corrugator and procerus muscles. Subsequent to the BoNTA injections, all six patients reported substantial pain relief, with five achieving complete remission of symptoms. The analgesic effect persisted for a duration of 3 months. No adverse events were reported in any of the cases. CONCLUSIONS: Our case series presents the first evidence of the potential of BoNTA as a safe and effective treatment option for PRTH. From a clinical standpoint, having a safer alternative is of paramount significance for patients with limited treatment options, such as those with PRTH. Further research is warranted to validate these findings and explore the long-term efficacy of BoNTA in PRTH management.

Botulinum Neurotoxin Type A in the Treatment of Facial Seborrhea and Acne: Evidence and a Proposed Mechanism.

Intradermal injection of botulinum neurotoxin is a frequently performed procedure in aesthetic dermatology to improve facial skin tone, texture, fine wrinkles, and enlarged pores. In practice, botulinum neurotoxin type A is also used to reduce skin oiliness of the face. There is increasing evidence that acetylcholine plays specific roles in sebum production, suggesting that botulinum neurotoxin type A may reduce sebum production by interfering with cholinergic transmission between sebaceous glands and autonomic nerve terminals. Botulinum neurotoxins can also inhibit several pathogenetic components of acne development, suggesting that botulinum neurotoxins can be used as a safe and effective treatment modality for acne and other skin disorders related to overactivity of sebaceous glands. This review aims to explore the current evidence behind the treatment of facial seborrhea and acne with botulinum neurotoxin type A.

The Effect of Botulinum Toxin on Flap Viability of the Posterior Thigh Perforator Flap in Rats.

BACKGROUND: The use of perforator propeller flaps in lower limb reconstruction has increased recently. Many pharmacological agents are used to increase flap viability. Botulinum toxin has been used in various types of flaps in the literature. However, there is no study regarding the use of botulinum toxin in the lower limb propeller flaps. This study investigates the effect of botulinum toxin administration on flap survival for lower limb propeller flap in rats. MATERIALS AND METHODS: The study included 20 male Wistar albino rats, divided into two groups with a flap rotation of 90° in group 1 and 180° in group 2. In both groups, botulinum toxin was administered to the right thigh and a physiological saline solution was applied to the left thigh. Five days later, flaps were elevated over the posterior aspect of the right and left thighs and inset after 90° and 180° rotation was performed. Histopathological, immunohistochemical, and necrosis area analyses were performed. RESULTS: Necrosis area, edema, polymorphonuclear leukocyte infiltration, and necrosis were found to be higher on the left side of the groups, whereas epidermal thickness, collagen density, vascularization, and hair root density were found to be higher on the right side of the groups. No significant difference was found between the right posterior thighs in either group on any parameter other than vascularization. Histopathologically and immunochemically statistically significant differences were found between the two groups. CONCLUSIONS: The present study found that botulinum toxin increases flap viability in lower limb perforator-based propeller flaps.

A Multicenter Study to Evaluate Subject Satisfaction With Two Treatments of AbobotulinumtoxinA a Year in the Glabellar Lines.

BACKGROUND: Real-world re-treatment intervals for botulinum toxins vary, but most subjects receive treatment less frequently than the manufacturer-recommended minimum intervals. In subjects receiving treatment with AbobotulinumtoxinA (ABO) less frequently, high levels of satisfaction and psychosocial improvements in well-being, self-confidence, and quality of life are observed. OBJECTIVE: To evaluate subject satisfaction with a twice yearly re-treatment schedule. METHODS AND MATERIALS: This open-label, multicenter, interventional study evaluated subject satisfaction following injections of ABO 50 U in the glabellar lines at baseline and 6 months. The primary end point was subject satisfaction at 12 months. Secondary endpoints included subject satisfaction, FACE-Q scales, and glabellar line severity scale (GLSS). RESULTS: Ninety-five percent of the 120 subjects were "highly satisfied" or "satisfied" with their treatment outcomes at 12 months. FACE-Q total scores suggested that subjects were less bothered by glabellar lines and felt better about their facial appearance with each treatment versus baseline. Approximately half of subjects had ≥1-grade improvement from baseline in GLSS at 12 months. Median onset of effect was 2 days. CONCLUSION: The majority of subjects (95%) were satisfied with ABO treatment every 6 months; results were supported by high subject satisfaction, long duration, rapid onset, natural-looking results, and overall psychological wellness and safety.

Microbotulinum: A Quantitative Evaluation of Aesthetic Skin Improvement in 62 Patients.

