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Medical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice.
Other
Hydroxychloroquine sulfate is an antimalarial and disease-modifying antirheumatic drug (DMARD) used to treat systemic lupus erythematosus, rheumatoid arthritis, and malaria. It works by modulating immune responses and interfering with parasitic lysosomal function.
Name
Hydroxychloroquine
Raw Name
HYDROXYCHLOROQUINE SULFATE
Category
Other
Salt Form
Sulfate
Drug Count
4
Variant Count
56
Last Verified
February 17, 2026
RxCUI
979092, 1119312, 2569281, 2569283, 979094, 2665282, 2665284
UNII
8Q2869CNVH
About Hydroxychloroquine
Hydroxychloroquine sulfate is an antimalarial and disease-modifying antirheumatic drug (DMARD) used to treat systemic lupus erythematosus, rheumatoid arthritis, and malaria. It works by modulating immune responses and interfering with parasitic lysosomal function.
Detailed information about Hydroxychloroquine
References used for this content
This page is for informational purposes only and does not replace medical advice. Consult a qualified healthcare professional before using any medication containing Hydroxychloroquine.
Hydroxychloroquine sulfate is a long-standing pharmacological agent that belongs to the class of medications known as 4-aminoquinolines. Originally developed as an alternative to chloroquine for the prevention and treatment of malaria (a disease caused by parasites that enter the body through the bite of infected mosquitoes), its therapeutic scope has expanded significantly over the decades. Today, it is more commonly recognized as a Disease-Modifying Antirheumatic Drug (DMARD). This classification means it does not merely treat the symptoms of autoimmune diseases but can actually modify the course of the disease by suppressing the overactive immune response that leads to tissue damage.
According to the FDA-approved labeling, Hydroxychloroquine was first approved in the United States in 1955. It has since become a cornerstone in the management of chronic autoimmune conditions, specifically Systemic Lupus Erythematosus (SLE) and Rheumatoid Arthritis (RA). In the context of SLE, it is often referred to as the 'insurance policy' for patients, as clinical data suggests it can significantly reduce the frequency of disease flares and improve long-term survival rates. While it is structurally related to chloroquine, hydroxychloroquine is generally considered to have a more favorable safety profile, particularly regarding ocular (eye-related) toxicity, though strict monitoring remains mandatory.
The mechanism of action for Hydroxychloroquine is multifaceted and involves several cellular pathways, though it is not yet fully understood in every clinical context. At the molecular level, Hydroxychloroquine is a 'lysosomotropic' agent, meaning it accumulates within the lysosomes (the waste-disposal centers of the cell). By increasing the pH (alkalinity) within these acidic compartments, the drug interferes with the cell's ability to process proteins and perform normal signaling functions.
In autoimmune diseases like lupus and rheumatoid arthritis, Hydroxychloroquine works by:
In its antimalarial capacity, the drug interferes with the parasite's ability to break down hemoglobin. As the malaria parasite digests the host's red blood cells, it releases toxic 'heme.' Hydroxychloroquine prevents the parasite from converting this toxic heme into non-toxic hemozoin, effectively poisoning the parasite from within.
Understanding how the body processes Hydroxychloroquine is vital for maintaining therapeutic levels while avoiding toxicity. The drug is characterized by an exceptionally long half-life and a vast volume of distribution.
Healthcare providers typically prescribe Hydroxychloroquine for the following FDA-approved indications:
Off-label uses, which your doctor may discuss, include the treatment of Sjogren’s syndrome, Porphyria Cutanea Tarda, and certain types of skin-related inflammatory conditions.
Hydroxychloroquine is primarily available in the following form:
Generic versions are widely available and are therapeutically equivalent to the brand-name versions. Tablets are typically film-coated to mask a bitter taste and facilitate swallowing.
> Important: Only your healthcare provider can determine if Hydroxychloroquine is right for your specific condition. The information provided here is for educational purposes and should not replace professional medical advice.
Dosage for Hydroxychloroquine is highly individualized based on the patient's total body weight, the condition being treated, and the risk of ocular toxicity. Healthcare providers aim to use the lowest effective dose.
Hydroxychloroquine is approved for use in children for malaria and certain autoimmune conditions, but dosing must be calculated strictly by a pediatrician based on body weight.
