WBR0462

Author	[[PageAuthor::Rim Halaby, M.D. [1]]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pharmacology
Sub Category	SubCategory::Cardiology
Prompt	[[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?]]
Answer A	AnswerA::Sildenafil
Answer A Explanation	AnswerAExp::Sildenafil is a phosphodiesterase (PDE) 5 inhibitor that maintains elevated cGMP and nitrous oxide (NO) levels. It is called the “blue pill” because of its color. Similarly, it causes a blue vision, not a green-yellow visual disturbance.
Answer B	AnswerB::Tadalafil
Answer B Explanation	AnswerBExp::Tadalafil, is a long-acting PDE 5 inhibitor. Although it might also cause a blue vision similar to sildenafil, it is not classically associated with visual color changes.
Answer C	AnswerC::Digitalis
Answer C Explanation	AnswerCExp::Digitalis causes a green-yellow color changes as seen in this patient.
Answer D	AnswerD::Ethambutol
Answer D Explanation	[[AnswerDExp::Ethambutol is an anti-tuberculous agent that causes green-red visual changes and optic neuritis, both of which are reversible after discontinuation of the medication. In addition, ethambutol is not given in latent tuberculosis (TB), as in this patient. It is an antibiotic that is given in active TB.]]
Answer E	AnswerE::Rifampin
Answer E Explanation	[[AnswerEExp::Rifampin is not associated with visual color changes. It is, however, associated with urine color changes into an orange color that has no clinical significance and self-resolves. Rifampin is also used in active TB, not latent TB as described in this patient.]]
Right Answer	RightAnswer::C
Explanation	[[Explanation::Digitalis is a direct Na/K/ATPase inhibitor that indirectly inhibits the Na/Ca exchanger by inhibiting the Na gradient that essentially plays a role in activating the exchanger. As a result, intracellular Ca increases and inotropy thus increased. Digitalis also has cholinomimetic effects due to its vagal activation that increases PR interval, delays AV node conduction, and decreases QT interval. Digitalis is commonly used in patients with congestive heart failure. Side effects of digitalis include change in vision color that is typically a green-yellow visual disturbance, as in the patient in the vignette. Educational Objective: Digitalis is a positive inotropic agent that acts as a direct Na/K/ATPase inhibitor and is used in congestive heart failure. Digitalis is associated with green-yellow color changes. Educational Objective: References: ]]
Approved	Approved::No
Keyword	WBRKeyword::digitalis, WBRKeyword::vision, WBRKeyword::change, WBRKeyword::color, WBRKeyword::disturbance, WBRKeyword::sildenafil, WBRKeyword::tadalafiil, WBRKeyword::ethambutol, WBRKeyword::side, WBRKeyword::effect, WBRKeyword::adverse, WBRKeyword::drug, WBRKeyword::reaction
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::