Chloroquine is used to treat or prevent malaria, a disease caused by parasites that enter the body through the bite of a mosquito. Chloroquine is not effective against all strains of malaria, or against malaria in areas where the infection has been resistant to a similar drug called hydroxychloroquine.

Chloroquine is also used to treat amebiasis (infection caused by amoebae).

Chloroquine may also be used for purposes not listed in this medication guide.

Chloroquine can cause dangerous effects on your heart, especially if you also use certain other medicines. Seek emergency medical attention if you have fast or pounding heartbeats and sudden dizziness (like you might pass out).

Taking chloroquine long-term or at high doses may cause irreversible damage to the retina of your eye that could progress to permanent vision problems. You may not be able to use chloroquine if you have a history of vision changes or damage to your retina.

Stop taking chloroquine and call your doctor at once if you have blurred vision, trouble focusing, distorted vision, blind spots, trouble reading, hazy or cloudy vision, increased sensitivity to light.

Chloroquine phosphate comes as a tablet to take by mouth. For prevention of malaria in adults, one dose is usually taken once a week on exactly the same day of the week. Your doctor will tell you how many tablets to take for each dose. One dose is taken beginning 2 weeks before traveling to an area where malaria is common, while you are in the area, and then for 8 weeks after you return from the area. If you are unable to start taking chloroquine for 2 weeks before traveling, your doctor may tell you to take double the dose right away (for the first dose).

For treatment of sudden, severe attacks of malaria in adults, one dose is usually taken right away, followed by half the dose 6 to 8 hours later and then half the dose once a day for the next 2 days.

For prevention and treatment of malaria in infants and children, the amount of chloroquine phosphate is based on the child's weight. Your doctor will calculate this amount and tell you how much chloroquine phosphate your child should receive.

For treatment of amebiasis, one dose is usually taken for 2 days and then half the dose every day for 2 to 3 weeks. It is usually taken in combination with other amebicides.

Chloroquine phosphate may cause an upset stomach. Take chloroquine phosphate with food.

Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Use chloroquine phosphate exactly as directed. Do not use more or less of it or use it more often than prescribed by your doctor.

Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

To prevent malaria: Chloroquine is usually taken once per week on the same day each week. Start taking the medicine 2 weeks before entering an area where malaria is common. Keep taking the medicine during your stay and for at least 8 weeks after you leave the area.

To treat malaria: Chloroquine is usually given as one high dose followed by smaller doses during the next 2 days in a row.

To treat amebiasis: Chloroquine is given in a high starting dose for 2 days followed by a smaller dose for 2 to 3 weeks. You may be given other medications to help prevent further infection.

Chloroquine doses are based on weight in children. Your child's dose needs may change if the child gains or loses weight.

Use chloroquine for the full prescribed length of time, even if your symptoms quickly improve.

Call your doctor as soon as possible if you have been exposed to malaria, or if you have fever or other symptoms of illness during or after a stay in an area where malaria is common.

Use protective clothing, insect repellents, and mosquito netting around your bed to further prevent mosquito bites that could cause malaria.

No medication is 100% effective in treating or preventing all types of malaria. Talk with your doctor if you have fever, vomiting, or diarrhea during your treatment.

While using chloroquine, you may need frequent medical tests and vision exams.

Store at room temperature away from moisture, heat, and light.

You should not use this medicine if you are allergic to chloroquine or hydroxychloroquine. You may not be able to use chloroquine if you have ever had vision changes or damage to your retina.

High doses or long-term use of chloroquine may cause irreversible damage to your retina (the membrane layer inside your eye that helps produce vision). This could progress to permanent vision problems. The risk of retinal damage is higher in people with pre-existing eye problems, kidney disease, or people who also take tamoxifen.

Tell your doctor if you have ever had:

• vision changes or damage to your retina caused by an anti-malaria medication;

• heart disease, heart rhythm disorder (such as long QT syndrome);

• an electrolyte imbalance (such as low levels of potassium or magnesium in your blood);

• diabetes;

• liver or kidney disease;

• psoriasis;

• alcoholism;

• porphyria (a genetic enzyme disorder that causes symptoms affecting the skin or nervous system); or

• a genetic enzyme deficiency called glucose-6-phosphate dehydrogenase (G6PD) deficiency.