In patients with decreased kidney function (low GFR), Hydroxychloroquine may accumulate in the body more rapidly. Your doctor may reduce the dose or increase the interval between doses to prevent toxicity.
Since the drug is partially metabolized by the liver, patients with significant liver disease or those taking other hepatotoxic drugs may require closer monitoring and potential dose reductions.
Geriatric patients are more likely to have decreased renal and hepatic function. Clinical guidelines suggest starting at the lower end of the dosing range and monitoring kidney function closely.
To ensure maximum efficacy and safety, follow these administration guidelines:
If you miss a dose, take it as soon as you remember. However, if it is almost time for your next scheduled dose, skip the missed dose and return to your regular schedule. Do not double the dose to catch up, as this increases the risk of toxicity.
An overdose of Hydroxychloroquine is a medical emergency. Symptoms can appear within 30 minutes and include:
In case of suspected overdose, call 911 or your local emergency services immediately. Emergency treatment often involves gastric lavage (stomach pumping) and the administration of activated charcoal.
> Important: Follow your healthcare provider's dosing instructions exactly. Do not adjust your dose or stop taking the medication without first consulting your medical team.
Many patients starting Hydroxychloroquine experience mild side effects as their body adjusts to the medication. These are typically dose-dependent and may include:
While Hydroxychloroquine is generally safe, it can cause severe complications in some patients. Stop taking the medication and contact your doctor immediately if you notice:
> Warning: Stop taking Hydroxychloroquine and call your doctor immediately if you experience any of these serious symptoms.
With prolonged use (typically over 5 years), the risk of Retinal Toxicity increases significantly. The American Academy of Ophthalmology (AAO) notes that the risk is low (less than 1%) for the first five years but can rise to 20% after 20 years of use. Another long-term concern is Neuromyopathy, a condition affecting both the nerves and muscles, leading to progressive weakness and diminished deep tendon reflexes. Regular physical exams and eye screenings are essential for patients on long-term therapy.
As of 2024, the FDA has not issued a specific Black Box Warning for Hydroxychloroquine. However, the agency has issued several Drug Safety Communications, particularly regarding the risk of serious heart rhythm problems (QT prolongation) when used in combination with other medications like azithromycin. Patients with pre-existing heart conditions or those taking other medications that affect heart rhythm must be monitored with periodic Electrocardiograms (ECGs).
Report any unusual symptoms to your healthcare provider promptly. Early detection of side effects is key to preventing long-term complications.
Hydroxychloroquine is a potent medication that requires careful medical supervision. It is not a 'quick fix' and often requires several weeks or months to reach full therapeutic effect. Patients must be aware that the drug remains in the body for a very long time (months) even after the last dose is taken. This means that side effects or interactions can potentially occur long after discontinuation.
No FDA black box warnings currently exist for Hydroxychloroquine. However, the FDA emphasizes that this drug is NOT approved for the treatment of COVID-19 outside of clinical trials or hospital settings, due to the risk of heart rhythm disturbances.
To ensure patient safety, healthcare providers typically order the following tests:
Hydroxychloroquine may cause blurred vision, dizziness, or lightheadedness in some patients. Do not drive or operate heavy machinery until you know how the medication affects you. If you notice any changes in your vision, stop these activities immediately and contact your doctor.
While there is no direct 'contraindication' for alcohol, it is generally advised to limit alcohol consumption while taking Hydroxychloroquine. Alcohol can increase the risk of liver strain and may exacerbate gastrointestinal side effects like nausea or stomach upset.
Do not stop taking Hydroxychloroquine abruptly without consulting your doctor, especially if you are taking it for lupus or rheumatoid arthritis. Stopping the medication can lead to a severe 'flare' or rebound of your autoimmune symptoms. There is no known 'withdrawal syndrome' in the traditional sense, but the return of underlying disease symptoms can be debilitating.
> Important: Discuss all your medical conditions, especially any history of heart, liver, kidney, or eye disease, with your healthcare provider before starting Hydroxychloroquine.
While few drugs are strictly 'contraindicated,' certain combinations are avoided due to the extreme risk of heart rhythm failure.
Hydroxychloroquine does not typically interfere with standard urine or blood chemistry panels, but it may occasionally cause false results on certain specialized protein tests or blood counts if the patient has G6PD deficiency.
