Short guide to chloroquine for malaria and amebiasis in the United States. All information is provided in English and organized with in-page links for fast navigation.

Overview and composition

Active ingredient: Chloroquine (as chloroquine phosphate).

Therapeutic areas: Antimalarial; antiparasitic activity also used in extraintestinal amebiasis. Sometimes grouped with antiprotozoals rather than antivirals.

Common strengths and forms in the USA: Tablets 250 mg and 500 mg (note: a 500 mg chloroquine phosphate tablet is equivalent to 300 mg chloroquine base).

For a quick jump to dosing details, see Dosing and schedules.

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What chloroquine is used for

Chloroquine is indicated for:

  • Suppressive prophylaxis and treatment of malaria caused by Plasmodium vivax, P. malariae, P. ovale, and chloroquine-susceptible P. falciparum strains.
  • Treatment of extraintestinal amebiasis, typically alongside a luminal amebicide.

Note: For radical cure of P. vivax or P. ovale, combine with an 8-aminoquinoline (for example, primaquine or tafenoquine) to eradicate hypnozoites in the liver. See Alternatives and similar medicines.

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How to take chloroquine

Take doses with food or milk to reduce stomach upset unless your prescriber advises otherwise. Use exactly as directed; do not take larger amounts, take it more often, or extend treatment longer than prescribed.

If used for malaria prevention, continue for the full course. If used for treatment, complete the regimen even if symptoms improve within a few days. Stopping early can lead to relapse.

For best results, keep a consistent schedule. For weekly prophylaxis, choose the same weekday each week. For twice-daily schedules, many patients use morning and evening dosing.

Missed dose: Take it when remembered unless it is close to the next scheduled dose; if so, skip the missed dose. Do not double up.

If you need exact dosing by weight for a child, go to Dosing and schedules.

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Dosing and schedules

Doses are sometimes expressed as chloroquine base. Each 500 mg chloroquine phosphate tablet contains 300 mg chloroquine base. In infants and children, calculate doses by body weight.

Malaria suppression (prophylaxis)

  • Adults: 500 mg chloroquine phosphate (300 mg base) once weekly, on the same day each week.
  • Pediatrics: 5 mg/kg/week calculated as base, not to exceed the adult dose.
  • Start 2 weeks before exposure when possible. If not feasible, adults may take a loading dose of 1,000 mg chloroquine phosphate (600 mg base) split into 2 doses 6 hours apart; children may receive 10 mg base/kg in two divided doses on day 1. Continue weekly while exposed and for 8 weeks after leaving the endemic area.

Treatment of acute malaria attack

  • Adults: 1,000 mg chloroquine phosphate (600 mg base) initially; then 500 mg (300 mg base) 6 to 8 hours later; then 500 mg (300 mg base) once daily on each of the next two days. Total over 3 days: 2.5 g chloroquine phosphate (1.5 g base).
  • Adults of low body weight, infants, and children (base-equivalent):
    • First dose: 10 mg/kg base (max single dose 600 mg base).
    • Second dose at 6 hours: 5 mg/kg base (max single dose 300 mg base).
    • Third dose at 24 hours: 5 mg/kg base.
    • Fourth dose at 36 hours: 5 mg/kg base.
  • For radical cure of P. vivax or P. ovale, add an appropriate 8-aminoquinoline. See Alternatives and similar medicines.

Extraintestinal amebiasis

  • Adults: 1,000 mg (600 mg base) daily for 2 days, then 500 mg (300 mg base) daily for at least 2 to 3 weeks. Combine with an effective luminal agent.

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Storage information

  • Keep tablets in a closed container at room temperature, away from moisture, heat, and light.
  • Do not freeze. Store out of reach of children.
  • Discard expired or unneeded medication according to local guidance; do not keep outdated medicine.

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Precautions and safety checks

Long-term or high-dose use raises the risk of serious adverse effects, particularly eye toxicity. If therapy is prolonged, periodic ophthalmologic examinations are recommended. Seek medical advice promptly if vision changes occur at any time during or after treatment.

  • Until you know how you respond, avoid driving or operating machinery if vision is blurred or if you feel lightheaded.
  • Discuss alcohol and tobacco use with your clinician; certain drug-food and drug-alcohol interactions may be relevant.
  • Pregnancy: well-controlled data are limited. Use during pregnancy should be limited to suppression or treatment of malaria when the expected benefit outweighs fetal risks, per prescriber judgment.
  • Tell your clinician about all medicines and supplements. Some combinations can increase risk of heart rhythm problems, low blood sugar, or seizures.

