<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 45-year-old man presents with a persistent cough for the past month. He says it started off with a runny nose and fever, from which he recovered in a week, but he says that the cough persists after the resolution of the fever. The patient denies any expectoration, chest pain, weight loss, or breathlessness. He reports no history of recent travel or sick contacts. Past medical history is significant for chronic constipation. He reports a 15-pack-year smoking history but denies any alcohol or current recreational drug use. He says he did use intravenous drugs in his late twenties but quit after going through a drug rehabilitation program. Physical examination is unremarkable. Laboratory findings and a chest radiograph are normal. Which of the following would be the best choice as a cough suppressant in this patient?? A: Codeine, B: Dextromethorphan, C: Pseudoephedrine, D: Guaifenesin, E: Oxymetazoline,  <response>: This is a clinical vignette about a 45-year-old man with a persistent cough after an upper respiratory infection. The key findings are a 1 month history of cough without fever, sputum production, chest pain, weight loss or breathlessness. He has a history of IV drug use and currently smokes. Workup so far including labs and CXR are normal. The question asks about choosing an appropriate cough suppressant for this patient. Codeine and dextromethorphan are opioid cough suppressants that can cause dependence, so should be avoided in someone with a history of substance abuse. Pseudoephedrine is a sympathomimetic that can increase blood pressure and heart rate, so is not ideal. Guaifenesin is an expectorant, which would not be helpful for a dry cough. Oxymetazoline is a topical nasal decongestant that would not treat a cough.Based on the history, dextromethorphan would be the best choice since it is effective for cough suppression and has lower abuse potential than codeine.B: Dextromethorphan 