Chloroquine Phopshate - Oral

What Is Chloroquine?

Chloroquine phosphate is an antimalarial and immunosuppressive drug used to treat and prevent malaria. It is also used to treat an infectious bowel disease called amebiasis. Chloroquine enters the blood cells and interrupts the processes of parasitic activity.

This medication is only available as a prescription. The brand name, Aralen, has been discontinued but chloroquine is still available in its generic form. It comes in tablet to be taken by mouth.

Drug Facts

Generic Name: Chloroquine phosphate

Brand Name(s): Aralen (discontinued)

Drug Availability: Prescription

Administration Route: Oral

Therapeutic Classification: Antimalarial agent 

Available Generically: Yes

Controlled Substance: N/A

Active Ingredient: Chloroquine phosphate 

Dosage Form(s): Oral tablet

What Is Chloroquine Used For?

The Food and Drug Administration (FDA) approved chloroquine to prevent or treat malaria, which is an infection of the blood cells from the bite of a mosquito. This is commonly used as a preventative treatment for travelers going to regions of the world with malaria that is not resistant to chloroquine.

Chloroquine treats acute attacks of malaria due to susceptible strains of:

  • P. falciparum
  • P. malariae
  • P. ovale
  • P. vivax

However, it does not prevent the relapse of vivax or ovale malaria.

Additionally, it is used to treat a type of bowel infection, also known as extraintestinal amebiasis. Chloroquine is also sometimes used off-label (not as an FDA-approved use) for the treatment of lupus.

How to Take Chloroquine

Treatment regimens for chloroquine vary based on what it is being used for. It is always important to take this medication as directed by your healthcare provider.

Take your doses with food to reduce stomach-related side effects such as nausea.

Prevention of Malaria

The treatment regimen for the prevention of malaria is usually 500 milligrams (mg) weekly on the same day each week. It is started one to two weeks prior to exposure and continued while in the endemic area (where malaria occurs), and four weeks after leaving the endemic area.

Treatment of Malaria

To treat malaria, you will usually take 1,000 milligrams on day one, and 500 milligrams at 6, 24, and 48 hours after the day one dose. 

Amebiasis

For extraintestinal amebiasis, the regimen is usually one dose taken for two days, followed by half the dose every day for two to three weeks. You will likely be prescribed other amebicides (drugs that target amoeba) to take as well.

Storage

Store chloroquine at room temperature in a dry place. Do not store it in the bathroom or kitchen. Containers should be closed tightly and kept away from direct sunlight, pets, and children.

Off-Label Uses

There are instances in which chloroquine may be prescribed for reasons other than what has been formally approved. This is known as "off-label use."

Chloroquine has been studied for the following non-approved uses: 

Lupus Erythematosus

Your healthcare provider may prescribe this medication to help control your skin lesions if you have lupus.

COVID-19

The FDA granted this medication an emergency use authorization to treat COVID-19 back in March 2020, but it was revoked in June 2020 because of safety concerns and lack of efficacy. It is strongly recommended not to use this medication to treat COVID-19, as it can cause more harm than good. Please consult with your healthcare provider for other effective therapy for COVID-19 treatment.

How Long Does Chloroquine Take to Work?

Chloroquine will take time to have maximal benefits in the body. For prevention, this medication is typically started one to two weeks prior to travel.

What Are Side Effects of Chloroquine?

This is not a complete list of side effects and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your pharmacist or a medical professional. You may report side effects to the FDA at www.fda.gov/medwatch or 800-FDA-1088.

Common Side Effects

The most common side effects of chloroquine include: 

  • Stomach pain or cramps, nausea, or vomiting
  • Lack of appetite 
  • Diarrhea 
  • Headache 
  • Skin and hair discoloration 
  • Hair loss 

Other side effects may occur that are not mentioned here. Contact your pharmacist or prescribing healthcare provider for any further advice or concerns about side effects. 

