Indications
Chloroquine is used to treat malaria caused by parasites that are still sensitive to it, mainly Plasmodium vivax, Plasmodium ovale and Plasmodium malariae, and sometimes to prevent malaria in travellers to areas where it still works. It is also used for amoebic liver abscess (with other medicines) and, less often now, for some autoimmune conditions such as rheumatoid arthritis and lupus.
How It Works
Inside red blood cells, malaria parasites digest haemoglobin and must make the toxic leftover (haem) harmless. Chloroquine builds up inside the parasite and blocks this step, so the toxic haem collects and kills the parasite. It also has mild effects on the immune system, which explains its use in some autoimmune diseases.
Dosage and Administration
Take as prescribed. For malaria, the doctor calculates a short course over 3 days, often based on body weight, and the dose may be stated as chloroquine base (each 250 mg chloroquine phosphate tablet contains about 155 mg base). For P. vivax and P. ovale, the doctor usually adds Primaquine afterwards to stop relapse. Take with food or after meals to reduce stomach upset. Complete the full course even if you feel better.
Interactions
Antacids and Kaolin reduce absorption, so take them at least 4 hours apart. Chloroquine can raise levels of Digoxin and Ciclosporin. Using it with other medicines that prolong the QT interval (such as Mefloquine, Amiodarone, some antibiotics and antidepressants) increases the risk of heart rhythm problems. It may reduce the response to the Rabies vaccine given into the skin. Cimetidine can increase chloroquine levels.
Contraindications
Do not use if you are allergic to chloroquine or hydroxychloroquine, or have existing retinal (back of the eye) damage from these drugs. Use with great caution in people with epilepsy, psoriasis, porphyria, G6PD deficiency, heart rhythm problems or severe liver disease.
Side Effects
Common effects include nausea, stomach upset, headache, dizziness, blurred vision and itching, which is common in dark-skinned people and is not dangerous. Long-term use can damage the retina and affect hearing, muscles and the heart.
Get urgent medical help for fainting, a fast or irregular heartbeat, fits, severe muscle weakness, sudden vision changes, unusual bruising or bleeding, severe skin reactions, or very low blood sugar (sweating, shaking, confusion).
Pregnancy and Lactation
Chloroquine at the doses used for malaria is considered acceptable in pregnancy, because malaria itself is very dangerous for mother and baby. Small amounts pass into breast milk, and breastfeeding can usually continue; the amount is not enough to protect the baby from malaria.
Precautions and Warnings
Keep chloroquine well away from children: even a few tablets can be fatal to a child. People on long-term treatment need regular eye checks. It may worsen psoriasis and trigger fits. Malaria in many areas is resistant to chloroquine, so use only when a doctor confirms it is suitable. It may cause dizziness or blurred vision; take care when driving.
Overdose
Chloroquine overdose is very dangerous and can quickly cause drowsiness, vision problems, fits, low blood pressure, heart rhythm problems and cardiac arrest. Take the person to hospital immediately, even if they seem well.
Therapeutic Class
Antimalarial (4-aminoquinoline).
Storage
Store below 30°C in a dry place, away from light. Keep in a locked place out of the reach of children.
Prepared by the Oshud Alo team from standard drug references. For information only; always follow your doctor's advice.