Indications and efficacy of botulinum toxin in disorders of the gastrointestinal tract

Gastrointestinal Uses of Botulinum Toxin

Botulinum toxin (BT), one of the most powerful inhibitors that prevents the release of acetylcholine from nerve endings, represents an alternative therapeutic approach for "spastic" disorders of the gastrointestinal tract such as achalasia, gastroparesis, sphincter of Oddi dysfunction, chronic anal fissures, and pelvic floor dyssynergia.BT has proven to be safe and this allows it to be a valid alternative in patients at high risk of invasive procedures but long-term efficacy in many disorders has not been observed, primarily due to its relatively short duration of action. Administration of BT has a low rate of adverse reactions and complications. However, not all patients respond to BT therapy, and large randomized controlled trials are lacking for many conditions commonly treated with BT.The local injection of BT in some conditions becomes a useful tool to decide to switch to more invasive therapies. Since 1980, the toxin has rapidly transformed from lethal poison to a safe therapeutic agent, with a significant impact on the quality of life.

Impact of Botulinum Neurotoxin Pyloric Injection During Laparoscopic Sleeve Gastrectomy on Postoperative Gastric Leak: a Clinical Randomized Study

BACKGROUND

The most frequent and most feared complication after laparoscopic sleeve gastrectomy (LSG) is gastric leak (GL). We hypothesize that botulinum neurotoxin (botulinum type A (BTX-A)) injection into the pyloric sphincter muscle at the time of operation may decrease the risk of postoperative GL.

METHODS

Consecutive patients with morbid obesity (MO) treated by LSG were enrolled. Patients were randomly allocated into two groups: group I (intrapyloric BTX-A injection was performed) and group II (no injection was performed). The primary outcome measure was number of patients developing GL. Secondary outcome measures were percent of excess weight loss, postoperative complications, and their management.

RESULTS

One hundred and fifteen patients (86 (74.8 %) females) were randomized into two groups of 57 patients (group I) and 58 patients (group II). Four patients in group II developed GL versus no patient in group I (P = 0.04). Ten patients in group I and two in group II developed refractory epigastric pain (P = 0.01). Other complication rates were comparable for both groups. Mean preoperative BMI of patients in both groups had significantly decreased from 54.64 ± 6.82 to 42.99 ± 5.3 at 6 months and to 39.09 ± 5.14 at 12 months (P < 0.001).

CONCLUSIONS

LSG is an effective, safe, and minimally invasive procedure for treatment of MO. No patient in whom pyloric BTX-A injection was performed developed postoperative GL versus four patients in whom injection was not performed. The difference in GL rate was statistically significant, thus favoring the use of pyloric BTX-A injection during LSG.

Treatment of gastrointestinal sphincters spasms with botulinum toxin A

Botulinum toxin A inhibits neuromuscular transmission. It has become a drug with many indications. The range of clinical applications has grown to encompass several neurological and non-neurological conditions. One of the most recent achievements in the field is the observation that botulinum toxin A provides benefit in diseases of the gastrointestinal tract. Although toxin blocks cholinergic nerve endings in the autonomic nervous system, it has also been shown that it does not block non-adrenergic non-cholinergic responses mediated by nitric oxide. This has promoted further interest in using botulinum toxin A as a treatment for overactive smooth muscles and sphincters. The introduction of this therapy has made the treatment of several clinical conditions easier, in the outpatient setting, at a lower cost and without permanent complications. This review presents current data on the use of botulinum toxin A in the treatment of pathological conditions of the gastrointestinal tract.

Botulinum toxin injection in dysphagia syndromes with preserved esophageal peristalsis and incomplete lower esophageal sphincter relaxation

BACKGROUND

Botulinum toxin injection into the lower esophageal sphincter (LES) treats dysphagia syndromes with preserved peristalsis and incomplete LES relaxation (LESR). We evaluated clinical and esophageal motor characteristics predicting response, and compared duration of efficacy to similarly treated achalasia patients.

METHODS

Thirty-six subjects (59 ± 2.2 years, 19F/17M) with incomplete LESR on high resolution manometry (HRM) treated with botulinum toxin injection were identified. Individual and composite symptom indices were calculated, and HRM characteristics extracted. Symptom resolution for 6 months was a primary outcome measure, and repeat botulinum toxin injection, dysphagia recurrence or employment of alternate therapeutic approaches were secondary outcome measures. Duration of response was compared using Kaplan-Meier survival curves to a historical cohort of similarly treated achalasia subjects.

