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Difficulty: HardPharmacologic Interventions

A 3535-year-old man comes to the clinic for follow-up after recently testing positive for human immunodeficiency virus (HIV). He is currently asymptomatic and feels well. Laboratory studies show an absolute CD4 T-lymphocyte count of 145145 cells/mm 3^3 and an HIV viral load of 150,000150,000 copies/mL. Serum Toxoplasma IgG testing is negative. Antiretroviral therapy is initiated. The physician also plans to prescribe primary prophylaxis against the opportunistic infection for which he is at greatest risk. The patient's medical history is significant for an episode of severe facial angioedema and airway compromise after taking trimethoprim-sulfamethoxazole for a skin infection three years ago. He also has a documented history of glucose-6-phosphate dehydrogenase (G6PD) deficiency, diagnosed after a severe hemolytic episode during a childhood illness. Which of the following is the most appropriate pharmacologic intervention for this patient's primary prophylaxis?

  1. Oral atovaquoneAnswer
  2. B
    Oral dapsone
  3. C
    Oral trimethoprim-sulfamethoxazole
  4. D
    Oral azithromycin
  5. E
    Oral fluconazole

Answer

Oral atovaquone is the correct pharmacologic intervention for this patient.
Oral atovaquone is the correct choice. This patient with HIV has a CD4 count of 145145 cells/mm 3^3, which is below the threshold of 200200 cells/mm 3^3, thereby requiring primary prophylaxis against Pneumocystis jirovecii pneumonia (PCP). The standard first-line therapy is trimethoprim-sulfamethoxazole; however, this patient's history of angioedema and airway compromise constitutes an absolute contraindication to sulfonamides. The standard second-line alternative is dapsone. Because dapsone is an oxidizing agent, it is strictly contraindicated in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency due to the high risk of precipitating acute hemolytic anemia. Therefore, the most appropriate next-line pharmacologic intervention is oral atovaquone, which is safe and effective for PCP prophylaxis in this scenario.

Step-by-Step Solution

1
Identify the primary infectious risk based on immunologic status.
The patient has a CD4 count of 145145 cells/mm 3^3 (which is <200< 200 cells/mm 3^3), placing him at high risk for Pneumocystis jirovecii pneumonia (PCP).
Current guidelines mandate primary prophylaxis against PCP when the CD4 count falls below 200200 cells/mm 3^3.
2
Evaluate the standard first-line pharmacologic intervention.
Trimethoprim-sulfamethoxazole is the standard first-line agent, but it must be bypassed.
The patient has a history of severe IgE-mediated anaphylaxis (angioedema, airway compromise) to sulfonamides, making its use an absolute contraindication.
3
Evaluate the standard second-line pharmacologic intervention.
Oral dapsone is the typical second-line agent, but it must also be bypassed.
Dapsone is a strong oxidizing agent. In a patient with known G6PD deficiency, it will precipitate an acute, potentially life-threatening hemolytic anemia.
4
Select the safest and most effective remaining alternative.
Oral atovaquone (or aerosolized pentamidine) is selected.
Atovaquone effectively prevents PCP and does not cross-react with sulfonamides or trigger oxidative hemolysis in G6PD deficiency.

Key Concept

In patients requiring PCP prophylaxis who have absolute contraindications to both trimethoprim-sulfamethoxazole (e.g., anaphylaxis) and dapsone (e.g., G6PD deficiency), oral atovaquone or aerosolized pentamidine are the pharmacologic interventions of choice.
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Pharmacologic Interventions

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