A 29-year-old man with recurrent herpes viral infections of the scrotum and penile shaft presents to his primary care physician because the medication is not working for him. He takes oral acyclovir for these outbreaks. Physical examination reveals active genitourinary herpes disease. What is the most likely explanation for the resistance to this medication?

A 29-year-old man with recurrent herpes viral infections of the scrotum and penile shaft presents to his primary care physician because the medication is not working for him. He takes oral acyclovir for these outbreaks. Physical examination reveals active genitourinary herpes disease. What is the most likely explanation for the resistance to this medication?

A 42-year-old woman with bilateral metastatic breast cancer undergoes surgery followed by radiation and a cycle of chemotherapy. PET scan still reveals the presence of metastatic disease. She undergoes therapy with a novel chemotherapy agent capecitabine. This medication works through inhibition of which of the following?

A 27-year-old man presented to the clinic for routine abroad trip preparation. He is traveling to the Caribbean in 1 month. Antidiarrheals and antimalarials are prescribed. It is noted that the patient has a history of epilepsy, latent TB, and has contracted malaria once on a prior trip. His vaccines are up to date, and he has no allergies. What medication is contraindicated for this patient?

A 3-month-old male infant is brought to the emergency department by his parents following a 30-min seizure at home. In the emergency department, the child is not seizing and is afebrile. Prenatal history is insignificant except for a few apparently mild illnesses experienced by his mother. They own three cats. A CT scan of the infant’s head reveals intracerebral calcifications and mild ventricular hypertrophy. The infant is given pyrimethamine for toxoplasmosis. Which of the following describes pyrimethamine’s mechanism of action?

A 22-year-old woman with HIV disease notes progressive visual disturbance noted by a decrease in visual acuity. She presents to the ambulatory care clinic for further evaluation and treatment. Funduscopic examination reveals large white areas proximal to the macula with perivascular exudates and hemorrhages. Treatment of this condition involves which of the following agents?