BACKGROUND: Microbotulinum refers to the systematic injection of tiny blebs of diluted botulinum toxin at repeated intervals into the skin. This targets the superficial fibers of the facial muscles, and weakens their insertion into the undersurface of the skin, which is responsible for the fine lines and wrinkles on the face. The authors present a pilot study based on quantitative evaluation, by means of a skin-scanning technology, of the aesthetic improvement of skin texture, microroughness, and enlarged pore size in a patient group treated with microbotulinum injections for cosmetic purposes. METHODS: The treatment was performed using a 32-gauge needle to deliver injections on a regular 1-cm grid from the forehead to the cheek and down to the jawline. RESULTS: Sixty of the 62 patients completed the study. All analyzed parameters improved significantly (p < 0.0001) at 90 days with respect to the pretreatment time point (skin texture, -1.93 ± 0.51; microroughness, -2.48 ± 0.79; and pore diameter, 2.1 ± 0.43). Best results have been obtained in patients aged between 42.7 and 46.8 years, and standard deviation calculation allows us to recommend it in patients aged between 36.5 and 53 years. CONCLUSIONS: The results of this pilot study suggest that intradermal botulinum toxin injection, or so-called microbotulinum, is a safe and effective method to treat skin flaws. Because of the high satisfaction rate among both physicians and patients, further studies are indeed mandatory to determine the optimal number of units needed for a longer and lasting effect with this particular novel dilution. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.

Abobotulinumtoxina injections in shoulder muscles to improve adult upper limb spasticity: Results from a phase 4 real-world study and a phase 3 open-label trial.

Botulinum toxins, such as abobotulinumtoxinA, are used to treat spasticity (muscle overactivity) in arm muscles. Spasticity in shoulder muscles occurs in many patients following a stroke. Shoulder spasticity can be painful and limit limb movement. This paper compares the results from patients who did and those who did not receive abobotulinumtoxinA injections in shoulder muscles (among other arm muscles) in 2 studies. In both studies, the results showed that more patients receiving treatment in shoulder muscles chose pain as a key goal for treatment and had reduced pain following treatment compared with patients not treated in the shoulder. In addition, patients receiving shoulder injections showed further improvement in arm movement compared with those not receiving shoulder injections. Overall, these results suggest that abobotulinumtoxinA treatment in shoulder muscles may improve outcomes for patients with arm spasticity involving the shoulder.

Analysis of Motor Neurons Differentiated from Human Induced Pluripotent Stem Cells for the Use in Cell-Based Botulinum Neurotoxin Activity Assays.

Botulinum neurotoxins (BoNTs) are potent neurotoxins produced by bacteria, which inhibit neurotransmitter release, specifically in their physiological target known as motor neurons (MNs). For the potency assessment of BoNTs produced for treatment in traditional and aesthetic medicine, the mouse lethality assay is still used by the majority of manufacturers, which is ethically questionable in terms of the 3Rs principle. In this study, MNs were differentiated from human induced pluripotent stem cells based on three published protocols. The resulting cell populations were analyzed for their MN yield and their suitability for the potency assessment of BoNTs. MNs produce specific gangliosides and synaptic proteins, which are bound by BoNTs in order to be taken up by receptor-mediated endocytosis, which is followed by cleavage of specific soluble N-ethylmaleimide-sensitive-factor attachment receptor (SNARE) proteins required for neurotransmitter release. The presence of receptors and substrates for all BoNT serotypes was demonstrated in MNs generated in vitro. In particular, the MN differentiation protocol based on Du et al. yielded high numbers of MNs in a short amount of time with high expression of BoNT receptors and targets. The resulting cells are more sensitive to BoNT/A1 than the commonly used neuroblastoma cell line SiMa. MNs are, therefore, an ideal tool for being combined with already established detection methods.

Application of botulinum toxin in pregnancy and its impact on female reproductive health.

Introduction: Botulinum toxin (BoNT) is a protein secreted by the anaerobic Gram-negative bacterium Clostridium botulinum. Among the seven known subtypes, type A is the most commonly used in women to treat diseases. It primarily blocks presynaptic release of acetylcholine at the neuromuscular junction, resulting in temporary muscle paralysis; thus, it is suitable for treating dystonia and other systemic diseases. BoNT is used widely for treating diseases that persist throughout, and may worsen during, pregnancy, such as cervical dystonia and achalasia. Thus, it is important to investigate whether BoNT injection during pregnancy causes side effects in pregnant women, fetuses, or newborns.Areas covered: This review highlights the efficiency and safety of BoNT injection in pregnancy. and assessed current literature with respect to the use of BoNT for disease treatment during pregnancy.Expert opinion: BoNT injection does not increase the risk of complications in pregnant women and fetuses. However, the use of BoNT to treat disease during pregnancy requires fully informed consent from patients. In addition, further research is needed to determine how to reduce the side effects of BoNT injection during pregnancy (e.g., by improving drug composition, or adjusting the amount of BoNT or the injection interval).

