Hydroxychloroquine

Hydroxychloroquine is an oral disease-modifying antirheumatic drug (DMARD) with immunomodulatory properties, widely prescribed for autoimmune disorders and malaria prophylaxis. This antimalarial quinoline derivative demonstrates significant efficacy in managing inflammatory pathways through complex mechanisms involving Toll-like receptor signaling and cytokine modulation. Clinical applications extend beyond its original antimalarial indications to chronic autoimmune conditions requiring long-term immunoregulation.

Features

• Chemical classification: 4-Aminoquinoline compound
• Available formulations: 200mg and 400mg oral tablets
• Mechanism: Lysosomal pH alteration and autophagy inhibition
• Bioavailability: Approximately 74% following oral administration
• Half-life: 40-50 days in plasma
• Metabolism: Hepatic via cytochrome P450 enzymes
• Excretion: Primarily renal (60%) with partial biliary elimination

Benefits

• Provides sustained suppression of autoimmune activity through immunomodulatory mechanisms
• Reduces disease progression and joint damage in inflammatory arthritides
• Demonstrates steroid-sparing effects in systemic lupus erythematosus management
• Offers convenient once-daily dosing regimen for improved adherence
• Shows favorable long-term safety profile compared to biologic DMARDs
• Provides cost-effective disease modification in resource-limited settings

Common use

Hydroxychloroquine is primarily indicated for the treatment of uncomplicated malaria caused by Plasmodium vivax, P. malariae, P. ovale, and susceptible strains of P. falciparum. In rheumatology practice, it is FDA-approved for rheumatoid arthritis and systemic lupus erythematosus management. Off-label applications include Sjögren’s syndrome, discoid lupus erythematosus, and porphyria cutanea tarda. The drug’s immunomodulatory effects make it particularly valuable in conditions characterized by abnormal antigen presentation and T-cell activation.

Dosage and direction

For rheumatoid arthritis and lupus erythematosus: Initial dose typically ranges from 400-600mg daily, divided into single or twice-daily administration. Maintenance dosing usually involves 200-400mg daily based on clinical response and tolerability. Malaria prophylaxis: 400mg once weekly starting 1-2 weeks before exposure and continuing for 4 weeks after leaving endemic areas. Dosing must be weight-based in pediatric populations, not exceeding 6.5mg/kg actual body weight. Administration with food or milk minimizes gastrointestinal discomfort. Regular ophthalmologic monitoring is mandatory due to retinal toxicity risk.

Precautions

Baseline ophthalmologic examination including visual fields, spectral-domain optical coherence tomography, and multifocal electroretinography is essential before initiation. Repeat evaluations every 6-12 months depending on risk factors including duration of therapy, renal impairment, and concomitant retinal disease. Monitor for neuromuscular reactions including proximal muscle weakness and depressed deep tendon reflexes. Regular complete blood counts and liver function tests recommended during long-term therapy. Use caution in patients with glucose-6-phosphate dehydrogenase deficiency due to hemolysis risk.

Contraindications

Absolute contraindications include known hypersensitivity to 4-aminoquinoline compounds, pre-existing macular changes, and retinal field changes attributable to antimalarial compounds. Relative contraindications include severe hepatic impairment, porphyria, psoriasis (may exacerbate symptoms), and myasthenia gravis. Concomitant use with other drugs known to cause retinal toxicity or ototoxicity requires careful risk-benefit assessment. Pregnancy category C: use only if potential benefit justifies potential fetal risk.

Possible side effect

Ocular: Vortex keratopathy (corneal deposits), accommodative dysfunction, retinal toxicity including bull’s eye maculopathy (0.5-1% incidence after 5 years of use). Dermatological: Pruritus, pigmentary changes, hair bleaching, exfoliative dermatitis. Gastrointestinal: Nausea, vomiting, abdominal cramps, anorexia (20-30% incidence). Neurological: Headache, dizziness, nervousness, emotional lability. Neuromuscular: Proximal myopathy, absent deep tendon reflexes. Hematological: Rare agranulocytosis, aplastic anemia, thrombocytopenia. Cardiac: QTc prolongation, conduction disorders particularly in overdose scenarios.

Drug interaction

Significant interactions occur with drugs that prolong QTc interval including antiarrhythmics (amiodarone, sotalol), antipsychotics (haloperidol, ziprasidone), and antibiotics (macrolides, fluoroquinolones). Concomitant use with penicillamine increases blood dyscrasia risk. Antacids and kaolin reduce absorption—separate administration by 4 hours. May enhance effects of hypoglycemic agents and insulin. CYP2D6 and CYP3A4 inhibitors may increase hydroxychloroquine levels. Digoxin levels may increase due to reduced renal clearance.

Missed dose

If a dose is missed, take it as soon as remembered unless it is nearly time for the next scheduled dose. Do not double doses to make up for missed administration. For weekly malaria prophylaxis: If missed, take immediately and resume weekly schedule from that day. For chronic autoimmune conditions: Maintain regular dosing schedule without compensation for missed doses to avoid toxicity. Consistent plasma levels are more important than exact timing for immunomodulatory effects.

Overdose

Acute overdose (>30mg/kg) constitutes a medical emergency with mortality rates up to 30%. Early symptoms include headache, visual disturbances, cardiovascular collapse, and hypokalemia. Cardiotoxicity manifests as QRS and QTc prolongation, ventricular tachycardia, and torsades de pointes. Management includes immediate gastric lavage, activated charcoal administration, and continuous cardiac monitoring. Intravenous diazepam may mitigate cardiotoxic effects. Potassium supplementation should be cautious due to potential paradoxical hypokalemia. Extracorporeal elimination methods are ineffective due to large volume of distribution.

Storage

Store at controlled room temperature (20-25°C/68-77°F) in original container protected from light and moisture. Keep tightly closed and away from excessive heat. Dispense in child-resistant containers. Do not freeze. Shelf life typically 36 months from manufacturing date. Proper disposal required for unused medication through take-back programs—do not flush or pour into drainage systems.

Disclaimer

This information provides educational content regarding hydroxychloroquine pharmacology and clinical use. It does not constitute medical advice, diagnosis, or treatment recommendation. Healthcare providers must exercise independent clinical judgment considering individual patient factors. Prescribing decisions should be based on current FDA labeling and clinical practice guidelines. Off-label use requires thorough risk-benefit discussion with patients. Regular monitoring and dose adjustments are essential for safe long-term therapy.

Reviews

Clinical studies demonstrate hydroxychloroquine’s efficacy in rheumatoid arthritis with ACR20 response rates of 60-70% at 24 weeks. Systematic reviews confirm statistically significant reduction in lupus disease activity scores (SLEDAI) and decreased flare frequency. Malaria prophylaxis studies show 90-95% efficacy in non-resistant regions. Patient-reported outcomes indicate improved quality of life measures particularly regarding fatigue and joint symptoms. Long-term observational data support sustained efficacy over decades of use with appropriate monitoring protocols.