Hydroxychloroquine 💊
⚠️ In obese patients, dosing of hydroxychloroquine should be based on ideal body weight. Retinal toxicity is very unlikely if the dose does not exceed 4 mg/kg chloroquine phosphate daily (≈2.5 mg/kg chloroquine base).
📖 About
- Hydroxychloroquine is an antimalarial widely used in rheumatology (RA, SLE, DLE).
- Check BNF or local guidance for up-to-date prescribing advice.
⚡ Mode of Action
- Similar to chloroquine: accumulates in lysosomes → increases pH → interferes with antigen processing.
- Blocks Toll-like receptor (TLR) signalling → reduced activation of dendritic cells and T-cells.
- Overall: immunomodulatory, anti-inflammatory, and antithrombotic effects.
💊 Indications & Dose
- Rheumatoid Arthritis, SLE/DLE: 200–400 mg daily (do not exceed 6.5 mg/kg/day based on ideal body weight).
- May be used in other autoimmune conditions (e.g. Sjögren’s, sarcoidosis, antiphospholipid syndrome).
🤝 Interactions
- Refer to BNF for full list.
- Caution with other QT-prolonging drugs.
⚠️ Cautions
- Check renal and liver function (dose adjustment may be required).
- Baseline ophthalmic exam if any pre-existing visual problems; thereafter, annual retinal screening after 5 years of therapy (earlier if high risk).
- Use caution in pregnancy and breastfeeding - seek specialist advice.
🚫 Contraindications
- Hypersensitivity to 4-aminoquinoline compounds.
- Pre-existing retinal disease (relative contraindication).
💥 Side Effects
- GI: Nausea, vomiting, diarrhoea, abdominal pain.
- Neuro: Headache, dizziness, convulsions, psychosis (rare).
- Ocular: Retinopathy, keratopathy, visual changes (dose/duration dependent).
- Cardiac: QTc prolongation, conduction abnormalities, cardiomyopathy.
- Skin: Rash, pruritus, photosensitivity, hair depigmentation, exfoliative dermatitis, SJS/TEN.
- Haematological: Agranulocytosis, aplastic anaemia, thrombocytopenia.
- Respiratory: Rare interstitial lung disease.
- Other: Neuromyopathy, DRESS syndrome.
- Overdose: Highly toxic - can cause seizures, arrhythmias, cardiovascular collapse.
📚 References
- BNF – Hydroxychloroquine
- Royal College of Ophthalmologists: Hydroxychloroquine and Chloroquine Retinopathy: Recommendations on Monitoring (2020)
