Hydroxychloroquine Side Effects

As of June 30, 2024, the overwhelming majority of hydroxychloroquine side effects reported to the U.S. Food and Drug Administration were classified by the agency as serious.

Since 1970, the FDA has received over 59,000 reports of adverse events associated with hydroxychloroquine and its brand-name form, Plaquenil.

Disclaimer: Reports sent to the FDA don’t necessarily mean the drug caused an adverse event. Consult a health care professional before stopping or changing medication.

Adverse events peaked sharply in 2020 and 2021 during the COVID-19 pandemic. Over 42% of all hydroxychloroquine adverse events were reported in those two years.

At the time, some people believed that the drug could protect them from COVID. Research has since found that hydroxychloroquine does not work as a treatment for COVID-19 nor prevent the virus, according to the Mayo Clinic.

The most commonly reported side effects of hydroxychloroquine are headache, diarrhea, nausea, stomach pain and dizziness.
Hydroxychloroquine is typically well-tolerated in healthy patients.

Most people who experience side effects find they improve as they adjust to the medication. The risk of side effects increases with a higher dose or long-term use. The Centers for Disease Control and Prevention recommends taking the medication with food to lessen the severity of gastrointestinal symptoms.

Most side effects associated with hydroxychloroquine only last a few days to a few weeks. In rare cases, however, patients may have long-term side effects. The risk increases for those who take hydroxychloroquine long-term for conditions such as lupus or arthritis.

Some patients may experience serious side effects, potentially affecting their heart, vision or liver. The risk increases in those who have underlying conditions, take certain medications or stay on a high dose of hydroxychloroquine for a long time.

Severe side effects are rare but require prompt medical treatment. Patients should seek emergency care or contact their doctor if they develop new or worsening symptoms.

Cardiomyopathy and Ventricular Arrhythmias

Long-term use of hydroxychloroquine can cause serious or fatal cases of cardiotoxicity. Patients with systemic lupus erythematosus seem to have a slightly increased risk, according to a 2021 review published in Rheumatology International. Symptoms range from structural heart abnormalities to QT prolongation, a type of heart rhythm abnormality.

Patients with existing QT prolongation or those who have risk factors such as cardiac disease, irregular heartbeat or low blood levels of magnesium or potassium should not take hydroxychloroquine. People already taking medications that may prolong the QT interval should also avoid hydroxychloroquine.

Ocular Toxicity

Retinal toxicity is the most studied eye-related side effect of hydroxychloroquine. Retinal toxicity causes lesions on the eye that affect vision and can lead to blindness. Lesions caught early may stop if patients discontinue the medication, but more advanced damage may be irreversible.
The prevalence of retinal toxicity is greater with prolonged hydroxychloroquine use. According to a study published in the Journal of Rheumatology International, estimates range from 0.5% to 2% but can surpass 3% after 20 years of continued treatment. More sensitive modern tests estimate the range to be closer to 2% in the first years of use to nearly 20% after 20 years of treatment.

Skin Reactions

The FDA-approved medication label warns patients on hydroxychloroquine to monitor for serious skin reactions.

The risk of these complications increases in patients who take medications that may induce dermatitis. Seek immediate medical attention if you develop itching, burning or blisters on the eyes, lips, skin or mouth.

Patients who have psoriatic arthritis may experience severe flare-ups while taking hydroxychloroquine, but others may benefit from the drug. Patient reactions have been mixed.

You should seek immediate medical attention if you experience any serious side effects, including symptoms of overdose. Overdose symptoms include slow or irregular heartbeat, dizziness, fainting, seizures, delirium and hallucinations. Attending all doctor appointments and undergoing the recommended testing is important to detect complications early.

Additionally, some patients may choose to stop taking hydroxychloroquine due to side effects. However, it’s important to follow a doctor or pharmacist’s instructions to gradually taper off the medication. Stopping abruptly can cause withdrawal flare-ups, especially for patients with preexisting conditions such as lupus.

During the peak of the COVID-19 pandemic, the FDA had authorized hydroxychloroquine as an emergency COVID-19 treatment only for patients who were involved in a drug study or could be closely monitored in a hospital.

However, there is little data that supports the efficacy of this treatment. On June 15, 2020, the FDA revoked their emergency authorization of hydroxychloroquine as a COVID-19 treatment.

Off-label use of hydroxychloroquine, such as using it to treat COVID-19, may increase the chances of heart rhythm irregularities that can lead to death.

Hydroxychloroquine has a higher risk factor for patients with a hypersensitivity to 4-aminoquinoline compounds. The drug can also interact with several others, including many common anti-seizure medications.

Patients who have a history of alcoholism or drug use should also communicate this to their doctor. While alcohol doesn’t directly interact with hydroxychloroquine, they are both metabolized through the liver and can cause gastrointestinal symptoms. Therefore, alcohol can exacerbate hydroxychloroquine side effects.

Editor Lindsay Donaldson contributed to this article.