Chloroquine
A 4-aminoquinoline antimalarial for treating and preventing malaria where parasites are still sensitive; resistance is now widespread.
Drug card
- Class
- 4-aminoquinoline
- How it works
- Blocking the parasite from turning toxic heme into harmless crystals
- Used for
- Vivax, ovale and malariae malaria where still sensitive
- Preventing malaria where there is no resistance
- Amebiasis outside the gut (extraintestinal)
- Known for
- Retinal damage (bull's-eye retinopathy)
- Long QT and ventricular arrhythmias
- Its name
- -quine means a quinoline drug, often an antimalarial
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does chloroquine work?
Chloroquine concentrates in the parasite's acidic vesicles and blocks heme polymerization, so toxic heme accumulates; it may also act by binding DNA. It kills blood stages of P. vivax, P. ovale, P. malariae and sensitive P. falciparum, but not hypnozoites or gametocytes. It is absorbed rapidly and completely and concentrates in the liver.
Like other 4-aminoquinolines: These drugs concentrate in the parasite's acidic food vacuole and stop toxic heme from being polymerized into harmless crystals (hemozoin), so free heme builds up and kills the parasite. They act on blood stages only, not on liver hypnozoites or gametocytes, and resistance is widespread in P. falciparum. How hydroxychloroquine calms rheumatoid arthritis and lupus is not fully known.
Uses
What is chloroquine used for?
- Vivax, ovale and malariae malaria where still sensitive
- Preventing malaria where there is no resistance
- Amebiasis outside the gut (extraintestinal)
Side effects
Side effects of chloroquine
- Retinal damage (bull's-eye retinopathy)Known forSerious
- Long QT and ventricular arrhythmiasKnown forSerious
- Nausea, vomiting and diarrhea
- Itching
- Blurred vision and trouble focusing
- Cardiomyopathy and heart blockSerious
- Low blood sugar (hypoglycemia)Serious
- Hemolysis in G6PD deficiencySerious
- Muscle weakness (myopathy) and neuropathySerious
- Psychosis, agitation and suicidal behaviorSerious
- Hearing loss and ringing in the earsSerious
- Seizures, more likely with epilepsySerious
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Resistance is widespread in P. falciparum: check the region before using it to treat or prevent malaria.
- Small overdoses can be fatal, in children above all, through arrhythmias and cardiac arrest.
- Long-term use needs baseline and regular eye exams; stop at signs of retinal damage.
- It does not prevent vivax or ovale relapse: an 8-aminoquinoline such as primaquine is added.
Good to know: Once the main antimalarial, now limited by resistance. WHO still lists it for vivax, ovale, malariae and knowlesi malaria where parasites remain sensitive.
Remember it
A way to remember it
Chloroquine stops the parasite taking out its trash.
The parasite must lock toxic heme away as harmless crystals (hemozoin). 4-aminoquinolines gather in its acidic food vacuole and block this, so free heme poisons it.
Written for biofideX
Its name
-quine means quinoline drug, often an antimalarial
Chloroquine, hydroxychloroquine, primaquine and mefloquine are antimalarials, but debrisoquine and oxamniquine, also quinolines, are not.
- Every drug name stem
Its class
4-aminoquinolines
Other 4-aminoquinolines with a card:
Easily mixed up with 8-aminoquinolines and artemisinins.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- Chloroquine phosphate tablets: label (DailyMed)
- Chloroquine (NCI Thesaurus)
- WHO guidelines for malaria (WHO)
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Antifungals and antiparasitics
Chloroquine is one of 14 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
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