H-Quin

• Approved Indications
• Malaria
• Prophylaxis: Prevention of Plasmodium vivax, P. ovale, P. malariae, and chloroquine-sensitive P. falciparum malaria in endemic regions
• Treatment: Acute attacks of chloroquine-sensitive uncomplicated malaria
• Autoimmune Diseases
• Rheumatoid Arthritis: Adjunct therapy for mild to moderate cases
• Systemic Lupus Erythematosus (SLE): Management of cutaneous manifestations and systemic disease
• Other Approved Uses
• Discoid lupus erythematosus and other dermatologic lupus manifestations
• Off-label / Clinically Accepted Uses
• Sjögren’s syndrome management (as part of immunomodulatory therapy)
• Certain chronic inflammatory skin disorders, under specialist guidance

• Malaria Prophylaxis
• Adults: 400 mg orally once weekly, starting 1–2 weeks before travel and continuing 4 weeks after leaving endemic area
• Children: 5 mg/kg orally once weekly; maximum 400 mg
• Malaria Treatment
• Adults: 800 mg orally initially, then 400 mg at 6, 24, and 48 hours (total 2 g over 3 days)
• Children: 10 mg/kg initially, then 5 mg/kg at 6, 24, and 48 hours; total dose not exceeding adult equivalent
• Rheumatoid Arthritis & SLE
• Adults: 200–400 mg orally daily (may be divided doses); adjust based on body weight (≤6.5 mg/kg/day ideal body weight)
• Elderly: Dose adjustments based on renal function and tolerance
• Special Populations
• Renal Impairment: Reduce dose if GFR <30 mL/min
• Hepatic Impairment: Use with caution; monitor liver function
• Administration Notes
• Take with food or milk to reduce gastrointestinal irritation
• Avoid abrupt discontinuation in chronic therapy

Hydroxychloroquine interferes with parasite lysosomal activity, increasing pH within vacuoles and inhibiting hemoglobin digestion in Plasmodium species. In autoimmune diseases, it modulates the innate immune system by inhibiting toll-like receptor signaling, reducing dendritic cell activation, and decreasing production of pro-inflammatory cytokines. These effects collectively reduce inflammation, autoantibody production, and tissue damage.

• Absorption: Well absorbed orally; peak plasma concentration within 3–4 hours
• Distribution: Widely distributed in tissues (liver, spleen, kidney, lungs, skin); crosses the placenta and into breast milk
• Metabolism: Partially metabolized in the liver via CYP2C8 and CYP3A4
• Elimination: Renal excretion of unchanged drug and metabolites; ~25% excreted in urine
• Half-life: Approximately 40–50 days (due to extensive tissue binding)
• Onset: Malaria prophylaxis: protective effect achieved after 1–2 weeks; rheumatoid arthritis: clinical improvement may take 4–12 weeks

• Pregnancy: Category C (FDA) – use only if potential benefit outweighs risk; generally considered safe in malaria prophylaxis at recommended doses
• Breastfeeding: Excreted in small amounts in milk; considered compatible with breastfeeding at standard doses
• Caution: Long-term high doses require monitoring of infant for potential hematologic effects

• Primary Class: Antimalarial / Disease-modifying antirheumatic drug (DMARD)
• Subclass: 4-Aminoquinoline derivative

• Known hypersensitivity to hydroxychloroquine or chloroquine
• Retinal or visual field changes due to previous 4-aminoquinoline use
• Severe hepatic or renal impairment (relative contraindication)
• Pre-existing maculopathy or retinopathy

• Ocular toxicity: Long-term use may cause retinopathy; baseline and annual eye exams recommended
• Cardiac risk: QT prolongation, arrhythmias, especially with other QT-prolonging drugs
• Blood disorders: Rare hemolysis in G6PD deficiency
• High-risk groups: Elderly, renal/hepatic impairment, pre-existing cardiac disease
• Monitor for neuromyopathy and hypoglycemia
• Avoid abrupt discontinuation in chronic autoimmune therapy

• Common: Nausea, vomiting, diarrhea, abdominal cramps, headache, dizziness, skin rash
• Ocular: Retinopathy, blurred vision, corneal deposits
• Cardiac: QT prolongation, cardiomyopathy (rare, dose-dependent)
• Hematologic: Hemolysis in G6PD deficiency, leukopenia (rare)
• Neurologic: Myopathy, neuropathy (long-term use)
• Timing: Gastrointestinal effects within hours to days; ocular and cardiac toxicity with chronic use

• QT-prolonging drugs: Increased risk of arrhythmias
• Digoxin: Hydroxychloroquine may increase digoxin levels
• Antiepileptics / Cyclosporine: Monitor for altered drug levels
• CYP450 interactions: Minor involvement with CYP2C8 and CYP3A4; strong inhibitors/inducers may require monitoring
• Antacids / Kaolin: May reduce absorption; separate administration by 4 hours

• Malaria: CDC recommends hydroxychloroquine for chloroquine-sensitive regions; avoid in resistant areas
• Rheumatology: EULAR and ACR guidelines emphasize weight-based dosing to reduce retinopathy risk (<6.5 mg/kg/day)
• Emphasis on regular ophthalmologic screening after 5 years of therapy or sooner with risk factors
• Avoid off-label COVID-19 use outside clinical trials due to lack of proven benefit and cardiac risk

• Store at 20°C to 25°C (room temperature)
• Protect from moisture and light
• Keep tablets in original container tightly closed
• Do not freeze; avoid exposure to excessive heat
• Keep out of reach of children