Hydroxychloroquine Side Effects and Risks

Immediate and Short-Term Side Effects

The American Thoracic Society recommends monitoring for gastrointestinal disturbances, including nausea, vomiting, diarrhea, and stomach discomfort, as the most frequently reported side effect of hydroxychloroquine 1, 2
Headache occurs commonly with oral hydroxychloroquine therapy, according to the American College of Chest Physicians 1, 2
Visual disturbances, including blurred vision and diplopia, may develop but typically reverse with discontinuation of hydroxychloroquine, as reported by the American Academy of Ophthalmology 1, 2
Pruritus and urticaria (itching and hives) are reported side effects of hydroxychloroquine, according to the American College of Chest Physicians 1, 2
Dizziness may occur as a side effect of hydroxychloroquine, as noted by the Centers for Disease Control and Prevention 3

The National Comprehensive Cancer Network recommends heightened vigilance for retinal toxicity in patients with pre-existing eye conditions or those on prolonged hydroxychloroquine therapy, as retinal toxicity is the most serious dose-limiting adverse effect 4, 5
Irreversible retinopathy can result from hydroxychloroquine binding to melanin in the retinal pigment epithelium, causing vision loss, according to the American Academy of Ophthalmology 4, 5
Vortex keratopathy (corneal deposits) can occur in patients taking hydroxychloroquine, as reported by the National Comprehensive Cancer Network 4, 5
Mandatory ophthalmologic assessment every 6 to 12 months is required for all patients on antimalarial therapy, including hydroxychloroquine, as recommended by the American College of Chest Physicians 1, 2, 6, 7

The American Heart Association notes that patients with pre-existing cardiac conditions face significant risks, as hydroxychloroquine can cause multiple cardiac complications, including cardiac conduction abnormalities and heart block 1, 2
Cardiovascular effects may progress through vasodilation, hypotension, suppressed myocardial function, cardiac arrhythmia, and cardiac arrest, particularly with parenteral administration or overdose of hydroxychloroquine, as reported by the American College of Chest Physicians 1, 2
Yearly ECGs are performed by some clinicians in asymptomatic patients, especially those on long-term hydroxychloroquine therapy, as recommended by the American College of Chest Physicians 1, 2

The American College of Chest Physicians reports that toxic myopathy, cardiomyopathy, and peripheral neuropathy can occur with prolonged hydroxychloroquine therapy but improve if the drug is promptly withdrawn 1, 2, 6
CNS effects may progress through confusion, convulsions, and coma (more common in overdose) in patients taking hydroxychloroquine, as noted by the American College of Chest Physicians 1, 2
Irreversible ototoxicity can develop if oral doses of hydroxychloroquine exceed 250 mg/day, according to the American College of Chest Physicians 1, 2, 6
Chloroquine may interfere with intradermal rabies vaccine antibody response, as reported by the Centers for Disease Control and Prevention 3
Hydroxychloroquine may exacerbate psoriasis, as noted by the Centers for Disease Control and Prevention 3

The American College of Rheumatology recommends that daily doses of hydroxychloroquine should not exceed 5 mg/kg of actual body weight to minimize the risk of retinal toxicity 8, 9
Patients with renal impairment are at higher risk of retinal toxicity due to decreased drug excretion, and concomitant use of tamoxifen also increases this risk 8, 9
The risk of retinopathy develops in fewer than 2% of patients with usage up to 10 years at doses ≤5.0 mg/kg actual body weight 8, 9
Higher daily doses increase the risk to approximately 10% after 10 years, with continued rise in risk with longer duration 8, 9

The American Heart Association recommends avoiding hydroxychloroquine in patients with congenital or acquired QT prolongation, cardiac disease, or proarrhythmic conditions due to the risk of cardiotoxicity 10, 11
Concomitant use of ondansetron, domperidone, and citalopram is contraindicated due to the risk of torsades de pointes 10, 11
Many tyrosine kinase inhibitors and other medications increase the QT interval and should be used with caution 10, 11

The National Kidney Foundation recommends that patients with renal insufficiency require lower doses and closer monitoring of hydroxychloroquine due to increased systemic levels 8, 9
Nephrotoxicity and hepatotoxicity require dose adjustment with reduced glomerular filtration rate or transaminase elevation 10

The American College of Rheumatology recommends that all women with systemic lupus erythematosus should take hydroxychloroquine during pregnancy if possible, and if already taking it, strongly continue during pregnancy 12
Hydroxychloroquine is present in human milk at low levels, but no adverse reactions have been reported in breastfed infants 12

The American College of Rheumatology recommends not stopping hydroxychloroquine casually for borderline findings, as the goal is to safely maintain use of this valuable medication for as long as possible 8, 9, 13

Hydroxychloroquine binds to melanin in inner‑ear structures, leading to damage of cochlear and vestibular tissues and producing audiovestibular symptoms such as tinnitus and hearing loss. This mechanism parallels its known retinal toxicity. (Clinical Microbiology and Infection, 2024) 14

The antimalarial regimen recommended in guidelines—800 mg loading dose followed by 400 mg at 6 h, 24 h, and 48 h—represents the standard dosing for short‑term use; higher or prolonged dosing regimens are associated with a substantially greater risk of ototoxicity. (Clinical Microbiology and Infection, 2024) 14