Achalasia is an esophageal motility disorder of unknown cause that manifests as symptoms of difficulty in swallowing, with pooling of food and secretions in the lower esophagus. Endoscopic treatment for achalasia is directed at disrupting or weakening the lower esophageal sphincter (LES). As botulinum toxin (botox) is a potent inhibitor of acetylcholine release from nerve endings, it counteracts the unopposed LES contraction that is mediated by cholinergic nerves, thereby lowering LES pressure. In general, a total dose of 100 IU is endoscopically injected in the LES using a sclerotherapy needle, in four gifts, one in each quadrant. The response rates at 1 month following administration are 78% on average (range, 63–90%). By 6 months, the clinical response rate drops to 58% (range, 25–78%); and by 12 months, this further drops to 49% (range, 15–64%). The predictors of response to botulinum toxin injection (BTI) include age greater than 50 years, and the presence of vigorous achalasia, defined by the finding of esophageal contractile waves, with amplitudes in excess of 40 mmHg. Meanwhile, the duration of illness, baseline radiographic features, initial symptom severity, and sex have not been shown to be predictive of response. Compared to both pneumatic dilation and myotomy, BTI has clearly shown to have been at a disadvantage with respect to therapeutic efficacy. However, BTI has several advantages—such as ease of technique, safety, ease of return to work, and higher success rate in vigorous achalasia—compared with pneumatic dilation and surgical myotomy. Botulinum toxin should be preferentially reserved for patients with significant comorbidity, and is not adequate for conventional treatment with laparoscopic Heller’s myotomy or pneumatic dilation, or for patients who are on a waiting list for surgery or who are refusing other forms of treatment.
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