Tell your doctor if you are pregnant or plan to become pregnant. Malaria is more likely to cause serious illness or death in a pregnant woman. Having malaria during pregnancy may also increase the risk of miscarriage, stillbirth, premature delivery, and low birth weight.

It is not known whether chloroquine will harm an unborn baby. If you are pregnant, ask your doctor about the risks of traveling to areas where malaria is common (such as Africa, South America, and Southern Asia).

You should not breastfeed while using chloroquine.

Call your doctor for instructions if you miss a dose.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222. An overdose of chloroquine can be fatal, and must be treated quickly.

Overdose symptoms may include drowsiness, vision changes, seizure, slow heart rate, weak pulse, pounding heartbeats, sudden dizziness, fainting, shortness of breath, or slow breathing (breathing may stop).

Keep chloroquine out of the reach of children. A chloroquine overdose can be fatal to a child who accidentally swallows this medicine.

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from light and excess heat and moisture (not in the bathroom).

Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA's Safe Disposal of Medicines website (http://goo.gl/c4Rm4p) for more information if you do not have access to a take-back program.

It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location – one that is up and away and out of their sight and reach. http://www.upandaway.org

Unless your doctor instructs you otherwise, continue your normal diet while taking chloroquine phosphate.

This medicine may cause blurred vision and may impair your reactions. Avoid driving or hazardous activity until you know how this medicine will affect you.

Avoid taking an antacid or Kaopectate (kaolin-pectin) within 4 hours before or 4 hours after you take chloroquine.

Get emergency medical help if you have signs of an allergic reaction (hives, difficult breathing, swelling in your face or throat) or a severe skin reaction (fever, sore throat, burning eyes, skin pain, red or purple skin rash with blistering and peeling).

Also seek emergency medical attention if you have symptoms of a serious heart problem: fast or pounding heartbeats, fluttering in your chest, shortness of breath, and sudden dizziness (like you might pass out).

Chloroquine may cause serious side effects. Call your doctor at once if you have:

• a seizure;

• ringing in your ears, trouble hearing;

• severe muscle weakness, loss of coordination, underactive reflexes;

• low blood cell counts--fever, chills, tiredness, mouth sores, skin sores, easy bruising, unusual bleeding, pale skin, cold hands and feet, feeling light-headed or short of breath;

• low blood sugar--headache, hunger, sweating, irritability, dizziness, fast heart rate, and feeling anxious or shaky; or

• a serious drug reaction that can affect many parts of your body--skin rash, fever, swollen glands, muscle aches, severe weakness, unusual bruising, or yellowing of your skin or eyes.

Taking chloroquine long-term or at high doses may cause irreversible damage to the retina of your eye. Stop taking chloroquine and tell your doctor if you have:

• blurred vision, trouble focusing, trouble reading;

• distorted vision, poor night vision;

• changes in your color vision;

• hazy or cloudy vision;

• seeing light flashes or streaks, seeing halos around lights; or

• increased sensitivity to light.

Common side effects of chloroquine may include:

• nausea, vomiting, diarrhea, stomach cramps;

• headache;

• unusual changes in mood or behavior;

• hair loss; or

• changes in hair or skin color.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Chloroquine can cause a serious heart problem. Your risk may be higher if you also use certain other medicines for infections, asthma, heart problems, high blood pressure, depression, mental illness, cancer, malaria, or HIV.

If you take an antibiotic called ampicillin, take it 2 hours before or 2 hours after you take your chloroquine dose.

Tell your doctor about all your other medicines, especially:

• cimetidine;

• cyclosporine;

• mefloquine;

• praziquantel;

• tamoxifen; or

• insulin or oral diabetes medicine.

This list is not complete. Other drugs may affect chloroquine, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

Children are especially sensitive to an overdose, so keep the medication out of the reach of children.

Keep all appointments with your doctor and the laboratory. Your doctor may order certain lab tests and electrocardiograms (EKG, a test to monitor your heart rate and rhythm) to check your response to chloroquine phosphate. Your doctor will also test your reflexes to see if you have muscle weakness that may be caused by the drug.

If you are taking chloroquine phosphate for a long period of time, your doctor will recommend frequent eye exams. It is very important that you keep these appointments. Chloroquine phosphate can cause serious vision problems. If you experience any changes in vision, stop taking chloroquine phosphate and call your doctor immediately.

Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.