Mechanism of Interactions:
Most interactions occur through one of three pathways:
> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking. Keep an updated list of your medications to share at every medical appointment.
There are specific scenarios where Hydroxychloroquine must NEVER be used because the risks far outweigh any potential benefits:
In these cases, a healthcare provider will perform a careful risk-benefit analysis:
Patients who are allergic to Chloroquine are almost certainly cross-sensitive to Hydroxychloroquine. There is also a theoretical risk of cross-sensitivity with other quinine derivatives used for leg cramps or in tonic water, though this is less common. Always inform your doctor of any 'quinine' related allergies.
> Important: Your healthcare provider will evaluate your complete medical history, including any genetic predispositions, before prescribing Hydroxychloroquine.
Hydroxychloroquine is a complex topic regarding pregnancy. It is classified by the FDA as a Category C medication (under the old system), but modern data from the American College of Rheumatology (ACR) suggests that for many women with lupus, the benefits of staying on the drug outweigh the risks.
Hydroxychloroquine is excreted into human breast milk in very small amounts (less than 2% of the maternal dose). The World Health Organization (WHO) and the American Academy of Pediatrics generally consider it compatible with breastfeeding, as the amount the infant receives is significantly lower than the dose used to treat pediatric malaria. No adverse effects on nursing infants have been documented in clinical literature, though monitoring for infant skin rashes is advised.
As noted in the dosage section, children are extremely sensitive to this drug. It is approved for the treatment of malaria in children of all ages, but the dose must be precisely calculated by weight. It is NOT recommended for long-term use in children for juvenile idiopathic arthritis (JIA) due to the risk of permanent vision damage and interference with growth if toxicity occurs.
In patients over age 65, the primary concern is the natural decline in kidney function (GFR). Since Hydroxychloroquine is partially excreted by the kidneys, the risk of toxic accumulation is higher. Geriatric patients also have a higher baseline risk of age-related macular degeneration (AMD), which can complicate the monitoring of drug-induced retinopathy. Doctors often perform more frequent eye exams for this age group.
For patients with a Creatinine Clearance (CrCl) of less than 30 mL/min, a dose reduction of 50% is often recommended. The drug is not significantly removed by hemodialysis or peritoneal dialysis, so 'booster' doses after dialysis are not required.
Patients with Child-Pugh Class B or C (moderate to severe liver disease) require cautious dosing. The liver is responsible for metabolizing the drug into its active and inactive forms; failure to do so can lead to unpredictable plasma levels and increased side effects.
> Important: Special populations require individualized medical assessment and frequent laboratory monitoring to ensure safety.
Hydroxychloroquine acts as a weak base that concentrates in the acidic organelles of cells, particularly lysosomes. By increasing the intralysosomal pH, it inhibits the activity of acid proteases and interferes with the glycosylation of proteins. In the immune system, this leads to the inhibition of Toll-like Receptor (TLR) signaling. TLRs are proteins that recognize 'danger signals' from pathogens or damaged cells; by blocking them, Hydroxychloroquine prevents the activation of the innate immune system and the subsequent 'cytokine storm' seen in autoimmune flares.
The onset of action for Hydroxychloroquine is slow. In rheumatoid arthritis, patients may not notice a significant reduction in joint swelling for 4 to 12 weeks. The duration of effect is exceptionally long due to its tissue binding; the drug can be detected in the urine for months after therapy is stopped. There is no evidence of the development of pharmacological tolerance (where the drug loses effectiveness over time) for its autoimmune indications.
| Parameter | Value |
|---|---|
| Bioavailability | 67% - 74% |
| Protein Binding | 45% (mainly to albumin) |
| Half-life | 40 - 50 Days |
| Tmax | 2 - 4 Hours |
| Metabolism | Hepatic (CYP2D6, CYP3A4) |
| Excretion | Renal (40-50%), Fecal (25%) |
Hydroxychloroquine is classified as an Antimalarial and a Disease-Modifying Antirheumatic Drug (DMARD). It is related to Chloroquine and Quinine. Within the DMARD category, it is considered a 'non-biologic' DMARD, often used as first-line therapy for mild to moderate disease or as an adjunct to biologic therapies.
