Antimalarial / Immunomodulator (Obstetric Use) Pregnancy: SPC 4.6: data from a population-based cohort study including 2045 hydroxychloroquine-exposed pregnancies suggest 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 there is evidence that hydroxychloroquine reduces disease activity during pregnancy, reinforcing the importance of continuing therapy; pregnancy itself can induce lupus flares with potential harm to the fetus. Preliminary studies suggest it can reduce the risk of neonatal lupus and congenital heart block in anti-Ro positive lupus patients, and a published study in antiphospholipid syndrome found exposure was linked to a significantly higher live birth rate. Taken together, in autoimmune diseases such as lupus and antiphospholipid syndrome the balance of benefit outweighs any potential harm to the foetus and hydroxychloroquine should be continued; a dose below 400 mg should be considered if thought sufficiently effective by the physician. In other diseases the prescribing physician should assess the risk/benefit ratio. In prolonged treatment during pregnancy the ophthalmological side effect profile should be taken into account for child monitoring; available evidence does not show an increased risk of retinal toxicity in infants after maternal therapy. Breast-feeding: data are limited but no harmful effects have been observed; hydroxychloroquine is excreted in small amounts in breast milk (estimated infant exposure 1% to about 3% of the adult dose) and its half-life is more than 40 days, so all infants exposed in pregnancy will also be exposed during breastfeeding; it seems to carry a low risk of harm to the infant and a careful benefit-risk assessment should be made. Fertility: there is no information on the effect on human fertility; in animal studies chloroquine, a related substance, showed adverse effects on male fertility.

Hydroxychloroquine

Brand names: Plaquenil

Hydroxychloroquine, an antimalarial and disease-modifying agent, used in the obstetric setting chiefly for maternal autoimmune disease such as systemic lupus erythematosus and antiphospholipid syndrome, where it is generally continued through pregnancy.

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. The SPC gives one posology for all licensed indications — there is no separate obstetric or gynaecological regimen. 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. Pregnancy-relevant dosing statement in SPC 4.6: in SLE and antiphospholipid syndrome the balance of benefit outweighs potential harm and hydroxychloroquine should be continued in pregnancy, but 'a dose below 400 mg should be considered if thought sufficiently effective by the physician'; see pregnancyCategory for the full statement. In case of prolonged treatment during pregnancy, the ophthalmological side effect profile should be taken into account for child monitoring. Retinopathy monitoring (SPC 4.4): refer for annual retinopathy monitoring once the patient has 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 for any pigmentary abnormality, visual field defect or unexplained ocular abnormality. 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.

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 (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

Hydroxychloroquine accumulates in lysosomes and interferes with antigen processing and toll-like receptor signalling, producing immunomodulatory and anti-inflammatory effects that reduce lupus disease activity.

Prescribing in practice

It is regarded as compatible with pregnancy and breastfeeding and stopping it abruptly can precipitate a maternal lupus flare, so continuation is usually advised after specialist discussion.
Long-term use carries a risk of irreversible retinal toxicity, warranting baseline and periodic ophthalmic screening.
Rare cardiac conduction effects and QT prolongation can occur, with caution where other QT-prolonging drugs are co-prescribed.

Monitoring

Arrange retinal screening per ophthalmology recommendations for long-term users and monitor maternal disease activity through the pregnancy.

Counselling the patient

Keep taking this medicine in pregnancy unless your specialist tells you otherwise, as stopping can worsen your condition.
Attend your eye screening appointments and report any change in vision.
It is taken regularly to control your condition rather than for immediate symptom relief.

Evidence & guidelines

Rheumatology and obstetric guidance supports continuing hydroxychloroquine in pregnancy for lupus, reflecting evidence that it reduces flares and adverse pregnancy outcomes.

Reference: MHRA hydroxychloroquine retinopathy guidance 2020; Izmirly et al. NEJM 2020 (PATCH trial); BSR/BHPR SLE in Pregnancy Guideline (2022); EULAR APS Guidelines (2019); 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