[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Antimalarials](https://durgical.com/en/pharmacology/classes/antimalarials/) › Chloroquine

# Chloroquine

## Antimalarials?

Antimalarials

Oral 4-aminoquinoline for P. vivax, P. ovale and P. malariae; in Colombia it treats vivax malaria, with primaquine against relapse.

Updated Nov 1, 2026

## Quick facts

**Group**
[Antimalarials](https://durgical.com/en/pharmacology/classes/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.

On this page

- The basics Mechanism of action
- Indications
- Adverse effects
- Pharmacokinetics
- Memory aid

- Safety Contraindications
- Key interactions
- What is monitored
- Administration and safety
- Pregnancy and breastfeeding
- Nursing care

- Study Test yourself

- Connections Connections

## 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 →](https://durgical.com/en/conditions/malaria/)
- Uncomplicated P. ovale, P. malariae and P. knowlesi malaria [Malaria →](https://durgical.com/en/conditions/malaria/)
- Weekly prophylaxis against P. vivax relapse during pregnancy and breastfeeding, when primaquine cannot be given [Malaria →](https://durgical.com/en/conditions/malaria/)
- Hepatic amoebiasis (older use) [Amoebic liver abscess →](https://durgical.com/en/conditions/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

### Serious (rare, important)

- Very dangerous in overdose: arrhythmias, low blood pressure, low potassium, convulsions and death within hours; children are especially at risk
- Retinopathy and keratopathy with long-term use
- Convulsions and mental changes (rare)
- Hearing loss, myopathy and blood disorders (rare)

## 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

## Memory aid

«Chloro-CLEAN-the-blood»: chloroquine CLEANs the blood stages of vivax but leaves the liver «sleepers», so primaquine finishes the job.

## 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.

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[More Pharmacology questions →](https://durgical.com/en/practice/?f=pharmacology)

## Connections

## Related drugs 3

- [Primaquine](https://durgical.com/en/pharmacology/primaquine/)
- [Hydroxychloroquine](https://durgical.com/en/pharmacology/hydroxychloroquine/)
- [Tafenoquine](https://durgical.com/en/pharmacology/tafenoquine/)

## Related conditions 2

- [Malaria](https://durgical.com/en/conditions/malaria/)
- [Amoebic liver abscess](https://durgical.com/en/conditions/amoebic-liver-abscess/)

[← Back to the class: Antimalarials](https://durgical.com/en/pharmacology/classes/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](https://medlineplus.gov/druginfo/meds/a682318.html) (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](https://www.minsalud.gov.co/sites/rid/Lists/BibliotecaDigital/RIDE/VS/PP/ET/Guia-atencion-clinica-malaria.pdf) (Ministerio de Salud y Protección Social (Colombia), 2022); [Treatment of Uncomplicated Malaria](https://www.cdc.gov/malaria/hcp/clinical-guidance/treatment-of-uncomplicated-malaria.html) (Centers for Disease Control and Prevention (CDC), 2026).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/chloroquine/