A 65-year-old man comes to the emergency department with palpitations. He also complains of headache, insomnia, and 2 episodes of vomiting this morning. His other medical problems include severe chronic obstructive pulmonary disease, pulmonary hypertension, essential hypertension, and hyperlipidemia. He had a puncture wound of the foot a week ago that is being treated with ciprofloxacin. His other medications include tiotropium, inhaled fluticasone/salmeterol, theophylline, simvastatin, lisinopril, and hydrochlorothiazide. He does not use tobacco or alcohol. His temperature is 36.7°C (98.0°F), blood pressure is 150/80 mm Hg, pulse is 115/min, and respirations are 18/min. Examination shows mildly decreased breath sounds throughout the lung fields consistent with his chronic obstructive pulmonary disease. Neurologic examination shows no focal deficits. Electrocardiogram shows multifocal atrial tachycardia and a single ventricular premature beat. Which of the following is the next best step in management of this patient?

Question

A 65-year-old man comes to the emergency department with palpitations.  He also complains of headache, insomnia, and 2 episodes of vomiting this morning.  His other medical problems include severe chronic obstructive pulmonary disease, pulmonary hypertension, essential hypertension, and hyperlipidemia.  He had a puncture wound of the foot a week ago that is being treated with ciprofloxacin.  His other medications include tiotropium, inhaled fluticasone/salmeterol, theophylline, simvastatin, lisinopril, and hydrochlorothiazide.  He does not use tobacco or alcohol.  His temperature is 36.7°C (98.0°F), blood pressure is 150/80 mm Hg, pulse is 115/min, and respirations are 18/min.  Examination shows mildly decreased breath sounds throughout the lung fields consistent with his chronic obstructive pulmonary disease.  Neurologic examination shows no focal deficits.  Electrocardiogram shows multifocal atrial tachycardia and a single ventricular premature beat.  Which of the following is the next best step in management of this patient?

Quizplus · Accepted Answer

The patient's symptoms are consistent with theophylline toxicity. Theophylline has a narrow therapeutic index, and toxicity can occur from accumulation by reduced clearance or decreased metabolism due to saturation of metabolic pathways. Theophylline is metabolized predominantly by the cytochrome oxidase system in the liver. Inhibition of these enzymes by concurrent illness (eg, cirrhosis, cholestasis, respiratory infections with fever) or drugs (eg, cimetidine, ciprofloxacin, erythromycin, clarithromycin, verapamil) can raise serum concentration and cause toxicity. Symptoms of toxicity usually manifest as central nervous system stimulation (eg, headache, insomnia, seizures), gastrointestinal disturbances (eg, nausea, vomiting), and cardiac toxicity (arrhythmia). This patient recently began taking ciprofloxacin, a drug known to decrease clearance of theophylline. Therefore, the best next step is to measure serum theophylline levels to assess for toxicity. (Choice A) Plasma fractionated metanephrines are elevated in pheochromocytoma. Patients usually present with headache, sweating, tachycardia, and paroxysmal hypertension. Although some of this patient's symptoms could be due to pheochromocytoma, given his recent intake of ciprofloxacin, theophylline toxicity is the most likely diagnosis. (Choice B) Although headache and vomiting can suggest elevated intracranial pressure due to an intracranial process (eg, tumor, hemorrhage), this patient has no other neurologic deficits (eg, leg weakness). (Choice C) Theophylline toxicity can cause atrial tachycardia, supraventricular tachycardia, and/or ventricular arrhythmias. Echocardiogram can assess left ventricular function and determine the associated conditions (eg, valvular disease). However, theophylline levels should be obtained first to rule out toxicity due to its interaction with ciprofloxacin. (Choice D) Elevated lipase levels are seen in patients with pancreatitis. Although this patient does have vomiting, he has no other risk factors (eg, alcohol use) or abdominal pain. Educational objective: Theophylline toxicity can manifest as central nervous system stimulation (eg, headache, insomnia, seizures), gastrointestinal disturbances (eg, nausea, vomiting), and cardiac toxicity (arrhythmia). Inhibition of the cytochrome oxidase system by other medications, diet, or underlying disease can alter its narrow therapeutic window. References: Adverse reactions and interactions with theophylline. (http://www.ncbi.nlm.nih.gov/pubmed/2198052)

A 65-Year-Old Man Comes to the Emergency Department with Palpitations