A 45-year-old woman complains of facial wrinkles and lines. She heard of a drug for wrinkles from a friend that is a bacterial toxin and works by paralyzing skeletal muscles. What is the mechanism of action of this drug?

A 45-year-old woman complains of facial wrinkles and lines. She heard of a drug for wrinkles from a friend that is a bacterial toxin and works by paralyzing skeletal muscles. What is the mechanism of action of this drug?

Five patients with cancer and/or inflammatory disease are being considered for treatment with single agent methotrexate therapy intravenously. Which of the following patients would be expected to have the greatest objective clinical response to therapy?

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?