Chloroquine is a 4-aminoquinoline compound with antimalarial and immunomodulatory properties. It is a weak base that accumulates in acidic organelles like lysosomes, disrupting cellular processes. In India, its use for uncomplicated malaria has been largely superseded by artemisinin-based combination therapies (ACTs) due to widespread resistance, but it retains a role in specific contexts and for autoimmune conditions.
Adult: **Malaria Treatment:** 1g (600mg base) initially, followed by 500mg (300mg base) at 6, 24, and 48 hours. Total dose = 2.5g chloroquine phosphate over 3 days. **RA/SLE:** 250-500mg daily, often starting at lower dose. **Prophylaxis:** 500mg once weekly, starting 1-2 weeks before exposure, during, and for 4 weeks after leaving endemic area.
Note: Take with food or a full glass of milk to minimize GI upset. Do not crush or chew the tablet. Maintain adequate hydration. For weekly prophylaxis, take on the same day each week.
As an antimalarial, chloroquine concentrates in the acidic food vacuole of the malaria parasite. It binds to heme (ferriprotoporphyrin IX), preventing its polymerization into non-toxic hemozoin. The accumulation of toxic heme leads to parasite death. As an immunomodulator, it raises the pH of intracellular vesicles, interfering with antigen processing, toll-like receptor signaling, and cytokine production.
Pregnancy: **Category C (US FDA).** Can be used for malaria treatment and prophylaxis in pregnancy as benefits outweigh risks. It crosses the placenta. For RA/SLE, use only if clearly needed. Not recommended for long-term high-dose use in pregnancy.
Driving: May cause dizziness, blurred vision, and accommodation disturbances. Patients should not drive or operate machinery until their individual response is known.
| Digoxin | Chloroquine may increase digoxin serum levels, risk of toxicity. | Major |
| Cyclosporine | Chloroquine may increase cyclosporine levels, increasing nephrotoxicity risk. | Major |
| Cimetidine | Inhibits metabolism of chloroquine, increasing its levels and toxicity risk. | Moderate |
| Ampicillin | Chloroquine reduces bioavailability of ampicillin. Separate administration by at least 2 hours. | Moderate |
| Mefloquine | Increased risk of convulsions and ECG abnormalities (QT prolongation). | Major |
| Praziquantel | Chloroquine reduces plasma levels of praziquantel, reducing efficacy. | Major |
| Insulin, Oral Hypoglycemics | Chloroquine has hypoglycemic effects; additive effect, risk of hypoglycemia. | Moderate |
| Tamoxifen, Hydroxychloroquine | Additive risk of retinal toxicity. | Major |
| Azithromycin, Fluoroquinolones | Increased risk of QT prolongation and cardiac arrhythmias. | Major |
| Antacids (Al, Mg) | Reduce absorption of chloroquine. Separate administration by at least 4 hours. | Moderate |