This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
[{'content': 'All are the pharmacologic therapeutic options for achalasia, EXCEPT: \nSelect and explain. \nA. Nitrates, B. Beta blockers, C. Botulinum toxin, D. Sildenafil', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Pharmacologicals therapies are usually ineffective. They can be used as a temporary measures. The agents used are: 1. Nitrates 2. Calcium channel blockers 3. Botulinum toxin 4. Sildenafil- phosphodiesterase inhibitors, effectively decrease LES pressure. Botulinum toxin, injected into the LES under endoscopic guidance, inhibits acetylcholine release from nerve endings and improves dysphagia in about 66% of cases for at least 6 months Ref: Harrison, Edition-18, Page-2432', 'role': 'assistant'}]