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.

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.

Use Aralen Phosphate (Oral) exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended.

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).

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 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.

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.