💊 Hydroxychloroquine

Hydroxychloroquine is an antimalarial drug with significant immunomodulatory and anti-inflammatory properties, classified as a disease-modifying antirheumatic drug (DMARD).

Its exact mechanism in autoimmune diseases is not fully understood, but it is thought to interfere with antigen presentation, inhibit lysosomal activity, and modulate cytokine production. It also stabilises lysosomal membranes and traps free radicals.

In the UK, it is widely used for systemic lupus erythematosus (SLE), particularly for skin and joint manifestations. It is also indicated for rheumatoid arthritis, often as a first-line DMARD, and for certain forms of juvenile idiopathic arthritis.

Absolute contraindications include hypersensitivity to 4-aminoquinoline compounds. It should be used with caution in patients with pre-existing maculopathy or retinal changes, porphyria, and severe gastrointestinal, neurological, or blood disorders.

Common side effects are mild and include nausea, diarrhoea, abdominal cramps, and skin rashes. The most serious adverse effect is irreversible retinal toxicity (maculopathy), which is dose-dependent and cumulative. Other rare effects include cardiomyopathy and neuropsychiatric disturbances.

Baseline and annual ophthalmological examinations are crucial to screen for retinal toxicity, especially in long-term use. This includes visual acuity, fundoscopy, and potentially visual field testing. No routine blood monitoring is typically required.

Always inquire about pre-existing eye conditions or visual disturbances. Counsel patients on the importance of regular eye checks and to report any changes in vision. Advise taking with food to minimise gastrointestinal upset.

A 'gentle' DMARD, often first-line due to its good safety profile and tolerability. High yield for its specific ocular toxicity and the monitoring required. Remember its role in SLE, where it can reduce flares and improve long-term outcomes.

SBAs frequently focus on the most serious adverse effect: retinal toxicity and the need for regular ophthalmological screening. Questions may also test its use in SLE and rheumatoid arthritis, and its relatively favourable safety profile compared to other DMARDs.