Pharmacology Antimicrobial and Chemotherapeutic Agents 5

Question 1

A patient requires treatment for Pneumocystis jirovecii pneumonia (PCP). Which drug is first-line therapy?

Accepted Answer

Trimethoprim-sulfamethoxazole (TMP-SMX)

Answer

TMP-SMX (Bactrim) is the drug of choice for both treatment and prophylaxis of PCP because Pneumocystis jirovecii lacks the ability to synthesize folate from external sources.

Question 2

Which antiviral agent is used for CMV (cytomegalovirus) retinitis in immunocompromised patients and works by inhibiting viral DNA polymerase?

Accepted Answer

Ganciclovir

Answer

Ganciclovir is phosphorylated by CMV-encoded kinase and inhibits viral DNA polymerase; it is the drug of choice for CMV disease in immunocompromised patients.

Question 3

A patient on linezolid for VRE infection is given serotonergic medications. What potentially fatal adverse interaction must be monitored?

Accepted Answer

Serotonin syndrome

Answer

Linezolid weakly inhibits monoamine oxidase (MAO), and when combined with serotonergic drugs (SSRIs, SNRIs, meperidine), can precipitate potentially fatal serotonin syndrome.

Question 4

Which beta-lactam antibiotic is specifically active against Pseudomonas aeruginosa and other gram-negative organisms but has poor gram-positive coverage?

Accepted Answer

Aztreonam

Answer

Aztreonam is a monobactam that selectively binds PBP3 of aerobic gram-negative rods including Pseudomonas; it has no activity against gram-positive or anaerobic organisms.

Question 5

Primaquine is used to eliminate the hypnozoite (dormant liver) stage of Plasmodium vivax malaria. Before prescribing, the clinician must first screen for:

Accepted Answer

G6PD deficiency

Answer

Primaquine causes severe hemolytic anemia in patients with G6PD deficiency because the drug generates oxidative stress that RBCs lacking G6PD cannot neutralize.

Pharmacology Practice Test

Pharmacology Practice Test

Pharmacology Antimicrobial and Chemotherapeutic Agents 5