A 28-year-old man with newly diagnosed HIV infection (CD4 count 45 cells/μL) presents to the emergency department with severe dysphagia, odynophagia, and retrosternal chest pain for 5 days. Oral examination reveals white plaques on the tongue and soft palate that do not scrape off easily. Endoscopy shows extensive white plaques and ulceration extending into the esophagus. Histopathology demonstrates fungal hyphae and pseudohyphae invading the esophageal mucosa. Which antifungal agent is contraindicated in this patient due to the risk of severe hepatotoxicity and drug interactions with antiretroviral therapy?

Explanation

## Candida Esophagitis in Advanced HIV and Antifungal Selection **Key Point:** Candida esophagitis in patients with CD4 <50 cells/μL is an AIDS-defining illness. While fluconazole is first-line, ketoconazole is contraindicated due to severe hepatotoxicity, CYP3A4 inhibition, and dangerous interactions with protease inhibitors and non-nucleoside reverse transcriptase inhibitors (NNRTIs). ### Clinical Diagnosis: Candida Esophagitis **High-Yield:** The constellation of odynophagia + esophageal involvement + CD4 <50 cells/μL + histologic confirmation of invasive hyphae is diagnostic for Candida esophagitis. Oral thrush (white plaques that scrape off) may precede esophageal disease. **Clinical Pearl:** Unlike oral thrush (which is superficial and responds to topical agents), esophageal candidiasis requires systemic antifungal therapy. The presence of ulceration and mucosal invasion indicates deeper tissue penetration. ### Antifungal Agents: Comparison and Contraindications | Agent | Mechanism | Hepatotoxicity | CYP3A4 Interaction | Use in HIV | Comments | |-------|-----------|----------------|-------------------|-----------|----------| | **Fluconazole** | Azole (ergosterol synthesis) | Low | Mild | First-line | Good esophageal penetration; safe with ARVs | | **Ketoconazole** | Azole (ergosterol synthesis) | **HIGH** | **Strong inhibitor** | **Contraindicated** | **Severe hepatotoxicity; blocks PI/NNRTI metabolism** | | **Amphotericin B** | Polyene (membrane disruption) | Moderate (nephrotoxicity) | None | Alternative | Liposomal formulation preferred; no drug interactions | | **Caspofungin** | Echinocandin (1,3-β-glucan synthase) | Low | None | Alternative | Good for azole-resistant strains; no interactions | **Mnemonic: KETO-AVOID** — Ketoconazole: Enzyme inhibitor (CYP3A4), Toxicity (hepatic), Overkill (interactions), Avoid in HIV. ### Why Ketoconazole is Contraindicated ```mermaid flowchart TD A[Ketoconazole in HIV patient]:::urgent --> B["Strong CYP3A4 inhibition"]:::outcome B --> C{Protease inhibitor or NNRTI?}:::decision C -->|Yes| D["Severe drug accumulation"]:::urgent D --> E["Toxicity + treatment failure"]:::urgent A --> F["Direct hepatotoxicity"]:::outcome F --> G["Liver injury, jaundice"]:::urgent H["Fluconazole (alternative)"] :::action --> I["Mild CYP3A4 interaction"] I --> J["Safe with ARVs"] ``` 1. **CYP3A4 inhibition** — Ketoconazole potently inhibits hepatic CYP3A4, blocking metabolism of protease inhibitors (ritonavir, lopinavir) and NNRTIs (efavirenz, nevirapine). This causes dangerous accumulation and toxicity. 2. **Direct hepatotoxicity** — Ketoconazole causes idiosyncratic hepatotoxicity (hepatitis, cholestasis) in 1–2% of patients, particularly those with advanced immunosuppression. 3. **Superior alternatives** — Fluconazole has excellent esophageal penetration, minimal CYP3A4 interaction, and is the WHO-recommended first-line agent for Candida esophagitis in HIV. **Warning:** Ketoconazole was widely used in the pre-HAART era but is now obsolete in HIV care. Modern guidelines explicitly contraindicate it. [cite:Harrison's Principles of Internal Medicine 21e Ch 197]