Severe Side Effects

Life-threatening side effects from chloroquine are rare. However, some symptoms may be severe and should not be taken lightly. Get medical help right away if you experience symptoms such as:

  • Signs of liver problems such as dark urine, feeling tired, appetite loss, stomach pain, light-colored stools, vomiting, or yellowing of the skin or eyes
  • Signs of low blood sugar such as dizziness, headache, fatigue, weakness, confusion, and increased hunger 
  • Vision changes such as blurred vision or loss of vision  
  • Restlessness 
  • Seizures 
  • Trouble sleeping 
  • Mood and behavioral changes 
  • Muscle weakness and/or pain 
  • Chills 

Although rare, call your healthcare provider right away if you experience any of these serious side effects. Call 911 if your symptoms feel life-threatening or if you think you’re having a medical emergency. 

Long-Term Side Effects

Long-term use of chloroquine should only be under the guidance of a healthcare provider. High doses or long-term use of this medication can cause irreversible damage to the eyes, resulting in permanent problems with one’s vision.

Proper and routine follow-up as recommended by your prescribing healthcare provider is important to monitor any unwanted side effects and ensure the medication works appropriately.

Report Side Effects

Chloroquine may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your provider may send a report to the FDA's MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

Dosage: How Much Chloroquine Should I Take?

Drug Content Provided and Reviewed by IBM Micromedex®

The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For oral dosage form (tablets):
    • For prevention of malaria:
      • Adults—500 milligrams (mg) once a week on the same day of each week starting 2 weeks before traveling to an area where malaria occurs, and continued for 8 weeks after leaving the area.
      • Children—Dose is based on body weight and must be determined by your doctor. The dose is usually 5 milligram (mg) per kilogram (kg) of body weight once per week on the same day each week starting 2 weeks before traveling to an area where malaria occurs, and continued for 8 weeks after leaving the area.
    • For treatment of malaria:
      • Adults—At first, 1000 milligrams (mg) once a day. Then, 500 mg 6 to 8 hours after the first dose, and 500 mg on the second and third days of treatment.
      • Adults with low body weight and children—Dose is based on body weight and must be determined by your doctor. At first, 10 milligram (mg) per kilogram (kg) of body weight. Then, 5 mg per kg of body weight taken 6 hours, 24 hours, and 36 hours after the first dose.
    • For treatment of liver infection caused by protozoa:
      • Adults—1000 milligrams (mg) once a day, taken for 2 days. This is followed by 500 mg once a day for at least 2 to 3 weeks.
      • Children—Use and dose must be determined by your doctor.

Modifications

Due to some of chloroquine's potential side effects, dose modifications may be needed for certain individuals:

  • Children: Dosing is based on weight and indication (whether it's being used for prevention or treatment). Your child's healthcare provider can help you calculate the proper dose.
  • Kidney or liver problems: Chloroquine usually does not need to be adjusted for people with liver or kidney impairment.
  • Pregnancy or breastfeeding: Discuss the risks and benefits of taking this medication with your healthcare provider if you are pregnant or breastfeeding. The drug can cross into the placenta and breast milk.

Missed Dose

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue your regular intake schedule. Do not take extra doses or multiple doses at the same time.  

Overdose: What Happens If I Take Too Much Chloroquine?

Chloroquine is absorbed quickly in the body. Symptoms of an overdose can occur within minutes and may include:

  • Vision changes
  • Nausea and vomiting
  • Headache
  • Seizure
  • Shortness of breath
  • Low heart rate

An overdose of chloroquine requires medical treatment. Overdoses can be fatal, and as little as 1 gram of chloroquine can be deadly in children. Be careful not to leave the tablets within reach of children or pets to prevent accidental consumption.

What Happens If I Overdose on Chloroquine?

If you think you or someone else may have overdosed on chloroquine, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn't breathing after taking chloroquine, call 911 immediately.

Precautions

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If you will be taking this medicine for a long time, it is very important that your doctor check your progress at regular visits. This is to make sure that the infection is cleared up completely, and to allow your doctor to check for any unwanted effects. Your doctor may check your blood, urine, eyes, ears, and knee or ankle reflexes during or after using this medicine.

