What it's for (Indications)
- Hydroxychloroquine sulphate is indicated for the treatment of uncomplicated malaria due to *Plasmodium falciparum* (not effective against chloroquine-resistant strains) and other susceptible species, as well as for the prophylaxis of malaria in travelers to areas where chloroquine-sensitive *Plasmodium* strains are prevalent.
- Beyond its antimalarial applications, it is widely utilized in rheumatology.
- Its immunomodulatory properties make it an essential therapeutic agent for the long-term treatment of chronic autoimmune diseases, specifically systemic lupus erythematosus (SLE), where it helps manage cutaneous manifestations, arthralgias, and fatigue, and rheumatoid arthritis (RA) in adults, often used as a disease-modifying antirheumatic drug (DMARD) to reduce joint inflammation and prevent joint damage.
- It is also sometimes used in certain pediatric rheumatologic conditions.
Dosage Information
| Type | Guideline |
|---|---|
| Standard | The dosage of hydroxychloroquine sulphate varies significantly based on the indication, patient weight, and individual response, and must always be determined by a qualified healthcare professional. For adult patients with rheumatoid arthritis, a common initial dose is 400 mg once daily, which may be reduced to 200 mg daily or 400 mg every other day once an adequate response is achieved, not exceeding 5.0 mg/kg actual body weight per day. In systemic lupus erythematosus, doses typically range from 200 mg to 400 mg daily, also generally not exceeding 5.0 mg/kg actual body weight per day. For acute malaria, a standard adult regimen might involve an initial dose of 800 mg, followed by 400 mg six hours later, and then 400 mg daily for the next two days. For malaria prophylaxis, 400 mg once weekly, starting two weeks prior to exposure and continuing for four weeks after leaving the endemic area. Pediatric dosages are weight-based and require careful calculation. It is crucial to use the lowest effective dose to minimize the risk of adverse effects, particularly ocular toxicity. The medication should be taken with food or milk to minimize gastrointestinal upset. |
Safety & Warnings
Common Side Effects
- Hydroxychloroquine sulphate can be associated with a range of side effects, varying in severity and frequency.
- Common adverse reactions often involve the gastrointestinal system, including nausea, vomiting, diarrhea, and abdominal cramps, which can sometimes be alleviated by taking the medication with food or milk.
- Dermatologic manifestations may include skin rash, pruritus, hyperpigmentation, alopecia, and, less frequently, serious bullous eruptions.
- Neurologic effects can encompass headache, dizziness, tinnitus, and, rarely, seizures or neuropsychiatric disturbances such as mood changes, anxiety, or psychosis.
- Ocular side effects, while less common, are of significant clinical concern due to the potential for irreversible retinopathy, including macular damage, which can lead to permanent vision loss; this is why regular ophthalmologic monitoring is critical.
- Cardiac adverse events, though rare, can be serious, including QT interval prolongation, Torsades de Pointes, and cardiomyopathy.
- Other less common side effects include musculoskeletal weakness, blood dyscrasias (e.
- g.
- , anemia, leukopenia, thrombocytopenia, aplastic anemia), and hepatic dysfunction, including elevated liver enzymes.