Medications containing this ingredient
Common questions about Hydroxychloroquine
Hydroxychloroquine is primarily used to treat autoimmune conditions such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). It is also an effective medication for the prevention and treatment of certain types of malaria. In lupus patients, it helps prevent organ damage and reduces the frequency of disease flares. For those with rheumatoid arthritis, it reduces joint pain and swelling. Your doctor may also prescribe it off-label for other inflammatory conditions like Sjogren's syndrome.
The most common side effects reported by patients are gastrointestinal in nature, including nausea, stomach cramps, and occasional diarrhea. Many people also experience mild headaches or dizziness when they first start the medication. These symptoms often improve if the tablet is taken with a full meal or a glass of milk. Skin itching and a temporary loss of appetite are also relatively common. Most of these effects are mild and tend to diminish as your body adjusts to the drug.
There is no direct, dangerous interaction between alcohol and Hydroxychloroquine, but moderation is strongly advised. Both alcohol and Hydroxychloroquine are processed by the liver, so excessive drinking could potentially increase the risk of liver strain. Additionally, alcohol can worsen the stomach upset and dizziness that some patients experience while taking this medication. It is best to discuss your alcohol consumption habits with your healthcare provider to ensure it is safe for your specific health profile.
Hydroxychloroquine is often continued during pregnancy for women with systemic lupus erythematosus because the risk of a disease flare is usually greater than the risk of the drug itself. While the medication does cross the placenta, large clinical studies have not found a significantly increased risk of birth defects. The American College of Rheumatology generally considers it one of the safer DMARDs for use during pregnancy. However, you must have a detailed discussion with your rheumatologist and obstetrician to weigh the specific risks and benefits for your situation.
Hydroxychloroquine is a slow-acting medication and does not provide immediate relief of symptoms. For conditions like rheumatoid arthritis or lupus, it typically takes 4 to 12 weeks of consistent use before you notice a significant improvement in joint pain or skin rashes. In some cases, the full therapeutic benefit may not be realized for up to six months. Because of this delay, doctors often prescribe other faster-acting medications, like NSAIDs or corticosteroids, to manage symptoms during the initial phase of treatment.
You should not stop taking Hydroxychloroquine suddenly without consulting your healthcare provider. For patients with lupus or arthritis, abrupt discontinuation can lead to a significant 'flare-up' of symptoms, which may be more severe than the original condition. While the drug does not cause a physical withdrawal syndrome like opioids do, its long half-life means that stopping it will cause a slow decline in blood levels, eventually leading to a loss of disease control. Your doctor will help you decide if and how to taper the medication safely.
If you miss a dose, take it as soon as you remember, provided it is not too close to your next scheduled dose. If it is almost time for your next dose, simply skip the missed one and continue with your regular schedule. Never take two doses at once to make up for a missed one, as this can increase the risk of side effects or toxicity. Because Hydroxychloroquine stays in your system for a very long time, a single missed dose is unlikely to cause an immediate flare of your symptoms.
Weight gain is not a typical side effect of Hydroxychloroquine; in fact, some patients report a slight decrease in weight due to a loss of appetite or mild nausea when starting the drug. If you experience significant weight gain while taking Hydroxychloroquine, it may be due to other medications often prescribed alongside it, such as prednisone (a corticosteroid). If you notice sudden swelling or rapid weight gain, contact your doctor, as this could be a sign of heart or kidney issues rather than simple fat gain.
Hydroxychloroquine can interact with several other drugs, so it is vital to provide your doctor with a complete list of your current medications. It can increase the levels of digoxin (a heart medicine) and may increase the risk of low blood sugar if taken with insulin or diabetes pills. You should also avoid taking antacids or heartburn medications at the same time as Hydroxychloroquine, as they can prevent the drug from being absorbed. Always separate antacids and Hydroxychloroquine by at least four hours to ensure the drug works correctly.
Yes, Hydroxychloroquine sulfate is widely available as a generic medication and is significantly less expensive than the brand-name version, Plaquenil. Generic versions are required by the FDA to have the same active ingredient, strength, dosage form, and route of administration as the brand-name drug. Most insurance plans cover the generic version. Whether you take the brand or the generic, the clinical effects and the requirement for regular eye examinations remain exactly the same.