Hydroxychloroquine sulfate

How it works

It raises lysosomal pH and modulates immune cell function—impairing antigen presentation and Toll-like receptor signalling—to reduce inflammatory activity in autoimmune disease.

Prescribing in practice

• Irreversible retinal maculopathy is the key long-term hazard, so use weight-based dosing, arrange baseline and ongoing retinal screening per Royal College of Ophthalmologists guidance, and report any visual change.
• It may prolong the QT interval and, rarely, cause cardiomyopathy, so use caution alongside other QT-prolonging drugs and in cardiac disease.
• Use caution in G6PD deficiency, hepatic or renal impairment, and psoriasis (which it may worsen).

Monitoring

Perform retinal screening as recommended, watch for visual disturbance, and review cardiac, hepatic and renal status where clinically relevant.

Counselling the patient

• Keep your eye-check appointments and report any blurring or changes in colour vision.
• The benefit builds gradually over weeks to months, so take it consistently.
• Store safely away from children because overdose can be life-threatening.

Evidence & guidelines

Hydroxychloroquine sulfate is the established UK salt form, with efficacy and the retinopathy screening framework documented in the SPC, NICE guidance and Royal College of Ophthalmologists recommendations.