A 32-year-old man with hepatitis B refractory to several treatments has begun on a course of lamivudine. The mechanism of action of this medication likely involves which of the following?

A 32-year-old man with hepatitis B refractory to several treatments has begun on a course of lamivudine. The mechanism of action of this medication likely involves which of the following?

A 49-year-old man with advanced squamous cell carcinoma of the skin is treated with topical 5-fluorouracil. He presents to his oncologist for follow-up. In addition to monitoring renal and hepatic function for toxicity, one could theoretically measure levels of which of the following excreted products?

A 24-year-old male soldier has just returned from a duty tour in Iraq. He complains of a 3-cm diameter nonhealing ulcer on his left forearm. He reports having an insect bite there while in Iraq. Which of the following drugs would be best for this patient?

A 4-year-old boy is brought by his mother to the clinic complaining of perianal itching. He spends the weekdays at a daycare center. The mother also brings a strip of adhesive tape from the night before which she had stuck to the child’s perianal area as the doctor had ordered on the phone. Microscopic examination of the tape revealed small, white, round worms. Which is the best treatment for this child?

A 31-year-old woman with HIV disease complains of vulvar itching, burning, and vaginal discharge with rancid odor for 2 months. She presents to the ambulatory care clinic for evaluation. She has had unprotected sexual intercourse with multiple male partners during the past several weeks. The vaginal discharge is yellow-green in color, frothy, and has a pH of 7.0. Vulvovaginal examination reveals vulvar edema and erythema and petechia on the cervix. Wet smear reveals large numbers of mature epithelial cells, white blood cells, and a fusiform protozoan organism. What is the most appropriate treatment for this patient?