Antimalarial — Lupus / Dermatoses Pregnancy: A population-based cohort study of 2045 exposed pregnancies suggests a small increase in the relative risk of congenital malformations with first-trimester exposure at doses higher than those normally used in rheumatological conditions (daily dose 400 mg or more: RR 1.33, 95% CI 1.08-1.65; daily dose of 400 mg: RR 0.95, 95% CI 0.60-1.50). In SLE, hydroxychloroquine reduces disease activity during pregnancy and should be continued; in autoimmune diseases such as lupus and antiphospholipid syndrome the balance of benefit outweighs potential harm, and a dose below 400 mg should be considered if the physician thinks it sufficiently effective. In other diseases the prescriber should assess the risk/benefit ratio. Breast-feeding: hydroxychloroquine is excreted in small amounts in breast milk (estimated infant exposure 1% to about 3% of the adult dose) and appears to carry a low risk of harm; make a careful benefit-risk assessment.

Hydroxychloroquine

Brand names: Plaquenil

Hydroxychloroquine is an antimalarial used as a disease-modifying treatment in lupus, rheumatoid arthritis and some skin conditions.

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: The minimum effective dose should be employed. The dose should not exceed 6.5 mg/kg/day (calculated from ideal body weight) and will be either 200 mg, 300 mg or 400 mg per day. In patients able to receive 300 mg daily: initially 300 mg daily in a single dose.

Route: Oral — each dose taken with a meal or a glass of milk

Frequency: Once daily (single dose)

Max: Must not exceed 6.5 mg/kg/day calculated from ideal body weight; the daily dose will be 200 mg, 300 mg or 400 mg

Source: eMC SPC for Hydroxychloroquine 300 mg film coated tablets. Adults and the elderly receive the same dose. Titration: the dose can be reduced to 200 mg when no further improvement is evident; the maintenance dose should be increased to 300 mg daily if the response lessens. Onset and duration: hydroxychloroquine is cumulative in action and requires several weeks to exert its beneficial effects, whereas minor side effects may occur relatively early; for rheumatic disease, treatment should be discontinued if there is no improvement by 6 months. Dermatology-relevant statement in SPC 4.2: 'In light-sensitive diseases, treatment should only be given during periods of maximum exposure to light.' Retinopathy monitoring (SPC 4.4): retinopathy is uncommon if the recommended daily dose is not exceeded; doses above the recommended maximum increase the risk and accelerate onset. Refer patients for annual retinopathy monitoring once they have been taking the medication for 5 years, or after 1 year if additional risk factors are present (concomitant tamoxifen use, or impaired renal function with eGFR less than 60 ml/min/1.73m2). Discontinue immediately if a pigmentary abnormality, visual field defect or other unexplained ocular abnormality develops, and advise patients to stop and seek advice for any visual disturbance including abnormal colour vision. Cardiac: clinical monitoring for cardiomyopathy is advised; discontinue if cardiomyopathy develops. Hepatitis B reactivation has been reported when combined with other immunosuppressants. Paediatric (SPC 4.2, non-per-kg detail): the minimum effective dose should be employed and should not exceed 6.5 mg/kg/day based on ideal body weight; the 300 mg tablet is therefore not suitable for use in children with an ideal body weight of less than 46 kg. The openFDA US label was fetched but NOT used — it carries different indication-specific regimens and a different tablet strength (200 mg).

Paediatric dose

Route: Oral — taken with a meal or a glass of milk

Frequency: Daily (SPC 4.2 expresses the paediatric instruction as a maximum per day; no separate paediatric dosing schedule is given)

Max: Must not exceed 6.5 mg/kg/day based on ideal body weight

dosePerKg left null because the SPC states only a per-kg ceiling for children, not a per-kg dose to administer: 'The minimum effective dose should be employed and should not exceed 6.5 mg/kg/day based on ideal body weight. The 300 mg tablet is therefore not suitable for use in children with an ideal body weight of less than 46 kg.' Verify against a children's formulary before prescribing.

Dose adjustments

Renal

No numerical renal dose reduction is given. SPC 4.4: use with caution in patients with renal disease and in those taking drugs known to affect the kidneys; estimation of plasma hydroxychloroquine levels should be undertaken in patients with severely compromised renal or hepatic function and the dosage adjusted accordingly. Impaired renal function (eGFR less than 60 ml/min/1.73m2) is a risk factor for retinopathy and triggers retinopathy monitoring after 1 year of treatment.

