Hydroxychloroquine

How it works

It accumulates in lysosomes and raises intracellular pH, interfering with antigen processing and immune signalling; this immunomodulatory effect underlies its use in autoimmune disease.

Prescribing in practice

• Long-term use carries a risk of irreversible retinal toxicity — baseline and ongoing annual retinal monitoring is recommended (Royal College of Ophthalmologists), with dose related to body weight.
• It can prolong the QT interval and has a very long half-life, so effects and interactions persist after stopping.
• It is generally continued during pregnancy in SLE, where the benefits of disease control are considered to outweigh the risks.

Monitoring

Arrange baseline retinal assessment and annual screening after a defined period of treatment per Royal College of Ophthalmologists guidance, dose according to body weight, and review renal and hepatic function and QT risk where relevant.

Counselling the patient

• Attend your eye-screening appointments and report any change in vision, such as difficulty reading, missing areas or altered colour vision.
• Take it as prescribed; the benefit in joint or lupus disease builds gradually over weeks to months.
• Do not stop it in pregnancy without advice, as continuing usually protects against lupus flares.

Evidence & guidelines

A cornerstone DMARD in SLE that reduces flares and is associated with better outcomes, and an established treatment in rheumatoid arthritis; supported by UK rheumatology and ophthalmology guidance.