A 65-year-old man is brought to the emergency department after developing sudden-onset right-side weakness and difficulty speaking. He has a history of paroxysmal atrial fibrillation and has been taking warfarin for the past several years with a stable prothrombin time. His wife adds that he started taking a new drug 2 weeks ago, but she does not remember its name. Physical examination shows right hemiplegia, right hemisensory loss, expressive aphasia, and right homonymous hemianopia. MRI of the head shows a left middle cerebral artery territory infarct. Transesophageal echocardiogram reveals a small thrombus in the left atrium. This patient most likely started taking which of the following drugs recently?

Question

A 65-year-old man is brought to the emergency department after developing sudden-onset right-side weakness and difficulty speaking.  He has a history of paroxysmal atrial fibrillation and has been taking warfarin for the past several years with a stable prothrombin time.  His wife adds that he started taking a new drug 2 weeks ago, but she does not remember its name.  Physical examination shows right hemiplegia, right hemisensory loss, expressive aphasia, and right homonymous hemianopia.  MRI of the head shows a left middle cerebral artery territory infarct.  Transesophageal echocardiogram reveals a small thrombus in the left atrium.  This patient most likely started taking which of the following drugs recently?

Quizplus · Accepted Answer

11ec160b_3c27_b866_9249_2919b9c6b29f_MD0001_00 This patient has suffered a thromboembolic stroke, likely the result of a dislodged left atrial thrombus that formed due to an adverse drug interaction leading to inadequate anticoagulation. Many substances cause induction or inhibition of cytochrome P450 (CYP450) hepatic microsomal enzymes, which are responsible for the majority of drug metabolism. CYP450 interactions should be considered when selecting and dosing medications, as changes in enzyme activity affect the rate of drug metabolism. Alterations in plasma drug levels are especially important when considering medications that are vital to a patient's health or have a high propensity for toxicity, such as warfarin. For example, warfarin can interact with St John's wort, an over-the-counter medicinal herb known for both its anti-inflammatory and antidepressant properties. St John's wort induces hepatic CYP450 enzymes, resulting in increased warfarin metabolism, decreased drug levels, and inadequate anticoagulation. (Choices A, B, C, D, and E) These drugs are known to inhibit CYP450 enzymes and increase warfarin levels, leading to an increased risk of bleeding complications. (Choice F) Oral penicillin V and warfarin do not have any significant interactions. Antibiotics in general reduce the intestinal bacterial load, which reduces vitamin K synthesis and could potentiate warfarin's anticoagulant effects. Educational objective: St John's wort induces cytochrome P450 hepatic microsomal enzymes. As a result, a wide variety of drugs that are metabolized by these enzymes, such as warfarin, will have lower plasma concentrations and decreased efficacy. __________ References: Effect of St John's wort and ginseng on the pharmacokinetics and pharmacodynamics of warfarin in healthy subjects. (http://www.ncbi.nlm.nih.gov/pubmed/15089812)

A 65-Year-Old Man Is Brought to the Emergency Department After