Safety and pharmacodynamics of a novel recombinant botulinum toxin E (rBoNT-E): Results of a phase 1 study in healthy male subjects compared with abobotulinumtoxinA (Dysport®).

Naturally occurring botulinum toxin (BoNT) serotypes have different pharmacological features of therapeutic and aesthetic interest. This phase 1, double-blind, placebo-controlled study (EudraCT: 2016-002609-20) assessed safety, tolerability and pharmacodynamics (PD) of the first recombinant BoNT serotype E (rBoNT-E) versus abobotulinumtoxinA (Dysport®), administered to extensor digitorum brevis (EDB) of healthy males. Subjects were randomised 3:1 (n = 28) to single ascending rBoNT-E (0.04-3.6 ng) doses or placebo. A further 24 subjects received abobotulinumtoxinA (20, 40, or 70 U) or placebo. PD were assessed using compound muscle action potential (CMAP) amplitude. Demographics were similar between groups. All rBoNT-E doses were well tolerated (no severe treatment-emergent adverse events [TEAEs], serious adverse events, or treatment-related toxicities). Most TEAEs were mild/moderate and treatment-unrelated. rBoNT-E had a faster onset of action (days 1-2 post-injection), greater peak effect (>90% CMAP inhibition), and shorter duration of effect at highest tested doses versus abobotulinumtoxinA (onset of action ≤7 days post-injection; 70% maximal CMAP inhibition). rBoNT-E duration of effect was 2-7 weeks versus >26 weeks for abobotulinumtoxinA. Dose-dependent effects were observed for magnitude and duration of EDB CMAP inhibition, plateauing at 0.9 and 3.6 ng. rBoNT-E demonstrated a good safety profile and a PD profile that may address unmet therapeutic and aesthetic patient needs.

An objective method to assess the improvements of skin texture roughness after botulinum toxin type a treatment of crow's feet.

BACKGROUND: Photo-numeric scales could lack precision and objectivity on evaluating the improvements on wrinkles after a treatment with botulinum toxin type A. The authors suggest a new digital evaluation method to analyze its effectiveness. OBJECTIVES: This study aims to investigate retrospectively the effect of intramuscular injection of botulinum toxin type A on skin texture in the lateral peri-orbital region with a new objective method. METHODS: Skin texture roughness (STR) in the lateral peri-orbital region is evaluated with a multi-directional light beam by light emitting diodes of different wavelengths (Antera 3D® ), before and after injections of 12 units of botulinum toxin type A. The wrinkles and lines deeper than 0.5 mm are filtered to measure accurately skin texture. RESULTS: We observed an improvement of STR in all cases treated with botulinum toxin type A. A significant decrease of STR was recorded as follows: 17.08% (P < .0001) at 4 weeks and 12.14% at 4 months (P = .001). CONCLUSION: Botulinum toxin type A treatment of crow's feet was able to improve STR. The Antera® device and software are a valuable, objective, easy and reproducible method to assess the effects of the toxin.

Use of botulinum toxin in Parkinson's disease.

Botulinum toxin has emerged as an important therapeutic intervention within the realm of movement disorders, especially for focal and generalized dystonias. Botulinum toxin has additionally been used for a variety of symptoms associated with parkinsonism. In this review, we will specifically evaluate use of botulinum toxin in idiopathic Parkinson's disease. We will discuss symptoms including sialorrhea, limb, dystonia, tremor, dyskinesias, freezing of gait, camptocormia, pisa syndrome, urinary dysfunction, constipation, dysphagia, eyelid opening apraxia, and blepharospasm.

Activity-dependent vs. neurotrophic modulation of acetylcholine receptor expression: Evidence from rat soleus and extensor digitorum longus muscles confirms the exclusive role of activity.

