Antimalarial DMARD Pregnancy: First-trimester exposure at doses higher than usual rheumatological doses suggests a small increase in relative risk of congenital malformations (RR 1.33 for >=400 mg/day; 0.95 for 400 mg/day). In SLE and antiphospholipid syndrome, benefit outweighs potential harm and hydroxychloroquine should be continued (consider a dose below 400 mg if sufficiently effective). Excreted in small amounts in breast milk (~1-3% of adult dose); low risk to the infant, make a careful benefit-risk assessment.

Hydroxychloroquine

Brand names: Plaquenil

Hydroxychloroquine is an oral disease-modifying antirheumatic drug (DMARD) used in rheumatology for rheumatoid arthritis and systemic and discoid lupus erythematosus, and also as an antimalarial.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 300 mg

Route: Oral

Frequency: Initially 300 mg once daily (single dose)

Max: 6.5 mg/kg/day (calculated from ideal body weight); daily dose 200 mg, 300 mg or 400 mg

SPC for the 300 mg film-coated tablet. Adults (including the elderly): use the minimum effective dose, not exceeding 6.5 mg/kg/day based on ideal body weight. In patients able to receive 300 mg daily: initially 300 mg once daily; dose can be reduced to 200 mg when no further improvement is evident; maintenance increased to 300 mg daily if response lessens. Cumulative in action, requiring several weeks for benefit. For rheumatic disease, discontinue if no improvement by 6 months. In light-sensitive diseases give only during periods of maximum light exposure. Take each dose with a meal or glass of milk. Paediatric use: minimum effective dose not exceeding 6.5 mg/kg/day based on ideal body weight; the 300 mg tablet is not suitable for children with ideal body weight below 46 kg - verify paediatric dosing against a children's formulary. Annual retinopathy monitoring advised after 5 years (or after 1 year if additional risk factors).

Dose adjustments

Renal

Use with caution in renal disease. Estimate plasma hydroxychloroquine levels in patients with severely compromised renal function and adjust dose accordingly. Impaired renal function (eGFR <60 mL/min/1.73m2) is a risk factor for retinopathy.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to hydroxychloroquine or to any of the excipients
Known hypersensitivity to 4-aminoquinoline compounds
Pre-existing maculopathy of the eye

Side effects

Blurring of vision due to a dose-dependent, reversible disturbance of accommodation (common)
Abdominal pain, nausea (very common); diarrhoea, vomiting (common)
Skin rash, pruritus (common); pigmentary disorders of skin/mucous membranes, bleaching of hair, alopecia (uncommon)
Headache (common); dizziness (uncommon)
Retinopathy with pigmentation changes and visual field defects (uncommon); maculopathy/macular degeneration (not known, may be irreversible)

Interactions

Other QT-prolonging or arrhythmogenic drugs: not recommended concomitantly (hydroxychloroquine prolongs the QT interval, increasing risk of ventricular arrhythmias) [US label]
Azithromycin or other macrolide antibiotics: carefully weigh benefits/risks before prescribing, because of potential increased risk of cardiovascular events and mortality
Insulin or other antidiabetic drugs: effects may be enhanced, increasing hypoglycaemic risk; a dose reduction of the antidiabetic may be needed [US label]
Drugs that lower the seizure threshold (e.g. mefloquine): may increase risk of seizures [US label]
Antiepileptic drugs: activity may be impaired if co-administered [US label]

Clinical monograph

How it works

It accumulates in lysosomes and raises intracellular pH, interfering with antigen processing, Toll-like receptor signalling and cytokine production to produce its immunomodulatory effect.

Prescribing in practice

Irreversible retinal toxicity (maculopathy) is the principal long-term risk, so dose by ideal body weight, arrange baseline and annual screening after the early years of therapy (per Royal College of Ophthalmologists guidance), and avoid exceeding recommended weight-based limits.
It can prolong the QT interval and cause cardiomyopathy with long-term use; use caution with other QT-prolonging drugs and pre-existing cardiac disease.
Caution is needed in G6PD deficiency, hepatic or renal impairment, and with concurrent drugs that lower the seizure threshold.

Monitoring

Arrange retinal screening as recommended and monitor for visual symptoms, with assessment of cardiac, hepatic and renal status as clinically indicated.

Counselling the patient

Attend your eye-screening appointments and report any change in vision or colour perception.
It may take several weeks to months to work, so continue taking it regularly.
Keep well out of reach of children, as overdose is dangerous.

Evidence & guidelines

Hydroxychloroquine is a well-established DMARD with efficacy in lupus and rheumatoid arthritis supported by long clinical use and reflected in NICE and specialist society guidance, including retinopathy screening recommendations.

Reference: BSR Monitoring Guidelines; RCOphth Hydroxychloroquine Guidelines 2020; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways