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{{WBRQuestion
{{WBRQuestion
|QuestionAuthor={{Rim}}, {{AJL}} {{Alison}}
|QuestionAuthor={{YD}} (Reviewed by {{AJL}} and {{YD}})
|ExamType=USMLE Step 1
|ExamType=USMLE Step 1
|MainCategory=Pharmacology
|MainCategory=Pharmacology
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|MainCategory=Pharmacology
|MainCategory=Pharmacology
|SubCategory=Cardiology
|SubCategory=Cardiology
|MainCategory=Pharmacology
|MainCategory=Pharmacology
|MainCategory=Pharmacology
|MainCategory=Pharmacology
|MainCategory=Pharmacology
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|MainCategory=Pharmacology
|MainCategory=Pharmacology
|SubCategory=Cardiology
|SubCategory=Cardiology
|Prompt=A 62-year-old male presents to the physician’s office with complaints of abnormal vision. The patient explains that he has been seeing yellow-green halos beginning upon the administration of a new drug. The patient’s past medical history is significant for latent tuberculosis, cardiac disease, and erectile dysfunction. Which of the following medications is most likely the cause of this patient’s symptoms?
|Prompt=A 62-year-old man presents to the physician’s office with complaints of abnormal vision. The patient explains that he has been seeing yellow-green halos ever since he was administered a new drug whose name he cannot recall. The patient’s past medical history is significant for latent tuberculosis, advanced cardiac disease, and erectile dysfunction. Which of the following medications most likely induced this patient’s symptoms?
|Explanation=[[Digitalis]], a direct [[Na/K/ATPase inhibitor]], inhibits the [[Na/Ca exchanger]] by hindering the creation of a sodium gradient. This results in increased inotropy by augmenting levels of intracellular Ca.  [[Digitalis]] has [[cholinomimetic]] effects, due to its vagal activation,  by increasing the [[PR interval]], delaying [[AV node]] conduction, and decreasing the [[QT interval]]. [[Digitalis]] is frequently administered to patients with [[congestive heart failure]]. The [[side effects]] of [[digitalis]] include a change in vision coloration, typically manifesting as a green-yellow visual disturbance.  
|Explanation=[[Digitalis]] is a cardiac glycoside. It is a direct [[Na/K/ATPase inhibitor]] that indirectly inhibits the [[Na/Ca exchanger]] by hindering the formation of a sodium gradient. This mechanism of action results in increased inotropy by augmenting levels of intracellular calcium.  Also, [[digitalis]] has [[cholinomimetic]] effects due to its vagal activation. Digitalis administration results in an increase in the [[PR interval]], delay in [[AV node]] conduction, and decrease the [[QT interval]]. [[Digitalis]] is frequently administered to patients with advanced [[congestive heart failure]] and atrial fibrillation. Because digitalis has a narrow therapeutic index, the risk of toxicity with digitalis is quite high, especially in the elderly population. Risk factors for digitalis toxicity include hypokalemia, hypomagnesemia, renal impairment, and concomitant use of other medications that interact with digitalis (eg. quinidine, amiodarone, and calcium channel blockers). Digitalis toxicity may manifest as non-specific GI symptoms, including nausea and vomiting, headaches, anorexia, or confusion. Visual distortion is also a common manifestation of digitalis toxicity; patients often report blurring, central scotomas, glare and halo effects, and green-yellow visual disturbance. Although other color disturbances have been reported, green-yellow discoloration remains the most common color alteration among patients who are administered digitalis.
 
|EducationalObjectives=
[[Digitalis]], a positive [[inotropic agent]], acts as a direct [[Na/K/ATPase inhibitor]] and is administered to patients with [[congestive heart failure]].  [[Digitalis]] is associated with green-yellow color changes.
|References= First Aid 2014 page 267
 
|AnswerA=Sildenafil
|AnswerA=Sildenafil
|AnswerAExp=[[Sildenafil]], a [[phosphodiesterase]] (PDE) 5 inhibitor, maintains elevated cGMP and nitrous oxide (NO) levels. It frequently manifests with blue colored vision, rather than a green-yellow visual disturbance.
|AnswerAExp=[[Sildenafil]], a [[phosphodiesterase]] (PDE) 5 inhibitor, maintains elevated cGMP and nitrous oxide (NO) levels. Sildenafil is associated with color disturbances that usually manifest as a blue-colored vision, rather than a green-yellow visual disturbance.
|AnswerB=Tadalafil
|AnswerB=Tadalafil
|AnswerBExp=[[Tadalafil]], a long-acting PDE 5 inhibitor, is not frequently associated with visual color changes.
|AnswerBExp=[[Tadalafil]], a long-acting PDE 5 inhibitor, is not frequently associated with visual color changes.
|AnswerC=Digitalis
|AnswerC=Digitalis
|AnswerCExp=See explanation.
|AnswerCExp=Visual distortion is a manifestation of digitalis toxicity; patients often report blurring, central scotomas, glare and halo effects, and green-yellow visual disturbance.
|AnswerD=Ethambutol
|AnswerD=Ethambutol
|AnswerDExp=[[Ethambutol]], an anti-tuberculous agent, frequently causes green-red visual changes and optic neuritis, both of which are reversible following discontinuation of the medication. [[Ethambutol]] is not administered in latent tuberculosis (TB), but rather in active TB.
|AnswerDExp=[[Ethambutol]], an anti-tuberculous agent, is associated with green-red visual changes and optic neuritis, both of which are reversible following discontinuation of the medication. [[Ethambutol]] is not administered in latent tuberculosis (TB), but rather in active TB.
|AnswerE=Rifampin
|AnswerE=Rifampin
|AnswerEExp=[[Rifampin]] is not associated with visual color changes. [[Rifampin]] is not administered in latent tuberculosis (TB), but rather in active TB.
|AnswerEExp=[[Rifampin]] is not associated with visual color changes. Classically, rifampin is associated with red-orange discoloration of body fluids.
|EducationalObjectives=[[Digitalis]] is a cardiac glycoside. It is a direct [[Na/K/ATPase inhibitor]] that indirectly inhibits the [[Na/Ca exchanger]] by hindering the creation of a sodium gradient. Visual distortion is a common manifestation of digitalis toxicity; patients often report blurring, central scotomas, glare and halo effects, and green-yellow visual disturbance.
|References=Lawrenson JG, Kelly C, Lawrenson AL, et al. Acquired colour vision deficiency in patients receiving digoxin maintenance therapy. Br J Ophthalmol. 2002;86(11):1259-61.<br>
First Aid 2014 page 301
|RightAnswer=C
|RightAnswer=C
|WBRKeyword=digitalis, vision, sildenafil, tadalafiil, ethambutol, side effect, adverse drug reaction, tuberculosis, medication, optic
|WBRKeyword=digitalis, vision, sildenafil, tadalafiil, ethambutol, side effect, adverse drug reaction, tuberculosis, medication, optic
|Approved=Yes
|Approved=Yes
}}
}}

