A 32-year-old woman from rural Odisha presents with fever, chills, and sweating for 3 days. She reports a 2-week history of travel to a malaria-endemic zone. Physical examination reveals hepatosplenomegaly and mild jaundice. Blood smear shows ring forms and multiple ring forms within a single RBC. She is started on chloroquine 600 mg base stat, followed by 300 mg at 6 hours, then 300 mg daily for 2 days. On day 3 of therapy, she develops severe pruritus, urticaria, and angioedema. What is the most appropriate management at this point?

Explanation

## Clinical Scenario Analysis The patient presents with **Plasmodium falciparum malaria** (evidenced by multiple ring forms per RBC — a hallmark of P. falciparum), and develops **acute hypersensitivity reaction** (pruritus, urticaria, angioedema) to chloroquine on day 3 of therapy. ## Management of Chloroquine Hypersensitivity in Malaria **Key Point:** Hypersensitivity reactions to chloroquine (pruritus, urticaria, angioedema, rarely Stevens-Johnson syndrome) require **immediate discontinuation** of the drug. Continuing the drug with symptomatic management risks progression to severe cutaneous adverse reactions or anaphylaxis. **High-Yield:** In P. falciparum malaria with chloroquine hypersensitivity, the standard alternative is: - **Artemisinin-based combination therapy (ACT)** — artemether-lumefantrine or artesunate-amodiaquine (first-line in most endemic areas) - **Quinine** — if ACT unavailable (though less preferred due to cinchonism and cardiac effects) - **Atovaquone-proguanil** — alternative for uncomplicated P. falciparum **Clinical Pearl:** Chloroquine hypersensitivity is distinct from chloroquine-resistant parasites. The reaction is immunologic, not parasitologic, and mandates drug withdrawal regardless of parasitemia control. ## Why Switching Is Mandatory | Feature | Continuing Chloroquine | Switching to ACT | | --- | --- | --- | | Risk of progression | High (anaphylaxis, SJS) | Minimal | | Efficacy in P. falciparum | Compromised (resistance likely) | Excellent | | Hypersensitivity resolution | No — reaction worsens | Yes — new drug class | | Standard guideline recommendation | Contraindicated | Recommended | **Mnemonic for antimalarial hypersensitivity management:** **STOP-SWITCH** - **S** — Stop the offending drug immediately - **T** — Test for severity (anaphylaxis risk) - **O** — Observe airway, breathing - **P** — Provide supportive care (antihistamines, steroids as adjuncts only) - **S** — Switch to alternative (ACT or quinine) - **W** — Warn patient of cross-reactivity (chloroquine + amodiaquine share risk) - **I** — Investigate Plasmodium species if not yet confirmed - **T** — Track response to new agent - **C** — Consider desensitization only in life-threatening settings (rare) - **H** — Have emergency equipment ready during switch [cite:KD Tripathi 8e Ch 51]