If symptoms fail to improve or worsen within a few days of treatment, contact your healthcare professional. For regulatory notes, see Legal and regulatory status in the USA.

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Possible side effects

Seek urgent medical attention for serious or uncommon reactions

  • Ringing or buzzing in the ears or hearing loss
  • Unusual bruising or bleeding; pinpoint red spots on the skin
  • Severe mood or other mental changes, confusion, or seizures
  • Eye pain, loss of vision, or new changes in vision
  • Black, tarry stools; blood in urine or stools
  • Fever, chills, cough, sore throat
  • Severe lightheadedness or fainting; increasing muscle weakness

Note: Some visual side effects can appear or worsen after stopping chloroquine. Contact an eye specialist if vision changes occur.

Common or usually mild effects

  • Nausea or vomiting
  • Diarrhea
  • Itching (reported more frequently in Black patients)
  • Loss of appetite
  • Headache
  • Stomach cramps or abdominal pain

Less common cosmetic or skin effects

  • Skin rash
  • Bleaching or increased loss of hair
  • Blue-black discoloration of skin, nails, or inside the mouth

Overdose symptoms

  • Drowsiness or severe headache
  • Marked excitability or agitation

This list is not complete. If you notice other effects, consult a healthcare professional. For dosing guidance, see Dosing and schedules.

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Alternatives and similar medicines

If chloroquine is not suitable due to resistance, availability, tolerability, or prescriber preference, consider the following, always under medical supervision:

  • Hydroxychloroquine: a closely related antimalarial/antirheumatic with a lower risk of retinal toxicity at comparable doses; used off-label for malaria prophylaxis in some regions where sensitivity persists.
  • Mefloquine: weekly prophylaxis and treatment for chloroquine-resistant P. falciparum; review neuropsychiatric precautions.
  • Atovaquone-proguanil: once-daily prophylaxis and treatment option; generally well tolerated; widely used for travel prophylaxis to resistant areas.
  • Doxycycline: daily prophylaxis effective against chloroquine-resistant malaria; photosensitivity is a consideration.
  • Primaquine: for radical cure of P. vivax or P. ovale and some prophylaxis strategies; requires G6PD testing before use.
  • Tafenoquine: single-dose radical cure option (Krintafel) and a weekly prophylaxis regimen (Arakoda); requires quantitative G6PD testing and has specific contraindications.
  • For extraintestinal amebiasis: Metronidazole or tinidazole for tissue infection, followed by a luminal agent such as paromomycin or iodoquinol to clear intestinal colonization.

Medication choice depends on destination resistance patterns, patient history, comorbidities, drug interactions, and cost. Discuss options with a travel medicine clinician or infectious disease specialist.

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Approximate prices in USD (USA)

Prices below are rough cash estimates for generics with common discount programs in the USA; brand-name products typically cost more. Local pharmacy pricing varies widely.

  • Chloroquine phosphate 500 mg (300 mg base): about 1 to 5 USD per tablet when available; note that supply in the USA can be limited.
  • Hydroxychloroquine 200 mg: roughly 0.30 to 1.50 USD per tablet generic; brand Plaquenil costs more.
  • Atovaquone-proguanil 250/100 mg: around 3 to 9 USD per generic tablet; brand Malarone often 8 to 15 USD per tablet.
  • Mefloquine 250 mg base: about 3 to 8 USD per generic tablet.
  • Doxycycline 100 mg: approximately 0.10 to 0.80 USD per capsule/tablet generic.
  • Primaquine 15 mg: about 1 to 4 USD per tablet; availability varies.
  • Tafenoquine (Krintafel, 150 mg): approximately 180 to 240 USD for a typical 2-tablet radical cure; prophylaxis brand Arakoda can be 250 to 350 USD for a monthly supply.

These figures are illustrative only and may change; always check current local pharmacy pricing or insurance copays.

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Additional notes

Food, alcohol, and tobacco may interact with medicines. Discuss your diet and habits with your prescriber or pharmacist.

If you have questions about scheduling or weight-based dosing, refer back to How to take chloroquine and Dosing and schedules.

This page is informational and does not replace medical advice from your healthcare professional.

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