KEY RESULTS

Response lasted a mean of 12.8 ± 2.3 months. Symptom relief for >6 months was seen in 58.3%; short (<6 months) response was associated with younger age, higher chest pain index, and esophageal body spastic features (P ≤ 0.04). On multivariate logistic regression, chest pain, younger age and contraction amplitudes >180 mmHg independently predicted <6 months relief (P < 0.05 for each). On survival analysis, relief with a single injection extended to 1 year in 54.8% and 1.5 years in 49.8%, statistically equivalent to that reported by 42 similarly treated achalasia subjects (59 ± 3.2 years, 24F/18M). Symptom relief was more prolonged compared to achalasia when repeat injections were performed on demand (P = 0.003).

CONCLUSIONS & INFERENCES

Botulinum toxin injections can provide lasting symptom relief in dysphagia syndromes with incomplete LESR. Prominent perceptive symptoms and non-specific spastic features may predict shorter relief.

Modification of blood vessel diameter following perivascular application of botulinum toxin-A

The purpose of this study was to demonstrate that perivascularly applied botulinum toxin-A (BTX) increases the diameter of treated blood vessels in a rat femoral vessel exposure model. Six adult Sprague-Dawley rats were used and bilateral femoral artery and vein exposures were performed. Five units of BTX were applied to the experimental side and an equal volume of sterile saline was applied to the control side. Digital images of the vessels were obtained at the following time points: pretreatment, immediately posttreatment, and postoperative days (POD) 1, 14, and 28. Vessel diameters were equivalent at baseline and immediately following application of BTX and saline. The BTX artery was significantly larger than the control artery on POD 1 and 14. The BTX treated artery was significantly larger than all other vessels on POD 14 (p < 0.05) as well as all prior time points (p < 0.01). Direct perivascular application of BTX increases the diameter of rat femoral vessels as early as POD 1. The affect is most robust on POD 14 where the artery was significantly larger than all other vessels at all time points. It is likely that the increased diameter of blood vessels results in an increased blood flow across the area of dilation. Such an increase in flow may serve to improve end-organ perfusion in microvascular procedures.

Mechanism of substrate recognition by botulinum neurotoxin serotype A

Botulinum neurotoxins (BoNTs) are zinc proteases that cleave SNARE proteins to elicit flaccid paralysis by inhibiting neurotransmitter-carrying vesicle fusion to the plasma membrane of peripheral neurons. Unlike other zinc proteases, BoNTs recognize extended regions of SNAP25 for cleavage; however, the molecular basis for this extended substrate recognition is unclear. Here, we define a multistep mechanism for recognition and cleavage of SNAP25 by BoNT/A. SNAP25 initially binds along the belt region of BoNT/A, which aligns the P5 residue to the S5 pocket at the periphery of the active site. Although the exact order of each step of recognition of SNAP25 by BoNT/A at the active site is not clear, the initial binding could subsequently orient the P4'-residue of SNAP25 to form a salt bridge with the S4'-residue, which opens the active site allowing the P1'-residue access to the S1'-pocket. Subsequent hydrophobic interactions between the P3 residue of SNAP25 and the S3 pocket optimize alignment of the scissile bond for cleavage. This explains how the BoNTs recognize and cleave specific coiled SNARE substrates and provides insight into the development of inhibitors to prevent botulism.

Botulinum Toxin Type A for Dysthyroid Upper Eyelid Retraction

PURPOSE

To evaluate the safety and efficacy of botulinum toxin type A for treatment of eyelid retraction resulting from thyroid eye disease (TED) during the inflammatory phase of the condition.

METHODS

In this prospective, nonrandomized case series, 18 patients with inflammatory eyelid retraction caused by active TED received botulinum toxin type A injection (10, 5, or 2.5 U) for treatment of upper eyelid retraction. Botulinum toxin type A (Allergan, Irvine, CA, U.S.A.) was injected transconjunctivally just above the superior tarsal border in the elevator complex of the upper eyelid.

