Chloroquine
Antimalarials
Antimalarials
Oral 4-aminoquinoline for P. vivax, P. ovale and P. malariae; in Colombia it treats vivax malaria, with primaquine against relapse.
Quick facts
- Group
- Antimalarials
- Target
- Heme detoxification (hemozoin formation) in the parasite's digestive vacuole
- Used for
- Uncomplicated P · Uncomplicated P · Hepatic amoebiasis
- Key effects
- Itching · Nausea · Headache
- Monitor
- Fever and parasite count · Vision
- ATC
- P01BA01
No doses: the clinician sets them by the current guideline.
Mechanism of action
A 4-aminoquinoline that concentrates in the acidic digestive vacuole of the blood-stage parasite. There the parasite digests haemoglobin and normally packs the toxic heme released into inert hemozoin pigment; chloroquine blocks that step, and free heme and drug-heme complexes damage the parasite's membranes. It does not act on liver stages. Resistance in P. falciparum comes from mutations in vacuole transport proteins (PfCRT, PfMDR1).
- Concentrates in the parasite's acidic food vacuole
- Blocks heme packing into hemozoin
- Free heme damages parasite membranes
- Blood stages die; liver forms survive
Indications
- Uncomplicated P. vivax malaria in chloroquine-sensitive areas such as Colombia (with primaquine for radical cure) Malaria →
- Uncomplicated P. ovale, P. malariae and P. knowlesi malaria Malaria →
- Weekly prophylaxis against P. vivax relapse during pregnancy and breastfeeding, when primaquine cannot be given Malaria →
- Hepatic amoebiasis (older use) Amoebic liver abscess →
Adverse effects
Common
- Itching, often more intense in people with dark skin
- Nausea, vomiting, diarrhoea and abdominal pain (better with food)
- Headache
- Rash and hair loss
- Blurred vision or difficulty focusing
Contraindications
- Hypersensitivity to chloroquine or other 4-aminoquinolines
- Caution: epilepsy, psoriasis, porphyria, retinal or visual disease, liver disease, G6PD deficiency, QT prolongation
Key interactions
- Antacids and kaolin
- Reduce chloroquine absorption; doses are separated
- Ampicillin
- Chloroquine reduces its bioavailability; doses are separated
- Cimetidine
- Reduces chloroquine metabolism and clearance
- Mefloquine
- Higher risk of convulsions
What is monitored
- Fever and parasite count: failure to improve by the second day suggests resistance
- Vision: eye examinations with long-term use
- ECG in patients with heart disease or other QT-prolonging drugs
- Safe storage at home (fatal in small children)
Administration and safety
- Oral, with food to reduce stomach upset, over a short course for acute malaria.
- Prophylaxis is weekly, on the same day of the week.
- Name looks like hydroxychloroquine, a related drug: confirm which one is ordered.
- Never given as a rapid injection: parenteral chloroquine has caused fatal toxicity.
Pregnancy and breastfeeding
Considered safe in pregnancy at malaria doses; it is also used weekly to prevent P. vivax relapse until primaquine can be given after delivery and breastfeeding.
Nursing care
- Before: confirm species and ask about pregnancy, epilepsy, psoriasis, heart disease and vision problems.
- Give with food; watch for itching, which is frequent and usually harmless.
- Check that the fever settles within the first two days; report persisting fever.
- Teaching: keep tablets locked away from children, report vision changes, ringing in the ears or palpitations; for P. vivax, finish the primaquine course too.
Pharmacokinetics
- Absorption
- Rapid and almost complete after oral intake
- Distribution
- Huge tissue uptake (liver, spleen, kidney, lung); moderately bound to plasma proteins; crosses the placenta and enters breast milk
- Metabolism
- Liver CYP2C8 and CYP3A4 to desethylchloroquine, which is also active
- Elimination
- Slow; about half by the kidneys; traces in urine for a long time
- Half-life
- Terminal half-life of 30 to 60 days
Test yourself
Think of the answer, then tap the question to see it.
Why does chloroquine alone not cure P. vivax malaria?
It only kills blood stages; dormant liver hypnozoites survive and cause relapses, so primaquine (or tafenoquine) is added.
How does chloroquine kill the parasite?
It concentrates in the acidic food vacuole and stops toxic heme from being packed into hemozoin; free heme damages the parasite.
Why is chloroquine overdose so feared?
It has a narrow margin of safety: overdose causes arrhythmias, hypotension, hypokalaemia and convulsions within hours, even in small children.
Is chloroquine used for P. falciparum in Colombia?
No. P. falciparum in South America is chloroquine-resistant; it is treated with artemether + lumefantrine.
Connections
← Back to the class: Antimalarials
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Chloroquine: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2025); Adopción Parcial de Guía de Práctica Clínica Diagnóstico y tratamiento de la malaria, OMS 2022. Guía para Colombia, GPC #67-2022 (Ministerio de Salud y Protección Social (Colombia), 2022); Treatment of Uncomplicated Malaria (Centers for Disease Control and Prevention (CDC), 2026).
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Representative model, for educational purposes only.