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Aralen Hydrochloride Side Effects

Generic name: chloroquine

Medically reviewed by Last updated on Oct 10, 2022.

Note: This document contains side effect information about chloroquine. Some dosage forms listed on this page may not apply to the brand name Aralen Hydrochloride.

Applies to chloroquine: oral tablet.

Serious side effects

Along with its needed effects, chloroquine (the active ingredient contained in Aralen Hydrochloride) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking chloroquine:

Incidence not known

  • Anxiety
  • attempts at killing oneself
  • back, leg, or stomach pains
  • black, tarry stools
  • bleeding gums
  • blistering, peeling, or loosening of the skin
  • blood in the urine or stools
  • blurred or decreased vision
  • change in near or distance vision
  • chest discomfort or pain
  • chills
  • cold sweats
  • confusion
  • continuing ringing or buzzing or other unexplained noise in the ears
  • cough
  • dark urine
  • diarrhea
  • difficulty in focusing the eyes
  • difficulty with speaking
  • difficulty with swallowing
  • disturbed color perception
  • dizziness
  • dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
  • double vision
  • drooling
  • fast, slow, irregular, or pounding heartbeat
  • feeling that others are watching you or controlling your behavior
  • feeling that others can hear your thoughts
  • feeling, seeing, or hearing things that are not there
  • fever
  • general tiredness and weakness
  • halos around lights
  • headache
  • hearing loss
  • inability to move the eyes
  • increased blinking or spasms of the eyelid
  • joint or muscle pain
  • large, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, or sex organs
  • light-colored stools
  • loss of balance control
  • lower back or side pain
  • muscle trembling, jerking, or stiffness
  • muscular pain, tenderness, wasting, or weakness
  • night blindness
  • nausea
  • overbright appearance of lights
  • painful or difficult urination
  • pale skin
  • pinpoint red spots on the skin
  • puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
  • red skin lesions, often with a purple center
  • red, irritated eyes
  • restlessness
  • shuffling walk
  • skin rash, hives, or itching
  • sore throat
  • sores, ulcers, or white spots on the lips or in the mouth
  • sticking out of the tongue
  • stiffness of the limbs
  • sweating
  • swollen or painful glands
  • tightness in the chest
  • trouble breathing
  • tunnel vision
  • twitching, twisting, or uncontrolled repetitive movements of the tongue, lips, face, arms, or legs
  • uncontrolled movements, especially of the face, neck, and back
  • unusual bleeding or bruising
  • unusual tiredness or weakness
  • upper right abdominal or stomach pain
  • vomiting
  • yellow eyes and skin

Get emergency help immediately if any of the following symptoms of overdose occur while taking chloroquine:

Symptoms of overdose

  • Cold, clammy skin
  • decreased urine
  • drowsiness
  • dry mouth
  • fast, weak pulse
  • increased thirst
  • lightheadedness, dizziness, or fainting
  • loss of appetite
  • muscle pain or cramps
  • numbness or tingling in the hands, feet, or lips

Other side effects

Some side effects of chloroquine may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Incidence not known

  • Change in hair color
  • hair loss
  • increased sensitivity of the skin to sunlight
  • redness or other discoloration of the skin
  • severe sunburn
  • stomach cramps
  • trouble sleeping
  • weight loss

For Healthcare Professionals

Applies to chloroquine: compounding powder, injectable solution, oral tablet.


Retinopathy and irreversible retinal damage have been reported during long-term, high-dose therapy.

Maculopathy and macular degeneration have been reported and may be irreversible.

Irreversible retinopathy with retinal pigmentation changes (bull's eye appearance) and visual field defects (paracentral scotomas) have been reported in patients receiving long-term or high-dose 4-aminoquinoline therapy.[Ref]

Common (1% to 10%): Transient blurred vision

Rare (0.01% to 0.1%): Reversible corneal opacity, retinopathy, irreversible retinal damage

Frequency not reported: Retinal degeneration, macular defects of color vision, pigmentation, optic atrophy, scotomas, blindness, corneal opacity, pigmented deposits, vision blurred/difficulty focusing, accommodation disorder, diplopia, field defects, double vision, decreased visual acuity, color-vision defects, pigmentary retinopathy, corneal deposits, keratopathy, decreased corneal sensitivity, corneal edema

Postmarketing reports: Maculopathy, macular degeneration, visual disturbances (blurred vision, focusing/accommodation difficulty), nyctalopia, scotomatous vision with field defects of paracentral/pericentral ring types/typically temporal scotomas (e.g., difficulty in reading with words tending to disappear, seeing half an object, misty vision, fog before the eyes), reversible corneal opacities

4-aminoquinoline therapy:

-Postmarketing reports: Irreversible retinopathy with retinal pigmentation changes (bull's eye appearance), visual field defects (paracentral scotomas)[Ref]


Pruritus has been seen more commonly in Africans. The onset was generally 6 to 48 hours after the first dose and antihistamines did not always control the pruritus.

Pigmentation disorder (including bluish-black pigmentation of the nails and mucosa) has been reported with long-term use. Increased pigmentation of the skin and mucous membranes was generally of a bluish color was not always reversible on discontinuation.

Several cases of hypopigmentation of the skin have been reported. Most of the patients described were African or of African descent with dark skin who had been exposed to the sun. One was a Hispanic patient who developed vitiligo-like skin depigmentation after 1 month of therapy for cutaneous lupus erythematosus. The skin rapidly repigmented after this drug was discontinued.

