Chloroquine (Aralen) - Uses, Side Effects, and More

What are the most common side effects of chloroquine?

The most common side effects of chloroquine are listed below. Tell your health care provider if you have any of these side effects that bother you.

• Nausea or vomiting
• Diarrhea
• Stomach pain
• Headache

There may be other side effects of chloroquine that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088 (800-332-1088). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of chloroquine?

While less common, the most serious side effects of chloroquine are described below, along with what to do if they happen.

Severe Allergic Reactions. Chloroquine may cause allergic reactions, including a specific type of allergic reaction called DRESS. DRESS stands for Drug Reaction with Eosinophilia and Systemic Symptoms. It is also sometimes called multi-organ hypersensitivity. This is a reaction that can affect multiple parts of the body including your liver, kidneys, and heart. Stop taking the medicine and get help right away if you have any of the following symptoms of a serious allergic reaction.

• Breathing problems or wheezing
• Racing heart
• Fever or general ill feeling
• Swollen lymph nodes
• Swelling of the face, lips, mouth, tongue, or throat
• Shortness of breath, trouble swallowing, or throat tightness
• Swelling in your feet, ankles, or legs
• Itching, skin rash
• Bumps on the skin called hives that can be red, brown, or other colors depending on skin tone
• Nausea or vomiting
• Dizziness, feeling lightheaded, or fainting
• Stomach cramps
• Joint pain
• Dark-colored pee
• Yellowing of your skin or the whites of your eyes (also called jaundice)

Heart Problems. Chloroquine may cause certain heart problems, such as cardiomyopathy. This can sometimes lead to death. Call your health care provider right away if you have any of the following symptoms.

• Dizziness or feeling lightheaded
• Changes in your heart rate or rhythm, such as a fast or skipping heartbeat
• Fainting
• Shortness of breath or trouble breathing

Heart Rhythm Changes. Chloroquine may cause ventricular arrhythmias or a rare dangerous heart rhythm problem called QT prolongation and torsade de pointes. Some people have a higher risk for this, including people who are older, have other people in their family who have had these conditions, have low potassium or magnesium levels, or who take some medicines for other heart rhythm problems. Tell your health care provider right away if you faint or have changes in your heart rate or rhythm, such as a fast or skipping heartbeat.

Eye Problems. Chloroquine may cause damage to part of your eye called the retina. This can lead to permanent vision problems. The risk is increased in people taking chloroquine for a long time or at high doses. Your health care provider may recommend an eye examination before or while you take chloroquine. Stop taking chloroquine and call your health care provider if you have any vision changes or notice any of the following symptoms.

• Trouble seeing (especially in the dark)
• Trouble adjusting to changes in brightness (especially going from light to dark)

Severe Skin Reactions. Chloroquine can cause severe skin reactions called Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) that can lead to death if not treated. If you get a rash, stop taking chloroquine and call your health care provider right away. Get emergency help right away if you have any of the following symptoms of SJS or TEN.

• Painful red or purple skin that looks burned and peels off
• Flat red rash or blisters on your skin, mouth, nose, and genitals
• Red, painful, watery eyes

Kidney Damage. Kidney damage can happen when taking chloroquine. You may be at higher risk for this if you have a connective tissue disorder. Stop taking chloroquine and call your health care provider if you have any of the following symptoms of kidney damage.

• Reduced need to pee
• Swelling in your feet, ankles, or legs
• Weakness or unusual tiredness
• Difficulty catching your breath or chest pain/pressure
• Confusion
• Nausea
• Seizures

Blood Disorders. Chloroquine can cause blood disorders, such as agranulocytosis, aplastic anemia, hemolytic anemia, low platelet levels (thrombocytopenia), and low white blood cell levels (leukopenia). Stop taking chloroquine and get help right away if you have any of the following symptoms of blood disorders.

• Fever
• Shortness of breath
• Pale or yellowish skin
• Easy bruising or bleeding
• Frequent infection
• Unusual weakness or tiredness
• Dizziness, lightheadedness, or feeling like you are about to pass out
• Headache
• Fast or abnormal heartbeat

Muscle Problems. Chloroquine can cause muscle problems, including muscle pain, weakness, and tenderness, called myopathy. In some people, the muscle may break down (rhabdomyolysis), which can be serious and rarely lead to kidney damage and death. Stop taking chloroquine and get help right away if you have any of the following symptoms of myopathy or rhabdomyolysis.

• Unexplained muscle pain, weakness, or tenderness
• Low energy levels or feeling easily tired, especially with activity
• Dark-colored urine (pee)
• Fever
• Muscle cramps
• Stomach pain
• Nausea or vomiting

Nerve Problems. Nerves are the fibers that carry sensations from your body to the brain. Damage to nerves, called peripheral neuropathy, can happen in people who are taking chloroquine. Stop taking chloroquine and call your health care provider if you have pain, burning, tingling, numbness, or weakness in your arms, hands, legs, or feet.

Low Blood Sugar (Hypoglycemia). Chloroquine can cause low blood sugar, which can be serious and may lead to death. Follow any instructions from your health care provider about checking your blood sugar. Stop taking chloroquine and call your health care provider right away if you have any of the following symptoms of hypoglycemia.

• Headache
• Crankiness or anxiety 
• Hunger
• Dizziness or confusion
• Blurry vision
• Slurred speech
• Sweating
• Feeling jittery or shakiness
• Fast heartbeat
• Seizures

Movement Problems. Chloroquine may rarely cause involuntary movement problems, including shakiness, stiffness, or jerkiness. Call your health care provider right away if you have any unusual or uncontrolled movements.

Hearing Loss. Chloroquine may be associated with hearing loss, which is also called ototoxicity. Tell your health care provider right away if you have hearing loss or if you hear a ringing or roaring sound in your ears.