Overview
Hydroxychloroquine is a 4-aminoquinoline antimalarial and immunomodulatory agent. It is used for the treatment and prophylaxis of malaria and for autoimmune disorders such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA).
Mechanism of Action
Hydroxychloroquine accumulates in lysosomes and increases the intralysosomal pH, interfering with lysosomal activity and antigen presentation. In autoimmune diseases, it: Inhibits toll-like receptor (TLR) signaling Reduces dendritic cell activation Decreases production of inflammatory cytokines In malaria, it: Inhibits heme polymerase activity in Plasmodium species Causes accumulation of toxic heme within the parasite, leading to parasite death
Indications
- Treatment of uncomplicated malaria caused by susceptible strains of Plasmodium species
- Prophylaxis of malaria
- Chronic discoid lupus erythematosus
- Systemic lupus erythematosus
- Rheumatoid arthritis
Dosage
Malaria – Treatment (Adults): 800 mg initially, followed by 400 mg at 6, 24, and 48 hours Malaria – Prophylaxis (Adults): 400 mg once weekly Rheumatoid Arthritis (Adults): 400–600 mg daily initially Maintenance: 200–400 mg daily Systemic Lupus Erythematosus: 200–400 mg daily Dosage adjustments may be required based on clinical response and tolerability.
Contraindications
- Known hypersensitivity to hydroxychloroquine or other 4-aminoquinoline compounds
- Pre-existing retinopathy
- Long-term use in patients with visual field changes attributable to 4-aminoquinoline compounds
Side Effects
- Nausea
- Vomiting
- Diarrhea
- Headache
- Irreversible retinopathy
- Cardiomyopathy
- QT prolongation
- Myopathy
- Severe hypoglycemia
- Hematologic abnormalities
Interactions
- Drugs that prolong QT interval (e.g., amiodarone, certain antipsychotics) → Increased arrhythmia risk
- Digoxin → May increase digoxin levels
- Antidiabetic agents/insulin → Increased risk of hypoglycemia
- Antiepileptics → May reduce seizure threshold
- CYP2D6 substrates → May alter metabolism
Counseling Points
- Eye exam required (Retinopathy risk). Prescription only.