If your symptoms do not improve within a few days, or if they become worse, check with your doctor.

This medicine may cause heart problems and changes in your heart rhythm. Check with your doctor right away if you have chest pain or tightness, decreased urine output, dilated neck veins, extreme fatigue, swelling of the face, fingers, feet, or lower legs, troubled breathing, or weight gain. You may also feel dizzy or faint, or you may have a fast, pounding, or uneven heartbeat.

This medicine may cause hypoglycemia (low blood sugar), which may be life-threatening. Low blood sugar must be treated before it causes you to pass out (unconsciousness). People feel different symptoms of low blood sugar. It is important that you learn which symptoms you usually have so you can treat it quickly. Talk to your doctor about the best way to treat low blood sugar.

Chloroquine may cause vision problems. It may also make you dizzy or lightheaded. Do not drive or do anything else that could be dangerous until you know how this medicine affects you. . If these reactions are especially bothersome, check with your doctor.

Check with your doctor immediately if blurred vision, difficulty with reading, or any other change in vision occurs during or after treatment. Your doctor may want your eyes be checked by an ophthalmologist (eye doctor).

This medicine may cause extrapyramidal disorders (eg, dystonia, dyskinesia, tongue protrusion, torticollis). Check with your doctor right away if you have the following symptoms after using the medicine: difficulty in speaking, drooling, loss of balance control, muscle trembling, jerking, or stiffness, restlessness, shuffling walk, stiffness of the limbs, twisting movements of the body, or uncontrolled movements, especially of the face, neck, and back.

Using this medicine for a long time may cause muscle weakness. Check with your doctor right away if you have muscle weakness while using this medicine.

Children are very sensitive to this medicine, and accidental overdoses have occurred with small amounts of chloroquine. Keep this medicine out of the reach of children.

Check with your doctor right away if you have continuing ringing or buzzing or other unexplained noise in the ears or hearing loss while using this medicine.

While you are being treated with chloroquine, do not have any immunizations (eg, rabies vaccine) without your doctor's approval.

Malaria is spread by the bites of certain kinds of infected female mosquitoes. If you are living in or will be traveling to an area where there is a chance of getting malaria, the following mosquito-control measures will help to prevent infection:

  • If possible, avoid going out between dusk and dawn because it is at these times that mosquitoes most commonly bite.
  • Remain in air-conditioned or well-screened rooms to reduce contact with mosquitoes.
  • Wear long-sleeved shirts or blouses and long trousers to protect your arms and legs, especially from dusk through dawn when mosquitoes are out.
  • Apply insect repellent, preferably one containing DEET, to uncovered areas of the skin from dusk through dawn when mosquitoes are out.
  • If possible, sleep in a screened or air-conditioned room or under mosquito netting, preferably coated or soaked with pyrethrum, to avoid being bitten by malaria-carrying mosquitoes.
  • Use mosquito coils or sprays to kill mosquitoes in living and sleeping quarters during evening and nighttime hours.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

What Are Reasons I Shouldn’t Take Chloroquine?

You must not take this medication if you have hypersensitivity to its ingredients (severe allergic reaction) and if you have a history of vision changes or damage to the eye.

Chloroquine should also not be used for:

  • Treatment of complicated malaria
  • Prevention of malaria in areas where chloroquine resistance occurs

What Other Medications Interact With Chloroquine?

It is important to inform your healthcare provider of all medications you take.

Medications that may interact with chloroquine include:

  • Antacids: Antacids may increase the amount of chloroquine in the body.
  • Antidiabetic drugs: Chloroquine may enhance its ability to cause low blood sugar levels in the body. 
  • Antipsychotics: QT-prolonging antipsychotics such as ziprasidone and haloperidol can have these increased effects when used in combination with chloroquine. 
  • Ciprofloxacin: Chloroquine may enhance the ability of ciprofloxacin to increase blood sugar levels. 
  • Remdesivir: Chloroquine may lower the effects of this medication. 
  • Selective serotonin reuptake inhibitors (SSRIs): Chloroquine may enhance SSRI's ability to cause low blood sugar levels. 
  • Tamoxifen: Chloroquine and tamoxifen both have the potential for eye toxicity, so they are not recommended to be used together.