RESULTS

Seventeen of 18 patients (94%) demonstrated a reduced marginal reflex distance (MRD1) after botulinum toxin injection. The average change in MRD1 of the treated eyelid after injection was -2.35 mm (range, 0 to -8.0 mm). Of the 27 eyelids injected, 33% had a 0- to 1-mm drop in eyelid height, 30% had a 1.5- to 2-mm decrease, 22% had a 2.5- to 3-mm decrease, and 15% had a greater than 3-mm decrease in eyelid height. None of the treated eyelids were noted to increase in height. One patient showed no alteration inafter treatment. One patient had clinically MRD1 significant ptosis and one patient reported worsening of preexisting diplopia after injection. Three patients undergoing unilateral injection had relative contralateral eyelid elevation. All untoward effects resolved spontaneously without sequelae.

CONCLUSIONS

: Botulinum toxin type A may be used in the inflammatory stage of thyroid eye disease to improve upper eyelid retraction. Individual response to treatment is variable, but this modality should be considered as a temporizing measure until stability for surgery is reached.

Treatment with botulinum neurotoxin of gastrointestinal smooth muscles and sphincters spasms

Local injections of botulinum neurotoxin are now considered an efficacious treatment for neurological and non-neurological conditions. One of the most recent achievements in the field is the observation that botulinum neurotoxin provides benefit in diseases of the gastrointestinal tract. Botulinum neurotoxin inhibits contraction of gastrointestinal smooth muscles and sphincters; it has also been shown that the neurotoxin blocks cholinergic nerve endings in the autonomic nervous system, but it does not block nonadrenergic responses mediated by nitric oxide. This aspect has further promoted the interest to use botulinum neurotoxin as a treatment for overactive smooth muscles, such as the anal sphincters to treat anal fissure and outlet-type constipation, or the lower esophageal sphincter to treat esophageal achalasia. Knowledge of the anatomical and functional organization of innervation of the gastrointestinal tract is a prerequisite to understanding many features of botulinum neurotoxin action on the gut and the effects of injections placed into specific sphincters. This review presents current data on the use of botulinum neurotoxin to treat diseases of the gastrointestinal tract and summarizes recent knowledge on the pathogenesis of disorders of the gut due to a dysfunction of the enteric nervous system.

Side effects of botulinum toxin injection for benign anal disorders

BACKGROUND

Botulinum toxin A (BT-A) is a powerful biological toxin. Nevertheless, it has proved to be a remarkable therapeutic agent for the treatment of benign anal disorders. Higher doses of BT-A could change the outcome of treatment. It is not known whether doses of BT-A higher than 20 units of Botox (or corresponding doses of Dysport) are as safe for patients as lower doses of BT-A.

METHODS

The side effects of BT-A injections in the treatment of chronic anal fissure (105 patients) and functional outlet obstruction (34 patients) were analysed prospectively. The patients received at least 25 units of Botox or 150 units of Dysport.

RESULTS

The patients with chronic anal fissure complained of incontinence of flatus (one severe case and eight mild cases), incontinence of faeces (five mild cases), anal haematoma (five cases), flu-like syndrome (three cases), an acute inflammation of external anal varices (two cases), epididymitis (one case) and haemorrhoid prolapse (one case). Patients with anismus suffered from intertrigo (one case); the pain after injection lasted for 2-4 days (four cases). No life-threatening side effects after 181 injections of BT-A were observed. Most of the side effects were only transient symptoms. No significant interdependence between injection methods (injection into one or two sites) and the risk of side effects was found.

CONCLUSION

Treatment with BT-A is safe. Despite the application of higher doses of BT-A in the treatment of benign anal disorders so far, no severe side effects were observed.

Botulinum neurotoxin and other treatments for fissure-in-ano and pelvic floor disorders

BACKGROUND

The management of disorders of the lower gastrointestinal tract, such as chronic anal fissure and pelvic floor dysfunction, has undergone re-evaluation recently. To a large extent this is due to the advent of neurochemical treatments, such as botulinum neurotoxin injections and topical nitrate ointment.

METHODS AND RESULTS

This review presents, inter alia, current data on the use of botulinum neurotoxin to treat lower gastrointestinal tract diseases, such as chronic anal fissure for which it promotes healing and symptom relief in up to 70 per cent of cases. This agent has also been used selectively to weaken the external anal sphincter and puborectalis muscle in constipation and in Parkinson's disease. Symptomatic improvement can also be induced in anterior rectocele by botulinum neurotoxin injections.

CONCLUSION

Botulinum neurotoxin appears to be a safe therapy for anal fissure. It is more efficacious than nitrate application and does not require patient compliance to complete treatment. While it may also be a promising approach for the treatment of chronic constipation due to pelvic floor dysfunction, further investigation of its efficacy and safety in this role is needed before general usage can be advocated.