Makindo Medical Notes

⚠️ 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)