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.

US labelling (FDA)

Reference — US labelling, may differ from UK

Malaria in Adult and Pediatric Patients ( 2.2 ): ● Prophylaxis: Begin weekly doses 2 weeks prior to travel to the endemic area, continue weekly doses while in the endemic area, and continue the weekly doses for 4 weeks after leaving the endemic area: - Adults: 400 mg once a week - Pediatric patients ≥ 31 kg: 6.5 mg/kg up to 400 mg, once a week ● Treatment of Uncomplicated Malaria: See Full Prescribing Information (FPI) for complete dosing information. Rheumatoid Arthritis in Adults ( 2.3 ): Initial dosage: 400 mg to 600 mg daily Chronic dosage: 200 mg once daily or 400 mg once daily (or in two divided doses) Systemic Lupus Erythematosus in Adults ( 2.4 ): 200 mg once daily or 400 mg once …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2025-10-09. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Contraindications

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

Side effects

Gastrointestinal: abdominal pain and nausea (very common); diarrhoea and vomiting (common) — usually resolve immediately on reducing the dose or stopping treatment
Eye: blurring of vision due to a dose-dependent, reversible disturbance of accommodation (common); retinopathy with pigmentary change and visual field defects, and corneal oedema/opacities (uncommon); maculopathy and macular degeneration, onset from 3 months to several years, which may be irreversible (frequency not known)
Skin: rash and pruritus (common); pigmentary disorders of skin and mucous membranes, bleaching of hair, alopecia (uncommon); severe cutaneous adverse reactions including erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis, DRESS and acute generalised exanthematous pustulosis, photosensitivity, exfoliative dermatitis — hydroxychloroquine may also precipitate attacks of psoriasis (frequency not known)
Nervous system: headache (common), dizziness (uncommon); convulsions and extrapyramidal disorders such as dystonia, dyskinesia and tremor (frequency not known)
Cardiac: QT interval prolongation in patients with specific risk factors, which may lead to torsade de pointes or ventricular tachycardia; cardiomyopathy which may result in cardiac failure and in some cases a fatal outcome (frequency not known)
Immune system: urticaria, angioedema, bronchospasm (frequency not known)

Interactions

Tamoxifen — concomitant use is a risk factor for retinopathy; refer for retinopathy monitoring after 1 year rather than 5 (SPC 4.4)
Azithromycin and other macrolide antibiotics — carefully consider the benefits and risks before prescribing hydroxychloroquine, because of the potential for an increased risk of cardiovascular events and cardiovascular mortality (SPC 4.4)
Medicines that may cause adverse ocular or skin reactions — use hydroxychloroquine with caution (SPC 4.4)
Drugs known to affect the liver or kidneys — caution in patients with hepatic or renal disease and in those taking such drugs; estimate plasma hydroxychloroquine levels in severely compromised renal or hepatic function and adjust dosage accordingly (SPC 4.4)
Other immunosuppressants — reactivation of hepatitis B virus has been reported when hydroxychloroquine is combined with other immunosuppressants (SPC 4.4)
Section 4.5 (interactions) was not captured in the fetched bundle — the items above are taken from SPC 4.3/4.4; check the full interaction list against the SPC before publication

Clinical monograph

How it works

It modulates immune and inflammatory responses (including lysosomal and antigen-presentation pathways); the precise mechanism in autoimmune disease is not fully defined.

Prescribing in practice

Retinal toxicity is the key long-term risk — baseline and, after a few years, regular ophthalmology screening is recommended, with dose related to body weight.
It is among the better-tolerated DMARDs and is generally considered compatible with pregnancy in autoimmune disease (specialist guidance).
Use caution with significant QT prolongation or other QT-prolonging drugs and in G6PD deficiency.

Monitoring

Baseline and periodic retinal screening per guidance; weight-based dosing; review skin/joint response.

Counselling the patient

Report any change in vision.
It can take weeks to months to work.
Do not exceed the prescribed dose; overdose is dangerous, especially for children.

Evidence & guidelines

A cornerstone treatment in SLE and an option in rheumatoid arthritis, with retinal-screening monitoring (Royal College of Ophthalmologists guidance).

Reference: MHRA Drug Safety Update (2018) Hydroxychloroquine dose; RCOphth Hydroxychloroquine Guidelines 2020; BAD CLE Guidelines; 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