A 45-year-old man with an elevated bleeding time is scheduled to undergo an elective hernia repair in approximately 12 h. He is given vitamin K orally and the bleeding time is still elevated. What is the most likely explanation for this finding?

A 45-year-old man with an elevated bleeding time is scheduled to undergo an elective hernia repair in approximately 12 h. He is given vitamin K orally and the bleeding time is still elevated. What is the most likely explanation for this finding?

A 21-year-old man presents to the ambulatory care clinic with an erythematous, swollen, painful left elbow. History is significant for untreated impetigo on his left forearm. A joint aspirate reveals gram-positive cocci in clusters. The physician begins empiric treatment with vancomycin while the organism is cultured. It is found to be methicillin susceptible. Methicillin is not widely used, but which of the following is an equivalent drug that could be used to treat this man's infection?

A 25-year-old man presents to the emergency department with severe abdominal pain, rigors, and a temperature of 39°C. For the past 2 days, he has suffered from right lower quadrant pain and only came to the hospital when it suddenly worsened. The physician suspects ruptured appendicitis and administers imipenem with cilastatin. Cilastatin blocks which of the following enzymes to increase imipenem's efficacy?

A 21-year-old woman college student complains of a skin lesion near her knee on the inside of her thigh. She recently returned from a trip to Africa where she played a handmade goatskin drum. The lesion is painless with a black center. The physician suspects cutaneous anthrax and prescribes oral ciprofloxacin. Which of the following should this patient avoid taking with ciprofloxacin?

A 55-year-old woman is hospitalized for treatment of osteomyelitis. The infectious organism is found to be susceptible to gentamicin so she is started on a once-daily dose of intravenous gentamicin. Which of the following symptoms may be a signal to the physician to stop gentamicin therapy?