What Medications Are Similar?

Hydroxychloroquine, another antimalarial medication, works similarly to chloroquine. However, it is FDA-approved to treat lupus and rheumatoid arthritis. Hydroxychloroquine is often preferred over chloroquine, when possible, for these conditions because it has lower toxicity and fewer side effects.

Other commonly used antimalarial medications are listed below. Your healthcare provider may prescribe the medications based on the area of travel, time of travel, drug interactions, and drug allergies:

  • Malarone (atovaquone and proguanil)
  • Doxycycline
  • Mefloquine 
  • Primaquine 

This is a list of similar drugs to chloroquine. It is NOT a list of drugs recommended to take with it. Ask your pharmacist or healthcare provider if you have questions

Frequently Asked Questions

  • How many days before travel should I start taking chloroquine?

    Chloroquine is typically taken as preventative treatment starting one to two weeks prior to travel. It is important to follow the directions from your prescribing healthcare provider.

  • How can I best take chloroquine?

    Chloroquine can be taken with or without food but taking it with food may help prevent an upset stomach, which is a common side effect. It is important to separate this medication from antacids by at least four hours.

How Can I Stay Healthy While Taking Chloroquine?

To stay healthy while taking chloroquine, it is important to take it as directed by your healthcare provider. Being adherent to the prescribed regimen is the only way to maximize the benefits of this medication.

In addition to your medication regimen, you can take other measures to protect yourself from malaria while traveling:

  • Use insect repellent containing 10% to 35% DEET.
  • Stay covered with bed netting and dress in clothes that cover your arms and legs.
  • Use permethrin spray (an insecticide that kills or repels mosquitoes) on clothing and gear

Routine follow-up appointments with your healthcare provider are necessary to ensure safe, effective use and minimize the risk of unwanted side effects.

Medical Disclaimer

Verywell Health's drug information is meant for educational purposes only and is not intended to replace medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

Acknowledgement

The author would like to recognize and thank Faith Awoniyi for contributing to this article.

9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Food and Drug Administration. Aralen label.

  2. Tan KR, Arguin PM. Chapter 4: Travel-related infectious diseases. In: CDC Yellow Book.

  3. Bezerra EL, Vilar MJ, da Trindade Neto PB, Sato EI. Double-blind, randomized, controlled clinical trial of clofazimine compared with chloroquine in patients with systemic lupus erythematosus. Arthritis Rheum. 2005 Oct;52(10):3073-8. doi:10.1002/art.21358

  4. MedlinePlus. Chloroquine.

  5. National Institutes of Health. Chloroquine or hydroxychloroquine and/or azithromycin.

  6. Marmor MF, Kellner U, Lai TY, Melles RB, Mieler WF, American Academy of Ophthalmology. Recommendations on screening for chloroquine and hydroxychloroquine retinopathy (2016 revision). Ophthalmology. 2016 Jun;123(6):1386-94. doi:10.1016/j.ophtha.2016.01.058.

  7. Rainsford KD, Parke AL, Clifford-Rashotte C, Kean WF. Therapy and pharmacological properties of hydroxychloroquine and chloroquine in treatment of systemic lupus erythematosus, rheumatoid arthritis and related diseases. Inflammopharmacology. 2015;23,231-269. doi:10.1007/s10787-015-0239-y

  8. Tan KR, Magill AJ, Parise ME, Arguin PM. Doxycycline for malaria chemoprophylaxis and treatment: report from the CDC expert meeting on malaria chemoprophylaxis. Am J Trop Med Hyg. 2011 Apr;84(4):517–31.

  9. Centers for Disease Control and Prevention. Prevent mosquito bites.