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: Pharmacology
[{'content': 'Drug given for metoclopramide dystonic reaction is- \nSelect and explain. \nA. Phenaramine, B. Promethazine, C. Chlorphenaramine, D. Prochlorperazine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. is \'b\' i.e., Promethazine o We all know, blockade of D2 receptors in brain produce extrapyramidal side effects (as caused by antipsychotics), and acute muscular dystonia (dystonic reaction) is one of them. o Treatment of choice for acute muscular dystonia is central anticholinergic. o But, in given options, they have not given typical central anticholinergics. All options are typical antihistaminics. o As we also know that antihistaminics have anticholinergic propeies. So, amongst the given options we will have to choose the drug which has maximum central anticholinergic propey. First generation antihistaminics : i) Have maximum anticholinergic propey ii) Have maximum penetration of blood brain barrier For these two reasons, first generation antihistaminics have maximum central anticholinergic propey. o Amongst the given options, only promethazine is first generation antihistaminic. o Following statement of KDT will clear all doubts: "Acute muscle dystonia caused by antiemetic-antipsychotic drugs is promptly relieved by parenteral promethazine or hydroxyzine." Remember o DOC for antipsychotic induced acute muscle dystonia central anticholinergic o If central anticholinergic is not given in the options --> antihistaminic with maximum central anticholinergic propey is the DOC.', 'role': 'assistant'}]