Chloroquine prevents the development of malaria parasites in the blood. Doctors use it to both prevent and treat malaria. Chloroquine does not destroy the Plasmodium (P.)vivax and P. ovale parasites that may remain in the liver.

To prevent some strains of malaria, you take chloroquine once, 1 to 2 weeks prior to travel to an area where malaria is present, and then weekly while you are in the area, and weekly for 4 weeks after you depart from the area.1

To treat malaria, you take chloroquine at several-hour intervals and at a higher dosage than when it’s taken to prevent malaria. Chloroquine is effective on all five species of parasites, including some strains of P. falciparum. But in many areas P. falciparum is resistant to chloroquine, and other medicines must be used.

Chloroquine can also be used to prevent and treat P. falciparum and P. vivax infections in areas where drug resistance to chloroquine has not been confirmed. These areas include Central America, the Caribbean, and parts of the Middle East.2 Other parts of the world have confirmed resistance to chloroquine.

How Well It Works

Chloroquine is an effective medicine to prevent and treat a malaria infection caused by P. ovale or P. malariae parasites. But how well it works depends on how resistant the parasites are in the geographic location where the malaria infection occurred.

Medicine to prevent malaria is most effective if you take the correct dosage regularly. It’s easier to remember if you take your weekly dosage with meals on the same day of the week each week, such as every Monday at lunch.
Side Effects

All medicines have side effects. But many people don’t feel the side effects, or they are able to deal with them. Ask your pharmacist about the side effects of each medicine you take. Side effects are also listed in the information that comes with your medicine.

Here are some important things to think about:

Usually the benefits of the medicine are more important than any minor side effects.
Side effects may go away after you take the medicine for a while.
If side effects still bother you and you wonder if you should keep taking the medicine, call your doctor. He or she may be able to lower your dose or change your medicine. Do not suddenly quit taking your medicine unless your doctor tells you to.

Call emergency if you have:

Trouble breathing.
Hives.
Swelling of your face, lips, tongue, or throat.

Side effects of chloroquine include:

Nausea or diarrhea.
Dizziness or blurred vision.
Sleep disturbances.
Headaches.
Itching, or worsening of psoriasis, a chronic skin condition.

What To Think About

Taking chloroquine with meals may help you avoid an upset stomach.

Chloroquine is the most effective medicine for preventing and treating a malaria infection caused by P. ovale, P. malariae, or P. knowlesi parasites.

In some areas where malaria is common, travellers are sometimes advised to get a rabies vaccine if they are staying longer than 30 days. If you are taking chloroquine, make sure the rabies vaccine is injected into your muscle (intramuscular). Chloroquine can reduce the effectiveness of this vaccine when it is injected into the skin (intradermal).

Medicines to prevent malaria destroy the malaria parasite when it enters the bloodstream. To completely rid yourself of the parasite, take the medicine for 4 weeks after you leave the area where malaria is present.
Taking medicine

Medicine is one of the many tools your doctor has to treat a health problem. Taking medicine as your doctor suggests will improve your health and may prevent future problems. If you don’t take your medicines properly, you may be putting your health (and perhaps your life) at risk.

There are many reasons why people have trouble taking their medicine. But in most cases, there is something you can do. For suggestions on how to work around common problems, see the topic Taking Medicines as Prescribed.
Advice for women

If you are pregnant, breast-feeding, or planning to get pregnant, do not use any medicines unless your doctor tells you to. Some medicines can harm your baby. This includes prescription and over-the-counter medicines, vitamins, herbs, and supplements. And make sure that all your doctors know that you are pregnant, breast-feeding, or planning to get pregnant.
Checkups

Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor if you are having problems. It’s also a good idea to know your test results and keep a list of the medicines you take.

Complete the new medication information form (PDF) to help you understand this medication.

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