4-aminoquinolines
Blocking the parasite from turning toxic heme into harmless crystals.
Class card
- Drugs
- Chloroquine and Hydroxychloroquine
- Used for
- Malaria from chloroquine-sensitive parasites
- Preventing malaria where there is no resistance
- Rheumatoid arthritis (hydroxychloroquine)
- Lupus erythematosus (hydroxychloroquine)
- Known for
- Retinal damage (bull's-eye retinopathy)
- Long QT and ventricular arrhythmias
- Name stems
- -quine
3 cards: the class, and each drug in it.
Mechanism of action
How do 4-aminoquinolines work?
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.
The drugs
4-aminoquinolines with a card
- ChloroquineOnce the main antimalarial, now limited by resistance. WHO still lists it for vivax, ovale, malariae and knowlesi malaria where parasites remain sensitive.
- HydroxychloroquineThe 4-aminoquinoline used for long-term rheumatic disease. Retinal damage rises with total dose and years of use, so regular eye screening is part of long-term treatment.
Uses
What are 4-aminoquinolines used for?
- Malaria from chloroquine-sensitive parasites
- Preventing malaria where there is no resistance
- Rheumatoid arthritis (hydroxychloroquine)
- Lupus erythematosus (hydroxychloroquine)
- Amebiasis outside the gut (chloroquine)
Side effects
Side effects of 4-aminoquinolines
- Retinal damage (bull's-eye retinopathy)Known forSerious
- Long QT and ventricular arrhythmiasKnown forSerious
- CardiomyopathySerious
- Low blood sugar (hypoglycemia)Serious
- Hemolysis in G6PD deficiencySerious
- Muscle weakness (myopathy) and neuropathySerious
- Mood changes, psychosis and suicidal thoughtsSerious
- Movement disorders such as dystonia (extrapyramidal)
- Hepatitis and raised liver enzymesSerious
- Skin and hair color changes
What the class has in common. Each drug's card has its own, and Known for marks what an exam expects you to know.
Watch for
Cautions
- Long-term use needs a baseline eye exam and regular retinal screening; damage can progress even after stopping.
- Avoid other QT-prolonging drugs; take care in heart disease and with low potassium or magnesium.
- Small overdoses can be fatal, in children above all, through arrhythmias and cardiac arrest.
- They can worsen psoriasis and porphyria, and cause hemolysis in G6PD deficiency.
Remember them
A way to remember them
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
Name stems
-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
Don't mix them up
Classes easily confused with these
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- Chloroquine phosphate tablets: label (DailyMed)
- Hydroxychloroquine sulfate tablets: label (DailyMed)
- Chloroquine (NCI Thesaurus)
- Hydroxychloroquine (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
Practice 4-aminoquinolines with the other classes in this group: what each drug is, how it works, what it treats and what it's known for.
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