At least 2 cases of exacerbation of psoriasis requiring hospitalization have been reported.[Ref]

Very common (10% or more): Pruritus

Common (1% to 10%): Skin eruptions, urticaria

Uncommon (0.1% to 1%): Alopecia, pigmentation disorder (including bluish-black pigmentation of the nails and mucosa)

Rare (0.01% to 0.1%): Exacerbation/precipitation of psoriasis, erythema multiforme, toxic epidermal necrolysis, Stevens-Johnson syndrome

Very rare (less than 0.01%): Exfoliative dermatitis, similar desquamation-type events

Frequency not reported: Macular/urticarial/purpuric skin eruptions, lichenoid keratosis, acute generalized exanthematous pustulosis, depigmentation, rashes

Postmarketing reports: Erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis, exfoliative dermatitis, pleomorphic skin eruptions, lichen planus-like eruptions, hair loss, skin/mucosal pigmentary changes, pruritus, drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome, bleaching of hair pigment, photosensitivity reaction[Ref]


Very common (10% or more): Gastrointestinal disturbances (e.g., nausea, vomiting, diarrhea)

Frequency not reported: Gastrointestinal disorder, abdominal pain

Postmarketing reports: Nausea, vomiting, diarrhea, abdominal cramps[Ref]

Nervous system

Very common (10% or more): Headache

Uncommon (0.1% to 1%): Neuropathy, ototoxicity (e.g., tinnitus, hypoacusis, deafness neurosensory/nerve deafness)

Rare (0.01% to 0.1%): Convulsions, polyneuropathy

Frequency not reported: Visual field defects, neuromyopathy, convulsive seizures, polyneuritis, dizziness, nonconvulsive status epilepticus/seizures, development of extrapyramidal rigidity

Postmarketing reports: Convulsions, mild headache (transient), polyneuropathy, acute extrapyramidal disorders (e.g., dystonia, dyskinesia, tongue protrusion, torticollis), sensorimotor disorders, depression of tendon reflexes, abnormal nerve conduction, nerve type deafness, tinnitus, reduced hearing (in patients with preexisting auditory damage)[Ref]


Mania has been reported in a patient taking this drug for malarial prophylaxis. These symptoms resolved after discontinuation and recurred with rechallenge.[Ref]

Very common (10% or more): Insomnia

Common (1% to 10%): Depression

Rare (0.01% to 0.1%): Hallucinations, psychiatric disorders (e.g., anxiety, agitation, confusion, hallucinations, delirium)

Frequency not reported: Mania, other psychiatric and neurologic disturbances, paranoia

Postmarketing reports: Neuropsychiatric changes, psychotic disorder/psychosis, delirium, anxiety, agitation, insomnia, confusion, hallucinations, personality changes, depression, suicidal behavior[Ref]


Common (1% to 10%): Hypersensitivity/allergic reaction (including urticaria, angioedema, vasculitis), anaphylactic reactions

Frequency not reported: Anaphylactoid reaction

Postmarketing reports: Anaphylactic reaction (including angioedema)


Uncommon (0.1% to 1%): Cardiomyopathy

Rare (0.01% to 0.1%): Cardiac arrhythmias (including QT prolongation, torsade de pointes, ventricular tachycardia, ventricular fibrillation)

Frequency not reported: Atrioventricular block, cardiac hypertrophy, restrictive cardiomyopathy, congestive heart failure, complete heart block

Postmarketing reports: Hypotension, ECG changes (particularly inversion/depression of T-wave with widening of QRS complex), cardiomyopathy (sometimes resulting in cardiac failure; some with fatal outcome), cardiac arrhythmias, conduction disorders (e.g., bundle branch block/atrioventricular block), QT interval prolongation, torsade de pointes, ventricular tachycardia, ventricular fibrillation[Ref]

Cardiomyopathy has been reported during long-term therapy at high doses.

Cardiac arrhythmias (including QT prolongation, torsade de pointes, ventricular tachycardia, and ventricular fibrillation) have been reported with therapeutic doses as well as with overdose; the risk was greater when high doses were administered. Fatal cases have been reported.

ECG changes have been reported at high doses. ECG changes observed included prolongation of the QRS interval and, rarely, complete heart block. Biopsies of cardiac tissue characteristically showed no inflammatory infiltrates, severe vacuolation, and myocytes containing myeloid bodies and lysosomes.

Conduction disorders (e.g., bundle branch block/atrioventricular block) have been reported with therapeutic doses as well as with overdose.[Ref]


Uncommon (0.1% to 1%): Myopathy

Frequency not reported: Myasthenia-like syndromes

Postmarketing reports: Skeletal muscle myopathy/neuromyopathy (leading to progressive weakness, atrophy of proximal muscle groups)[Ref]


Rare (0.01% to 0.1%): Bone marrow failure/depression (including aplastic anemia, agranulocytosis, pancytopenia, thrombocytopenia, neutropenia)

Postmarketing reports: Pancytopenia, aplastic anemia, reversible agranulocytosis, thrombocytopenia, neutropenia, hemolytic anemia (in glucose-6-phosphate dehydrogenase deficient patients)[Ref]


Rare (0.01% to 0.1%): Changes in liver function (including hepatitis, abnormal liver function tests)

Frequency not reported: Hepatotoxicity (in a patient with porphyria cutanea tarda)

Postmarketing reports: Hepatitis, elevated liver enzymes[Ref]


Frequency not reported: Hypokalemia (associated with acute ingestion)

Postmarketing reports: Anorexia, hypoglycemia[Ref]

The usefulness of hypokalemia as an indicator in the evaluation of chloroquine toxicity was studied in a retrospective series of 191 acute chloroquine poisonings. Results indicated that the risk of severe poisoning and death were proportional to the degree of hypokalemia.[Ref]


Frequency not reported: Diffuse parenchymal lung disease[Ref]

Frequently asked questions

More about Aralen Hydrochloride (chloroquine)

Patient resources

Other brands

Aralen Phosphate

Professional resources

Related treatment guides


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Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.