Evoked electrical muscle activity suppresses the transcription of mRNAs for acetylcholine receptors in extrajunctional myonuclei. Muscle denervation or disuse releases such inhibition and extrajunctional receptors appear. However, in soleus muscles paralysed with nerve-applied tetrodotoxin, a restricted perijunctional region has been described where myonuclei remain inhibited, a finding attributed to nerve-derived trophic factor(s). Here, we reinvestigate extrajunctional acetylcholine receptor expression in soleus and extensor digitorum longus muscles up to 90 days after denervation or up to 20 days of disuse, to clarify the role of trophic factors, if any. The perijunctional region of soleus muscles strongly expressed acetylcholine receptors during the first 2-3 weeks of denervation. After 2-3 months, this expression had disappeared. No perijunctional expression was seen after paralysis by tetrodotoxin or botulinum toxin A. In contrast, the extensor digitorum longus never displayed suppressed perijunctional acetylcholine receptor expression after any treatment, suggesting that it is an intrinsic property of soleus muscles. Soleus denervation only transiently removed the suppression, and its presence in long-term denervated soleus muscles contradicts any contribution from nerve-derived trophic factor(s). In conclusion, our results confirm that evoked electrical activity is the physiological factor controlling the expression of acetylcholine receptors in the entire extrajunctional membrane of skeletal muscles.

Minimal clinically important change in the Toronto Western Spasmodic Torticollis Rating Scale.

OBJECTIVES: To characterize the minimal clinically important change (MCIC) after treatment in cervical dystonia patients using the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS). METHODS: Changes in the TWSTRS from an observational study of abobotulinumtoxinA in the routine management of cervical dystonia (NCT01314365) were analyzed using the Patient Global Impression of Change (PGIC) as anchor. RESULTS: For the overall population (N = 304, baseline TWSTRS-Total score 43.4 ±â€¯19.4), the MCIC for the TWSTRS Total score was -11.9 (95%CI: -13.9, -10.0; p < 0.0001). However, thresholds ranged from -3.2 to -18.0 dependent on baseline severity. TWSTRS-Total scores improved linearly by 3 points for every one-point PGIC increase. There was similar linearity between the graded PGIC categories and TWSTRS subscale scores (severity, disability, and pain). CONCLUSIONS: A 3-point change is the minimal clinically important change after treatment using TWSTRS as endpoint with higher cutoffs for greater baseline disease severity. For an average trial population (TWSTRS-total: 40-45), a 12-point decrease is clinically meaningful.

Influence of the neural microenvironment on prostate cancer.

BACKGROUND: Nerves are key factors in prostate cancer (PCa), but the functional role of innervation in prostate cancer is poorly understood. PCa induced neurogenesis and perineural invasion (PNI), are associated with aggressive disease. METHOD: We denervated rodent prostates chemically and physically, before orthotopically implanting cancer cells. We also performed a human neoadjuvant clinical trial using botulinum toxin type A (Botox) and saline in the same patient, before prostatectomy. RESULT: Bilateral denervation resulted in reduced tumor incidence and size in mice. Botox treatment in humans resulted in increased apoptosis of cancer cells in the Botox treated side. A similar denervation gene array profile was identified in tumors arising in denervated rodent prostates, in spinal cord injury patients and in the Botox treated side of patients. Denervation induced exhibited a signature gene profile, indicating translation and bioenergetic shutdown. Nerves also regulate basic cellular functions of non-neoplastic epithelial cells. CONCLUSION: Nerves play a role in the homeostasis of normal epithelial tissues and are involved in prostate cancer tumor survival. This study confirms that interactions between human cancer and nerves are essential to disease progression. This work may make a major impact in general cancer treatment strategies, as nerve/cancer interactions are likely important in other cancers as well. Targeting the neural microenvironment may represent a therapeutic approach for the treatment of human prostate cancer.

The impact of onabotulinumtoxinA on severe headache days: PREEMPT 56-week pooled analysis.

