ATI RN
Chemotherapy drugs Questions
Question 1 of 5
A 27-year-old man presents to the urgent care clinic with multiple painful ulcers on the shaft of his penis. Some strains of the causative virus are resistant because of a mutated thymidine kinase enzyme. Which of the following antivirals may be less effective in treating this man's infection if his strain of virus has a mutated thymidine kinase?
Correct Answer: A
Rationale: Acyclovir requires viral thymidine kinase for activation; a mutated enzyme in herpes simplex virus (HSV) reduces its effectiveness, unlike foscarnet, which acts directly on viral DNA polymerase.
Question 2 of 5
A 3-year-old girl presents to the emergency department with a history of recurrent UTIs with costovertebral angle tenderness, high fever, and dysuria. A urine culture grows gram-negative lactose-fermenting rods. The physician suspects E. coli pyelonephritis. Ciprofloxacin is highly effective against E. coli in vitro, but the physician chooses not to use it in this case. Why would she choose not to prescribe ciprofloxacin?
Correct Answer: B
Rationale: Ciprofloxacin is contraindicated in children (<18 years) due to the risk of cartilage damage and impaired growth, despite its efficacy against E. coli.
Question 3 of 5
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?
Correct Answer: C
Rationale: Oxacillin is a penicillinase-resistant penicillin equivalent to methicillin, effective against methicillin-susceptible Staphylococcus aureus (gram-positive cocci in clusters).
Question 4 of 5
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?
Correct Answer: C
Rationale: Cilastatin inhibits renal dehydropeptidase, preventing imipenem breakdown in the kidneys, thus increasing its efficacy and duration in treating infections like ruptured appendicitis.
Question 5 of 5
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?
Correct Answer: C
Rationale: Ciprofloxacin’s absorption is reduced by divalent cations (e.g., calcium in milk), which chelate the drug in the gut, decreasing its bioavailability and efficacy against anthrax.