A 32-year-old woman from rural Odisha presents with fever, chills, and headache for 3 days. Blood smear microscopy confirms Plasmodium vivax malaria. She is started on chloroquine for the acute attack. Which is the most common adverse effect encountered during chloroquine therapy for malaria?

Explanation

## Most Common Adverse Effect of Chloroquine **Key Point:** Pruritus (itching) is the most frequent adverse effect of chloroquine in malaria patients, occurring in up to 50–80% of patients, particularly in individuals of African descent and those with darker skin pigmentation. ### Mechanism of Pruritus Chloroquine causes pruritus through: - Direct mast cell degranulation - Increased histamine release in the skin - Particularly pronounced in patients with genetic predisposition (especially those with G6PD deficiency) ### Frequency of Chloroquine Adverse Effects | Adverse Effect | Frequency | Timing | Clinical Significance | |---|---|---|---| | Pruritus | 50–80% (very common) | Early, during therapy | Mild, self-limiting, rarely discontinues therapy | | Retinopathy | 0.5–1% (rare) | Chronic use (>5 years) | Serious, requires baseline ophthalmology | | Hepatotoxicity | <1% | Variable | Uncommon, usually mild | | Ototoxicity | <0.5% | Rare | Uncommon with chloroquine alone | **Clinical Pearl:** Pruritus from chloroquine is so common in African populations that it is sometimes used as a marker of drug compliance. It typically resolves within days to weeks despite continued therapy. **High-Yield:** For NEET PG exams, remember: **Chloroquine = Pruritus is the most common side effect**. Retinopathy is the most serious but requires chronic use (years), not acute malaria therapy. ### Management of Chloroquine-Induced Pruritus - Reassurance and antihistamines (H1 blockers) - Topical emollients - Rarely requires drug discontinuation - Dose reduction may help in severe cases **Warning:** Do not confuse acute pruritus (common, benign) with retinopathy (rare, serious, requires long-term use).