Chloroquine phosphate is in a class of drugs called antimalarials and amebicides. It is used to prevent and treat malaria. It is also used to treat amebiasis.
This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information.
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 2 weeks before traveling, your doctor may tell you to take double the dose right away.
For treatment of acute 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.
Chloroquine phosphate is used occasionally to decrease the symptoms of rheumatoid arthritis and to treat systemic and discoid lupus erythematosus, scleroderma, pemphigus, lichen planus, polymyositis, sarcoidosis, and porphyria cutanea tarda. Talk to your doctor about the possible risks of using this drug for your condition.
Before using chloroquine phosphate,
- tell your doctor and pharmacist if you are allergic to chloroquine phosphate, chloroquine hydrochloride (Aralen HCl), hydroxychloroquine (Plaquenil), or any other drugs.
- tell your doctor and pharmacist what prescription and nonprescription medications you are taking, especially acetaminophen (Tylenol, others), cimetidine (Tagamet), iron products, isoniazid (Nydrazid), kaolin, magnesium trisilicate (Gaviscon), methotrexate (Rheumatrex), niacin, rifampin (Rifadin, Rimactane), and vitamins and herbal products.
- tell your doctor if you have or have ever had liver disease, G-6-PD deficiency, hearing problems, porphyria or other blood disorders, psoriasis, vision changes, weakness in your knees and ankles, or if you drink large amounts of alcohol.
- tell your doctor if you have ever had vision changes while taking chloroquine phosphate, chloroquine hydrochloride (Aralen HCl), or hydroxychloroquine (Plaquenil).
- tell your doctor if you are pregnant or plan to become pregnant. If you become pregnant while using chloroquine phosphate, call your doctor.
- tell your doctor if you are breast-feeding or plan to breast-feed. Chloroquine phosphate can harm a nursing infant.
Unless your doctor instructs you otherwise, continue your normal diet while taking chloroquine phosphate.
Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.
Side effects from chloroquine phosphate can occur. Tell your doctor if any of these symptoms are severe or do not go away:
- loss of appetite
- upset stomach
- stomach pain
- skin rash or itching
- hair loss
- mood or mental changes
If you experience any of the following symptoms, call your doctor immediately:
- seeing light flashes and streaks
- blurred vision
- reading or seeing difficulties (words disappear, seeing half an object, misty or foggy vision)
- difficulty hearing
- ringing in ears
- muscle weakness
- irregular heartbeats
- difficulty breathing
If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online [at Web Site] or by phone [1-800-332-1088].
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). Throw away any medication that is outdated or no longer needed. Talk to your pharmacist about the proper disposal of your medication.
In case of overdose, call your local poison control center at 1-800-222-1222. If the victim has collapsed or is not breathing, call local emergency services at 911.
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 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.
AHFS® Consumer Medication Information. © Copyright, The American Society of Health-System Pharmacists, Inc., 7272 Wisconsin Avenue, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.
Last Reviewed: September 1, 2010.