Revision as of 21:37, 21 October 2014
Author [[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Alison Leibowitz [1] and Yazan Daaboul, M.D.)]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Pharmacology
Sub Category SubCategory::Cardiology
Prompt [[Prompt::A 62-year-old man presents to the physician’s office with complaints of abnormal vision. The patient explains that he has been seeing yellow-green halos ever since he was administered a new drug whose name he cannot recall. The patient’s past medical history is significant for latent tuberculosis, advanced cardiac disease, and erectile dysfunction. Which of the following medications most likely induced this patient’s symptoms?]]
Answer A AnswerA::Sildenafil
Answer A Explanation [[AnswerAExp::Sildenafil, a phosphodiesterase (PDE) 5 inhibitor, maintains elevated cGMP and nitrous oxide (NO) levels. Sildenafil is associated with color disturbances that usually manifest as a blue-colored vision, rather than a green-yellow visual disturbance.]]
Answer B AnswerB::Tadalafil
Answer B Explanation [[AnswerBExp::Tadalafil, a long-acting PDE 5 inhibitor, is not frequently associated with visual color changes.]]
Answer C AnswerC::Digitalis
Answer C Explanation AnswerCExp::Visual distortion is a manifestation of digitalis toxicity; patients often report blurring, central scotomas, glare and halo effects, and green-yellow visual disturbance.
Answer D AnswerD::Ethambutol
Answer D Explanation [[AnswerDExp::Ethambutol, an anti-tuberculous agent, is associated with green-red visual changes and optic neuritis, both of which are reversible following discontinuation of the medication. Ethambutol is not administered in latent tuberculosis (TB), but rather in active TB.]]
Answer E AnswerE::Rifampin
Answer E Explanation [[AnswerEExp::Rifampin is not associated with visual color changes. Classically, rifampin is associated with red-orange discoloration of body fluids.]]
Right Answer RightAnswer::C
Explanation [[Explanation::Digitalis is a cardiac glycoside. It is a direct Na/K/ATPase inhibitor that indirectly inhibits the Na/Ca exchanger by hindering the formation of a sodium gradient. This mechanism of action results in increased inotropy by augmenting levels of intracellular calcium. Also, digitalis has cholinomimetic effects due to its vagal activation. Digitalis administration results in an increase in the PR interval, delay in AV node conduction, and decrease the QT interval. Digitalis is frequently administered to patients with advanced congestive heart failure and atrial fibrillation. Because digitalis has a narrow therapeutic index, the risk of toxicity with digitalis is quite high, especially in the elderly population. Risk factors for digitalis toxicity include hypokalemia, hypomagnesemia, renal impairment, and concomitant use of other medications that interact with digitalis (eg. quinidine, amiodarone, and calcium channel blockers). Digitalis toxicity may manifest as non-specific GI symptoms, including nausea and vomiting, headaches, anorexia, or confusion. Visual distortion is also a common manifestation of digitalis toxicity; patients often report blurring, central scotomas, glare and halo effects, and green-yellow visual disturbance. Although other color disturbances have been reported, green-yellow discoloration remains the most common color alteration among patients who are administered digitalis.

Educational Objective: Digitalis is a cardiac glycoside. It is a direct Na/K/ATPase inhibitor that indirectly inhibits the Na/Ca exchanger by hindering the creation of a sodium gradient. Visual distortion is a common manifestation of digitalis toxicity; patients often report blurring, central scotomas, glare and halo effects, and green-yellow visual disturbance.
References: Lawrenson JG, Kelly C, Lawrenson AL, et al. Acquired colour vision deficiency in patients receiving digoxin maintenance therapy. Br J Ophthalmol. 2002;86(11):1259-61.
First Aid 2014 page 301]]

Approved Approved::Yes
Keyword WBRKeyword::digitalis, WBRKeyword::vision, WBRKeyword::sildenafil, WBRKeyword::tadalafiil, WBRKeyword::ethambutol, WBRKeyword::side effect, WBRKeyword::adverse drug reaction, WBRKeyword::tuberculosis, WBRKeyword::medication, WBRKeyword::optic
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