BACKGROUND: OnabotulinumtoxinA has been shown to reduce headache-days among patients with chronic migraine (CM). The objective of this analysis was to determine whether onabotulinumtoxinA has an impact on headache-day severity in patients with CM among those patients who were deemed non-responders based on reduction in the frequency of headache days alone. METHODS: Data from the Phase 3 REsearch Evaluating Migraine Prophylaxis Therapy (PREEMPT) clinical trial program (a 24-week, 2-treatment cycle, double-blind, randomized, placebo-controlled, parallel-group phase, followed by a 32-week, 3-treatment cycle, open-label phase) were pooled for analysis. Patients kept a daily diary to record headache severity on a 4-point scale (from none to severe), and a 6-domain Headache Impact Test (HIT-6) was used to determine the clinical impact of headaches. Analysis was undertaken to assess whether the subset of patients that were headache-day frequency non-responders at week 24 (patients with <50% reduction in headache-day frequency) experienced a reduction in headache severity whilst receiving onabotulinumtoxinA. RESULTS: For headache-day frequency non-responders, significant reductions in the number of severe headache days, average daily headache severity, pooled percentage of severe headache days and headache severity score were observed at week 24 for patients who had received onabotulinumtoxinA compared with those who had received placebo. The between-group differences were reduced and non-significant at week 56. Similarly, headache-day frequency non-responders receiving onabotulinumtoxinA were found to have an improvement in the clinical impact of headaches using results from the HIT-6. CONCLUSIONS: These results suggest that even those patients with CM who are deemed non-responders based on analysis of headache frequency alone experience clinically meaningful relief from headache intensity following treatment with onabotulinumtoxinA.

Adult Spasticity International Registry Study: methodology and baseline patient, healthcare provider, and caregiver characteristics.

OBJECTIVE: The main aim of this study was to determine the utilization patterns and effectiveness of onabotulinumtoxinA (Botox®) for treatment of spasticity in clinical practice. DESIGN: An international, multicentre, prospective, observational study at selected sites in North America, Europe, and Asia. PATIENTS: Adult patients with newly diagnosed or established focal spasticity, including those who had previously received treatment with onabotulinum-toxin A. METHODS: Patients were treated with onabotulinumtoxinA, approximately every 12 weeks, according to their physician's usual clinical practice over a period of up to 96 weeks, with a final follow-up interview at 108 weeks. Patient, physician and caregiver data were collected. RESULTS: Baseline characteristics are reported. Of the 745 patients enrolled by 75 healthcare providers from 54 sites, 474 patients had previously received onabotulinumtoxinA treatment for spasticity. Lower limb spasticity was more common than upper limb spasticity, with stroke the most common underlying aetiology. The Short-Form 12 (SF-12) health survey scores showed that patients' spasticity had a greater perceived impact on physical rather than mental aspects. CONCLUSION: The data collected in this study will guide the development of administration strategies to optimize the effectiveness of onabotulinumtoxinA in the management of spasticity of various underlying aetiologies.

Overactive bladder treatment: application of methylene blue to improve the injection technique of onabotulinum toxin A.

OBJECTIVE: The aim of this study was to test the addition of methylene blue (MB) to onabotulinum toxin A (BTX-A) solution in overactive bladder (OAB) treatment, as a means of facilitating observation of the injection site and assessing the distribution of the drug under the bladder mucosa during injection. Pharmacological interactions between BTX-A and MB were also evaluated. MATERIALS AND METHODS: The study was conducted between December 2014 and April 2016 on 30 patients: six males and 24 females (median age 57.7, range 23-80 years) diagnosed with OAB, who qualified for intravesical BTX-A injection. Each received 100 IU of BTX-A (Botox®; Allergan), dissolved in 9.5 ml of 0.9% NaCl with the addition of 0.5 ml of MB. Cystoscopy with submucosal injection of the solution was performed systematically, including the bladder triangle. For pharmacological evaluation, quantitative determination of MB was performed on a capillary electrophoresis system with diode array detection. RESULTS: In the course of 600 injections, the addition of MB facilitated the observation of the procedure; the exact distribution of the solution could not be observed in only 43 injections in seven patients. The range of distribution of the drug varied from 1 to 2.5 cm. Pharmacological evaluation based on visual observations and experiments showed that pharmaceutical interactions do not occur between MB and this commercially available formulation of BTX-A. CONCLUSIONS: Applying a coloured solution of BTX-A significantly facilitates observation of the procedure and assessment of drug distribution. There are no pharmaceutical interactions between MB and BTX-A.

Engineered botulinum neurotoxin B with improved efficacy for targeting human receptors.