Serious Warnings
- Black Box Warning: **SERIOUS WARNINGS: POTENTIAL FOR IRREVERSIBLE RETINOPATHY AND CARDIAC TOXICITY** Hydroxychloroquine sulphate does not carry a formal FDA Black Box Warning. However, it is imperative for healthcare providers and patients to be fully aware of several serious risks associated with its use, warranting close monitoring and careful patient selection. **Ocular Toxicity (Retinopathy):** Prolonged treatment with hydroxychloroquine, especially at higher doses or in patients with renal impairment, can lead to irreversible retinopathy, including maculopathy, which may result in permanent vision loss. Early symptoms may include difficulty reading, blurring of vision, or abnormal color vision. All patients should undergo a thorough ophthalmologic examination at baseline, including best-corrected visual acuity, automated visual fields (central 10 degrees), and spectral domain optical coherence tomography (SD-OCT). Subsequent examinations should be performed annually after five years of use, or earlier and more frequently if risk factors are present (e.g., daily dose exceeding 5.0 mg/kg actual body weight, renal insufficiency, concomitant tamoxifen therapy, pre-existing retinal or macular disease, advanced age). If visual disturbances or retinal changes indicative of toxicity occur, discontinue the drug immediately, as retinal changes and visual impairment may progress even after cessation of therapy. **Cardiac Toxicity:** Rare but serious and potentially fatal cardiac adverse reactions have been reported with hydroxychloroquine, including QT interval prolongation, Torsades de Pointes (TdP), and cardiomyopathy. Patients with pre-existing cardiac disease, electrolyte disturbances, or those concurrently taking other QT-prolonging medications are at increased risk. ECG monitoring may be warranted, particularly in patients with risk factors for QT prolongation. Cases of cardiomyopathy, sometimes leading to cardiac failure and death, have also been reported. Patients should be advised to seek immediate medical attention if they experience symptoms such as palpitations, dizziness, syncope, or chest pain. Discontinue hydroxychloroquine if cardiotoxicity is suspected. Patients should be carefully evaluated for risk factors prior to initiation and periodically throughout treatment.
- Patients receiving hydroxychloroquine sulphate require careful monitoring to detect potential adverse effects.
- **Ocular Toxicity:** Retinopathy, particularly maculopathy, is a serious and potentially irreversible adverse effect, especially with prolonged use or high cumulative doses.
- All patients should undergo a thorough ophthalmologic examination at baseline and at least annually thereafter, with increased frequency in high-risk individuals (e.
- g.
- , daily dose > 5.
- 0 mg/kg actual body weight, renal impairment, concomitant tamoxifen use, pre-existing retinal disease, or advanced age).
- **Cardiac Toxicity:** Hydroxychloroquine can prolong the QT interval, increasing the risk of life-threatening arrhythmias, including Torsades de Pointes, especially in patients with pre-existing cardiac conditions, electrolyte imbalances, or concomitant use of other QT-prolonging drugs.
- Cardiomyopathy, although rare, has also been reported.
- **Hypoglycemia:** Severe hypoglycemia, including loss of consciousness, has been reported, sometimes without antidiabetic therapy.
- Blood glucose levels should be monitored, especially in diabetic patients.
- **Neuropsychiatric Events:** Rare but serious neuropsychiatric reactions such as psychosis, suicidal ideation, and behavioral changes have been observed.
- **Dermatologic Reactions:** Exacerbation of psoriasis or porphyria cutanea tarda may occur.
- **Hematologic Effects:** Aplastic anemia, agranulocytosis, leukopenia, and thrombocytopenia have been reported; therefore, periodic monitoring of complete blood counts is advised.
- Caution is also warranted in patients with G6PD deficiency due to the risk of hemolysis.
- Use in pregnancy and lactation should be carefully considered, weighing potential benefits against risks.
How it Works (Mechanism of Action)
Hydroxychloroquine sulphate exerts its therapeutic effects through a complex and multifaceted mechanism, acting as both an antimalarial and an immunomodulatory agent. As an antimalarial, it concentrates within the acidic food vacuoles of susceptible *Plasmodium* species. Here, it is believed to interfere with the parasite's ability to detoxify heme, a byproduct of hemoglobin digestion, by increasing the pH within the vacuole and inhibiting the formation of hemozoin. This leads to the accumulation of toxic heme and ultimately parasite death. In autoimmune conditions such as rheumatoid arthritis and systemic lupus erythematosus, its immunomodulatory actions are attributed to several mechanisms. It can interfere with antigen presentation by increasing the pH in endosomes, thus reducing the expression of major histocompatibility complex (MHC) class II molecules and altering the processing of autoantigens. Furthermore, it inhibits the activation of Toll-like receptors (TLRs), particularly TLR7 and TLR9, which are involved in the recognition of nucleic acids and play a role in the pathogenesis of SLE. Hydroxychloroquine also stabilizes lysosomal membranes, reduces cytokine production (e.g., IL-1, IL-6, TNF-alpha), inhibits complement-mediated immune responses, and interferes with cellular signaling pathways, thereby dampening overall inflammatory and autoimmune activity.