## Treatment of Acute Plasmodium vivax Malaria **Key Point:** Chloroquine remains the first-line drug for acute P. vivax malaria in India, despite emerging resistance in some endemic zones. It rapidly clears parasitemia and resolves clinical symptoms. ### Mechanism of Action Chloroquine is a 4-aminoquinoline that: - Accumulates in the parasite's food vacuole - Inhibits heme polymerase, causing toxic heme accumulation - Effective against erythrocytic (blood) stage parasites - Acts within 48–72 hours to clear fever and parasites ### Dosing Regimen for P. vivax | Parameter | Details | |-----------|----------| | **Loading dose** | 10 mg base/kg on day 1 | | **Maintenance** | 5 mg base/kg on days 2 and 3 | | **Total course** | 25 mg base/kg over 3 days | | **Onset of action** | 24–48 hours | **Clinical Pearl:** Schüffner's stippling and ring forms are pathognomonic for P. vivax. The presence of these morphologic features confirms the species diagnosis and guides drug choice. **High-Yield:** Chloroquine is used for acute attack (erythrocytic stage). Primaquine is reserved for hypnozoite eradication (liver stage) to prevent relapse — it is NOT used for acute symptoms. ### Why Chloroquine First? 1. Rapid parasiticide action (kills circulating parasites) 2. Fever resolution within 48 hours 3. Well-tolerated in therapeutic doses 4. Cost-effective and widely available in India 5. Resistance, though emerging, is not yet universal in P. vivax **Warning:** Do NOT confuse acute attack treatment (chloroquine) with relapse prevention (primaquine). Primaquine is given AFTER chloroquine to eliminate hypnozoites.
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