Botulinum neurotoxin B is a Food and Drug Administration-approved therapeutic toxin. However, it has lower binding affinity toward the human version of its major receptor, synaptotagmin II (h-Syt II), compared to mouse Syt II, because of a residue difference. Increasing the binding affinity to h-Syt II may improve botulinum neurotoxin B's therapeutic efficacy and reduce adverse effects. Here we utilized the bacterial adenylate cyclase two-hybrid method and carried out a saturation mutagenesis screen in the Syt II-binding pocket of botulinum neurotoxin B. The screen identifies E1191 as a key residue: replacing it with M/C/V/Q enhances botulinum neurotoxin B binding to human synaptotagmin II. Adding S1199Y/W or W1178Q as a secondary mutation further increases binding affinity. Mutant botulinum neurotoxin B containing E1191M/S1199Y exhibits ~11-fold higher efficacy in blocking neurotransmission than wild-type botulinum neurotoxin B in neurons expressing human synaptotagmin II, demonstrating that enhancing receptor binding increases the overall efficacy at functional levels. The engineered botulinum neurotoxin B provides a platform to develop therapeutic toxins with improved efficacy.Humans are less sensitive to the therapeutic effects of botulinum neurotoxin B (BoNT/B) than the animal models it is tested on due to differences between the human and the mouse receptors. Here, the authors engineer BoNT/B to improve its affinity to human receptors and enhance its therapeutic efficacy.

Long-Term Treatment with OnabotulinumtoxinA Results in Consistent, Durable Improvements in Health Related Quality of Life in Patients with Overactive Bladder.

PURPOSE: We present the long-term effects of repeat onabotulinumtoxinA 100 U treatment on health related quality of life in patients with overactive bladder and urinary incontinence who had an inadequate response to and/or were intolerant of an anticholinergic. MATERIALS AND METHODS: Patients who completed either of 2, 24-week phase III trials could enter a 3-year extension study and request multiple onabotulinumtoxinA 100 U treatments as needed. Results of the I-QOL (Incontinence-Quality of Life) and KHQ (King's Health Questionnaire) are reported for up to 6 treatments. Consistency of the response to repeat onabotulinumtoxinA treatments was evaluated by classifying patients by the I-QOL response to the first treatment and analyzing responses to treatments 2 to 6. RESULTS: After onabotulinumtoxinA treatments 1 to 6, improvements in I-QOL scores were consistently 2 to 3 times the minimally important difference, and improvements in KHQ role limitations and social limitations domain scores were 5 to 6 and 3 to 4 times the minimally important difference, respectively. Most patients achieved or exceeded the minimally important difference for I-QOL and KHQ domain scores. Furthermore, 72.9% of patients who achieved or exceeded the minimally important difference for I-QOL after treatment 1 did so for all subsequent treatments. Of patients with a poor response after treatment 1, 38.3% achieved improvements greater than the minimally important difference for all subsequent treatments. CONCLUSIONS: In patients with overactive bladder and incontinence consistent and clinically meaningful improvements in health related quality of life were observed with repeat onabotulinumtoxinA 100 U treatments. A positive response after treatment 1 tended to predict similar responses to subsequent treatments, whereas a lack of response to treatment 1 did not preclude positive response(s) to later treatments.

Key Parameters for the Use of AbobotulinumtoxinA in Aesthetics: Onset and Duration.

Time to onset of response and duration of response are key measures of botulinum toxin efficacy that have a considerable influence on patient satisfaction with aesthetic treatment. However, there is no overall accepted definition of efficacy for aesthetic uses of botulinumtoxinA (BoNT-A). Mechanical methods of assessment do not lend themselves to clinical practice and clinicians rely instead on assessment scales such as the Frontalis Activity Measurement Standard, Frontalis Rating Scale, Wrinkle Severity Scale, and Subject Global Assessment Scale, but not all of these have been fully validated. Onset of activity is typically seen within 5 days of injection, but has also been recorded within 12 hours with abobotulinumtoxinA. Duration of effect is more variable, and is influenced by parameters such as muscle mass (including the effects of age and sex) and type of product used. Even when larger muscles are treated with higher doses of BoNT-A, the duration of effect is still shorter than that for smaller muscles. Muscle injection technique, including dilution of the toxin, the volume of solution injected, and the positioning of the injections, can also have an important influence on onset and duration of activity. Comparison of the efficacy of different forms of BoNT-A must be made with the full understanding that the dosing units are not equivalent. Range of equivalence studies for abobotulinumtoxinA (Azzalure; Ipsen Limited, Slough UK/Galderma, Lausanne CH/Dysport, Ipsen Biopharm Limited, Wrexham UK/Galderma LP, Fort Worth, TX) and onabotulinumtoxinA (Botox; Allergan, Parsippany, NJ) have been conducted, and results indicate that the number of units of abobotulinumtoxinA needs to be approximately twice as high as that of onabotulinumtoxinA to achieve the same effect. An appreciation of the potential influence of all of the parameters that influence onset and duration of activity of BoNT-A, along with a thorough understanding of the anatomy of the face and potency of doses, are essential to tailoring treatment to individual patient needs and expectations.