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
Cardiac or central nervous system toxicity may result when standard lidocaine doses are administered to patients with circulatory failure. This may be due to the following reason - 
Select and explain. 
A. Lidocaine concentration are initially higher in relatively well perfused tissues such as brain and hea, B. Histamine receptors in brain and hea gets suddenly activated in circulatroy failure, C. There is a sudden out-burst of release of adreneline, noradreneline and dopamine in brain and hea, D. Lidocaine is conveed into a toxic metabolite due to its longer stay in liver
A: Lidocaine concentration are initially higher in relatively well perfused tissues such as brain and hea
Answer: A: Lidocaine concentration are initially higher in relatively well perfused tissues such as brain and hea 
Explanation: Ans. is 'a' i.e., Lidocaine concentration are initially higher in relatively well perfused tissues such as brain and hea o Lidocaine is a rapidly acting drug because of its rapid distributtion to well perfused tissues such as brain and hea.o Circulatory failure is characterized by decreased cardiac output and a consequent decrease in hepatic blood flow.As a result metabolic clearance ofLidocaine in liver is diminshed and its elemination t 1/2 is increased. Consequently Lidocaine concentration is initially increased in these relatively well perfused tissues (brain and hea) even with usual doses and toxicity results.