What to Know About Chloroquine (Aralen)

An Antimalarial Drug Also Used to Treat Autoimmune Diseases

In This Article

Chloroquine is an antimalarial drug. In addition to being used as a malaria treatment, it can also be used as prophylaxis to prevent malaria for travelers planning a trip to regions where the disease is both endemic and known to be treated by this medication. Chloroquine can be used to treat lupus and rheumatoid arthritis.

Chloroquine is taken as an oral tablet.

Chloroquine was proposed as a possible therapy for the novel coronavirus (SARS-CoV-2) that causes COVID-19. While the FDA granted emergency use authorization for both chloroquine phosphate and hydroxychloroquine sulfate products for COVID-19 in March, on June 15, it revoked the authorization, citing ineffectiveness and serious side effects.

Prescription and medication
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Uses

Chloroquine is used as a suppressive treatment for acute attacks of malaria due to P. vivax, P. malariae, P. ovale, and susceptible strains of P. falciparum. Depending on what parasite is causing malaria, it can either lengthen the time between attacks or cure the infection. Chloroquine is also indicated for the treatment of extraintestinal amebiasis.

Off-Label Uses

Chloroquine can be used to treat lupus and rheumatoid arthritis, but the treatment is off-label.

Hydroxychloroquine

Hydroxychloroquine is another antimalarial with mechanisms of action similar to chloroquine. It is FDA-approved to treat lupus erythematosus and both chronic and acute rheumatoid arthritis. It is often preferred over chloroquine, where possible, for these conditions, due to lower toxicity and having somewhat fewer side effects.

Before Taking

Before this drug is prescribed for malaria, your doctor should determine the cause of your malaria and whether it is susceptible to chloroquine. If you are traveling to a region where you will be at risk for malaria and have been prescribed chloroquine to prevent infection, your doctor should review whether the malarial parasites in that region are susceptible to chloroquine.

Before chloroquine is prescribed for rheumatoid arthritis or lupus, your doctor may explore other treatment options with fewer side effects.

Precautions and Contraindications

Chloroquine should not be used in patients who have psoriasis, porphyria (rare disorders that affect the skin and nervous system), retina damage, or visual field changes, whether or not they have been linked to 4-aminoquinoline exposure (i.e., amodiaquine, chloroquine, hydroxychloroquine, and related drugs).

It should also not be used by individuals who have a known hypersensitivity to 4-aminoquinoline compounds.

Other Antimalarials

In addition to chloroquine and hydroxychloroquine, the most common antimalarial drugs include:

  • Artemisinin-based combination therapies (ACTs). Each ACT contains at least two drugs that work together to attack the malarial parasite.
  • Quinine
  • Primaquine
  • Doxycycline
  • Mefloquine

Dosage

Chloroquine is available in several formulations. Chloroquine phosphate is the one available in the United States as a generic. The dosing is based on the amount of chloroquine in the pill, or the "base" amount. For example, in a 500 mg prescription of chloroquine phosphate, 300 mg of that will be chloroquine.

According to West-ward Pharmaceuticals, dosing should be as follows:

Chloroquine Phosphate Dosing
adults, malaria suppression 500 mg chloroquine phosphate (300 mg base) on exactly the same day every week. 
children, malaria suppression 8.3 mg/kg base, not exceeding the adult dose. Treatment: 16.7 mg/kg (max 1000mg or 1g) followed by 8.3mg/kg (max 500)

 

adults, malaria acute 1 g (600 mg base) followed by 500 mg (300 mg base) after 6 hours, and again on each of two consecutive days. This is a total dose of 2.5g (1.5g base) over three days. Low body weight adults should follow the dosing for children. 
children, malaria acute 10mg/kg base (< 600mg), followed by 5 mg/kg base  (<300 mg) after six hours, followed by the same 5mg/kg dose 24 hours after the first dose, and again 36 hours after the first dose.
adults, extraintestinal amebiasis 1g (600mg base) for two days, followed by 500mg (300mg base) daily for 2-3 weeks. Usually combined with an intestinal amebicide. 

Chloroquine Side Effects

The most common side effect of chloroquine is damage to the eyes. Damage to the retina may be irreversible. Eye damage is more common in people taking the medication at a high-dose or long-term. Symptoms of eye damage from chloroquine may include:

  • Blurred vision
  • Changes in the visual field
  • Difficulty reading

Other relatively common side effects include:

  • Deafness or reduced hearing
  • Photosensitivity
  • Gastrointestinal symptoms
  • Tinnitus (ringing of the ears)
  • Damage to the muscles or nerves
  • Liver damage
  • Seizures
  • Headaches
  • Neuropsychiatric changes, such as psychosis, anxiety, and personality changes

Less common side effects include:

  • Skin problems
  • Blood disorders
  • Low blood pressure
  • Cardiomyopathy
  • Changes in heart rhythm

Overdose Warning

Chloroquine is quickly absorbed in the body. Toxic doses can be fatal. Symptoms of toxicity can occur within minutes and include:

  • Headache
  • Drowsiness
  • Vision changes
  • Nausea
  • Shock
  • Convulsions
  • Respiratory and/or cardiac arrest

As little as 1 gram of chloroquine can be fatal in children. If an overdose is suspected, vomiting should be induced immediately, if possible, and the person should be taken to the hospital for further treatment.

Chloroquine Warnings and Interactions

Chloroquine should be used with caution in patients who:

  • Are pregnant
  • Have kidney damage
  • Have liver disease or liver damage
  • Are taking other drugs that can damage the liver
  • Have history of alcoholism
  • Have epilepsy
  • Have auditory damage
  • Have risk of hypoglycemia
  • Have history of heart failure

Warnings

Irreversible damage to the eyes has been reported by some people who have taken high doses or chloroquine or used it for long-term treatment. An eye exam should be done before starting treatment, during treatment, and after treatment. If you take antacids, they need to be separated from chloroquine administration by at least 4 hours.

If patients experience muscle weakness while taking chloroquine, treatment should be discontinued.

If patients experience severe blood disorders not attributable to the underlying disease, treatment should be discontinued

Chloroquine can be fatal. This drug should be kept out of the reach of children.

Not all types of malaria can be treated with chloroquine. Doctors should not prescribe chloroquine prophylaxis unless patients are traveling to areas where the malaria parasite is susceptible to treatment.

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  1. Rainsford KD, Parke AL, Clifford-rashotte M, Kean WF. Therapy and pharmacological properties of hydroxychloroquine and chloroquine in treatment of systemic lupus erythematosus, rheumatoid arthritis and related diseases. Inflammopharmacology. 2015;23(5):231-69. doi:10.1007/s10787-015-0239-y

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