A 32-year-old man is brought to the emergency department by police after an altercation at a local pub. He is agitated and says that his chest hurts. Blood pressure is 170/100 mm Hg and pulse is 130/min and regular. On physical examination, the patient is combative and uncooperative. There are no signs of physical injury. His pupils are dilated and reactive to light. Examination shows nasal perforation. ECG reveals myocardial ischemia. Inhibition of which of the following processes is most likely responsible for this patient's presentation?

Question

A 32-year-old man is brought to the emergency department by police after an altercation at a local pub.  He is agitated and says that his chest hurts.  Blood pressure is 170/100 mm Hg and pulse is 130/min and regular.  On physical examination, the patient is combative and uncooperative.  There are no signs of physical injury.  His pupils are dilated and reactive to light.  Examination shows nasal perforation.  ECG reveals myocardial ischemia.  Inhibition of which of the following processes is most likely responsible for this patient's presentation?

Quizplus · Accepted Answer

11ec160b_3c51_d5eb_9249_e77a059cbce7_MD0001_00 This patient is most likely acutely intoxicated with cocaine. Cocaine is a stimulant that inhibits presynaptic reuptake of monoamines (norepinephrine, dopamine, serotonin), resulting in sympathetic stimulation (eg, hypertension, tachycardia, light-responsive mydriasis) and CNS activation (eg, increased arousal, euphoria, agitation, seizures). Cocaine's ability to increase synaptic availability of norepinephrine, combined with some of its other effects (eg, sodium channel antagonism), makes it a potent vasoconstrictor that can promote myocardial ischemia by causing coronary artery vasospasm and increased platelet aggregation (ie, thrombus formation). When cocaine is used intranasally, its vasoconstrictive effects cause local ischemia resulting in mucosal atrophy that can then lead to nasal septal perforation; these findings are highly suggestive of cocaine abuse. (Choices A, D, and E) Inhibition of neuronal tyrosine uptake, impaired norepinephrine release into the synaptic cleft, or blockade of postsynaptic adrenergic receptors would result in sympatholytic effects (reduced blood pressure and heart rate). (Choice B) Metyrosine blocks the rate-limiting step of catecholamine synthesis (tyrosine hydroxylase). This results in decreased levels of catecholamines and sympatholytic effects. (Choice C) Reserpine (an antihypertensive agent no longer in clinical use) blocks monoamine entry into presynaptic vesicles, resulting in sympatholytic effects. (Choice G) Catechol-O-methyl transferase (COMT) is found in the brain and liver and degrades catecholamine neurotransmitters. Entacapone and tolcapone are COMT inhibitors used to prolong the effects of levodopa treatment in patients with Parkinson disease. Educational objective: Cocaine is a stimulant that inhibits the presynaptic reuptake of norepinephrine, dopamine, and serotonin. Intoxicated patients develop agitation, tachycardia, hypertension, and light-responsive mydriasis due to increased sympathetic activity. Cocaine is also a potent vasoconstrictor that can cause myocardial ischemia and atrophy of the nasal mucosa and septum. __________ References: Cardiovascular consequences of cocaine use. (http://www.ncbi.nlm.nih.gov/pubmed/25657055) Cocaine intoxication. (http://www.ncbi.nlm.nih.gov/pubmed/22998988)

A 32-Year-Old Man Is Brought to the Emergency Department by Police